Updated assimp to commit 1d565b0 with iFire

Signed-off-by: RevoluPowered <gordon@gordonite.tech>
Signed-off-by: K. S. Ernest (iFIre) Lee <ernest.lee@chibifire.com>

58 files changed, 14370 insertions, 0 deletions

diff --git a/thirdparty/assimp/code/PostProcessing/CalcTangentsProcess.cpp b/thirdparty/assimp/code/PostProcessing/CalcTangentsProcess.cpp
new file mode 100644
index 0000000000..b30f39c274
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/CalcTangentsProcess.cpp
@@ -0,0 +1,319 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file Implementation of the post processing step to calculate
+ *  tangents and bitangents for all imported meshes
+ */
+
+// internal headers
+#include "CalcTangentsProcess.h"
+#include "ProcessHelper.h"
+#include <assimp/TinyFormatter.h>
+#include <assimp/qnan.h>
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+CalcTangentsProcess::CalcTangentsProcess()
+: configMaxAngle( AI_DEG_TO_RAD(45.f) )
+, configSourceUV( 0 ) {
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+CalcTangentsProcess::~CalcTangentsProcess()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool CalcTangentsProcess::IsActive( unsigned int pFlags) const
+{
+    return (pFlags & aiProcess_CalcTangentSpace) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void CalcTangentsProcess::SetupProperties(const Importer* pImp)
+{
+    ai_assert( NULL != pImp );
+
+    // get the current value of the property
+    configMaxAngle = pImp->GetPropertyFloat(AI_CONFIG_PP_CT_MAX_SMOOTHING_ANGLE,45.f);
+    configMaxAngle = std::max(std::min(configMaxAngle,45.0f),0.0f);
+    configMaxAngle = AI_DEG_TO_RAD(configMaxAngle);
+
+    configSourceUV = pImp->GetPropertyInteger(AI_CONFIG_PP_CT_TEXTURE_CHANNEL_INDEX,0);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void CalcTangentsProcess::Execute( aiScene* pScene)
+{
+    ai_assert( NULL != pScene );
+
+    ASSIMP_LOG_DEBUG("CalcTangentsProcess begin");
+
+    bool bHas = false;
+    for ( unsigned int a = 0; a < pScene->mNumMeshes; a++ ) {
+        if(ProcessMesh( pScene->mMeshes[a],a))bHas = true;
+    }
+
+    if ( bHas ) {
+        ASSIMP_LOG_INFO("CalcTangentsProcess finished. Tangents have been calculated");
+    } else {
+        ASSIMP_LOG_DEBUG("CalcTangentsProcess finished");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Calculates tangents and bi-tangents for the given mesh
+bool CalcTangentsProcess::ProcessMesh( aiMesh* pMesh, unsigned int meshIndex)
+{
+    // we assume that the mesh is still in the verbose vertex format where each face has its own set
+    // of vertices and no vertices are shared between faces. Sadly I don't know any quick test to
+    // assert() it here.
+    // assert( must be verbose, dammit);
+
+    if (pMesh->mTangents) // this implies that mBitangents is also there
+        return false;
+
+    // If the mesh consists of lines and/or points but not of
+    // triangles or higher-order polygons the normal vectors
+    // are undefined.
+    if (!(pMesh->mPrimitiveTypes & (aiPrimitiveType_TRIANGLE | aiPrimitiveType_POLYGON)))
+    {
+        ASSIMP_LOG_INFO("Tangents are undefined for line and point meshes");
+        return false;
+    }
+
+    // what we can check, though, is if the mesh has normals and texture coordinates. That's a requirement
+    if( pMesh->mNormals == NULL)
+    {
+        ASSIMP_LOG_ERROR("Failed to compute tangents; need normals");
+        return false;
+    }
+    if( configSourceUV >= AI_MAX_NUMBER_OF_TEXTURECOORDS || !pMesh->mTextureCoords[configSourceUV] )
+    {
+        ASSIMP_LOG_ERROR((Formatter::format("Failed to compute tangents; need UV data in channel"),configSourceUV));
+        return false;
+    }
+
+    const float angleEpsilon = 0.9999f;
+
+    std::vector<bool> vertexDone( pMesh->mNumVertices, false);
+    const float qnan = get_qnan();
+
+    // create space for the tangents and bitangents
+    pMesh->mTangents = new aiVector3D[pMesh->mNumVertices];
+    pMesh->mBitangents = new aiVector3D[pMesh->mNumVertices];
+
+    const aiVector3D* meshPos = pMesh->mVertices;
+    const aiVector3D* meshNorm = pMesh->mNormals;
+    const aiVector3D* meshTex = pMesh->mTextureCoords[configSourceUV];
+    aiVector3D* meshTang = pMesh->mTangents;
+    aiVector3D* meshBitang = pMesh->mBitangents;
+
+    // calculate the tangent and bitangent for every face
+    for( unsigned int a = 0; a < pMesh->mNumFaces; a++)
+    {
+        const aiFace& face = pMesh->mFaces[a];
+        if (face.mNumIndices < 3)
+        {
+            // There are less than three indices, thus the tangent vector
+            // is not defined. We are finished with these vertices now,
+            // their tangent vectors are set to qnan.
+            for (unsigned int i = 0; i < face.mNumIndices;++i)
+            {
+                unsigned int idx = face.mIndices[i];
+                vertexDone  [idx] = true;
+                meshTang    [idx] = aiVector3D(qnan);
+                meshBitang  [idx] = aiVector3D(qnan);
+            }
+
+            continue;
+        }
+
+        // triangle or polygon... we always use only the first three indices. A polygon
+        // is supposed to be planar anyways....
+        // FIXME: (thom) create correct calculation for multi-vertex polygons maybe?
+        const unsigned int p0 = face.mIndices[0], p1 = face.mIndices[1], p2 = face.mIndices[2];
+
+        // position differences p1->p2 and p1->p3
+        aiVector3D v = meshPos[p1] - meshPos[p0], w = meshPos[p2] - meshPos[p0];
+
+        // texture offset p1->p2 and p1->p3
+        float sx = meshTex[p1].x - meshTex[p0].x, sy = meshTex[p1].y - meshTex[p0].y;
+        float tx = meshTex[p2].x - meshTex[p0].x, ty = meshTex[p2].y - meshTex[p0].y;
+        float dirCorrection = (tx * sy - ty * sx) < 0.0f ? -1.0f : 1.0f;
+        // when t1, t2, t3 in same position in UV space, just use default UV direction.
+        if (  sx * ty == sy * tx ) {
+            sx = 0.0; sy = 1.0;
+            tx = 1.0; ty = 0.0;
+        }
+
+        // tangent points in the direction where to positive X axis of the texture coord's would point in model space
+        // bitangent's points along the positive Y axis of the texture coord's, respectively
+        aiVector3D tangent, bitangent;
+        tangent.x = (w.x * sy - v.x * ty) * dirCorrection;
+        tangent.y = (w.y * sy - v.y * ty) * dirCorrection;
+        tangent.z = (w.z * sy - v.z * ty) * dirCorrection;
+        bitangent.x = (w.x * sx - v.x * tx) * dirCorrection;
+        bitangent.y = (w.y * sx - v.y * tx) * dirCorrection;
+        bitangent.z = (w.z * sx - v.z * tx) * dirCorrection;
+
+        // store for every vertex of that face
+        for( unsigned int b = 0; b < face.mNumIndices; ++b ) {
+            unsigned int p = face.mIndices[b];
+
+            // project tangent and bitangent into the plane formed by the vertex' normal
+            aiVector3D localTangent = tangent - meshNorm[p] * (tangent * meshNorm[p]);
+            aiVector3D localBitangent = bitangent - meshNorm[p] * (bitangent * meshNorm[p]);
+            localTangent.Normalize(); localBitangent.Normalize();
+
+            // reconstruct tangent/bitangent according to normal and bitangent/tangent when it's infinite or NaN.
+            bool invalid_tangent = is_special_float(localTangent.x) || is_special_float(localTangent.y) || is_special_float(localTangent.z);
+            bool invalid_bitangent = is_special_float(localBitangent.x) || is_special_float(localBitangent.y) || is_special_float(localBitangent.z);
+            if (invalid_tangent != invalid_bitangent) {
+                if (invalid_tangent) {
+                    localTangent = meshNorm[p] ^ localBitangent;
+                    localTangent.Normalize();
+                } else {
+                    localBitangent = localTangent ^ meshNorm[p];
+                    localBitangent.Normalize();
+                }
+            }
+
+            // and write it into the mesh.
+            meshTang[ p ]   = localTangent;
+            meshBitang[ p ] = localBitangent;
+        }
+    }
+
+
+    // create a helper to quickly find locally close vertices among the vertex array
+    // FIX: check whether we can reuse the SpatialSort of a previous step
+    SpatialSort* vertexFinder = NULL;
+    SpatialSort  _vertexFinder;
+    float posEpsilon;
+    if (shared)
+    {
+        std::vector<std::pair<SpatialSort,float> >* avf;
+        shared->GetProperty(AI_SPP_SPATIAL_SORT,avf);
+        if (avf)
+        {
+            std::pair<SpatialSort,float>& blubb = avf->operator [] (meshIndex);
+            vertexFinder = &blubb.first;
+            posEpsilon = blubb.second;;
+        }
+    }
+    if (!vertexFinder)
+    {
+        _vertexFinder.Fill(pMesh->mVertices, pMesh->mNumVertices, sizeof( aiVector3D));
+        vertexFinder = &_vertexFinder;
+        posEpsilon = ComputePositionEpsilon(pMesh);
+    }
+    std::vector<unsigned int> verticesFound;
+
+    const float fLimit = std::cos(configMaxAngle);
+    std::vector<unsigned int> closeVertices;
+
+    // in the second pass we now smooth out all tangents and bitangents at the same local position
+    // if they are not too far off.
+    for( unsigned int a = 0; a < pMesh->mNumVertices; a++)
+    {
+        if( vertexDone[a])
+            continue;
+
+        const aiVector3D& origPos = pMesh->mVertices[a];
+        const aiVector3D& origNorm = pMesh->mNormals[a];
+        const aiVector3D& origTang = pMesh->mTangents[a];
+        const aiVector3D& origBitang = pMesh->mBitangents[a];
+        closeVertices.resize( 0 );
+
+        // find all vertices close to that position
+        vertexFinder->FindPositions( origPos, posEpsilon, verticesFound);
+
+        closeVertices.reserve (verticesFound.size()+5);
+        closeVertices.push_back( a);
+
+        // look among them for other vertices sharing the same normal and a close-enough tangent/bitangent
+        for( unsigned int b = 0; b < verticesFound.size(); b++)
+        {
+            unsigned int idx = verticesFound[b];
+            if( vertexDone[idx])
+                continue;
+            if( meshNorm[idx] * origNorm < angleEpsilon)
+                continue;
+            if(  meshTang[idx] * origTang < fLimit)
+                continue;
+            if( meshBitang[idx] * origBitang < fLimit)
+                continue;
+
+            // it's similar enough -> add it to the smoothing group
+            closeVertices.push_back( idx);
+            vertexDone[idx] = true;
+        }
+
+        // smooth the tangents and bitangents of all vertices that were found to be close enough
+        aiVector3D smoothTangent( 0, 0, 0), smoothBitangent( 0, 0, 0);
+        for( unsigned int b = 0; b < closeVertices.size(); ++b)
+        {
+            smoothTangent += meshTang[ closeVertices[b] ];
+            smoothBitangent += meshBitang[ closeVertices[b] ];
+        }
+        smoothTangent.Normalize();
+        smoothBitangent.Normalize();
+
+        // and write it back into all affected tangents
+        for( unsigned int b = 0; b < closeVertices.size(); ++b)
+        {
+            meshTang[ closeVertices[b] ] = smoothTangent;
+            meshBitang[ closeVertices[b] ] = smoothBitangent;
+        }
+    }
+    return true;
+}
diff --git a/thirdparty/assimp/code/PostProcessing/CalcTangentsProcess.h b/thirdparty/assimp/code/PostProcessing/CalcTangentsProcess.h
new file mode 100644
index 0000000000..3568a624f8
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/CalcTangentsProcess.h
@@ -0,0 +1,117 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+
+/** @file Defines a post processing step to calculate tangents and
+    bi-tangents on all imported meshes.*/
+#ifndef AI_CALCTANGENTSPROCESS_H_INC
+#define AI_CALCTANGENTSPROCESS_H_INC
+
+#include "Common/BaseProcess.h"
+
+struct aiMesh;
+
+namespace Assimp
+{
+
+// ---------------------------------------------------------------------------
+/** The CalcTangentsProcess calculates the tangent and bitangent for any vertex
+ * of all meshes. It is expected to be run before the JoinVerticesProcess runs
+ * because the joining of vertices also considers tangents and bitangents for
+ * uniqueness.
+ */
+class ASSIMP_API_WINONLY CalcTangentsProcess : public BaseProcess
+{
+public:
+
+    CalcTangentsProcess();
+    ~CalcTangentsProcess();
+
+public:
+    // -------------------------------------------------------------------
+    /** Returns whether the processing step is present in the given flag.
+    * @param pFlags The processing flags the importer was called with.
+    *   A bitwise combination of #aiPostProcessSteps.
+    * @return true if the process is present in this flag fields,
+    *   false if not.
+    */
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    /** Called prior to ExecuteOnScene().
+    * The function is a request to the process to update its configuration
+    * basing on the Importer's configuration property list.
+    */
+    void SetupProperties(const Importer* pImp);
+
+
+    // setter for configMaxAngle
+    inline void SetMaxSmoothAngle(float f)
+    {
+        configMaxAngle =f;
+    }
+
+protected:
+
+    // -------------------------------------------------------------------
+    /** Calculates tangents and bitangents for a specific mesh.
+    * @param pMesh The mesh to process.
+    * @param meshIndex Index of the mesh
+    */
+    bool ProcessMesh( aiMesh* pMesh, unsigned int meshIndex);
+
+    // -------------------------------------------------------------------
+    /** Executes the post processing step on the given imported data.
+    * @param pScene The imported data to work at.
+    */
+    void Execute( aiScene* pScene);
+
+private:
+
+    /** Configuration option: maximum smoothing angle, in radians*/
+    float configMaxAngle;
+    unsigned int configSourceUV;
+};
+
+} // end of namespace Assimp
+
+#endif // AI_CALCTANGENTSPROCESS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/ComputeUVMappingProcess.cpp b/thirdparty/assimp/code/PostProcessing/ComputeUVMappingProcess.cpp
new file mode 100644
index 0000000000..bb571a551b
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/ComputeUVMappingProcess.cpp
@@ -0,0 +1,506 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file GenUVCoords step */
+
+
+#include "ComputeUVMappingProcess.h"
+#include "ProcessHelper.h"
+#include <assimp/Exceptional.h>
+
+using namespace Assimp;
+
+namespace {
+
+    const static aiVector3D base_axis_y(0.0,1.0,0.0);
+    const static aiVector3D base_axis_x(1.0,0.0,0.0);
+    const static aiVector3D base_axis_z(0.0,0.0,1.0);
+    const static ai_real angle_epsilon = ai_real( 0.95 );
+}
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+ComputeUVMappingProcess::ComputeUVMappingProcess()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+ComputeUVMappingProcess::~ComputeUVMappingProcess()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool ComputeUVMappingProcess::IsActive( unsigned int pFlags) const
+{
+    return  (pFlags & aiProcess_GenUVCoords) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Check whether a ray intersects a plane and find the intersection point
+inline bool PlaneIntersect(const aiRay& ray, const aiVector3D& planePos,
+    const aiVector3D& planeNormal, aiVector3D& pos)
+{
+    const ai_real b = planeNormal * (planePos - ray.pos);
+    ai_real h = ray.dir * planeNormal;
+    if ((h < 10e-5 && h > -10e-5) || (h = b/h) < 0)
+        return false;
+
+    pos = ray.pos + (ray.dir * h);
+    return true;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Find the first empty UV channel in a mesh
+inline unsigned int FindEmptyUVChannel (aiMesh* mesh)
+{
+    for (unsigned int m = 0; m < AI_MAX_NUMBER_OF_TEXTURECOORDS;++m)
+        if (!mesh->mTextureCoords[m])return m;
+
+    ASSIMP_LOG_ERROR("Unable to compute UV coordinates, no free UV slot found");
+    return UINT_MAX;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Try to remove UV seams
+void RemoveUVSeams (aiMesh* mesh, aiVector3D* out)
+{
+    // TODO: just a very rough algorithm. I think it could be done
+    // much easier, but I don't know how and am currently too tired to
+    // to think about a better solution.
+
+    const static ai_real LOWER_LIMIT = ai_real( 0.1 );
+    const static ai_real UPPER_LIMIT = ai_real( 0.9 );
+
+    const static ai_real LOWER_EPSILON = ai_real( 10e-3 );
+    const static ai_real UPPER_EPSILON = ai_real( 1.0-10e-3 );
+
+    for (unsigned int fidx = 0; fidx < mesh->mNumFaces;++fidx)
+    {
+        const aiFace& face = mesh->mFaces[fidx];
+        if (face.mNumIndices < 3) continue; // triangles and polygons only, please
+
+        unsigned int small = face.mNumIndices, large = small;
+        bool zero = false, one = false, round_to_zero = false;
+
+        // Check whether this face lies on a UV seam. We can just guess,
+        // but the assumption that a face with at least one very small
+        // on the one side and one very large U coord on the other side
+        // lies on a UV seam should work for most cases.
+        for (unsigned int n = 0; n < face.mNumIndices;++n)
+        {
+            if (out[face.mIndices[n]].x < LOWER_LIMIT)
+            {
+                small = n;
+
+                // If we have a U value very close to 0 we can't
+                // round the others to 0, too.
+                if (out[face.mIndices[n]].x <= LOWER_EPSILON)
+                    zero = true;
+                else round_to_zero = true;
+            }
+            if (out[face.mIndices[n]].x > UPPER_LIMIT)
+            {
+                large = n;
+
+                // If we have a U value very close to 1 we can't
+                // round the others to 1, too.
+                if (out[face.mIndices[n]].x >= UPPER_EPSILON)
+                    one = true;
+            }
+        }
+        if (small != face.mNumIndices && large != face.mNumIndices)
+        {
+            for (unsigned int n = 0; n < face.mNumIndices;++n)
+            {
+                // If the u value is over the upper limit and no other u
+                // value of that face is 0, round it to 0
+                if (out[face.mIndices[n]].x > UPPER_LIMIT && !zero)
+                    out[face.mIndices[n]].x = 0.0;
+
+                // If the u value is below the lower limit and no other u
+                // value of that face is 1, round it to 1
+                else if (out[face.mIndices[n]].x < LOWER_LIMIT && !one)
+                    out[face.mIndices[n]].x = 1.0;
+
+                // The face contains both 0 and 1 as UV coords. This can occur
+                // for faces which have an edge that lies directly on the seam.
+                // Due to numerical inaccuracies one U coord becomes 0, the
+                // other 1. But we do still have a third UV coord to determine
+                // to which side we must round to.
+                else if (one && zero)
+                {
+                    if (round_to_zero && out[face.mIndices[n]].x >=  UPPER_EPSILON)
+                        out[face.mIndices[n]].x = 0.0;
+                    else if (!round_to_zero && out[face.mIndices[n]].x <= LOWER_EPSILON)
+                        out[face.mIndices[n]].x = 1.0;
+                }
+            }
+        }
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+void ComputeUVMappingProcess::ComputeSphereMapping(aiMesh* mesh,const aiVector3D& axis, aiVector3D* out)
+{
+    aiVector3D center, min, max;
+    FindMeshCenter(mesh, center, min, max);
+
+    // If the axis is one of x,y,z run a faster code path. It's worth the extra effort ...
+    // currently the mapping axis will always be one of x,y,z, except if the
+    // PretransformVertices step is used (it transforms the meshes into worldspace,
+    // thus changing the mapping axis)
+    if (axis * base_axis_x >= angle_epsilon)    {
+
+        // For each point get a normalized projection vector in the sphere,
+        // get its longitude and latitude and map them to their respective
+        // UV axes. Problems occur around the poles ... unsolvable.
+        //
+        // The spherical coordinate system looks like this:
+        // x = cos(lon)*cos(lat)
+        // y = sin(lon)*cos(lat)
+        // z = sin(lat)
+        //
+        // Thus we can derive:
+        // lat  = arcsin (z)
+        // lon  = arctan (y/x)
+        for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)  {
+            const aiVector3D diff = (mesh->mVertices[pnt]-center).Normalize();
+            out[pnt] = aiVector3D((std::atan2(diff.z, diff.y) + AI_MATH_PI_F ) / AI_MATH_TWO_PI_F,
+                (std::asin  (diff.x) + AI_MATH_HALF_PI_F) / AI_MATH_PI_F, 0.0);
+        }
+    }
+    else if (axis * base_axis_y >= angle_epsilon)   {
+        // ... just the same again
+        for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)  {
+            const aiVector3D diff = (mesh->mVertices[pnt]-center).Normalize();
+            out[pnt] = aiVector3D((std::atan2(diff.x, diff.z) + AI_MATH_PI_F ) / AI_MATH_TWO_PI_F,
+                (std::asin  (diff.y) + AI_MATH_HALF_PI_F) / AI_MATH_PI_F, 0.0);
+        }
+    }
+    else if (axis * base_axis_z >= angle_epsilon)   {
+        // ... just the same again
+        for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)  {
+            const aiVector3D diff = (mesh->mVertices[pnt]-center).Normalize();
+            out[pnt] = aiVector3D((std::atan2(diff.y, diff.x) + AI_MATH_PI_F ) / AI_MATH_TWO_PI_F,
+                (std::asin  (diff.z) + AI_MATH_HALF_PI_F) / AI_MATH_PI_F, 0.0);
+        }
+    }
+    // slower code path in case the mapping axis is not one of the coordinate system axes
+    else    {
+        aiMatrix4x4 mTrafo;
+        aiMatrix4x4::FromToMatrix(axis,base_axis_y,mTrafo);
+
+        // again the same, except we're applying a transformation now
+        for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)  {
+            const aiVector3D diff = ((mTrafo*mesh->mVertices[pnt])-center).Normalize();
+            out[pnt] = aiVector3D((std::atan2(diff.y, diff.x) + AI_MATH_PI_F ) / AI_MATH_TWO_PI_F,
+                (std::asin(diff.z) + AI_MATH_HALF_PI_F) / AI_MATH_PI_F, 0.0);
+        }
+    }
+
+
+    // Now find and remove UV seams. A seam occurs if a face has a tcoord
+    // close to zero on the one side, and a tcoord close to one on the
+    // other side.
+    RemoveUVSeams(mesh,out);
+}
+
+// ------------------------------------------------------------------------------------------------
+void ComputeUVMappingProcess::ComputeCylinderMapping(aiMesh* mesh,const aiVector3D& axis, aiVector3D* out)
+{
+    aiVector3D center, min, max;
+
+    // If the axis is one of x,y,z run a faster code path. It's worth the extra effort ...
+    // currently the mapping axis will always be one of x,y,z, except if the
+    // PretransformVertices step is used (it transforms the meshes into worldspace,
+    // thus changing the mapping axis)
+    if (axis * base_axis_x >= angle_epsilon)    {
+        FindMeshCenter(mesh, center, min, max);
+        const ai_real diff = max.x - min.x;
+
+        // If the main axis is 'z', the z coordinate of a point 'p' is mapped
+        // directly to the texture V axis. The other axis is derived from
+        // the angle between ( p.x - c.x, p.y - c.y ) and (1,0), where
+        // 'c' is the center point of the mesh.
+        for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)  {
+            const aiVector3D& pos = mesh->mVertices[pnt];
+            aiVector3D& uv  = out[pnt];
+
+            uv.y = (pos.x - min.x) / diff;
+            uv.x = (std::atan2( pos.z - center.z, pos.y - center.y) +(ai_real)AI_MATH_PI ) / (ai_real)AI_MATH_TWO_PI;
+        }
+    }
+    else if (axis * base_axis_y >= angle_epsilon)   {
+        FindMeshCenter(mesh, center, min, max);
+        const ai_real diff = max.y - min.y;
+
+        // just the same ...
+        for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)  {
+            const aiVector3D& pos = mesh->mVertices[pnt];
+            aiVector3D& uv  = out[pnt];
+
+            uv.y = (pos.y - min.y) / diff;
+            uv.x = (std::atan2( pos.x - center.x, pos.z - center.z) +(ai_real)AI_MATH_PI ) / (ai_real)AI_MATH_TWO_PI;
+        }
+    }
+    else if (axis * base_axis_z >= angle_epsilon)   {
+        FindMeshCenter(mesh, center, min, max);
+        const ai_real diff = max.z - min.z;
+
+        // just the same ...
+        for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)  {
+            const aiVector3D& pos = mesh->mVertices[pnt];
+            aiVector3D& uv  = out[pnt];
+
+            uv.y = (pos.z - min.z) / diff;
+            uv.x = (std::atan2( pos.y - center.y, pos.x - center.x) +(ai_real)AI_MATH_PI ) / (ai_real)AI_MATH_TWO_PI;
+        }
+    }
+    // slower code path in case the mapping axis is not one of the coordinate system axes
+    else {
+        aiMatrix4x4 mTrafo;
+        aiMatrix4x4::FromToMatrix(axis,base_axis_y,mTrafo);
+        FindMeshCenterTransformed(mesh, center, min, max,mTrafo);
+        const ai_real diff = max.y - min.y;
+
+        // again the same, except we're applying a transformation now
+        for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt){
+            const aiVector3D pos = mTrafo* mesh->mVertices[pnt];
+            aiVector3D& uv  = out[pnt];
+
+            uv.y = (pos.y - min.y) / diff;
+            uv.x = (std::atan2( pos.x - center.x, pos.z - center.z) +(ai_real)AI_MATH_PI ) / (ai_real)AI_MATH_TWO_PI;
+        }
+    }
+
+    // Now find and remove UV seams. A seam occurs if a face has a tcoord
+    // close to zero on the one side, and a tcoord close to one on the
+    // other side.
+    RemoveUVSeams(mesh,out);
+}
+
+// ------------------------------------------------------------------------------------------------
+void ComputeUVMappingProcess::ComputePlaneMapping(aiMesh* mesh,const aiVector3D& axis, aiVector3D* out)
+{
+    ai_real diffu,diffv;
+    aiVector3D center, min, max;
+
+    // If the axis is one of x,y,z run a faster code path. It's worth the extra effort ...
+    // currently the mapping axis will always be one of x,y,z, except if the
+    // PretransformVertices step is used (it transforms the meshes into worldspace,
+    // thus changing the mapping axis)
+    if (axis * base_axis_x >= angle_epsilon)    {
+        FindMeshCenter(mesh, center, min, max);
+        diffu = max.z - min.z;
+        diffv = max.y - min.y;
+
+        for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)  {
+            const aiVector3D& pos = mesh->mVertices[pnt];
+            out[pnt].Set((pos.z - min.z) / diffu,(pos.y - min.y) / diffv,0.0);
+        }
+    }
+    else if (axis * base_axis_y >= angle_epsilon)   {
+        FindMeshCenter(mesh, center, min, max);
+        diffu = max.x - min.x;
+        diffv = max.z - min.z;
+
+        for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)  {
+            const aiVector3D& pos = mesh->mVertices[pnt];
+            out[pnt].Set((pos.x - min.x) / diffu,(pos.z - min.z) / diffv,0.0);
+        }
+    }
+    else if (axis * base_axis_z >= angle_epsilon)   {
+        FindMeshCenter(mesh, center, min, max);
+        diffu = max.y - min.y;
+        diffv = max.z - min.z;
+
+        for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)  {
+            const aiVector3D& pos = mesh->mVertices[pnt];
+            out[pnt].Set((pos.y - min.y) / diffu,(pos.x - min.x) / diffv,0.0);
+        }
+    }
+    // slower code path in case the mapping axis is not one of the coordinate system axes
+    else
+    {
+        aiMatrix4x4 mTrafo;
+        aiMatrix4x4::FromToMatrix(axis,base_axis_y,mTrafo);
+        FindMeshCenterTransformed(mesh, center, min, max,mTrafo);
+        diffu = max.x - min.x;
+        diffv = max.z - min.z;
+
+        // again the same, except we're applying a transformation now
+        for (unsigned int pnt = 0; pnt < mesh->mNumVertices;++pnt)  {
+            const aiVector3D pos = mTrafo * mesh->mVertices[pnt];
+            out[pnt].Set((pos.x - min.x) / diffu,(pos.z - min.z) / diffv,0.0);
+        }
+    }
+
+    // shouldn't be necessary to remove UV seams ...
+}
+
+// ------------------------------------------------------------------------------------------------
+void ComputeUVMappingProcess::ComputeBoxMapping( aiMesh*, aiVector3D* )
+{
+    ASSIMP_LOG_ERROR("Mapping type currently not implemented");
+}
+
+// ------------------------------------------------------------------------------------------------
+void ComputeUVMappingProcess::Execute( aiScene* pScene)
+{
+    ASSIMP_LOG_DEBUG("GenUVCoordsProcess begin");
+    char buffer[1024];
+
+    if (pScene->mFlags & AI_SCENE_FLAGS_NON_VERBOSE_FORMAT)
+        throw DeadlyImportError("Post-processing order mismatch: expecting pseudo-indexed (\"verbose\") vertices here");
+
+    std::list<MappingInfo> mappingStack;
+
+    /*  Iterate through all materials and search for non-UV mapped textures
+     */
+    for (unsigned int i = 0; i < pScene->mNumMaterials;++i)
+    {
+        mappingStack.clear();
+        aiMaterial* mat = pScene->mMaterials[i];
+        for (unsigned int a = 0; a < mat->mNumProperties;++a)
+        {
+            aiMaterialProperty* prop = mat->mProperties[a];
+            if (!::strcmp( prop->mKey.data, "$tex.mapping"))
+            {
+                aiTextureMapping& mapping = *((aiTextureMapping*)prop->mData);
+                if (aiTextureMapping_UV != mapping)
+                {
+                    if (!DefaultLogger::isNullLogger())
+                    {
+                        ai_snprintf(buffer, 1024, "Found non-UV mapped texture (%s,%u). Mapping type: %s",
+                            TextureTypeToString((aiTextureType)prop->mSemantic),prop->mIndex,
+                            MappingTypeToString(mapping));
+
+                        ASSIMP_LOG_INFO(buffer);
+                    }
+
+                    if (aiTextureMapping_OTHER == mapping)
+                        continue;
+
+                    MappingInfo info (mapping);
+
+                    // Get further properties - currently only the major axis
+                    for (unsigned int a2 = 0; a2 < mat->mNumProperties;++a2)
+                    {
+                        aiMaterialProperty* prop2 = mat->mProperties[a2];
+                        if (prop2->mSemantic != prop->mSemantic || prop2->mIndex != prop->mIndex)
+                            continue;
+
+                        if ( !::strcmp( prop2->mKey.data, "$tex.mapaxis"))  {
+                            info.axis = *((aiVector3D*)prop2->mData);
+                            break;
+                        }
+                    }
+
+                    unsigned int idx( 99999999 );
+
+                    // Check whether we have this mapping mode already
+                    std::list<MappingInfo>::iterator it = std::find (mappingStack.begin(),mappingStack.end(), info);
+                    if (mappingStack.end() != it)
+                    {
+                        idx = (*it).uv;
+                    }
+                    else
+                    {
+                        /*  We have found a non-UV mapped texture. Now
+                        *   we need to find all meshes using this material
+                        *   that we can compute UV channels for them.
+                        */
+                        for (unsigned int m = 0; m < pScene->mNumMeshes;++m)
+                        {
+                            aiMesh* mesh = pScene->mMeshes[m];
+                            unsigned int outIdx = 0;
+                            if ( mesh->mMaterialIndex != i || ( outIdx = FindEmptyUVChannel(mesh) ) == UINT_MAX ||
+                                !mesh->mNumVertices)
+                            {
+                                continue;
+                            }
+
+                            // Allocate output storage
+                            aiVector3D* p = mesh->mTextureCoords[outIdx] = new aiVector3D[mesh->mNumVertices];
+
+                            switch (mapping)
+                            {
+                            case aiTextureMapping_SPHERE:
+                                ComputeSphereMapping(mesh,info.axis,p);
+                                break;
+                            case aiTextureMapping_CYLINDER:
+                                ComputeCylinderMapping(mesh,info.axis,p);
+                                break;
+                            case aiTextureMapping_PLANE:
+                                ComputePlaneMapping(mesh,info.axis,p);
+                                break;
+                            case aiTextureMapping_BOX:
+                                ComputeBoxMapping(mesh,p);
+                                break;
+                            default:
+                                ai_assert(false);
+                            }
+                            if (m && idx != outIdx)
+                            {
+                                ASSIMP_LOG_WARN("UV index mismatch. Not all meshes assigned to "
+                                    "this material have equal numbers of UV channels. The UV index stored in  "
+                                    "the material structure does therefore not apply for all meshes. ");
+                            }
+                            idx = outIdx;
+                        }
+                        info.uv = idx;
+                        mappingStack.push_back(info);
+                    }
+
+                    // Update the material property list
+                    mapping = aiTextureMapping_UV;
+                    ((aiMaterial*)mat)->AddProperty(&idx,1,AI_MATKEY_UVWSRC(prop->mSemantic,prop->mIndex));
+                }
+            }
+        }
+    }
+    ASSIMP_LOG_DEBUG("GenUVCoordsProcess finished");
+}
diff --git a/thirdparty/assimp/code/PostProcessing/ComputeUVMappingProcess.h b/thirdparty/assimp/code/PostProcessing/ComputeUVMappingProcess.h
new file mode 100644
index 0000000000..a6d36e06ea
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/ComputeUVMappingProcess.h
@@ -0,0 +1,149 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file Defines a post processing step to compute UV coordinates
+  from abstract mappings, such as box or spherical*/
+#ifndef AI_COMPUTEUVMAPPING_H_INC
+#define AI_COMPUTEUVMAPPING_H_INC
+
+#include "Common/BaseProcess.h"
+
+#include <assimp/mesh.h>
+#include <assimp/material.h>
+#include <assimp/types.h>
+
+class ComputeUVMappingTest;
+
+namespace Assimp {
+
+// ---------------------------------------------------------------------------
+/** ComputeUVMappingProcess - converts special mappings, such as spherical,
+ *  cylindrical or boxed to proper UV coordinates for rendering.
+*/
+class ComputeUVMappingProcess : public BaseProcess
+{
+public:
+    ComputeUVMappingProcess();
+    ~ComputeUVMappingProcess();
+
+public:
+
+    // -------------------------------------------------------------------
+    /** Returns whether the processing step is present in the given flag field.
+    * @param pFlags The processing flags the importer was called with. A bitwise
+    *   combination of #aiPostProcessSteps.
+    * @return true if the process is present in this flag fields, false if not.
+    */
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    /** Executes the post processing step on the given imported data.
+    * At the moment a process is not supposed to fail.
+    * @param pScene The imported data to work at.
+    */
+    void Execute( aiScene* pScene);
+
+protected:
+
+    // -------------------------------------------------------------------
+    /** Computes spherical UV coordinates for a mesh
+     *
+     *  @param mesh Mesh to be processed
+     *  @param axis Main axis
+     *  @param out Receives output UV coordinates
+    */
+    void ComputeSphereMapping(aiMesh* mesh,const aiVector3D& axis,
+        aiVector3D* out);
+
+    // -------------------------------------------------------------------
+    /** Computes cylindrical UV coordinates for a mesh
+     *
+     *  @param mesh Mesh to be processed
+     *  @param axis Main axis
+     *  @param out Receives output UV coordinates
+    */
+    void ComputeCylinderMapping(aiMesh* mesh,const aiVector3D& axis,
+        aiVector3D* out);
+
+    // -------------------------------------------------------------------
+    /** Computes planar UV coordinates for a mesh
+     *
+     *  @param mesh Mesh to be processed
+     *  @param axis Main axis
+     *  @param out Receives output UV coordinates
+    */
+    void ComputePlaneMapping(aiMesh* mesh,const aiVector3D& axis,
+        aiVector3D* out);
+
+    // -------------------------------------------------------------------
+    /** Computes cubic UV coordinates for a mesh
+     *
+     *  @param mesh Mesh to be processed
+     *  @param out Receives output UV coordinates
+    */
+    void ComputeBoxMapping(aiMesh* mesh, aiVector3D* out);
+
+private:
+
+    // temporary structure to describe a mapping
+    struct MappingInfo
+    {
+        explicit MappingInfo(aiTextureMapping _type)
+            : type  (_type)
+            , axis  (0.f,1.f,0.f)
+            , uv    (0u)
+        {}
+
+        aiTextureMapping type;
+        aiVector3D axis;
+        unsigned int uv;
+
+        bool operator== (const MappingInfo& other)
+        {
+            return type == other.type && axis == other.axis;
+        }
+    };
+};
+
+} // end of namespace Assimp
+
+#endif // AI_COMPUTEUVMAPPING_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/ConvertToLHProcess.cpp b/thirdparty/assimp/code/PostProcessing/ConvertToLHProcess.cpp
new file mode 100644
index 0000000000..b7cd4f0bc6
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/ConvertToLHProcess.cpp
@@ -0,0 +1,414 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file  MakeLeftHandedProcess.cpp
+ *  @brief Implementation of the post processing step to convert all
+ *  imported data to a left-handed coordinate system.
+ *
+ *  Face order & UV flip are also implemented here, for the sake of a
+ *  better location.
+ */
+
+
+#include "ConvertToLHProcess.h"
+#include <assimp/scene.h>
+#include <assimp/postprocess.h>
+#include <assimp/DefaultLogger.hpp>
+
+using namespace Assimp;
+
+#ifndef ASSIMP_BUILD_NO_MAKELEFTHANDED_PROCESS
+
+namespace {
+
+template <typename aiMeshType>
+void flipUVs(aiMeshType* pMesh) {
+    if (pMesh == nullptr) { return; }
+    // mirror texture y coordinate
+    for (unsigned int tcIdx = 0; tcIdx < AI_MAX_NUMBER_OF_TEXTURECOORDS; tcIdx++) {
+        if (!pMesh->HasTextureCoords(tcIdx)) {
+            break;
+        }
+
+        for (unsigned int vIdx = 0; vIdx < pMesh->mNumVertices; vIdx++) {
+            pMesh->mTextureCoords[tcIdx][vIdx].y = 1.0f - pMesh->mTextureCoords[tcIdx][vIdx].y;
+        }
+    }
+}
+
+} // namespace
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+MakeLeftHandedProcess::MakeLeftHandedProcess()
+: BaseProcess() {
+    // empty
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+MakeLeftHandedProcess::~MakeLeftHandedProcess() {
+    // empty
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool MakeLeftHandedProcess::IsActive( unsigned int pFlags) const
+{
+    return 0 != (pFlags & aiProcess_MakeLeftHanded);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void MakeLeftHandedProcess::Execute( aiScene* pScene)
+{
+    // Check for an existent root node to proceed
+    ai_assert(pScene->mRootNode != NULL);
+    ASSIMP_LOG_DEBUG("MakeLeftHandedProcess begin");
+
+    // recursively convert all the nodes
+    ProcessNode( pScene->mRootNode, aiMatrix4x4());
+
+    // process the meshes accordingly
+    for ( unsigned int a = 0; a < pScene->mNumMeshes; ++a ) {
+        ProcessMesh( pScene->mMeshes[ a ] );
+    }
+
+    // process the materials accordingly
+    for ( unsigned int a = 0; a < pScene->mNumMaterials; ++a ) {
+        ProcessMaterial( pScene->mMaterials[ a ] );
+    }
+
+    // transform all animation channels as well
+    for( unsigned int a = 0; a < pScene->mNumAnimations; a++)
+    {
+        aiAnimation* anim = pScene->mAnimations[a];
+        for( unsigned int b = 0; b < anim->mNumChannels; b++)
+        {
+            aiNodeAnim* nodeAnim = anim->mChannels[b];
+            ProcessAnimation( nodeAnim);
+        }
+    }
+    ASSIMP_LOG_DEBUG("MakeLeftHandedProcess finished");
+}
+
+// ------------------------------------------------------------------------------------------------
+// Recursively converts a node, all of its children and all of its meshes
+void MakeLeftHandedProcess::ProcessNode( aiNode* pNode, const aiMatrix4x4& pParentGlobalRotation)
+{
+    // mirror all base vectors at the local Z axis
+    pNode->mTransformation.c1 = -pNode->mTransformation.c1;
+    pNode->mTransformation.c2 = -pNode->mTransformation.c2;
+    pNode->mTransformation.c3 = -pNode->mTransformation.c3;
+    pNode->mTransformation.c4 = -pNode->mTransformation.c4;
+
+    // now invert the Z axis again to keep the matrix determinant positive.
+    // The local meshes will be inverted accordingly so that the result should look just fine again.
+    pNode->mTransformation.a3 = -pNode->mTransformation.a3;
+    pNode->mTransformation.b3 = -pNode->mTransformation.b3;
+    pNode->mTransformation.c3 = -pNode->mTransformation.c3;
+    pNode->mTransformation.d3 = -pNode->mTransformation.d3; // useless, but anyways...
+
+    // continue for all children
+    for( size_t a = 0; a < pNode->mNumChildren; ++a ) {
+        ProcessNode( pNode->mChildren[ a ], pParentGlobalRotation * pNode->mTransformation );
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Converts a single mesh to left handed coordinates.
+void MakeLeftHandedProcess::ProcessMesh( aiMesh* pMesh) {
+    if ( nullptr == pMesh ) {
+        ASSIMP_LOG_ERROR( "Nullptr to mesh found." );
+        return;
+    }
+    // mirror positions, normals and stuff along the Z axis
+    for( size_t a = 0; a < pMesh->mNumVertices; ++a)
+    {
+        pMesh->mVertices[a].z *= -1.0f;
+        if (pMesh->HasNormals()) {
+            pMesh->mNormals[a].z *= -1.0f;
+        }
+        if( pMesh->HasTangentsAndBitangents())
+        {
+            pMesh->mTangents[a].z *= -1.0f;
+            pMesh->mBitangents[a].z *= -1.0f;
+        }
+    }
+
+    // mirror anim meshes positions, normals and stuff along the Z axis
+    for (size_t m = 0; m < pMesh->mNumAnimMeshes; ++m)
+    {
+        for (size_t a = 0; a < pMesh->mAnimMeshes[m]->mNumVertices; ++a)
+        {
+            pMesh->mAnimMeshes[m]->mVertices[a].z *= -1.0f;
+            if (pMesh->mAnimMeshes[m]->HasNormals()) {
+                pMesh->mAnimMeshes[m]->mNormals[a].z *= -1.0f;
+            }
+            if (pMesh->mAnimMeshes[m]->HasTangentsAndBitangents())
+            {
+                pMesh->mAnimMeshes[m]->mTangents[a].z *= -1.0f;
+                pMesh->mAnimMeshes[m]->mBitangents[a].z *= -1.0f;
+            }
+        }
+    }
+
+    // mirror offset matrices of all bones
+    for( size_t a = 0; a < pMesh->mNumBones; ++a)
+    {
+        aiBone* bone = pMesh->mBones[a];
+        bone->mOffsetMatrix.a3 = -bone->mOffsetMatrix.a3;
+        bone->mOffsetMatrix.b3 = -bone->mOffsetMatrix.b3;
+        bone->mOffsetMatrix.d3 = -bone->mOffsetMatrix.d3;
+        bone->mOffsetMatrix.c1 = -bone->mOffsetMatrix.c1;
+        bone->mOffsetMatrix.c2 = -bone->mOffsetMatrix.c2;
+        bone->mOffsetMatrix.c4 = -bone->mOffsetMatrix.c4;
+    }
+
+    // mirror bitangents as well as they're derived from the texture coords
+    if( pMesh->HasTangentsAndBitangents())
+    {
+        for( unsigned int a = 0; a < pMesh->mNumVertices; a++)
+            pMesh->mBitangents[a] *= -1.0f;
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Converts a single material to left handed coordinates.
+void MakeLeftHandedProcess::ProcessMaterial( aiMaterial* _mat) {
+    if ( nullptr == _mat ) {
+        ASSIMP_LOG_ERROR( "Nullptr to aiMaterial found." );
+        return;
+    }
+
+    aiMaterial* mat = (aiMaterial*)_mat;
+    for (unsigned int a = 0; a < mat->mNumProperties;++a)   {
+        aiMaterialProperty* prop = mat->mProperties[a];
+
+        // Mapping axis for UV mappings?
+        if (!::strcmp( prop->mKey.data, "$tex.mapaxis"))    {
+            ai_assert( prop->mDataLength >= sizeof(aiVector3D)); /* something is wrong with the validation if we end up here */
+            aiVector3D* pff = (aiVector3D*)prop->mData;
+            pff->z *= -1.f;
+        }
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Converts the given animation to LH coordinates.
+void MakeLeftHandedProcess::ProcessAnimation( aiNodeAnim* pAnim)
+{
+    // position keys
+    for( unsigned int a = 0; a < pAnim->mNumPositionKeys; a++)
+        pAnim->mPositionKeys[a].mValue.z *= -1.0f;
+
+    // rotation keys
+    for( unsigned int a = 0; a < pAnim->mNumRotationKeys; a++)
+    {
+        /* That's the safe version, but the float errors add up. So we try the short version instead
+        aiMatrix3x3 rotmat = pAnim->mRotationKeys[a].mValue.GetMatrix();
+        rotmat.a3 = -rotmat.a3; rotmat.b3 = -rotmat.b3;
+        rotmat.c1 = -rotmat.c1; rotmat.c2 = -rotmat.c2;
+        aiQuaternion rotquat( rotmat);
+        pAnim->mRotationKeys[a].mValue = rotquat;
+        */
+        pAnim->mRotationKeys[a].mValue.x *= -1.0f;
+        pAnim->mRotationKeys[a].mValue.y *= -1.0f;
+    }
+}
+
+#endif // !!  ASSIMP_BUILD_NO_MAKELEFTHANDED_PROCESS
+#ifndef  ASSIMP_BUILD_NO_FLIPUVS_PROCESS
+// # FlipUVsProcess
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+FlipUVsProcess::FlipUVsProcess()
+{}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+FlipUVsProcess::~FlipUVsProcess()
+{}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool FlipUVsProcess::IsActive( unsigned int pFlags) const
+{
+    return 0 != (pFlags & aiProcess_FlipUVs);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void FlipUVsProcess::Execute( aiScene* pScene)
+{
+    ASSIMP_LOG_DEBUG("FlipUVsProcess begin");
+    for (unsigned int i = 0; i < pScene->mNumMeshes;++i)
+        ProcessMesh(pScene->mMeshes[i]);
+
+    for (unsigned int i = 0; i < pScene->mNumMaterials;++i)
+        ProcessMaterial(pScene->mMaterials[i]);
+    ASSIMP_LOG_DEBUG("FlipUVsProcess finished");
+}
+
+// ------------------------------------------------------------------------------------------------
+// Converts a single material
+void FlipUVsProcess::ProcessMaterial (aiMaterial* _mat)
+{
+    aiMaterial* mat = (aiMaterial*)_mat;
+    for (unsigned int a = 0; a < mat->mNumProperties;++a)   {
+        aiMaterialProperty* prop = mat->mProperties[a];
+        if( !prop ) {
+            ASSIMP_LOG_DEBUG( "Property is null" );
+            continue;
+        }
+
+        // UV transformation key?
+        if (!::strcmp( prop->mKey.data, "$tex.uvtrafo"))    {
+            ai_assert( prop->mDataLength >= sizeof(aiUVTransform));  /* something is wrong with the validation if we end up here */
+            aiUVTransform* uv = (aiUVTransform*)prop->mData;
+
+            // just flip it, that's everything
+            uv->mTranslation.y *= -1.f;
+            uv->mRotation *= -1.f;
+        }
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Converts a single mesh
+void FlipUVsProcess::ProcessMesh( aiMesh* pMesh)
+{
+    flipUVs(pMesh);
+    for (unsigned int idx = 0; idx < pMesh->mNumAnimMeshes; idx++) {
+        flipUVs(pMesh->mAnimMeshes[idx]);
+    }
+}
+
+#endif // !ASSIMP_BUILD_NO_FLIPUVS_PROCESS
+#ifndef  ASSIMP_BUILD_NO_FLIPWINDING_PROCESS
+// # FlipWindingOrderProcess
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+FlipWindingOrderProcess::FlipWindingOrderProcess()
+{}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+FlipWindingOrderProcess::~FlipWindingOrderProcess()
+{}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool FlipWindingOrderProcess::IsActive( unsigned int pFlags) const
+{
+    return 0 != (pFlags & aiProcess_FlipWindingOrder);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void FlipWindingOrderProcess::Execute( aiScene* pScene)
+{
+    ASSIMP_LOG_DEBUG("FlipWindingOrderProcess begin");
+    for (unsigned int i = 0; i < pScene->mNumMeshes;++i)
+        ProcessMesh(pScene->mMeshes[i]);
+    ASSIMP_LOG_DEBUG("FlipWindingOrderProcess finished");
+}
+
+// ------------------------------------------------------------------------------------------------
+// Converts a single mesh
+void FlipWindingOrderProcess::ProcessMesh( aiMesh* pMesh)
+{
+    // invert the order of all faces in this mesh
+    for( unsigned int a = 0; a < pMesh->mNumFaces; a++)
+    {
+        aiFace& face = pMesh->mFaces[a];
+        for (unsigned int b = 0; b < face.mNumIndices / 2; b++) {
+            std::swap(face.mIndices[b], face.mIndices[face.mNumIndices - 1 - b]);
+        }
+    }
+
+    // invert the order of all components in this mesh anim meshes
+    for (unsigned int m = 0; m < pMesh->mNumAnimMeshes; m++) {
+        aiAnimMesh* animMesh = pMesh->mAnimMeshes[m];
+        unsigned int numVertices = animMesh->mNumVertices;
+        if (animMesh->HasPositions()) {
+            for (unsigned int a = 0; a < numVertices; a++)
+            {
+                std::swap(animMesh->mVertices[a], animMesh->mVertices[numVertices - 1 - a]);
+            }
+        }
+        if (animMesh->HasNormals()) {
+            for (unsigned int a = 0; a < numVertices; a++)
+            {
+                std::swap(animMesh->mNormals[a], animMesh->mNormals[numVertices - 1 - a]);
+            }
+        }
+        for (unsigned int i = 0; i < AI_MAX_NUMBER_OF_TEXTURECOORDS; i++) {
+            if (animMesh->HasTextureCoords(i)) {
+                for (unsigned int a = 0; a < numVertices; a++)
+                {
+                    std::swap(animMesh->mTextureCoords[i][a], animMesh->mTextureCoords[i][numVertices - 1 - a]);
+                }
+            }
+        }
+        if (animMesh->HasTangentsAndBitangents()) {
+            for (unsigned int a = 0; a < numVertices; a++)
+            {
+                std::swap(animMesh->mTangents[a], animMesh->mTangents[numVertices - 1 - a]);
+                std::swap(animMesh->mBitangents[a], animMesh->mBitangents[numVertices - 1 - a]);
+            }
+        }
+        for (unsigned int v = 0; v < AI_MAX_NUMBER_OF_COLOR_SETS; v++) {
+            if (animMesh->HasVertexColors(v)) {
+                for (unsigned int a = 0; a < numVertices; a++)
+                {
+                    std::swap(animMesh->mColors[v][a], animMesh->mColors[v][numVertices - 1 - a]);
+                }
+            }
+        }
+    }
+}
+
+#endif // !! ASSIMP_BUILD_NO_FLIPWINDING_PROCESS
diff --git a/thirdparty/assimp/code/PostProcessing/ConvertToLHProcess.h b/thirdparty/assimp/code/PostProcessing/ConvertToLHProcess.h
new file mode 100644
index 0000000000..f32b91fc39
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/ConvertToLHProcess.h
@@ -0,0 +1,171 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file  MakeLeftHandedProcess.h
+ *  @brief Defines a bunch of post-processing steps to handle
+ *    coordinate system conversions.
+ *
+ *  - LH to RH
+ *  - UV origin upper-left to lower-left
+ *  - face order cw to ccw
+ */
+#ifndef AI_CONVERTTOLHPROCESS_H_INC
+#define AI_CONVERTTOLHPROCESS_H_INC
+
+#include <assimp/types.h>
+
+#include "Common/BaseProcess.h"
+
+struct aiMesh;
+struct aiNodeAnim;
+struct aiNode;
+struct aiMaterial;
+
+namespace Assimp    {
+
+// -----------------------------------------------------------------------------------
+/** @brief The MakeLeftHandedProcess converts all imported data to a left-handed
+ *   coordinate system.
+ *
+ * This implies a mirroring of the Z axis of the coordinate system. But to keep
+ * transformation matrices free from reflections we shift the reflection to other
+ * places. We mirror the meshes and adapt the rotations.
+ *
+ * @note RH-LH and LH-RH is the same, so this class can be used for both
+ */
+class MakeLeftHandedProcess : public BaseProcess
+{
+
+
+public:
+    MakeLeftHandedProcess();
+    ~MakeLeftHandedProcess();
+
+    // -------------------------------------------------------------------
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    void Execute( aiScene* pScene);
+
+protected:
+
+    // -------------------------------------------------------------------
+    /** Recursively converts a node and all of its children
+     */
+    void ProcessNode( aiNode* pNode, const aiMatrix4x4& pParentGlobalRotation);
+
+    // -------------------------------------------------------------------
+    /** Converts a single mesh to left handed coordinates.
+     * This means that positions, normals and tangents are mirrored at
+     * the local Z axis and the order of all faces are inverted.
+     * @param pMesh The mesh to convert.
+     */
+    void ProcessMesh( aiMesh* pMesh);
+
+    // -------------------------------------------------------------------
+    /** Converts a single material to left-handed coordinates
+     * @param pMat Material to convert
+     */
+    void ProcessMaterial( aiMaterial* pMat);
+
+    // -------------------------------------------------------------------
+    /** Converts the given animation to LH coordinates.
+     * The rotation and translation keys are transformed, the scale keys
+     * work in local space and can therefore be left untouched.
+     * @param pAnim The bone animation to transform
+     */
+    void ProcessAnimation( aiNodeAnim* pAnim);
+};
+
+
+// ---------------------------------------------------------------------------
+/** Postprocessing step to flip the face order of the imported data
+ */
+class FlipWindingOrderProcess : public BaseProcess
+{
+    friend class Importer;
+
+public:
+    /** Constructor to be privately used by Importer */
+    FlipWindingOrderProcess();
+
+    /** Destructor, private as well */
+    ~FlipWindingOrderProcess();
+
+    // -------------------------------------------------------------------
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    void Execute( aiScene* pScene);
+
+protected:
+    void ProcessMesh( aiMesh* pMesh);
+};
+
+// ---------------------------------------------------------------------------
+/** Postprocessing step to flip the UV coordinate system of the import data
+ */
+class FlipUVsProcess : public BaseProcess
+{
+    friend class Importer;
+
+public:
+    /** Constructor to be privately used by Importer */
+    FlipUVsProcess();
+
+    /** Destructor, private as well */
+    ~FlipUVsProcess();
+
+    // -------------------------------------------------------------------
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    void Execute( aiScene* pScene);
+
+protected:
+    void ProcessMesh( aiMesh* pMesh);
+    void ProcessMaterial( aiMaterial* mat);
+};
+
+} // end of namespace Assimp
+
+#endif // AI_CONVERTTOLHPROCESS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/DeboneProcess.cpp b/thirdparty/assimp/code/PostProcessing/DeboneProcess.cpp
new file mode 100644
index 0000000000..83b8336bc9
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/DeboneProcess.cpp
@@ -0,0 +1,465 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/// @file DeboneProcess.cpp
+/** Implementation of the DeboneProcess post processing step */
+
+
+
+// internal headers of the post-processing framework
+#include "ProcessHelper.h"
+#include "DeboneProcess.h"
+#include <stdio.h>
+
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+DeboneProcess::DeboneProcess()
+{
+    mNumBones = 0;
+    mNumBonesCanDoWithout = 0;
+
+    mThreshold = AI_DEBONE_THRESHOLD;
+    mAllOrNone = false;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+DeboneProcess::~DeboneProcess()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool DeboneProcess::IsActive( unsigned int pFlags) const
+{
+    return (pFlags & aiProcess_Debone) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void DeboneProcess::SetupProperties(const Importer* pImp)
+{
+    // get the current value of the property
+    mAllOrNone = pImp->GetPropertyInteger(AI_CONFIG_PP_DB_ALL_OR_NONE,0)?true:false;
+    mThreshold = pImp->GetPropertyFloat(AI_CONFIG_PP_DB_THRESHOLD,AI_DEBONE_THRESHOLD);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void DeboneProcess::Execute( aiScene* pScene)
+{
+    ASSIMP_LOG_DEBUG("DeboneProcess begin");
+
+    if(!pScene->mNumMeshes) {
+        return;
+    }
+
+    std::vector<bool> splitList(pScene->mNumMeshes);
+    for( unsigned int a = 0; a < pScene->mNumMeshes; a++) {
+        splitList[a] = ConsiderMesh( pScene->mMeshes[a] );
+    }
+
+    int numSplits = 0;
+
+    if(!!mNumBonesCanDoWithout && (!mAllOrNone||mNumBonesCanDoWithout==mNumBones))  {
+        for(unsigned int a = 0; a < pScene->mNumMeshes; a++)    {
+            if(splitList[a]) {
+                numSplits++;
+            }
+        }
+    }
+
+    if(numSplits)   {
+        // we need to do something. Let's go.
+        //mSubMeshIndices.clear();                  // really needed?
+        mSubMeshIndices.resize(pScene->mNumMeshes); // because we're doing it here anyway
+
+        // build a new array of meshes for the scene
+        std::vector<aiMesh*> meshes;
+
+        for(unsigned int a=0;a<pScene->mNumMeshes;a++)
+        {
+            aiMesh* srcMesh = pScene->mMeshes[a];
+
+            std::vector<std::pair<aiMesh*,const aiBone*> > newMeshes;
+
+            if(splitList[a]) {
+                SplitMesh(srcMesh,newMeshes);
+            }
+
+            // mesh was split
+            if(!newMeshes.empty())  {
+                unsigned int out = 0, in = srcMesh->mNumBones;
+
+                // store new meshes and indices of the new meshes
+                for(unsigned int b=0;b<newMeshes.size();b++)    {
+                    const aiString *find = newMeshes[b].second?&newMeshes[b].second->mName:0;
+
+                    aiNode *theNode = find?pScene->mRootNode->FindNode(*find):0;
+                    std::pair<unsigned int,aiNode*> push_pair(static_cast<unsigned int>(meshes.size()),theNode);
+
+                    mSubMeshIndices[a].push_back(push_pair);
+                    meshes.push_back(newMeshes[b].first);
+
+                    out+=newMeshes[b].first->mNumBones;
+                }
+
+                if(!DefaultLogger::isNullLogger()) {
+                    ASSIMP_LOG_INFO_F("Removed %u bones. Input bones:", in - out, ". Output bones: ", out);
+                }
+
+                // and destroy the source mesh. It should be completely contained inside the new submeshes
+                delete srcMesh;
+            }
+            else    {
+                // Mesh is kept unchanged - store it's new place in the mesh array
+                mSubMeshIndices[a].push_back(std::pair<unsigned int,aiNode*>(static_cast<unsigned int>(meshes.size()),(aiNode*)0));
+                meshes.push_back(srcMesh);
+            }
+        }
+
+        // rebuild the scene's mesh array
+        pScene->mNumMeshes = static_cast<unsigned int>(meshes.size());
+        delete [] pScene->mMeshes;
+        pScene->mMeshes = new aiMesh*[pScene->mNumMeshes];
+        std::copy( meshes.begin(), meshes.end(), pScene->mMeshes);
+
+        // recurse through all nodes and translate the node's mesh indices to fit the new mesh array
+        UpdateNode( pScene->mRootNode);
+    }
+
+    ASSIMP_LOG_DEBUG("DeboneProcess end");
+}
+
+// ------------------------------------------------------------------------------------------------
+// Counts bones total/removable in a given mesh.
+bool DeboneProcess::ConsiderMesh(const aiMesh* pMesh)
+{
+    if(!pMesh->HasBones()) {
+        return false;
+    }
+
+    bool split = false;
+
+    //interstitial faces not permitted
+    bool isInterstitialRequired = false;
+
+    std::vector<bool> isBoneNecessary(pMesh->mNumBones,false);
+    std::vector<unsigned int> vertexBones(pMesh->mNumVertices,UINT_MAX);
+
+    const unsigned int cUnowned = UINT_MAX;
+    const unsigned int cCoowned = UINT_MAX-1;
+
+    for(unsigned int i=0;i<pMesh->mNumBones;i++)    {
+        for(unsigned int j=0;j<pMesh->mBones[i]->mNumWeights;j++)   {
+            float w = pMesh->mBones[i]->mWeights[j].mWeight;
+
+            if(w==0.0f) {
+                continue;
+            }
+
+            unsigned int vid = pMesh->mBones[i]->mWeights[j].mVertexId;
+            if(w>=mThreshold)   {
+
+                if(vertexBones[vid]!=cUnowned)  {
+                    if(vertexBones[vid]==i) //double entry
+                    {
+                        ASSIMP_LOG_WARN("Encountered double entry in bone weights");
+                    }
+                    else //TODO: track attraction in order to break tie
+                    {
+                        vertexBones[vid] = cCoowned;
+                    }
+                }
+                else vertexBones[vid] = i;
+            }
+
+            if(!isBoneNecessary[i]) {
+                isBoneNecessary[i] = w<mThreshold;
+            }
+        }
+
+        if(!isBoneNecessary[i])  {
+            isInterstitialRequired = true;
+        }
+    }
+
+    if(isInterstitialRequired) {
+        for(unsigned int i=0;i<pMesh->mNumFaces;i++) {
+            unsigned int v = vertexBones[pMesh->mFaces[i].mIndices[0]];
+
+            for(unsigned int j=1;j<pMesh->mFaces[i].mNumIndices;j++) {
+                unsigned int w = vertexBones[pMesh->mFaces[i].mIndices[j]];
+
+                if(v!=w)    {
+                    if(v<pMesh->mNumBones) isBoneNecessary[v] = true;
+                    if(w<pMesh->mNumBones) isBoneNecessary[w] = true;
+                }
+            }
+        }
+    }
+
+    for(unsigned int i=0;i<pMesh->mNumBones;i++)    {
+        if(!isBoneNecessary[i]) {
+            mNumBonesCanDoWithout++;
+            split = true;
+        }
+
+        mNumBones++;
+    }
+    return split;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Splits the given mesh by bone count.
+void DeboneProcess::SplitMesh( const aiMesh* pMesh, std::vector< std::pair< aiMesh*,const aiBone* > >& poNewMeshes) const
+{
+    // same deal here as ConsiderMesh basically
+
+    std::vector<bool> isBoneNecessary(pMesh->mNumBones,false);
+    std::vector<unsigned int> vertexBones(pMesh->mNumVertices,UINT_MAX);
+
+    const unsigned int cUnowned = UINT_MAX;
+    const unsigned int cCoowned = UINT_MAX-1;
+
+    for(unsigned int i=0;i<pMesh->mNumBones;i++)    {
+        for(unsigned int j=0;j<pMesh->mBones[i]->mNumWeights;j++)   {
+            float w = pMesh->mBones[i]->mWeights[j].mWeight;
+
+            if(w==0.0f) {
+                continue;
+            }
+
+            unsigned int vid = pMesh->mBones[i]->mWeights[j].mVertexId;
+
+            if(w>=mThreshold) {
+                if(vertexBones[vid]!=cUnowned)  {
+                    if(vertexBones[vid]==i) //double entry
+                    {
+                        ASSIMP_LOG_WARN("Encountered double entry in bone weights");
+                    }
+                    else //TODO: track attraction in order to break tie
+                    {
+                        vertexBones[vid] = cCoowned;
+                    }
+                }
+                else vertexBones[vid] = i;
+            }
+
+            if(!isBoneNecessary[i]) {
+                isBoneNecessary[i] = w<mThreshold;
+            }
+        }
+    }
+
+    unsigned int nFacesUnowned = 0;
+
+    std::vector<unsigned int> faceBones(pMesh->mNumFaces,UINT_MAX);
+    std::vector<unsigned int> facesPerBone(pMesh->mNumBones,0);
+
+    for(unsigned int i=0;i<pMesh->mNumFaces;i++) {
+        unsigned int nInterstitial = 1;
+
+        unsigned int v = vertexBones[pMesh->mFaces[i].mIndices[0]];
+
+        for(unsigned int j=1;j<pMesh->mFaces[i].mNumIndices;j++) {
+            unsigned int w = vertexBones[pMesh->mFaces[i].mIndices[j]];
+
+            if(v!=w)    {
+                if(v<pMesh->mNumBones) isBoneNecessary[v] = true;
+                if(w<pMesh->mNumBones) isBoneNecessary[w] = true;
+            }
+            else nInterstitial++;
+        }
+
+        if(v<pMesh->mNumBones &&nInterstitial==pMesh->mFaces[i].mNumIndices)    {
+            faceBones[i] = v; //primitive belongs to bone #v
+            facesPerBone[v]++;
+        }
+        else nFacesUnowned++;
+    }
+
+    // invalidate any "cojoined" faces
+    for(unsigned int i=0;i<pMesh->mNumFaces;i++) {
+        if(faceBones[i]<pMesh->mNumBones&&isBoneNecessary[faceBones[i]])
+        {
+            ai_assert(facesPerBone[faceBones[i]]>0);
+            facesPerBone[faceBones[i]]--;
+
+            nFacesUnowned++;
+            faceBones[i] = cUnowned;
+        }
+    }
+
+    if(nFacesUnowned) {
+        std::vector<unsigned int> subFaces;
+
+        for(unsigned int i=0;i<pMesh->mNumFaces;i++)    {
+            if(faceBones[i]==cUnowned) {
+                subFaces.push_back(i);
+            }
+        }
+
+        aiMesh *baseMesh = MakeSubmesh(pMesh,subFaces,0);
+        std::pair<aiMesh*,const aiBone*> push_pair(baseMesh,(const aiBone*)0);
+
+        poNewMeshes.push_back(push_pair);
+    }
+
+    for(unsigned int i=0;i<pMesh->mNumBones;i++) {
+
+        if(!isBoneNecessary[i]&&facesPerBone[i]>0)  {
+            std::vector<unsigned int> subFaces;
+
+            for(unsigned int j=0;j<pMesh->mNumFaces;j++)    {
+                if(faceBones[j]==i) {
+                    subFaces.push_back(j);
+                }
+            }
+
+            unsigned int f = AI_SUBMESH_FLAGS_SANS_BONES;
+            aiMesh *subMesh =MakeSubmesh(pMesh,subFaces,f);
+
+            //Lifted from PretransformVertices.cpp
+            ApplyTransform(subMesh,pMesh->mBones[i]->mOffsetMatrix);
+            std::pair<aiMesh*,const aiBone*> push_pair(subMesh,pMesh->mBones[i]);
+
+            poNewMeshes.push_back(push_pair);
+        }
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Recursively updates the node's mesh list to account for the changed mesh list
+void DeboneProcess::UpdateNode(aiNode* pNode) const
+{
+    // rebuild the node's mesh index list
+
+    std::vector<unsigned int> newMeshList;
+
+    // this will require two passes
+
+    unsigned int m = static_cast<unsigned int>(pNode->mNumMeshes), n = static_cast<unsigned int>(mSubMeshIndices.size());
+
+    // first pass, look for meshes which have not moved
+
+    for(unsigned int a=0;a<m;a++)   {
+
+        unsigned int srcIndex = pNode->mMeshes[a];
+        const std::vector< std::pair< unsigned int,aiNode* > > &subMeshes = mSubMeshIndices[srcIndex];
+        unsigned int nSubmeshes = static_cast<unsigned int>(subMeshes.size());
+
+        for(unsigned int b=0;b<nSubmeshes;b++) {
+            if(!subMeshes[b].second) {
+                newMeshList.push_back(subMeshes[b].first);
+            }
+        }
+    }
+
+    // second pass, collect deboned meshes
+
+    for(unsigned int a=0;a<n;a++)
+    {
+        const std::vector< std::pair< unsigned int,aiNode* > > &subMeshes = mSubMeshIndices[a];
+        unsigned int nSubmeshes = static_cast<unsigned int>(subMeshes.size());
+
+        for(unsigned int b=0;b<nSubmeshes;b++) {
+            if(subMeshes[b].second == pNode)    {
+                newMeshList.push_back(subMeshes[b].first);
+            }
+        }
+    }
+
+    if( pNode->mNumMeshes > 0 ) {
+        delete [] pNode->mMeshes; pNode->mMeshes = NULL;
+    }
+
+    pNode->mNumMeshes = static_cast<unsigned int>(newMeshList.size());
+
+    if(pNode->mNumMeshes)   {
+        pNode->mMeshes = new unsigned int[pNode->mNumMeshes];
+        std::copy( newMeshList.begin(), newMeshList.end(), pNode->mMeshes);
+    }
+
+    // do that also recursively for all children
+    for( unsigned int a = 0; a < pNode->mNumChildren; ++a ) {
+        UpdateNode( pNode->mChildren[a]);
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Apply the node transformation to a mesh
+void DeboneProcess::ApplyTransform(aiMesh* mesh, const aiMatrix4x4& mat)const
+{
+    // Check whether we need to transform the coordinates at all
+    if (!mat.IsIdentity()) {
+
+        if (mesh->HasPositions()) {
+            for (unsigned int i = 0; i < mesh->mNumVertices; ++i) {
+                mesh->mVertices[i] = mat * mesh->mVertices[i];
+            }
+        }
+        if (mesh->HasNormals() || mesh->HasTangentsAndBitangents()) {
+            aiMatrix4x4 mWorldIT = mat;
+            mWorldIT.Inverse().Transpose();
+
+            // TODO: implement Inverse() for aiMatrix3x3
+            aiMatrix3x3 m = aiMatrix3x3(mWorldIT);
+
+            if (mesh->HasNormals()) {
+                for (unsigned int i = 0; i < mesh->mNumVertices; ++i) {
+                    mesh->mNormals[i] = (m * mesh->mNormals[i]).Normalize();
+                }
+            }
+            if (mesh->HasTangentsAndBitangents()) {
+                for (unsigned int i = 0; i < mesh->mNumVertices; ++i) {
+                    mesh->mTangents[i]   = (m * mesh->mTangents[i]).Normalize();
+                    mesh->mBitangents[i] = (m * mesh->mBitangents[i]).Normalize();
+                }
+            }
+        }
+    }
+}
diff --git a/thirdparty/assimp/code/PostProcessing/DeboneProcess.h b/thirdparty/assimp/code/PostProcessing/DeboneProcess.h
new file mode 100644
index 0000000000..8b64c2acc6
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/DeboneProcess.h
@@ -0,0 +1,131 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** Defines a post processing step to limit the number of bones affecting a single vertex. */
+#ifndef AI_DEBONEPROCESS_H_INC
+#define AI_DEBONEPROCESS_H_INC
+
+#include "Common/BaseProcess.h"
+
+#include <assimp/mesh.h>
+#include <assimp/scene.h>
+
+#include <vector>
+#include <utility>
+
+#// Forward declarations
+class DeboneTest;
+
+namespace Assimp {
+
+#if (!defined AI_DEBONE_THRESHOLD)
+#   define AI_DEBONE_THRESHOLD  1.0f
+#endif // !! AI_DEBONE_THRESHOLD
+
+// ---------------------------------------------------------------------------
+/** This post processing step removes bones nearly losslessly or according to
+* a configured threshold. In order to remove the bone, the primitives affected by
+* the bone are split from the mesh. The split off (new) mesh is boneless. At any
+* point in time, bones without affect upon a given mesh are to be removed.
+*/
+class DeboneProcess : public BaseProcess {
+public:
+    DeboneProcess();
+    ~DeboneProcess();
+
+    // -------------------------------------------------------------------
+    /** Returns whether the processing step is present in the given flag.
+    * @param pFlags The processing flags the importer was called with.
+    *   A bitwise combination of #aiPostProcessSteps.
+    * @return true if the process is present in this flag fields,
+    *   false if not.
+    */
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    /** Called prior to ExecuteOnScene().
+    * The function is a request to the process to update its configuration
+    * basing on the Importer's configuration property list.
+    */
+    void SetupProperties(const Importer* pImp);
+
+protected:
+    // -------------------------------------------------------------------
+    /** Executes the post processing step on the given imported data.
+    * At the moment a process is not supposed to fail.
+    * @param pScene The imported data to work at.
+    */
+    void Execute( aiScene* pScene);
+
+    // -------------------------------------------------------------------
+    /** Counts bones total/removable in a given mesh.
+    * @param pMesh The mesh to process.
+    */
+    bool ConsiderMesh( const aiMesh* pMesh);
+
+    /// Splits the given mesh by bone count.
+    /// @param pMesh the Mesh to split. Is not changed at all, but might be superfluous in case it was split.
+    /// @param poNewMeshes Array of submeshes created in the process. Empty if splitting was not necessary.
+    void SplitMesh(const aiMesh* pMesh, std::vector< std::pair< aiMesh*,const aiBone* > >& poNewMeshes) const;
+
+    /// Recursively updates the node's mesh list to account for the changed mesh list
+    void UpdateNode(aiNode* pNode) const;
+
+    // -------------------------------------------------------------------
+    // Apply transformation to a mesh
+    void ApplyTransform(aiMesh* mesh, const aiMatrix4x4& mat)const;
+
+public:
+    /** Number of bones present in the scene. */
+    unsigned int mNumBones;
+    unsigned int mNumBonesCanDoWithout;
+
+    float mThreshold;
+    bool mAllOrNone;
+
+    /// Per mesh index: Array of indices of the new submeshes.
+    std::vector< std::vector< std::pair< unsigned int,aiNode* > > > mSubMeshIndices;
+};
+
+} // end of namespace Assimp
+
+#endif // AI_DEBONEPROCESS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/DropFaceNormalsProcess.cpp b/thirdparty/assimp/code/PostProcessing/DropFaceNormalsProcess.cpp
new file mode 100644
index 0000000000..b11615bb82
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/DropFaceNormalsProcess.cpp
@@ -0,0 +1,109 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file Implementation of the post processing step to drop face
+* normals for all imported faces.
+*/
+
+
+#include "DropFaceNormalsProcess.h"
+#include <assimp/postprocess.h>
+#include <assimp/scene.h>
+#include <assimp/DefaultLogger.hpp>
+#include <assimp/Exceptional.h>
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+DropFaceNormalsProcess::DropFaceNormalsProcess()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+DropFaceNormalsProcess::~DropFaceNormalsProcess()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool DropFaceNormalsProcess::IsActive( unsigned int pFlags) const {
+    return  (pFlags & aiProcess_DropNormals) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void DropFaceNormalsProcess::Execute( aiScene* pScene) {
+    ASSIMP_LOG_DEBUG("DropFaceNormalsProcess begin");
+
+    if (pScene->mFlags & AI_SCENE_FLAGS_NON_VERBOSE_FORMAT) {
+        throw DeadlyImportError("Post-processing order mismatch: expecting pseudo-indexed (\"verbose\") vertices here");
+    }
+
+    bool bHas = false;
+    for( unsigned int a = 0; a < pScene->mNumMeshes; a++) {
+        bHas |= this->DropMeshFaceNormals( pScene->mMeshes[a]);
+    }
+    if (bHas)   {
+        ASSIMP_LOG_INFO("DropFaceNormalsProcess finished. "
+            "Face normals have been removed");
+    } else {
+        ASSIMP_LOG_DEBUG("DropFaceNormalsProcess finished. "
+            "No normals were present");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+bool DropFaceNormalsProcess::DropMeshFaceNormals (aiMesh* pMesh) {
+    if (NULL == pMesh->mNormals) {
+        return false;
+    }
+    
+    delete[] pMesh->mNormals;
+    pMesh->mNormals = nullptr;
+    return true;
+}
diff --git a/thirdparty/assimp/code/PostProcessing/DropFaceNormalsProcess.h b/thirdparty/assimp/code/PostProcessing/DropFaceNormalsProcess.h
new file mode 100644
index 0000000000..c710c5a5ee
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/DropFaceNormalsProcess.h
@@ -0,0 +1,83 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file Defines a post processing step to compute face normals for all loaded faces*/
+#ifndef AI_DROPFACENORMALPROCESS_H_INC
+#define AI_DROPFACENORMALPROCESS_H_INC
+
+#include "Common/BaseProcess.h"
+
+#include <assimp/mesh.h>
+
+namespace Assimp {
+
+// ---------------------------------------------------------------------------
+/** The DropFaceNormalsProcess computes face normals for all faces of all meshes
+*/
+class ASSIMP_API_WINONLY DropFaceNormalsProcess : public BaseProcess {
+public:
+    DropFaceNormalsProcess();
+    ~DropFaceNormalsProcess();
+
+    // -------------------------------------------------------------------
+    /** Returns whether the processing step is present in the given flag field.
+    * @param pFlags The processing flags the importer was called with. A bitwise
+    *   combination of #aiPostProcessSteps.
+    * @return true if the process is present in this flag fields, false if not.
+    */
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    /** Executes the post processing step on the given imported data.
+    * At the moment a process is not supposed to fail.
+    * @param pScene The imported data to work at.
+    */
+    void Execute( aiScene* pScene);
+
+
+private:
+    bool DropMeshFaceNormals(aiMesh* pcMesh);
+};
+
+} // end of namespace Assimp
+
+#endif // !!AI_DROPFACENORMALPROCESS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/EmbedTexturesProcess.cpp b/thirdparty/assimp/code/PostProcessing/EmbedTexturesProcess.cpp
new file mode 100644
index 0000000000..739382a057
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/EmbedTexturesProcess.cpp
@@ -0,0 +1,152 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+copyright notice, this list of conditions and the
+following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the
+following disclaimer in the documentation and/or other
+materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+contributors may be used to endorse or promote products
+derived from this software without specific prior
+written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+#include "EmbedTexturesProcess.h"
+#include <assimp/ParsingUtils.h>
+#include "ProcessHelper.h"
+
+#include <fstream>
+
+using namespace Assimp;
+
+EmbedTexturesProcess::EmbedTexturesProcess()
+: BaseProcess() {
+}
+
+EmbedTexturesProcess::~EmbedTexturesProcess() {
+}
+
+bool EmbedTexturesProcess::IsActive(unsigned int pFlags) const {
+    return (pFlags & aiProcess_EmbedTextures) != 0;
+}
+
+void EmbedTexturesProcess::SetupProperties(const Importer* pImp) {
+    mRootPath = pImp->GetPropertyString("sourceFilePath");
+    mRootPath = mRootPath.substr(0, mRootPath.find_last_of("\\/") + 1u);
+}
+
+void EmbedTexturesProcess::Execute(aiScene* pScene) {
+    if (pScene == nullptr || pScene->mRootNode == nullptr) return;
+
+    aiString path;
+
+    uint32_t embeddedTexturesCount = 0u;
+
+    for (auto matId = 0u; matId < pScene->mNumMaterials; ++matId) {
+        auto material = pScene->mMaterials[matId];
+
+        for (auto ttId = 1u; ttId < AI_TEXTURE_TYPE_MAX; ++ttId) {
+            auto tt = static_cast<aiTextureType>(ttId);
+            auto texturesCount = material->GetTextureCount(tt);
+
+            for (auto texId = 0u; texId < texturesCount; ++texId) {
+                material->GetTexture(tt, texId, &path);
+                if (path.data[0] == '*') continue; // Already embedded
+
+                // Indeed embed
+                if (addTexture(pScene, path.data)) {
+                    auto embeddedTextureId = pScene->mNumTextures - 1u;
+                    ::ai_snprintf(path.data, 1024, "*%u", embeddedTextureId);
+                    material->AddProperty(&path, AI_MATKEY_TEXTURE(tt, texId));
+                    embeddedTexturesCount++;
+                }
+            }
+        }
+    }
+
+    ASSIMP_LOG_INFO_F("EmbedTexturesProcess finished. Embedded ", embeddedTexturesCount, " textures." );
+}
+
+bool EmbedTexturesProcess::addTexture(aiScene* pScene, std::string path) const {
+    std::streampos imageSize = 0;
+    std::string    imagePath = path;
+
+    // Test path directly
+    std::ifstream file(imagePath, std::ios::binary | std::ios::ate);
+    if ((imageSize = file.tellg()) == std::streampos(-1)) {
+        ASSIMP_LOG_WARN_F("EmbedTexturesProcess: Cannot find image: ", imagePath, ". Will try to find it in root folder.");
+
+        // Test path in root path
+        imagePath = mRootPath + path;
+        file.open(imagePath, std::ios::binary | std::ios::ate);
+        if ((imageSize = file.tellg()) == std::streampos(-1)) {
+            // Test path basename in root path
+            imagePath = mRootPath + path.substr(path.find_last_of("\\/") + 1u);
+            file.open(imagePath, std::ios::binary | std::ios::ate);
+            if ((imageSize = file.tellg()) == std::streampos(-1)) {
+                ASSIMP_LOG_ERROR_F("EmbedTexturesProcess: Unable to embed texture: ", path, ".");
+                return false;
+            }
+        }
+    }
+
+    aiTexel* imageContent = new aiTexel[ 1ul + static_cast<unsigned long>( imageSize ) / sizeof(aiTexel)];
+    file.seekg(0, std::ios::beg);
+    file.read(reinterpret_cast<char*>(imageContent), imageSize);
+
+    // Enlarging the textures table
+    unsigned int textureId = pScene->mNumTextures++;
+    auto oldTextures = pScene->mTextures;
+    pScene->mTextures = new aiTexture*[pScene->mNumTextures];
+    ::memmove(pScene->mTextures, oldTextures, sizeof(aiTexture*) * (pScene->mNumTextures - 1u));
+
+    // Add the new texture
+    auto pTexture = new aiTexture;
+    pTexture->mHeight = 0; // Means that this is still compressed
+    pTexture->mWidth = static_cast<uint32_t>(imageSize);
+    pTexture->pcData = imageContent;
+
+    auto extension = path.substr(path.find_last_of('.') + 1u);
+    std::transform(extension.begin(), extension.end(), extension.begin(), ::tolower);
+    if (extension == "jpeg") {
+        extension = "jpg";
+    }
+
+    size_t len = extension.size();
+    if (len > HINTMAXTEXTURELEN -1 ) {
+        len = HINTMAXTEXTURELEN - 1;
+    }
+    ::strncpy(pTexture->achFormatHint, extension.c_str(), len);
+    pScene->mTextures[textureId] = pTexture;
+
+    return true;
+}
diff --git a/thirdparty/assimp/code/PostProcessing/EmbedTexturesProcess.h b/thirdparty/assimp/code/PostProcessing/EmbedTexturesProcess.h
new file mode 100644
index 0000000000..3c4b2eab4e
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/EmbedTexturesProcess.h
@@ -0,0 +1,85 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+copyright notice, this list of conditions and the
+following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the
+following disclaimer in the documentation and/or other
+materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+contributors may be used to endorse or promote products
+derived from this software without specific prior
+written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+#pragma once
+
+#include "Common/BaseProcess.h"
+
+#include <string>
+
+struct aiNode;
+
+namespace Assimp {
+
+/**
+ *  Force embedding of textures (using the path = "*1" convention).
+ *  If a texture's file does not exist at the specified path
+ *  (due, for instance, to an absolute path generated on another system),
+ *  it will check if a file with the same name exists at the root folder
+ *  of the imported model. And if so, it uses that.
+ */
+class ASSIMP_API EmbedTexturesProcess : public BaseProcess {
+public:
+    /// The default class constructor.
+    EmbedTexturesProcess();
+
+    /// The class destructor.
+    virtual ~EmbedTexturesProcess();
+
+    /// Overwritten, @see BaseProcess
+    virtual bool IsActive(unsigned int pFlags) const;
+
+    /// Overwritten, @see BaseProcess
+    virtual void SetupProperties(const Importer* pImp);
+
+    /// Overwritten, @see BaseProcess
+    virtual void Execute(aiScene* pScene);
+
+private:
+    // Resolve the path and add the file content to the scene as a texture.
+    bool addTexture(aiScene* pScene, std::string path) const;
+
+private:
+    std::string mRootPath;
+};
+
+} // namespace Assimp
diff --git a/thirdparty/assimp/code/PostProcessing/FindDegenerates.cpp b/thirdparty/assimp/code/PostProcessing/FindDegenerates.cpp
new file mode 100644
index 0000000000..50fac46dba
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/FindDegenerates.cpp
@@ -0,0 +1,301 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file  FindDegenerates.cpp
+ *  @brief Implementation of the FindDegenerates post-process step.
+*/
+
+
+
+// internal headers
+#include "ProcessHelper.h"
+#include "FindDegenerates.h"
+#include <assimp/Exceptional.h>
+
+using namespace Assimp;
+
+//remove mesh at position 'index' from the scene
+static void removeMesh(aiScene* pScene, unsigned const index);
+//correct node indices to meshes and remove references to deleted mesh
+static void updateSceneGraph(aiNode* pNode, unsigned const index);
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+FindDegeneratesProcess::FindDegeneratesProcess()
+: mConfigRemoveDegenerates( false )
+, mConfigCheckAreaOfTriangle( false ){
+    // empty
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+FindDegeneratesProcess::~FindDegeneratesProcess() {
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool FindDegeneratesProcess::IsActive( unsigned int pFlags) const {
+    return 0 != (pFlags & aiProcess_FindDegenerates);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Setup import configuration
+void FindDegeneratesProcess::SetupProperties(const Importer* pImp) {
+    // Get the current value of AI_CONFIG_PP_FD_REMOVE
+    mConfigRemoveDegenerates = (0 != pImp->GetPropertyInteger(AI_CONFIG_PP_FD_REMOVE,0));
+    mConfigCheckAreaOfTriangle = ( 0 != pImp->GetPropertyInteger(AI_CONFIG_PP_FD_CHECKAREA) );
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void FindDegeneratesProcess::Execute( aiScene* pScene) {
+    ASSIMP_LOG_DEBUG("FindDegeneratesProcess begin");
+    for (unsigned int i = 0; i < pScene->mNumMeshes;++i)
+    {
+        //Do not process point cloud, ExecuteOnMesh works only with faces data
+        if ((pScene->mMeshes[i]->mPrimitiveTypes != aiPrimitiveType::aiPrimitiveType_POINT) && ExecuteOnMesh(pScene->mMeshes[i])) {
+            removeMesh(pScene, i);
+            --i; //the current i is removed, do not skip the next one
+        }
+    }
+    ASSIMP_LOG_DEBUG("FindDegeneratesProcess finished");
+}
+
+static void removeMesh(aiScene* pScene, unsigned const index) {
+    //we start at index and copy the pointers one position forward
+    //save the mesh pointer to delete it later
+    auto delete_me = pScene->mMeshes[index];
+    for (unsigned i = index; i < pScene->mNumMeshes - 1; ++i) {
+        pScene->mMeshes[i] = pScene->mMeshes[i+1];
+    }
+    pScene->mMeshes[pScene->mNumMeshes - 1] = nullptr;
+    --(pScene->mNumMeshes);
+    delete delete_me;
+
+    //removing a mesh also requires updating all references to it in the scene graph
+    updateSceneGraph(pScene->mRootNode, index);
+}
+
+static void updateSceneGraph(aiNode* pNode, unsigned const index) {
+    for (unsigned i = 0; i < pNode->mNumMeshes; ++i) {
+        if (pNode->mMeshes[i] > index) {
+            --(pNode->mMeshes[i]);
+            continue;
+        }
+        if (pNode->mMeshes[i] == index) {
+            for (unsigned j = i; j < pNode->mNumMeshes -1; ++j) {
+                pNode->mMeshes[j] = pNode->mMeshes[j+1];
+            }
+            --(pNode->mNumMeshes);
+            --i;
+            continue;
+        }
+    }
+    //recurse to all children
+    for (unsigned i = 0; i < pNode->mNumChildren; ++i) {
+        updateSceneGraph(pNode->mChildren[i], index);
+    }
+}
+
+static ai_real heron( ai_real a, ai_real b, ai_real c ) {
+    ai_real s = (a + b + c) / 2;
+    ai_real area = pow((s * ( s - a ) * ( s - b ) * ( s - c ) ), (ai_real)0.5 );
+    return area;
+}
+
+static ai_real distance3D( const aiVector3D &vA, aiVector3D &vB ) {
+    const ai_real lx = ( vB.x - vA.x );
+    const ai_real ly = ( vB.y - vA.y );
+    const ai_real lz = ( vB.z - vA.z );
+    ai_real a = lx*lx + ly*ly + lz*lz;
+    ai_real d = pow( a, (ai_real)0.5 );
+
+    return d;
+}
+
+static ai_real calculateAreaOfTriangle( const aiFace& face, aiMesh* mesh ) {
+    ai_real area = 0;
+
+    aiVector3D vA( mesh->mVertices[ face.mIndices[ 0 ] ] );
+    aiVector3D vB( mesh->mVertices[ face.mIndices[ 1 ] ] );
+    aiVector3D vC( mesh->mVertices[ face.mIndices[ 2 ] ] );
+
+    ai_real a( distance3D( vA, vB ) );
+    ai_real b( distance3D( vB, vC ) );
+    ai_real c( distance3D( vC, vA ) );
+    area = heron( a, b, c );
+
+    return area;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported mesh
+bool FindDegeneratesProcess::ExecuteOnMesh( aiMesh* mesh) {
+    mesh->mPrimitiveTypes = 0;
+
+    std::vector<bool> remove_me;
+    if (mConfigRemoveDegenerates) {
+        remove_me.resize( mesh->mNumFaces, false );
+    }
+
+    unsigned int deg = 0, limit;
+    for ( unsigned int a = 0; a < mesh->mNumFaces; ++a ) {
+        aiFace& face = mesh->mFaces[a];
+        bool first = true;
+
+        // check whether the face contains degenerated entries
+        for (unsigned int i = 0; i < face.mNumIndices; ++i) {
+            // Polygons with more than 4 points are allowed to have double points, that is
+            // simulating polygons with holes just with concave polygons. However,
+            // double points may not come directly after another.
+            limit = face.mNumIndices;
+            if (face.mNumIndices > 4) {
+                limit = std::min( limit, i+2 );
+            }
+
+            for (unsigned int t = i+1; t < limit; ++t) {
+                if (mesh->mVertices[face.mIndices[ i ] ] == mesh->mVertices[ face.mIndices[ t ] ]) {
+                    // we have found a matching vertex position
+                    // remove the corresponding index from the array
+                    --face.mNumIndices;
+                    --limit;
+                    for (unsigned int m = t; m < face.mNumIndices; ++m) {
+                        face.mIndices[ m ] = face.mIndices[ m+1 ];
+                    }
+                    --t;
+
+                    // NOTE: we set the removed vertex index to an unique value
+                    // to make sure the developer gets notified when his
+                    // application attempts to access this data.
+                    face.mIndices[ face.mNumIndices ] = 0xdeadbeef;
+
+                    if(first) {
+                        ++deg;
+                        first = false;
+                    }
+
+                    if ( mConfigRemoveDegenerates ) {
+                        remove_me[ a ] = true;
+                        goto evil_jump_outside; // hrhrhrh ... yeah, this rocks baby!
+                    }
+                }
+            }
+
+            if ( mConfigCheckAreaOfTriangle ) {
+                if ( face.mNumIndices == 3 ) {
+                    ai_real area = calculateAreaOfTriangle( face, mesh );
+                    if ( area < 1e-6 ) {
+                        if ( mConfigRemoveDegenerates ) {
+                            remove_me[ a ] = true;
+                            ++deg;
+                            goto evil_jump_outside;
+                        }
+
+                        // todo: check for index which is corrupt.
+                    }
+                }
+            }
+        }
+
+        // We need to update the primitive flags array of the mesh.
+        switch (face.mNumIndices)
+        {
+        case 1u:
+            mesh->mPrimitiveTypes |= aiPrimitiveType_POINT;
+            break;
+        case 2u:
+            mesh->mPrimitiveTypes |= aiPrimitiveType_LINE;
+            break;
+        case 3u:
+            mesh->mPrimitiveTypes |= aiPrimitiveType_TRIANGLE;
+            break;
+        default:
+            mesh->mPrimitiveTypes |= aiPrimitiveType_POLYGON;
+            break;
+        };
+evil_jump_outside:
+        continue;
+    }
+
+    // If AI_CONFIG_PP_FD_REMOVE is true, remove degenerated faces from the import
+    if (mConfigRemoveDegenerates && deg) {
+        unsigned int n = 0;
+        for (unsigned int a = 0; a < mesh->mNumFaces; ++a)
+        {
+            aiFace& face_src = mesh->mFaces[a];
+            if (!remove_me[a]) {
+                aiFace& face_dest = mesh->mFaces[n++];
+
+                // Do a manual copy, keep the index array
+                face_dest.mNumIndices = face_src.mNumIndices;
+                face_dest.mIndices    = face_src.mIndices;
+
+                if (&face_src != &face_dest) {
+                    // clear source
+                    face_src.mNumIndices = 0;
+                    face_src.mIndices = nullptr;
+                }
+            }
+            else {
+                // Otherwise delete it if we don't need this face
+                delete[] face_src.mIndices;
+                face_src.mIndices = nullptr;
+                face_src.mNumIndices = 0;
+            }
+        }
+        // Just leave the rest of the array unreferenced, we don't care for now
+        mesh->mNumFaces = n;
+        if (!mesh->mNumFaces) {
+            //The whole mesh consists of degenerated faces
+            //signal upward, that this mesh should be deleted.
+            ASSIMP_LOG_DEBUG("FindDegeneratesProcess removed a mesh full of degenerated primitives");
+            return true;
+        }
+    }
+
+    if (deg && !DefaultLogger::isNullLogger()) {
+        ASSIMP_LOG_WARN_F( "Found ", deg, " degenerated primitives");
+    }
+    return false;
+}
diff --git a/thirdparty/assimp/code/PostProcessing/FindDegenerates.h b/thirdparty/assimp/code/PostProcessing/FindDegenerates.h
new file mode 100644
index 0000000000..7a15e77cf1
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/FindDegenerates.h
@@ -0,0 +1,130 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file Defines a post processing step to search all meshes for
+  degenerated faces */
+#ifndef AI_FINDDEGENERATESPROCESS_H_INC
+#define AI_FINDDEGENERATESPROCESS_H_INC
+
+#include "Common/BaseProcess.h"
+
+#include <assimp/mesh.h>
+
+class FindDegeneratesProcessTest;
+namespace Assimp    {
+
+
+// ---------------------------------------------------------------------------
+/** FindDegeneratesProcess: Searches a mesh for degenerated triangles.
+*/
+class ASSIMP_API FindDegeneratesProcess : public BaseProcess {
+public:
+    FindDegeneratesProcess();
+    ~FindDegeneratesProcess();
+
+    // -------------------------------------------------------------------
+    // Check whether step is active
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    // Execute step on a given scene
+    void Execute( aiScene* pScene);
+
+    // -------------------------------------------------------------------
+    // Setup import settings
+    void SetupProperties(const Importer* pImp);
+
+    // -------------------------------------------------------------------
+    // Execute step on a given mesh
+    ///@returns true if the current mesh should be deleted, false otherwise
+    bool ExecuteOnMesh( aiMesh* mesh);
+
+    // -------------------------------------------------------------------
+    /// @brief Enable the instant removal of degenerated primitives
+    /// @param enabled  true for enabled.
+    void EnableInstantRemoval(bool enabled);
+
+    // -------------------------------------------------------------------
+    /// @brief Check whether instant removal is currently enabled
+    /// @return The instant removal state.
+    bool IsInstantRemoval() const;
+
+    // -------------------------------------------------------------------
+    /// @brief Enable the area check for triangles.
+    /// @param enabled  true for enabled.
+    void EnableAreaCheck( bool enabled );
+
+    // -------------------------------------------------------------------
+    /// @brief Check whether the area check is enabled.
+    /// @return The area check state.
+    bool isAreaCheckEnabled() const;
+
+private:
+    //! Configuration option: remove degenerates faces immediately
+    bool mConfigRemoveDegenerates;
+    //! Configuration option: check for area
+    bool mConfigCheckAreaOfTriangle;
+};
+
+inline
+void FindDegeneratesProcess::EnableInstantRemoval(bool enabled) {
+    mConfigRemoveDegenerates = enabled;
+}
+
+inline
+bool FindDegeneratesProcess::IsInstantRemoval() const {
+    return mConfigRemoveDegenerates;
+}
+
+inline
+void FindDegeneratesProcess::EnableAreaCheck( bool enabled ) {
+    mConfigCheckAreaOfTriangle = enabled;
+}
+
+inline
+bool FindDegeneratesProcess::isAreaCheckEnabled() const {
+    return mConfigCheckAreaOfTriangle;
+}
+
+} // Namespace Assimp
+
+#endif // !! AI_FINDDEGENERATESPROCESS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/FindInstancesProcess.cpp b/thirdparty/assimp/code/PostProcessing/FindInstancesProcess.cpp
new file mode 100644
index 0000000000..64907458a1
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/FindInstancesProcess.cpp
@@ -0,0 +1,277 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file  FindInstancesProcess.cpp
+ *  @brief Implementation of the aiProcess_FindInstances postprocessing step
+*/
+
+
+#include "FindInstancesProcess.h"
+#include <memory>
+#include <stdio.h>
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+FindInstancesProcess::FindInstancesProcess()
+:   configSpeedFlag (false)
+{}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+FindInstancesProcess::~FindInstancesProcess()
+{}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool FindInstancesProcess::IsActive( unsigned int pFlags) const
+{
+    // FindInstances makes absolutely no sense together with PreTransformVertices
+    // fixme: spawn error message somewhere else?
+    return 0 != (pFlags & aiProcess_FindInstances) && 0 == (pFlags & aiProcess_PreTransformVertices);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Setup properties for the step
+void FindInstancesProcess::SetupProperties(const Importer* pImp)
+{
+    // AI_CONFIG_FAVOUR_SPEED
+    configSpeedFlag = (0 != pImp->GetPropertyInteger(AI_CONFIG_FAVOUR_SPEED,0));
+}
+
+// ------------------------------------------------------------------------------------------------
+// Compare the bones of two meshes
+bool CompareBones(const aiMesh* orig, const aiMesh* inst)
+{
+    for (unsigned int i = 0; i < orig->mNumBones;++i) {
+        aiBone* aha = orig->mBones[i];
+        aiBone* oha = inst->mBones[i];
+
+        if (aha->mNumWeights   != oha->mNumWeights   ||
+            aha->mOffsetMatrix != oha->mOffsetMatrix) {
+            return false;
+        }
+
+        // compare weight per weight ---
+        for (unsigned int n = 0; n < aha->mNumWeights;++n) {
+            if  (aha->mWeights[n].mVertexId != oha->mWeights[n].mVertexId ||
+                (aha->mWeights[n].mWeight - oha->mWeights[n].mWeight) < 10e-3f) {
+                return false;
+            }
+        }
+    }
+    return true;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Update mesh indices in the node graph
+void UpdateMeshIndices(aiNode* node, unsigned int* lookup)
+{
+    for (unsigned int n = 0; n < node->mNumMeshes;++n)
+        node->mMeshes[n] = lookup[node->mMeshes[n]];
+
+    for (unsigned int n = 0; n < node->mNumChildren;++n)
+        UpdateMeshIndices(node->mChildren[n],lookup);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void FindInstancesProcess::Execute( aiScene* pScene)
+{
+    ASSIMP_LOG_DEBUG("FindInstancesProcess begin");
+    if (pScene->mNumMeshes) {
+
+        // use a pseudo hash for all meshes in the scene to quickly find
+        // the ones which are possibly equal. This step is executed early
+        // in the pipeline, so we could, depending on the file format,
+        // have several thousand small meshes. That's too much for a brute
+        // everyone-against-everyone check involving up to 10 comparisons
+        // each.
+        std::unique_ptr<uint64_t[]> hashes (new uint64_t[pScene->mNumMeshes]);
+        std::unique_ptr<unsigned int[]> remapping (new unsigned int[pScene->mNumMeshes]);
+
+        unsigned int numMeshesOut = 0;
+        for (unsigned int i = 0; i < pScene->mNumMeshes; ++i) {
+
+            aiMesh* inst = pScene->mMeshes[i];
+            hashes[i] = GetMeshHash(inst);
+
+            // Find an appropriate epsilon 
+            // to compare position differences against
+            float epsilon = ComputePositionEpsilon(inst);
+            epsilon *= epsilon;
+
+            for (int a = i-1; a >= 0; --a) {
+                if (hashes[i] == hashes[a])
+                {
+                    aiMesh* orig = pScene->mMeshes[a];
+                    if (!orig)
+                        continue;
+
+                    // check for hash collision .. we needn't check
+                    // the vertex format, it *must* match due to the
+                    // (brilliant) construction of the hash
+                    if (orig->mNumBones       != inst->mNumBones      ||
+                        orig->mNumFaces       != inst->mNumFaces      ||
+                        orig->mNumVertices    != inst->mNumVertices   ||
+                        orig->mMaterialIndex  != inst->mMaterialIndex ||
+                        orig->mPrimitiveTypes != inst->mPrimitiveTypes)
+                        continue;
+
+                    // up to now the meshes are equal. Now compare vertex positions, normals,
+                    // tangents and bitangents using this epsilon.
+                    if (orig->HasPositions()) {
+                        if(!CompareArrays(orig->mVertices,inst->mVertices,orig->mNumVertices,epsilon))
+                            continue;
+                    }
+                    if (orig->HasNormals()) {
+                        if(!CompareArrays(orig->mNormals,inst->mNormals,orig->mNumVertices,epsilon))
+                            continue;
+                    }
+                    if (orig->HasTangentsAndBitangents()) {
+                        if (!CompareArrays(orig->mTangents,inst->mTangents,orig->mNumVertices,epsilon) ||
+                            !CompareArrays(orig->mBitangents,inst->mBitangents,orig->mNumVertices,epsilon))
+                            continue;
+                    }
+
+                    // use a constant epsilon for colors and UV coordinates
+                    static const float uvEpsilon = 10e-4f;
+                    {
+                        unsigned int j, end = orig->GetNumUVChannels();
+                        for(j = 0; j < end; ++j) {
+                            if (!orig->mTextureCoords[j]) {
+                                continue;
+                            }
+                            if(!CompareArrays(orig->mTextureCoords[j],inst->mTextureCoords[j],orig->mNumVertices,uvEpsilon)) {
+                                break;
+                            }
+                        }
+                        if (j != end) {
+                            continue;
+                        }
+                    }
+                    {
+                        unsigned int j, end = orig->GetNumColorChannels();
+                        for(j = 0; j < end; ++j) {
+                            if (!orig->mColors[j]) {
+                                continue;
+                            }
+                            if(!CompareArrays(orig->mColors[j],inst->mColors[j],orig->mNumVertices,uvEpsilon)) {
+                                break;
+                            }
+                        }
+                        if (j != end) {
+                            continue;
+                        }
+                    }
+
+                    // These two checks are actually quite expensive and almost *never* required.
+                    // Almost. That's why they're still here. But there's no reason to do them
+                    // in speed-targeted imports.
+                    if (!configSpeedFlag) {
+
+                        // It seems to be strange, but we really need to check whether the
+                        // bones are identical too. Although it's extremely unprobable
+                        // that they're not if control reaches here, we need to deal
+                        // with unprobable cases, too. It could still be that there are
+                        // equal shapes which are deformed differently.
+                        if (!CompareBones(orig,inst))
+                            continue;
+
+                        // For completeness ... compare even the index buffers for equality
+                        // face order & winding order doesn't care. Input data is in verbose format.
+                        std::unique_ptr<unsigned int[]> ftbl_orig(new unsigned int[orig->mNumVertices]);
+                        std::unique_ptr<unsigned int[]> ftbl_inst(new unsigned int[orig->mNumVertices]);
+
+                        for (unsigned int tt = 0; tt < orig->mNumFaces;++tt) {
+                            aiFace& f = orig->mFaces[tt];
+                            for (unsigned int nn = 0; nn < f.mNumIndices;++nn)
+                                ftbl_orig[f.mIndices[nn]] = tt;
+
+                            aiFace& f2 = inst->mFaces[tt];
+                            for (unsigned int nn = 0; nn < f2.mNumIndices;++nn)
+                                ftbl_inst[f2.mIndices[nn]] = tt;
+                        }
+                        if (0 != ::memcmp(ftbl_inst.get(),ftbl_orig.get(),orig->mNumVertices*sizeof(unsigned int)))
+                            continue;
+                    }
+
+                    // We're still here. Or in other words: 'inst' is an instance of 'orig'.
+                    // Place a marker in our list that we can easily update mesh indices.
+                    remapping[i] = remapping[a];
+
+                    // Delete the instanced mesh, we don't need it anymore
+                    delete inst;
+                    pScene->mMeshes[i] = NULL;
+                    break;
+                }
+            }
+
+            // If we didn't find a match for the current mesh: keep it
+            if (pScene->mMeshes[i]) {
+                remapping[i] = numMeshesOut++;
+            }
+        }
+        ai_assert(0 != numMeshesOut);
+        if (numMeshesOut != pScene->mNumMeshes) {
+
+            // Collapse the meshes array by removing all NULL entries
+            for (unsigned int real = 0, i = 0; real < numMeshesOut; ++i) {
+                if (pScene->mMeshes[i])
+                    pScene->mMeshes[real++] = pScene->mMeshes[i];
+            }
+
+            // And update the node graph with our nice lookup table
+            UpdateMeshIndices(pScene->mRootNode,remapping.get());
+
+            // write to log
+            if (!DefaultLogger::isNullLogger()) {
+                ASSIMP_LOG_INFO_F( "FindInstancesProcess finished. Found ", (pScene->mNumMeshes - numMeshesOut), " instances" );
+            }
+            pScene->mNumMeshes = numMeshesOut;
+        } else {
+            ASSIMP_LOG_DEBUG("FindInstancesProcess finished. No instanced meshes found");
+        }
+    }
+}
diff --git a/thirdparty/assimp/code/PostProcessing/FindInstancesProcess.h b/thirdparty/assimp/code/PostProcessing/FindInstancesProcess.h
new file mode 100644
index 0000000000..64b838d7cc
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/FindInstancesProcess.h
@@ -0,0 +1,137 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file  FindInstancesProcess.h
+ *  @brief Declares the aiProcess_FindInstances post-process step
+ */
+#ifndef AI_FINDINSTANCES_H_INC
+#define AI_FINDINSTANCES_H_INC
+
+#include "Common/BaseProcess.h"
+#include "PostProcessing/ProcessHelper.h"
+
+class FindInstancesProcessTest;
+namespace Assimp    {
+
+// -------------------------------------------------------------------------------
+/** @brief Get a pseudo(!)-hash representing a mesh.
+ *
+ *  The hash is built from number of vertices, faces, primitive types,
+ *  .... but *not* from the real mesh data. The funcction is not a perfect hash.
+ *  @param in Input mesh
+ *  @return Hash.
+ */
+inline
+uint64_t GetMeshHash(aiMesh* in) {
+    ai_assert(nullptr != in);
+
+    // ... get an unique value representing the vertex format of the mesh
+    const unsigned int fhash = GetMeshVFormatUnique(in);
+
+    // and bake it with number of vertices/faces/bones/matidx/ptypes
+    return ((uint64_t)fhash << 32u) | ((
+        (in->mNumBones << 16u) ^  (in->mNumVertices)       ^
+        (in->mNumFaces<<4u)    ^  (in->mMaterialIndex<<15) ^
+        (in->mPrimitiveTypes<<28)) & 0xffffffff );
+}
+
+// -------------------------------------------------------------------------------
+/** @brief Perform a component-wise comparison of two arrays
+ *
+ *  @param first First array
+ *  @param second Second array
+ *  @param size Size of both arrays
+ *  @param e Epsilon
+ *  @return true if the arrays are identical
+ */
+inline
+bool CompareArrays(const aiVector3D* first, const aiVector3D* second,
+        unsigned int size, float e) {
+    for (const aiVector3D* end = first+size; first != end; ++first,++second) {
+        if ( (*first - *second).SquareLength() >= e)
+            return false;
+    }
+    return true;
+}
+
+// and the same for colors ...
+inline bool CompareArrays(const aiColor4D* first, const aiColor4D* second,
+    unsigned int size, float e)
+{
+    for (const aiColor4D* end = first+size; first != end; ++first,++second) {
+        if ( GetColorDifference(*first,*second) >= e)
+            return false;
+    }
+    return true;
+}
+
+// ---------------------------------------------------------------------------
+/** @brief A post-processing steps to search for instanced meshes
+*/
+class FindInstancesProcess : public BaseProcess
+{
+public:
+
+    FindInstancesProcess();
+    ~FindInstancesProcess();
+
+public:
+    // -------------------------------------------------------------------
+    // Check whether step is active in given flags combination
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    // Execute step on a given scene
+    void Execute( aiScene* pScene);
+
+    // -------------------------------------------------------------------
+    // Setup properties prior to executing the process
+    void SetupProperties(const Importer* pImp);
+
+private:
+
+    bool configSpeedFlag;
+
+}; // ! end class FindInstancesProcess
+}  // ! end namespace Assimp
+
+#endif // !! AI_FINDINSTANCES_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/FindInvalidDataProcess.cpp b/thirdparty/assimp/code/PostProcessing/FindInvalidDataProcess.cpp
new file mode 100644
index 0000000000..433f042448
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/FindInvalidDataProcess.cpp
@@ -0,0 +1,424 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file Defines a post processing step to search an importer's output
+    for data that is obviously invalid  */
+
+
+
+#ifndef ASSIMP_BUILD_NO_FINDINVALIDDATA_PROCESS
+
+// internal headers
+#include "FindInvalidDataProcess.h"
+#include "ProcessHelper.h"
+
+#include <assimp/Macros.h>
+#include <assimp/Exceptional.h>
+#include <assimp/qnan.h>
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+FindInvalidDataProcess::FindInvalidDataProcess()
+: configEpsilon(0.0)
+, mIgnoreTexCoods( false ){
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+FindInvalidDataProcess::~FindInvalidDataProcess() {
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool FindInvalidDataProcess::IsActive( unsigned int pFlags) const {
+    return 0 != (pFlags & aiProcess_FindInvalidData);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Setup import configuration
+void FindInvalidDataProcess::SetupProperties(const Importer* pImp) {
+    // Get the current value of AI_CONFIG_PP_FID_ANIM_ACCURACY
+    configEpsilon = (0 != pImp->GetPropertyFloat(AI_CONFIG_PP_FID_ANIM_ACCURACY,0.f));
+    mIgnoreTexCoods = pImp->GetPropertyBool(AI_CONFIG_PP_FID_IGNORE_TEXTURECOORDS, false);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Update mesh references in the node graph
+void UpdateMeshReferences(aiNode* node, const std::vector<unsigned int>& meshMapping) {
+    if (node->mNumMeshes)   {
+        unsigned int out = 0;
+        for (unsigned int a = 0; a < node->mNumMeshes;++a)  {
+
+            unsigned int ref = node->mMeshes[a];
+            if (UINT_MAX != (ref = meshMapping[ref]))   {
+                node->mMeshes[out++] = ref;
+            }
+        }
+        // just let the members that are unused, that's much cheaper
+        // than a full array realloc'n'copy party ...
+        if(!(node->mNumMeshes = out))   {
+
+            delete[] node->mMeshes;
+            node->mMeshes = NULL;
+        }
+    }
+    // recursively update all children
+    for (unsigned int i = 0; i < node->mNumChildren;++i) {
+        UpdateMeshReferences(node->mChildren[i],meshMapping);
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void FindInvalidDataProcess::Execute( aiScene* pScene) {
+    ASSIMP_LOG_DEBUG("FindInvalidDataProcess begin");
+
+    bool out = false;
+    std::vector<unsigned int> meshMapping(pScene->mNumMeshes);
+    unsigned int real = 0;
+
+    // Process meshes
+    for( unsigned int a = 0; a < pScene->mNumMeshes; a++)   {
+
+        int result;
+        if ((result = ProcessMesh( pScene->mMeshes[a])))    {
+            out = true;
+
+            if (2 == result)    {
+                // remove this mesh
+                delete pScene->mMeshes[a];
+                AI_DEBUG_INVALIDATE_PTR(pScene->mMeshes[a]);
+
+                meshMapping[a] = UINT_MAX;
+                continue;
+            }
+        }
+        pScene->mMeshes[real] = pScene->mMeshes[a];
+        meshMapping[a] = real++;
+    }
+
+    // Process animations
+    for (unsigned int a = 0; a < pScene->mNumAnimations;++a) {
+        ProcessAnimation( pScene->mAnimations[a]);
+    }
+
+
+    if (out)    {
+        if ( real != pScene->mNumMeshes)    {
+            if (!real) {
+                throw DeadlyImportError("No meshes remaining");
+            }
+
+            // we need to remove some meshes.
+            // therefore we'll also need to remove all references
+            // to them from the scenegraph
+            UpdateMeshReferences(pScene->mRootNode,meshMapping);
+            pScene->mNumMeshes = real;
+        }
+
+        ASSIMP_LOG_INFO("FindInvalidDataProcess finished. Found issues ...");
+    } else {
+        ASSIMP_LOG_DEBUG("FindInvalidDataProcess finished. Everything seems to be OK.");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+template <typename T>
+inline
+const char* ValidateArrayContents(const T* /*arr*/, unsigned int /*size*/,
+        const std::vector<bool>& /*dirtyMask*/, bool /*mayBeIdentical = false*/, bool /*mayBeZero = true*/)
+{
+    return nullptr;
+}
+
+// ------------------------------------------------------------------------------------------------
+template <>
+inline
+const char* ValidateArrayContents<aiVector3D>(const aiVector3D* arr, unsigned int size,
+        const std::vector<bool>& dirtyMask, bool mayBeIdentical , bool mayBeZero ) {
+    bool b = false;
+    unsigned int cnt = 0;
+    for (unsigned int i = 0; i < size;++i)  {
+
+        if (dirtyMask.size() && dirtyMask[i]) {
+            continue;
+        }
+        ++cnt;
+
+        const aiVector3D& v = arr[i];
+        if (is_special_float(v.x) || is_special_float(v.y) || is_special_float(v.z))    {
+            return "INF/NAN was found in a vector component";
+        }
+        if (!mayBeZero && !v.x && !v.y && !v.z )    {
+            return "Found zero-length vector";
+        }
+        if (i && v != arr[i-1])b = true;
+    }
+    if (cnt > 1 && !b && !mayBeIdentical) {
+        return "All vectors are identical";
+    }
+    return nullptr;
+}
+
+// ------------------------------------------------------------------------------------------------
+template <typename T>
+inline 
+bool ProcessArray(T*& in, unsigned int num,const char* name,
+        const std::vector<bool>& dirtyMask, bool mayBeIdentical = false, bool mayBeZero = true) {
+    const char* err = ValidateArrayContents(in,num,dirtyMask,mayBeIdentical,mayBeZero);
+    if (err)    {
+        ASSIMP_LOG_ERROR_F( "FindInvalidDataProcess fails on mesh ", name, ": ", err);
+        delete[] in;
+        in = NULL;
+        return true;
+    }
+    return false;
+}
+
+// ------------------------------------------------------------------------------------------------
+template <typename T>
+AI_FORCE_INLINE bool EpsilonCompare(const T& n, const T& s, ai_real epsilon);
+
+// ------------------------------------------------------------------------------------------------
+AI_FORCE_INLINE bool EpsilonCompare(ai_real n, ai_real s, ai_real epsilon) {
+    return std::fabs(n-s)>epsilon;
+}
+
+// ------------------------------------------------------------------------------------------------
+template <>
+bool EpsilonCompare<aiVectorKey>(const aiVectorKey& n, const aiVectorKey& s, ai_real epsilon) {
+    return
+        EpsilonCompare(n.mValue.x,s.mValue.x,epsilon) &&
+        EpsilonCompare(n.mValue.y,s.mValue.y,epsilon) &&
+        EpsilonCompare(n.mValue.z,s.mValue.z,epsilon);
+}
+
+// ------------------------------------------------------------------------------------------------
+template <>
+bool EpsilonCompare<aiQuatKey>(const aiQuatKey& n, const aiQuatKey& s, ai_real epsilon)   {
+    return
+        EpsilonCompare(n.mValue.x,s.mValue.x,epsilon) &&
+        EpsilonCompare(n.mValue.y,s.mValue.y,epsilon) &&
+        EpsilonCompare(n.mValue.z,s.mValue.z,epsilon) &&
+        EpsilonCompare(n.mValue.w,s.mValue.w,epsilon);
+}
+
+// ------------------------------------------------------------------------------------------------
+template <typename T>
+inline
+bool AllIdentical(T* in, unsigned int num, ai_real epsilon) {
+    if (num <= 1) {
+        return true;
+    }
+
+    if (fabs(epsilon) > 0.f) {
+        for (unsigned int i = 0; i < num-1;++i) {
+            if (!EpsilonCompare(in[i],in[i+1],epsilon)) {
+                return false;
+            }
+        }
+    } else {
+        for (unsigned int i = 0; i < num-1;++i) {
+            if (in[i] != in[i+1]) {
+                return false;
+            }
+        }
+    }
+    return true;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Search an animation for invalid content
+void FindInvalidDataProcess::ProcessAnimation (aiAnimation* anim) {
+    // Process all animation channels
+    for ( unsigned int a = 0; a < anim->mNumChannels; ++a ) {
+        ProcessAnimationChannel( anim->mChannels[a]);
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+void FindInvalidDataProcess::ProcessAnimationChannel (aiNodeAnim* anim) {
+    ai_assert( nullptr != anim );
+    if (anim->mNumPositionKeys == 0 && anim->mNumRotationKeys == 0 && anim->mNumScalingKeys == 0) {
+        ai_assert_entry();
+        return;
+    }
+
+    // Check whether all values in a tracks are identical - in this case
+    // we can remove al keys except one.
+    // POSITIONS
+    int i = 0;
+    if (anim->mNumPositionKeys > 1 && AllIdentical(anim->mPositionKeys,anim->mNumPositionKeys,configEpsilon)) {
+        aiVectorKey v = anim->mPositionKeys[0];
+
+        // Reallocate ... we need just ONE element, it makes no sense to reuse the array
+        delete[] anim->mPositionKeys;
+        anim->mPositionKeys = new aiVectorKey[anim->mNumPositionKeys = 1];
+        anim->mPositionKeys[0] = v;
+        i = 1;
+    }
+
+    // ROTATIONS
+    if (anim->mNumRotationKeys > 1 && AllIdentical(anim->mRotationKeys,anim->mNumRotationKeys,configEpsilon)) {
+        aiQuatKey v = anim->mRotationKeys[0];
+
+        // Reallocate ... we need just ONE element, it makes no sense to reuse the array
+        delete[] anim->mRotationKeys;
+        anim->mRotationKeys = new aiQuatKey[anim->mNumRotationKeys = 1];
+        anim->mRotationKeys[0] = v;
+        i = 1;
+    }
+
+    // SCALINGS
+    if (anim->mNumScalingKeys > 1 && AllIdentical(anim->mScalingKeys,anim->mNumScalingKeys,configEpsilon)) {
+        aiVectorKey v = anim->mScalingKeys[0];
+
+        // Reallocate ... we need just ONE element, it makes no sense to reuse the array
+        delete[] anim->mScalingKeys;
+        anim->mScalingKeys = new aiVectorKey[anim->mNumScalingKeys = 1];
+        anim->mScalingKeys[0] = v;
+        i = 1;
+    }
+    if ( 1 == i ) {
+        ASSIMP_LOG_WARN("Simplified dummy tracks with just one key");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Search a mesh for invalid contents
+int FindInvalidDataProcess::ProcessMesh(aiMesh* pMesh)
+{
+    bool ret = false;
+    std::vector<bool> dirtyMask(pMesh->mNumVertices, pMesh->mNumFaces != 0);
+
+    // Ignore elements that are not referenced by vertices.
+    // (they are, for example, caused by the FindDegenerates step)
+    for (unsigned int m = 0; m < pMesh->mNumFaces; ++m) {
+        const aiFace& f = pMesh->mFaces[m];
+
+        for (unsigned int i = 0; i < f.mNumIndices; ++i) {
+            dirtyMask[f.mIndices[i]] = false;
+        }
+    }
+
+    // Process vertex positions
+    if (pMesh->mVertices && ProcessArray(pMesh->mVertices, pMesh->mNumVertices, "positions", dirtyMask)) {
+        ASSIMP_LOG_ERROR("Deleting mesh: Unable to continue without vertex positions");
+
+        return 2;
+    }
+
+    // process texture coordinates
+    if (!mIgnoreTexCoods) {
+        for (unsigned int i = 0; i < AI_MAX_NUMBER_OF_TEXTURECOORDS && pMesh->mTextureCoords[i]; ++i) {
+            if (ProcessArray(pMesh->mTextureCoords[i], pMesh->mNumVertices, "uvcoords", dirtyMask)) {
+                pMesh->mNumUVComponents[i] = 0;
+
+                // delete all subsequent texture coordinate sets.
+                for (unsigned int a = i + 1; a < AI_MAX_NUMBER_OF_TEXTURECOORDS; ++a) {
+                    delete[] pMesh->mTextureCoords[a];
+                    pMesh->mTextureCoords[a] = NULL;
+                    pMesh->mNumUVComponents[a] = 0;
+                }
+
+                ret = true;
+            }
+        }
+    }
+
+    // -- we don't validate vertex colors, it's difficult to say whether
+    // they are invalid or not.
+
+    // Normals and tangents are undefined for point and line faces.
+    if (pMesh->mNormals || pMesh->mTangents)    {
+
+        if (aiPrimitiveType_POINT & pMesh->mPrimitiveTypes ||
+            aiPrimitiveType_LINE  & pMesh->mPrimitiveTypes)
+        {
+            if (aiPrimitiveType_TRIANGLE & pMesh->mPrimitiveTypes ||
+                aiPrimitiveType_POLYGON  & pMesh->mPrimitiveTypes)
+            {
+                // We need to update the lookup-table
+                for (unsigned int m = 0; m < pMesh->mNumFaces;++m) {
+                    const aiFace& f = pMesh->mFaces[ m ];
+
+                    if (f.mNumIndices < 3)  {
+                        dirtyMask[f.mIndices[0]] = true;
+                        if (f.mNumIndices == 2) {
+                            dirtyMask[f.mIndices[1]] = true;
+                        }
+                    }
+                }
+            }
+            // Normals, tangents and bitangents are undefined for
+            // the whole mesh (and should not even be there)
+            else {
+                return ret;
+            }
+        }
+
+        // Process mesh normals
+        if (pMesh->mNormals && ProcessArray(pMesh->mNormals,pMesh->mNumVertices,
+            "normals",dirtyMask,true,false))
+            ret = true;
+
+        // Process mesh tangents
+        if (pMesh->mTangents && ProcessArray(pMesh->mTangents,pMesh->mNumVertices,"tangents",dirtyMask))    {
+            delete[] pMesh->mBitangents; pMesh->mBitangents = NULL;
+            ret = true;
+        }
+
+        // Process mesh bitangents
+        if (pMesh->mBitangents && ProcessArray(pMesh->mBitangents,pMesh->mNumVertices,"bitangents",dirtyMask))  {
+            delete[] pMesh->mTangents; pMesh->mTangents = NULL;
+            ret = true;
+        }
+    }
+    return ret ? 1 : 0;
+}
+
+#endif // !! ASSIMP_BUILD_NO_FINDINVALIDDATA_PROCESS
diff --git a/thirdparty/assimp/code/PostProcessing/FindInvalidDataProcess.h b/thirdparty/assimp/code/PostProcessing/FindInvalidDataProcess.h
new file mode 100644
index 0000000000..ce7375f34f
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/FindInvalidDataProcess.h
@@ -0,0 +1,106 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file Defines a post processing step to search an importer's output
+ *   for data that is obviously invalid
+ */
+#ifndef AI_FINDINVALIDDATA_H_INC
+#define AI_FINDINVALIDDATA_H_INC
+
+#include "Common/BaseProcess.h"
+
+#include <assimp/types.h>
+#include <assimp/anim.h>
+
+struct aiMesh;
+
+class FindInvalidDataProcessTest;
+
+namespace Assimp    {
+
+// ---------------------------------------------------------------------------
+/** The FindInvalidData post-processing step. It searches the mesh data
+ *  for parts that are obviously invalid and removes them.
+ *
+ *  Originally this was a workaround for some models written by Blender
+ *  which have zero normal vectors. */
+class ASSIMP_API FindInvalidDataProcess : public BaseProcess {
+public:
+    FindInvalidDataProcess();
+    ~FindInvalidDataProcess();
+
+    // -------------------------------------------------------------------
+    //
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    // Setup import settings
+    void SetupProperties(const Importer* pImp);
+
+    // -------------------------------------------------------------------
+    // Run the step
+    void Execute( aiScene* pScene);
+
+    // -------------------------------------------------------------------
+    /** Executes the post-processing step on the given mesh
+     * @param pMesh The mesh to process.
+     * @return 0 - nothing, 1 - removed sth, 2 - please delete me  */
+    int ProcessMesh( aiMesh* pMesh);
+
+    // -------------------------------------------------------------------
+    /** Executes the post-processing step on the given animation
+     * @param anim The animation to process.  */
+    void ProcessAnimation (aiAnimation* anim);
+
+    // -------------------------------------------------------------------
+    /** Executes the post-processing step on the given anim channel
+     * @param anim The animation channel to process.*/
+    void ProcessAnimationChannel (aiNodeAnim* anim);
+
+private:
+    ai_real configEpsilon;
+    bool mIgnoreTexCoods;
+};
+
+} // end of namespace Assimp
+
+#endif // AI_AI_FINDINVALIDDATA_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/FixNormalsStep.cpp b/thirdparty/assimp/code/PostProcessing/FixNormalsStep.cpp
new file mode 100644
index 0000000000..bbbe6899b4
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/FixNormalsStep.cpp
@@ -0,0 +1,184 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file Implementation of the post processing step to invert
+ * all normals in meshes with infacing normals.
+ */
+
+// internal headers
+#include "FixNormalsStep.h"
+#include <assimp/StringUtils.h>
+#include <assimp/DefaultLogger.hpp>
+#include <assimp/postprocess.h>
+#include <assimp/scene.h>
+#include <stdio.h>
+
+
+using namespace Assimp;
+
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+FixInfacingNormalsProcess::FixInfacingNormalsProcess()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+FixInfacingNormalsProcess::~FixInfacingNormalsProcess()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool FixInfacingNormalsProcess::IsActive( unsigned int pFlags) const
+{
+    return (pFlags & aiProcess_FixInfacingNormals) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void FixInfacingNormalsProcess::Execute( aiScene* pScene)
+{
+    ASSIMP_LOG_DEBUG("FixInfacingNormalsProcess begin");
+
+    bool bHas( false );
+    for (unsigned int a = 0; a < pScene->mNumMeshes; ++a) {
+        if (ProcessMesh(pScene->mMeshes[a], a)) {
+            bHas = true;
+        }
+    }
+
+    if (bHas) {
+        ASSIMP_LOG_DEBUG("FixInfacingNormalsProcess finished. Found issues.");
+    } else {
+        ASSIMP_LOG_DEBUG("FixInfacingNormalsProcess finished. No changes to the scene.");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Apply the step to the mesh
+bool FixInfacingNormalsProcess::ProcessMesh( aiMesh* pcMesh, unsigned int index)
+{
+    ai_assert(nullptr != pcMesh);
+
+    // Nothing to do if there are no model normals
+    if (!pcMesh->HasNormals()) {
+        return false;
+    }
+
+    // Compute the bounding box of both the model vertices + normals and
+    // the unmodified model vertices. Then check whether the first BB
+    // is smaller than the second. In this case we can assume that the
+    // normals need to be flipped, although there are a few special cases ..
+    // convex, concave, planar models ...
+
+    aiVector3D vMin0 (1e10f,1e10f,1e10f);
+    aiVector3D vMin1 (1e10f,1e10f,1e10f);
+    aiVector3D vMax0 (-1e10f,-1e10f,-1e10f);
+    aiVector3D vMax1 (-1e10f,-1e10f,-1e10f);
+
+    for (unsigned int i = 0; i < pcMesh->mNumVertices;++i)
+    {
+        vMin1.x = std::min(vMin1.x,pcMesh->mVertices[i].x);
+        vMin1.y = std::min(vMin1.y,pcMesh->mVertices[i].y);
+        vMin1.z = std::min(vMin1.z,pcMesh->mVertices[i].z);
+
+        vMax1.x = std::max(vMax1.x,pcMesh->mVertices[i].x);
+        vMax1.y = std::max(vMax1.y,pcMesh->mVertices[i].y);
+        vMax1.z = std::max(vMax1.z,pcMesh->mVertices[i].z);
+
+        const aiVector3D vWithNormal = pcMesh->mVertices[i] + pcMesh->mNormals[i];
+
+        vMin0.x = std::min(vMin0.x,vWithNormal.x);
+        vMin0.y = std::min(vMin0.y,vWithNormal.y);
+        vMin0.z = std::min(vMin0.z,vWithNormal.z);
+
+        vMax0.x = std::max(vMax0.x,vWithNormal.x);
+        vMax0.y = std::max(vMax0.y,vWithNormal.y);
+        vMax0.z = std::max(vMax0.z,vWithNormal.z);
+    }
+
+    const float fDelta0_x = (vMax0.x - vMin0.x);
+    const float fDelta0_y = (vMax0.y - vMin0.y);
+    const float fDelta0_z = (vMax0.z - vMin0.z);
+
+    const float fDelta1_x = (vMax1.x - vMin1.x);
+    const float fDelta1_y = (vMax1.y - vMin1.y);
+    const float fDelta1_z = (vMax1.z - vMin1.z);
+
+    // Check whether the boxes are overlapping
+    if ((fDelta0_x > 0.0f) != (fDelta1_x > 0.0f))return false;
+    if ((fDelta0_y > 0.0f) != (fDelta1_y > 0.0f))return false;
+    if ((fDelta0_z > 0.0f) != (fDelta1_z > 0.0f))return false;
+
+    // Check whether this is a planar surface
+    const float fDelta1_yz = fDelta1_y * fDelta1_z;
+
+    if (fDelta1_x < 0.05f * std::sqrt( fDelta1_yz ))return false;
+    if (fDelta1_y < 0.05f * std::sqrt( fDelta1_z * fDelta1_x ))return false;
+    if (fDelta1_z < 0.05f * std::sqrt( fDelta1_y * fDelta1_x ))return false;
+
+    // now compare the volumes of the bounding boxes
+    if (std::fabs(fDelta0_x * fDelta0_y * fDelta0_z) < std::fabs(fDelta1_x * fDelta1_yz)) {
+        if (!DefaultLogger::isNullLogger()) {
+            ASSIMP_LOG_INFO_F("Mesh ", index, ": Normals are facing inwards (or the mesh is planar)", index);
+        }
+
+        // Invert normals
+        for (unsigned int i = 0; i < pcMesh->mNumVertices;++i)
+            pcMesh->mNormals[i] *= -1.0f;
+
+        // ... and flip faces
+        for (unsigned int i = 0; i < pcMesh->mNumFaces;++i)
+        {
+            aiFace& face = pcMesh->mFaces[i];
+            for( unsigned int b = 0; b < face.mNumIndices / 2; b++)
+                std::swap( face.mIndices[b], face.mIndices[ face.mNumIndices - 1 - b]);
+        }
+        return true;
+    }
+    return false;
+}
diff --git a/thirdparty/assimp/code/PostProcessing/FixNormalsStep.h b/thirdparty/assimp/code/PostProcessing/FixNormalsStep.h
new file mode 100644
index 0000000000..f60ce596a4
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/FixNormalsStep.h
@@ -0,0 +1,91 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+
+/** @file Defines a post processing step to fix infacing normals */
+#ifndef AI_FIXNORMALSPROCESS_H_INC
+#define AI_FIXNORMALSPROCESS_H_INC
+
+#include "Common/BaseProcess.h"
+
+struct aiMesh;
+
+namespace Assimp
+{
+
+// ---------------------------------------------------------------------------
+/** The FixInfacingNormalsProcess tries to determine whether the normal
+ * vectors of an object are facing inwards. In this case they will be
+ * flipped.
+ */
+class FixInfacingNormalsProcess : public BaseProcess {
+public:
+    FixInfacingNormalsProcess();
+    ~FixInfacingNormalsProcess();
+
+    // -------------------------------------------------------------------
+    /** Returns whether the processing step is present in the given flag field.
+     * @param pFlags The processing flags the importer was called with. A bitwise
+     *   combination of #aiPostProcessSteps.
+     * @return true if the process is present in this flag fields, false if not.
+    */
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    /** Executes the post processing step on the given imported data.
+    * At the moment a process is not supposed to fail.
+    * @param pScene The imported data to work at.
+    */
+    void Execute( aiScene* pScene);
+
+protected:
+
+    // -------------------------------------------------------------------
+    /** Executes the step on the given mesh
+     * @param pMesh The mesh to process.
+     */
+    bool ProcessMesh( aiMesh* pMesh, unsigned int index);
+};
+
+} // end of namespace Assimp
+
+#endif // AI_FIXNORMALSPROCESS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/GenBoundingBoxesProcess.cpp b/thirdparty/assimp/code/PostProcessing/GenBoundingBoxesProcess.cpp
new file mode 100644
index 0000000000..c013454fc3
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/GenBoundingBoxesProcess.cpp
@@ -0,0 +1,115 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+#ifndef ASSIMP_BUILD_NO_GENBOUNDINGBOXES_PROCESS
+
+#include "PostProcessing/GenBoundingBoxesProcess.h"
+
+#include <assimp/postprocess.h>
+#include <assimp/scene.h>
+
+namespace Assimp {
+
+GenBoundingBoxesProcess::GenBoundingBoxesProcess()
+: BaseProcess() {
+
+}
+
+GenBoundingBoxesProcess::~GenBoundingBoxesProcess() {
+    // empty
+}
+
+bool GenBoundingBoxesProcess::IsActive(unsigned int pFlags) const {
+    return 0 != ( pFlags & aiProcess_GenBoundingBoxes );
+}
+
+void checkMesh(aiMesh* mesh, aiVector3D& min, aiVector3D& max) {
+    ai_assert(nullptr != mesh);
+
+    if (0 == mesh->mNumVertices) {
+        return;
+    }
+
+    for (unsigned int i = 0; i < mesh->mNumVertices; ++i) {
+        const aiVector3D &pos = mesh->mVertices[i];
+        if (pos.x < min.x) {
+            min.x = pos.x;
+        }
+        if (pos.y < min.y) {
+            min.y = pos.y;
+        }
+        if (pos.z < min.z) {
+            min.z = pos.z;
+        }
+
+        if (pos.x > max.x) {
+            max.x = pos.x;
+        }
+        if (pos.y > max.y) {
+            max.y = pos.y;
+        }
+        if (pos.z > max.z) {
+            max.z = pos.z;
+        }
+    }
+}
+
+void GenBoundingBoxesProcess::Execute(aiScene* pScene) {
+    if (nullptr == pScene) {
+        return;
+    }
+
+    for (unsigned int i = 0; i < pScene->mNumMeshes; ++i) {
+        aiMesh* mesh = pScene->mMeshes[i];
+        if (nullptr == mesh) {
+            continue;
+        }
+
+        aiVector3D min(999999, 999999, 999999), max(-999999, -999999, -999999);
+        checkMesh(mesh, min, max);
+        mesh->mAABB.mMin = min;
+        mesh->mAABB.mMax = max;
+    }
+}
+
+} // Namespace Assimp
+
+#endif // ASSIMP_BUILD_NO_GENBOUNDINGBOXES_PROCESS
diff --git a/thirdparty/assimp/code/PostProcessing/GenBoundingBoxesProcess.h b/thirdparty/assimp/code/PostProcessing/GenBoundingBoxesProcess.h
new file mode 100644
index 0000000000..4b43c82a42
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/GenBoundingBoxesProcess.h
@@ -0,0 +1,76 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file Defines a post-processing step to generate Axis-aligned bounding
+ *        volumes for all meshes.
+ */
+
+#pragma once
+
+#ifndef AI_GENBOUNDINGBOXESPROCESS_H_INC
+#define AI_GENBOUNDINGBOXESPROCESS_H_INC
+
+#ifndef ASSIMP_BUILD_NO_GENBOUNDINGBOXES_PROCESS
+
+#include "Common/BaseProcess.h"
+
+namespace Assimp {
+
+/** Post-processing process to find axis-aligned bounding volumes for amm meshes
+ *  used in a scene
+ */
+class ASSIMP_API GenBoundingBoxesProcess : public BaseProcess {
+public:
+    /// The class constructor.
+    GenBoundingBoxesProcess();
+    /// The class destructor.
+    ~GenBoundingBoxesProcess();
+    /// Will return true, if aiProcess_GenBoundingBoxes is defined.
+    bool IsActive(unsigned int pFlags) const override;
+    /// The execution callback.
+    void Execute(aiScene* pScene) override;
+};
+
+} // Namespace Assimp
+
+#endif // #ifndef ASSIMP_BUILD_NO_GENBOUNDINGBOXES_PROCESS
+
+#endif // AI_GENBOUNDINGBOXESPROCESS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/GenFaceNormalsProcess.cpp b/thirdparty/assimp/code/PostProcessing/GenFaceNormalsProcess.cpp
new file mode 100644
index 0000000000..028334dec7
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/GenFaceNormalsProcess.cpp
@@ -0,0 +1,146 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file Implementation of the post processing step to generate face
+* normals for all imported faces.
+*/
+
+
+#include "GenFaceNormalsProcess.h"
+#include <assimp/postprocess.h>
+#include <assimp/scene.h>
+#include <assimp/DefaultLogger.hpp>
+#include <assimp/Exceptional.h>
+#include <assimp/qnan.h>
+
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+GenFaceNormalsProcess::GenFaceNormalsProcess()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+GenFaceNormalsProcess::~GenFaceNormalsProcess()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool GenFaceNormalsProcess::IsActive( unsigned int pFlags) const {
+    force_ = (pFlags & aiProcess_ForceGenNormals) != 0;
+    return  (pFlags & aiProcess_GenNormals) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void GenFaceNormalsProcess::Execute( aiScene* pScene) {
+    ASSIMP_LOG_DEBUG("GenFaceNormalsProcess begin");
+
+    if (pScene->mFlags & AI_SCENE_FLAGS_NON_VERBOSE_FORMAT) {
+        throw DeadlyImportError("Post-processing order mismatch: expecting pseudo-indexed (\"verbose\") vertices here");
+    }
+
+    bool bHas = false;
+    for( unsigned int a = 0; a < pScene->mNumMeshes; a++)   {
+        if(this->GenMeshFaceNormals( pScene->mMeshes[a])) {
+            bHas = true;
+        }
+    }
+    if (bHas)   {
+        ASSIMP_LOG_INFO("GenFaceNormalsProcess finished. "
+            "Face normals have been calculated");
+    } else {
+        ASSIMP_LOG_DEBUG("GenFaceNormalsProcess finished. "
+            "Normals are already there");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+bool GenFaceNormalsProcess::GenMeshFaceNormals (aiMesh* pMesh)
+{
+    if (NULL != pMesh->mNormals) {
+        if (force_) delete[] pMesh->mNormals;
+        else return false;
+    }
+
+    // If the mesh consists of lines and/or points but not of
+    // triangles or higher-order polygons the normal vectors
+    // are undefined.
+    if (!(pMesh->mPrimitiveTypes & (aiPrimitiveType_TRIANGLE | aiPrimitiveType_POLYGON)))   {
+        ASSIMP_LOG_INFO("Normal vectors are undefined for line and point meshes");
+        return false;
+    }
+
+    // allocate an array to hold the output normals
+    pMesh->mNormals = new aiVector3D[pMesh->mNumVertices];
+    const float qnan = get_qnan();
+
+    // iterate through all faces and compute per-face normals but store them per-vertex.
+    for( unsigned int a = 0; a < pMesh->mNumFaces; a++) {
+        const aiFace& face = pMesh->mFaces[a];
+        if (face.mNumIndices < 3)   {
+            // either a point or a line -> no well-defined normal vector
+            for (unsigned int i = 0;i < face.mNumIndices;++i) {
+                pMesh->mNormals[face.mIndices[i]] = aiVector3D(qnan);
+            }
+            continue;
+        }
+
+        const aiVector3D* pV1 = &pMesh->mVertices[face.mIndices[0]];
+        const aiVector3D* pV2 = &pMesh->mVertices[face.mIndices[1]];
+        const aiVector3D* pV3 = &pMesh->mVertices[face.mIndices[face.mNumIndices-1]];
+        const aiVector3D vNor = ((*pV2 - *pV1) ^ (*pV3 - *pV1)).NormalizeSafe();
+
+        for (unsigned int i = 0;i < face.mNumIndices;++i) {
+            pMesh->mNormals[face.mIndices[i]] = vNor;
+        }
+    }
+    return true;
+}
diff --git a/thirdparty/assimp/code/PostProcessing/GenFaceNormalsProcess.h b/thirdparty/assimp/code/PostProcessing/GenFaceNormalsProcess.h
new file mode 100644
index 0000000000..c641fd6353
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/GenFaceNormalsProcess.h
@@ -0,0 +1,87 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file Defines a post processing step to compute face normals for all loaded faces*/
+#ifndef AI_GENFACENORMALPROCESS_H_INC
+#define AI_GENFACENORMALPROCESS_H_INC
+
+#include "Common/BaseProcess.h"
+#include <assimp/mesh.h>
+
+namespace Assimp
+{
+
+// ---------------------------------------------------------------------------
+/** The GenFaceNormalsProcess computes face normals for all faces of all meshes
+*/
+class ASSIMP_API_WINONLY GenFaceNormalsProcess : public BaseProcess
+{
+public:
+
+    GenFaceNormalsProcess();
+    ~GenFaceNormalsProcess();
+
+public:
+    // -------------------------------------------------------------------
+    /** Returns whether the processing step is present in the given flag field.
+    * @param pFlags The processing flags the importer was called with. A bitwise
+    *   combination of #aiPostProcessSteps.
+    * @return true if the process is present in this flag fields, false if not.
+    */
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    /** Executes the post processing step on the given imported data.
+    * At the moment a process is not supposed to fail.
+    * @param pScene The imported data to work at.
+    */
+    void Execute( aiScene* pScene);
+
+
+private:
+    bool GenMeshFaceNormals(aiMesh* pcMesh);
+    mutable bool force_ = false;
+};
+
+} // end of namespace Assimp
+
+#endif // !!AI_GENFACENORMALPROCESS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/GenVertexNormalsProcess.cpp b/thirdparty/assimp/code/PostProcessing/GenVertexNormalsProcess.cpp
new file mode 100644
index 0000000000..3f6c2f86bd
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/GenVertexNormalsProcess.cpp
@@ -0,0 +1,239 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file Implementation of the post processing step to generate face
+* normals for all imported faces.
+*/
+
+
+
+// internal headers
+#include "GenVertexNormalsProcess.h"
+#include "ProcessHelper.h"
+#include <assimp/Exceptional.h>
+#include <assimp/qnan.h>
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+GenVertexNormalsProcess::GenVertexNormalsProcess()
+: configMaxAngle( AI_DEG_TO_RAD( 175.f ) ) {
+    // empty
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+GenVertexNormalsProcess::~GenVertexNormalsProcess() {
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool GenVertexNormalsProcess::IsActive( unsigned int pFlags) const
+{
+    force_ = (pFlags & aiProcess_ForceGenNormals) != 0;
+    return (pFlags & aiProcess_GenSmoothNormals) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void GenVertexNormalsProcess::SetupProperties(const Importer* pImp)
+{
+    // Get the current value of the AI_CONFIG_PP_GSN_MAX_SMOOTHING_ANGLE property
+    configMaxAngle = pImp->GetPropertyFloat(AI_CONFIG_PP_GSN_MAX_SMOOTHING_ANGLE,(ai_real)175.0);
+    configMaxAngle = AI_DEG_TO_RAD(std::max(std::min(configMaxAngle,(ai_real)175.0),(ai_real)0.0));
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void GenVertexNormalsProcess::Execute( aiScene* pScene)
+{
+    ASSIMP_LOG_DEBUG("GenVertexNormalsProcess begin");
+
+    if (pScene->mFlags & AI_SCENE_FLAGS_NON_VERBOSE_FORMAT) {
+        throw DeadlyImportError("Post-processing order mismatch: expecting pseudo-indexed (\"verbose\") vertices here");
+    }
+
+    bool bHas = false;
+    for( unsigned int a = 0; a < pScene->mNumMeshes; ++a) {
+        if(GenMeshVertexNormals( pScene->mMeshes[a],a))
+            bHas = true;
+    }
+
+    if (bHas)   {
+        ASSIMP_LOG_INFO("GenVertexNormalsProcess finished. "
+            "Vertex normals have been calculated");
+    } else {
+        ASSIMP_LOG_DEBUG("GenVertexNormalsProcess finished. "
+            "Normals are already there");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+bool GenVertexNormalsProcess::GenMeshVertexNormals (aiMesh* pMesh, unsigned int meshIndex)
+{
+    if (NULL != pMesh->mNormals) {
+        if (force_) delete[] pMesh->mNormals;
+        else return false;
+    }
+
+    // If the mesh consists of lines and/or points but not of
+    // triangles or higher-order polygons the normal vectors
+    // are undefined.
+    if (!(pMesh->mPrimitiveTypes & (aiPrimitiveType_TRIANGLE | aiPrimitiveType_POLYGON)))
+    {
+        ASSIMP_LOG_INFO("Normal vectors are undefined for line and point meshes");
+        return false;
+    }
+
+    // Allocate the array to hold the output normals
+    const float qnan = std::numeric_limits<ai_real>::quiet_NaN();
+    pMesh->mNormals = new aiVector3D[pMesh->mNumVertices];
+
+    // Compute per-face normals but store them per-vertex
+    for( unsigned int a = 0; a < pMesh->mNumFaces; a++)
+    {
+        const aiFace& face = pMesh->mFaces[a];
+        if (face.mNumIndices < 3)
+        {
+            // either a point or a line -> no normal vector
+            for (unsigned int i = 0;i < face.mNumIndices;++i) {
+                pMesh->mNormals[face.mIndices[i]] = aiVector3D(qnan);
+            }
+
+            continue;
+        }
+
+        const aiVector3D* pV1 = &pMesh->mVertices[face.mIndices[0]];
+        const aiVector3D* pV2 = &pMesh->mVertices[face.mIndices[1]];
+        const aiVector3D* pV3 = &pMesh->mVertices[face.mIndices[face.mNumIndices-1]];
+        const aiVector3D vNor = ((*pV2 - *pV1) ^ (*pV3 - *pV1)).NormalizeSafe();
+
+        for (unsigned int i = 0;i < face.mNumIndices;++i) {
+            pMesh->mNormals[face.mIndices[i]] = vNor;
+        }
+    }
+
+    // Set up a SpatialSort to quickly find all vertices close to a given position
+    // check whether we can reuse the SpatialSort of a previous step.
+    SpatialSort* vertexFinder = NULL;
+    SpatialSort  _vertexFinder;
+    ai_real posEpsilon = ai_real( 1e-5 );
+    if (shared) {
+        std::vector<std::pair<SpatialSort,ai_real> >* avf;
+        shared->GetProperty(AI_SPP_SPATIAL_SORT,avf);
+        if (avf)
+        {
+            std::pair<SpatialSort,ai_real>& blubb = avf->operator [] (meshIndex);
+            vertexFinder = &blubb.first;
+            posEpsilon = blubb.second;
+        }
+    }
+    if (!vertexFinder)  {
+        _vertexFinder.Fill(pMesh->mVertices, pMesh->mNumVertices, sizeof( aiVector3D));
+        vertexFinder = &_vertexFinder;
+        posEpsilon = ComputePositionEpsilon(pMesh);
+    }
+    std::vector<unsigned int> verticesFound;
+    aiVector3D* pcNew = new aiVector3D[pMesh->mNumVertices];
+
+    if (configMaxAngle >= AI_DEG_TO_RAD( 175.f ))   {
+        // There is no angle limit. Thus all vertices with positions close
+        // to each other will receive the same vertex normal. This allows us
+        // to optimize the whole algorithm a little bit ...
+        std::vector<bool> abHad(pMesh->mNumVertices,false);
+        for (unsigned int i = 0; i < pMesh->mNumVertices;++i)   {
+            if (abHad[i]) {
+                continue;
+            }
+
+            // Get all vertices that share this one ...
+            vertexFinder->FindPositions( pMesh->mVertices[i], posEpsilon, verticesFound);
+
+            aiVector3D pcNor;
+            for (unsigned int a = 0; a < verticesFound.size(); ++a) {
+                const aiVector3D& v = pMesh->mNormals[verticesFound[a]];
+                if (is_not_qnan(v.x))pcNor += v;
+            }
+            pcNor.NormalizeSafe();
+
+            // Write the smoothed normal back to all affected normals
+            for (unsigned int a = 0; a < verticesFound.size(); ++a)
+            {
+                unsigned int vidx = verticesFound[a];
+                pcNew[vidx] = pcNor;
+                abHad[vidx] = true;
+            }
+        }
+    }
+    // Slower code path if a smooth angle is set. There are many ways to achieve
+    // the effect, this one is the most straightforward one.
+    else    {
+        const ai_real fLimit = std::cos(configMaxAngle);
+        for (unsigned int i = 0; i < pMesh->mNumVertices;++i)   {
+            // Get all vertices that share this one ...
+            vertexFinder->FindPositions( pMesh->mVertices[i] , posEpsilon, verticesFound);
+
+            aiVector3D vr = pMesh->mNormals[i];
+
+            aiVector3D pcNor;
+            for (unsigned int a = 0; a < verticesFound.size(); ++a) {
+                aiVector3D v = pMesh->mNormals[verticesFound[a]];
+
+                // Check whether the angle between the two normals is not too large.
+                // Skip the angle check on our own normal to avoid false negatives
+                // (v*v is not guaranteed to be 1.0 for all unit vectors v)
+                if (is_not_qnan(v.x) && (verticesFound[a] == i || (v * vr >= fLimit)))
+                    pcNor += v;
+            }
+            pcNew[i] = pcNor.NormalizeSafe();
+        }
+    }
+
+    delete[] pMesh->mNormals;
+    pMesh->mNormals = pcNew;
+
+    return true;
+}
diff --git a/thirdparty/assimp/code/PostProcessing/GenVertexNormalsProcess.h b/thirdparty/assimp/code/PostProcessing/GenVertexNormalsProcess.h
new file mode 100644
index 0000000000..2ceee17e85
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/GenVertexNormalsProcess.h
@@ -0,0 +1,111 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file Defines a post processing step to compute vertex normals
+    for all loaded vertizes */
+#ifndef AI_GENVERTEXNORMALPROCESS_H_INC
+#define AI_GENVERTEXNORMALPROCESS_H_INC
+
+#include "Common/assbin_chunks.h"
+#include "Common/BaseProcess.h"
+
+#include <assimp/mesh.h>
+
+// Forward declarations
+class GenNormalsTest;
+
+namespace Assimp {
+
+// ---------------------------------------------------------------------------
+/** The GenFaceNormalsProcess computes vertex normals for all vertices
+*/
+class ASSIMP_API GenVertexNormalsProcess : public BaseProcess {
+public:
+    GenVertexNormalsProcess();
+    ~GenVertexNormalsProcess();
+
+    // -------------------------------------------------------------------
+    /** Returns whether the processing step is present in the given flag.
+    * @param pFlags The processing flags the importer was called with.
+    *   A bitwise combination of #aiPostProcessSteps.
+    * @return true if the process is present in this flag fields,
+    *   false if not.
+    */
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    /** Called prior to ExecuteOnScene().
+    * The function is a request to the process to update its configuration
+    * basing on the Importer's configuration property list.
+    */
+    void SetupProperties(const Importer* pImp);
+
+    // -------------------------------------------------------------------
+    /** Executes the post processing step on the given imported data.
+    * At the moment a process is not supposed to fail.
+    * @param pScene The imported data to work at.
+    */
+    void Execute( aiScene* pScene);
+
+
+    // setter for configMaxAngle
+    inline void SetMaxSmoothAngle(ai_real f) {
+        configMaxAngle =f;
+    }
+
+    // -------------------------------------------------------------------
+    /** Computes normals for a specific mesh
+    *  @param pcMesh Mesh
+    *  @param meshIndex Index of the mesh
+    *  @return true if vertex normals have been computed
+    */
+    bool GenMeshVertexNormals (aiMesh* pcMesh, unsigned int meshIndex);
+
+private:
+    /** Configuration option: maximum smoothing angle, in radians*/
+    ai_real configMaxAngle;
+    mutable bool force_ = false;
+};
+
+} // end of namespace Assimp
+
+#endif // !!AI_GENVERTEXNORMALPROCESS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/ImproveCacheLocality.cpp b/thirdparty/assimp/code/PostProcessing/ImproveCacheLocality.cpp
new file mode 100644
index 0000000000..d0a016fa42
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/ImproveCacheLocality.cpp
@@ -0,0 +1,379 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file Implementation of the post processing step to improve the cache locality of a mesh.
+ * <br>
+ * The algorithm is roughly basing on this paper:
+ * http://www.cs.princeton.edu/gfx/pubs/Sander_2007_%3ETR/tipsy.pdf
+ *   .. although overdraw reduction isn't implemented yet ...
+ */
+
+// internal headers
+#include "PostProcessing/ImproveCacheLocality.h"
+#include "Common/VertexTriangleAdjacency.h"
+
+#include <assimp/StringUtils.h>
+#include <assimp/postprocess.h>
+#include <assimp/scene.h>
+#include <assimp/DefaultLogger.hpp>
+#include <stdio.h>
+#include <stack>
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+ImproveCacheLocalityProcess::ImproveCacheLocalityProcess()
+: mConfigCacheDepth(PP_ICL_PTCACHE_SIZE) {
+    // empty
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+ImproveCacheLocalityProcess::~ImproveCacheLocalityProcess() {
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool ImproveCacheLocalityProcess::IsActive( unsigned int pFlags) const {
+    return (pFlags & aiProcess_ImproveCacheLocality) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Setup configuration
+void ImproveCacheLocalityProcess::SetupProperties(const Importer* pImp) {
+    // AI_CONFIG_PP_ICL_PTCACHE_SIZE controls the target cache size for the optimizer
+    mConfigCacheDepth = pImp->GetPropertyInteger(AI_CONFIG_PP_ICL_PTCACHE_SIZE,PP_ICL_PTCACHE_SIZE);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void ImproveCacheLocalityProcess::Execute( aiScene* pScene) {
+    if (!pScene->mNumMeshes) {
+        ASSIMP_LOG_DEBUG("ImproveCacheLocalityProcess skipped; there are no meshes");
+        return;
+    }
+
+    ASSIMP_LOG_DEBUG("ImproveCacheLocalityProcess begin");
+
+    float out = 0.f;
+    unsigned int numf = 0, numm = 0;
+    for( unsigned int a = 0; a < pScene->mNumMeshes; ++a ){
+        const float res = ProcessMesh( pScene->mMeshes[a],a);
+        if (res) {
+            numf += pScene->mMeshes[a]->mNumFaces;
+            out  += res;
+            ++numm;
+        }
+    }
+    if (!DefaultLogger::isNullLogger()) {
+        if (numf > 0) {
+            ASSIMP_LOG_INFO_F("Cache relevant are ", numm, " meshes (", numf, " faces). Average output ACMR is ", out / numf);
+        }
+        ASSIMP_LOG_DEBUG("ImproveCacheLocalityProcess finished. ");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Improves the cache coherency of a specific mesh
+ai_real ImproveCacheLocalityProcess::ProcessMesh( aiMesh* pMesh, unsigned int meshNum) {
+    // TODO: rewrite this to use std::vector or boost::shared_array
+    ai_assert(nullptr != pMesh);
+
+    // Check whether the input data is valid
+    // - there must be vertices and faces
+    // - all faces must be triangulated or we can't operate on them
+    if (!pMesh->HasFaces() || !pMesh->HasPositions())
+        return static_cast<ai_real>(0.f);
+
+    if (pMesh->mPrimitiveTypes != aiPrimitiveType_TRIANGLE) {
+        ASSIMP_LOG_ERROR("This algorithm works on triangle meshes only");
+        return static_cast<ai_real>(0.f);
+    }
+
+    if(pMesh->mNumVertices <= mConfigCacheDepth) {
+        return static_cast<ai_real>(0.f);
+    }
+
+    ai_real fACMR = 3.f;
+    const aiFace* const pcEnd = pMesh->mFaces+pMesh->mNumFaces;
+
+    // Input ACMR is for logging purposes only
+    if (!DefaultLogger::isNullLogger())     {
+
+        unsigned int* piFIFOStack = new unsigned int[mConfigCacheDepth];
+        memset(piFIFOStack,0xff,mConfigCacheDepth*sizeof(unsigned int));
+        unsigned int* piCur = piFIFOStack;
+        const unsigned int* const piCurEnd = piFIFOStack + mConfigCacheDepth;
+
+        // count the number of cache misses
+        unsigned int iCacheMisses = 0;
+        for (const aiFace* pcFace = pMesh->mFaces;pcFace != pcEnd;++pcFace) {
+            for (unsigned int qq = 0; qq < 3;++qq) {
+                bool bInCache = false;
+                for (unsigned int* pp = piFIFOStack;pp < piCurEnd;++pp) {
+                    if (*pp == pcFace->mIndices[qq])    {
+                        // the vertex is in cache
+                        bInCache = true;
+                        break;
+                    }
+                }
+                if (!bInCache)  {
+                    ++iCacheMisses;
+                    if (piCurEnd == piCur) {
+                        piCur = piFIFOStack;
+                    }
+                    *piCur++ = pcFace->mIndices[qq];
+                }
+            }
+        }
+        delete[] piFIFOStack;
+        fACMR = (ai_real) iCacheMisses / pMesh->mNumFaces;
+        if (3.0 == fACMR)   {
+            char szBuff[128]; // should be sufficiently large in every case
+
+            // the JoinIdenticalVertices process has not been executed on this
+            // mesh, otherwise this value would normally be at least minimally
+            // smaller than 3.0 ...
+            ai_snprintf(szBuff,128,"Mesh %u: Not suitable for vcache optimization",meshNum);
+            ASSIMP_LOG_WARN(szBuff);
+            return static_cast<ai_real>(0.f);
+        }
+    }
+
+    // first we need to build a vertex-triangle adjacency list
+    VertexTriangleAdjacency adj(pMesh->mFaces,pMesh->mNumFaces, pMesh->mNumVertices,true);
+
+    // build a list to store per-vertex caching time stamps
+    unsigned int* const piCachingStamps = new unsigned int[pMesh->mNumVertices];
+    memset(piCachingStamps,0x0,pMesh->mNumVertices*sizeof(unsigned int));
+
+    // allocate an empty output index buffer. We store the output indices in one large array.
+    // Since the number of triangles won't change the input faces can be reused. This is how
+    // we save thousands of redundant mini allocations for aiFace::mIndices
+    const unsigned int iIdxCnt = pMesh->mNumFaces*3;
+    unsigned int* const piIBOutput = new unsigned int[iIdxCnt];
+    unsigned int* piCSIter = piIBOutput;
+
+    // allocate the flag array to hold the information
+    // whether a face has already been emitted or not
+    std::vector<bool> abEmitted(pMesh->mNumFaces,false);
+
+    // dead-end vertex index stack
+    std::stack<unsigned int, std::vector<unsigned int> > sDeadEndVStack;
+
+    // create a copy of the piNumTriPtr buffer
+    unsigned int* const piNumTriPtr = adj.mLiveTriangles;
+    const std::vector<unsigned int> piNumTriPtrNoModify(piNumTriPtr, piNumTriPtr + pMesh->mNumVertices);
+
+    // get the largest number of referenced triangles and allocate the "candidate buffer"
+    unsigned int iMaxRefTris = 0; {
+        const unsigned int* piCur = adj.mLiveTriangles;
+        const unsigned int* const piCurEnd = adj.mLiveTriangles+pMesh->mNumVertices;
+        for (;piCur != piCurEnd;++piCur) {
+            iMaxRefTris = std::max(iMaxRefTris,*piCur);
+        }
+    }
+    ai_assert(iMaxRefTris > 0);
+    unsigned int* piCandidates = new unsigned int[iMaxRefTris*3];
+    unsigned int iCacheMisses = 0;
+
+    // ...................................................................................
+    /** PSEUDOCODE for the algorithm
+
+        A = Build-Adjacency(I) Vertex-triangle adjacency
+        L = Get-Triangle-Counts(A) Per-vertex live triangle counts
+        C = Zero(Vertex-Count(I)) Per-vertex caching time stamps
+        D = Empty-Stack() Dead-end vertex stack
+        E = False(Triangle-Count(I)) Per triangle emitted flag
+        O = Empty-Index-Buffer() Empty output buffer
+        f = 0 Arbitrary starting vertex
+        s = k+1, i = 1 Time stamp and cursor
+        while f >= 0 For all valid fanning vertices
+            N = Empty-Set() 1-ring of next candidates
+            for each Triangle t in Neighbors(A, f)
+                if !Emitted(E,t)
+                    for each Vertex v in t
+                        Append(O,v) Output vertex
+                        Push(D,v) Add to dead-end stack
+                        Insert(N,v) Register as candidate
+                        L[v] = L[v]-1 Decrease live triangle count
+                        if s-C[v] > k If not in cache
+                            C[v] = s Set time stamp
+                            s = s+1 Increment time stamp
+                    E[t] = true Flag triangle as emitted
+            Select next fanning vertex
+            f = Get-Next-Vertex(I,i,k,N,C,s,L,D)
+        return O
+        */
+    // ...................................................................................
+
+    int ivdx = 0;
+    int ics = 1;
+    int iStampCnt = mConfigCacheDepth+1;
+    while (ivdx >= 0)   {
+
+        unsigned int icnt = piNumTriPtrNoModify[ivdx];
+        unsigned int* piList = adj.GetAdjacentTriangles(ivdx);
+        unsigned int* piCurCandidate = piCandidates;
+
+        // get all triangles in the neighborhood
+        for (unsigned int tri = 0; tri < icnt;++tri)    {
+
+            // if they have not yet been emitted, add them to the output IB
+            const unsigned int fidx = *piList++;
+            if (!abEmitted[fidx])   {
+
+                // so iterate through all vertices of the current triangle
+                const aiFace* pcFace = &pMesh->mFaces[ fidx ];
+                unsigned nind = pcFace->mNumIndices;
+                for (unsigned ind = 0; ind < nind; ind++) {
+                    unsigned dp = pcFace->mIndices[ind];
+
+                    // the current vertex won't have any free triangles after this step
+                    if (ivdx != (int)dp) {
+                        // append the vertex to the dead-end stack
+                        sDeadEndVStack.push(dp);
+
+                        // register as candidate for the next step
+                        *piCurCandidate++ = dp;
+
+                        // decrease the per-vertex triangle counts
+                        piNumTriPtr[dp]--;
+                    }
+
+                    // append the vertex to the output index buffer
+                    *piCSIter++ = dp;
+
+                    // if the vertex is not yet in cache, set its cache count
+                    if (iStampCnt-piCachingStamps[dp] > mConfigCacheDepth) {
+                        piCachingStamps[dp] = iStampCnt++;
+                        ++iCacheMisses;
+                    }
+                }
+                // flag triangle as emitted
+                abEmitted[fidx] = true;
+            }
+        }
+
+        // the vertex has now no living adjacent triangles anymore
+        piNumTriPtr[ivdx] = 0;
+
+        // get next fanning vertex
+        ivdx = -1;
+        int max_priority = -1;
+        for (unsigned int* piCur = piCandidates;piCur != piCurCandidate;++piCur)    {
+            const unsigned int dp = *piCur;
+
+            // must have live triangles
+            if (piNumTriPtr[dp] > 0)    {
+                int priority = 0;
+
+                // will the vertex be in cache, even after fanning occurs?
+                unsigned int tmp;
+                if ((tmp = iStampCnt-piCachingStamps[dp]) + 2*piNumTriPtr[dp] <= mConfigCacheDepth) {
+                    priority = tmp;
+                }
+
+                // keep best candidate
+                if (priority > max_priority) {
+                    max_priority = priority;
+                    ivdx = dp;
+                }
+            }
+        }
+        // did we reach a dead end?
+        if (-1 == ivdx) {
+            // need to get a non-local vertex for which we have a good chance that it is still
+            // in the cache ...
+            while (!sDeadEndVStack.empty()) {
+                unsigned int iCachedIdx = sDeadEndVStack.top();
+                sDeadEndVStack.pop();
+                if (piNumTriPtr[ iCachedIdx ] > 0)  {
+                    ivdx = iCachedIdx;
+                    break;
+                }
+            }
+
+            if (-1 == ivdx) {
+                // well, there isn't such a vertex. Simply get the next vertex in input order and
+                // hope it is not too bad ...
+                while (ics < (int)pMesh->mNumVertices)  {
+                    ++ics;
+                    if (piNumTriPtr[ics] > 0)   {
+                        ivdx = ics;
+                        break;
+                    }
+                }
+            }
+        }
+    }
+    ai_real fACMR2 = 0.0f;
+    if (!DefaultLogger::isNullLogger()) {
+        fACMR2 = (float)iCacheMisses / pMesh->mNumFaces;
+
+        // very intense verbose logging ... prepare for much text if there are many meshes
+        if ( DefaultLogger::get()->getLogSeverity() == Logger::VERBOSE) {
+            ASSIMP_LOG_DEBUG_F("Mesh %u | ACMR in: ", meshNum, " out: ", fACMR, " | ~", fACMR2, ((fACMR - fACMR2) / fACMR) * 100.f);
+        }
+
+        fACMR2 *= pMesh->mNumFaces;
+    }
+    // sort the output index buffer back to the input array
+    piCSIter = piIBOutput;
+    for (aiFace* pcFace = pMesh->mFaces; pcFace != pcEnd;++pcFace)  {
+        unsigned nind = pcFace->mNumIndices;
+        unsigned * ind = pcFace->mIndices;
+        if (nind > 0) ind[0] = *piCSIter++;
+        if (nind > 1) ind[1] = *piCSIter++;
+        if (nind > 2) ind[2] = *piCSIter++;
+    }
+
+    // delete temporary storage
+    delete[] piCachingStamps;
+    delete[] piIBOutput;
+    delete[] piCandidates;
+
+    return fACMR2;
+}
diff --git a/thirdparty/assimp/code/PostProcessing/ImproveCacheLocality.h b/thirdparty/assimp/code/PostProcessing/ImproveCacheLocality.h
new file mode 100644
index 0000000000..de25ecd9fb
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/ImproveCacheLocality.h
@@ -0,0 +1,101 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file Defines a post processing step to reorder faces for
+ better cache locality*/
+#ifndef AI_IMPROVECACHELOCALITY_H_INC
+#define AI_IMPROVECACHELOCALITY_H_INC
+
+#include "Common/BaseProcess.h"
+
+#include <assimp/types.h>
+
+struct aiMesh;
+
+namespace Assimp
+{
+
+// ---------------------------------------------------------------------------
+/** The ImproveCacheLocalityProcess reorders all faces for improved vertex
+ *  cache locality. It tries to arrange all faces to fans and to render
+ *  faces which share vertices directly one after the other.
+ *
+ *  @note This step expects triagulated input data.
+ */
+class ImproveCacheLocalityProcess : public BaseProcess
+{
+public:
+
+    ImproveCacheLocalityProcess();
+    ~ImproveCacheLocalityProcess();
+
+public:
+
+    // -------------------------------------------------------------------
+    // Check whether the pp step is active
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    // Executes the pp step on a given scene
+    void Execute( aiScene* pScene);
+
+    // -------------------------------------------------------------------
+    // Configures the pp step
+    void SetupProperties(const Importer* pImp);
+
+protected:
+    // -------------------------------------------------------------------
+    /** Executes the postprocessing step on the given mesh
+     * @param pMesh The mesh to process.
+     * @param meshNum Index of the mesh to process
+     */
+    ai_real ProcessMesh( aiMesh* pMesh, unsigned int meshNum);
+
+private:
+    //! Configuration parameter: specifies the size of the cache to
+    //! optimize the vertex data for.
+    unsigned int mConfigCacheDepth;
+};
+
+} // end of namespace Assimp
+
+#endif // AI_IMPROVECACHELOCALITY_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/JoinVerticesProcess.cpp b/thirdparty/assimp/code/PostProcessing/JoinVerticesProcess.cpp
new file mode 100644
index 0000000000..914ec05b46
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/JoinVerticesProcess.cpp
@@ -0,0 +1,463 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file Implementation of the post processing step to join identical vertices
+ * for all imported meshes
+ */
+
+
+#ifndef ASSIMP_BUILD_NO_JOINVERTICES_PROCESS
+
+#include "JoinVerticesProcess.h"
+#include "ProcessHelper.h"
+#include <assimp/Vertex.h>
+#include <assimp/TinyFormatter.h>
+#include <stdio.h>
+#include <unordered_set>
+
+using namespace Assimp;
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+JoinVerticesProcess::JoinVerticesProcess()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+JoinVerticesProcess::~JoinVerticesProcess()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool JoinVerticesProcess::IsActive( unsigned int pFlags) const
+{
+    return (pFlags & aiProcess_JoinIdenticalVertices) != 0;
+}
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void JoinVerticesProcess::Execute( aiScene* pScene)
+{
+    ASSIMP_LOG_DEBUG("JoinVerticesProcess begin");
+
+    // get the total number of vertices BEFORE the step is executed
+    int iNumOldVertices = 0;
+    if (!DefaultLogger::isNullLogger()) {
+        for( unsigned int a = 0; a < pScene->mNumMeshes; a++)   {
+            iNumOldVertices +=  pScene->mMeshes[a]->mNumVertices;
+        }
+    }
+
+    // execute the step
+    int iNumVertices = 0;
+    for( unsigned int a = 0; a < pScene->mNumMeshes; a++)
+        iNumVertices += ProcessMesh( pScene->mMeshes[a],a);
+
+    // if logging is active, print detailed statistics
+    if (!DefaultLogger::isNullLogger()) {
+        if (iNumOldVertices == iNumVertices) {
+            ASSIMP_LOG_DEBUG("JoinVerticesProcess finished ");
+        } else {
+            ASSIMP_LOG_INFO_F("JoinVerticesProcess finished | Verts in: ", iNumOldVertices,
+                " out: ", iNumVertices, " | ~",
+                ((iNumOldVertices - iNumVertices) / (float)iNumOldVertices) * 100.f );
+        }
+    }
+
+    pScene->mFlags |= AI_SCENE_FLAGS_NON_VERBOSE_FORMAT;
+}
+
+namespace {
+
+bool areVerticesEqual(const Vertex &lhs, const Vertex &rhs, bool complex)
+{
+    // A little helper to find locally close vertices faster.
+    // Try to reuse the lookup table from the last step.
+    const static float epsilon = 1e-5f;
+    // Squared because we check against squared length of the vector difference
+    static const float squareEpsilon = epsilon * epsilon;
+
+    // Square compare is useful for animeshes vertices compare
+    if ((lhs.position - rhs.position).SquareLength() > squareEpsilon) {
+        return false;
+    }
+
+    // We just test the other attributes even if they're not present in the mesh.
+    // In this case they're initialized to 0 so the comparison succeeds.
+    // By this method the non-present attributes are effectively ignored in the comparison.
+    if ((lhs.normal - rhs.normal).SquareLength() > squareEpsilon) {
+        return false;
+    }
+
+    if ((lhs.texcoords[0] - rhs.texcoords[0]).SquareLength() > squareEpsilon) {
+        return false;
+    }
+
+    if ((lhs.tangent - rhs.tangent).SquareLength() > squareEpsilon) {
+        return false;
+    }
+
+    if ((lhs.bitangent - rhs.bitangent).SquareLength() > squareEpsilon) {
+        return false;
+    }
+
+    // Usually we won't have vertex colors or multiple UVs, so we can skip from here
+    // Actually this increases runtime performance slightly, at least if branch
+    // prediction is on our side.
+    if (complex) {
+        for (int i = 0; i < 8; i++) {
+            if (i > 0 && (lhs.texcoords[i] - rhs.texcoords[i]).SquareLength() > squareEpsilon) {
+                return false;
+            }
+            if (GetColorDifference(lhs.colors[i], rhs.colors[i]) > squareEpsilon) {
+                return false;
+            }
+        }
+    }
+    return true;
+}
+
+template<class XMesh>
+void updateXMeshVertices(XMesh *pMesh, std::vector<Vertex> &uniqueVertices) {
+    // replace vertex data with the unique data sets
+    pMesh->mNumVertices = (unsigned int)uniqueVertices.size();
+
+    // ----------------------------------------------------------------------------
+    // NOTE - we're *not* calling Vertex::SortBack() because it would check for
+    // presence of every single vertex component once PER VERTEX. And our CPU
+    // dislikes branches, even if they're easily predictable.
+    // ----------------------------------------------------------------------------
+
+    // Position, if present (check made for aiAnimMesh)
+    if (pMesh->mVertices)
+    {
+        delete [] pMesh->mVertices;
+        pMesh->mVertices = new aiVector3D[pMesh->mNumVertices];
+        for (unsigned int a = 0; a < pMesh->mNumVertices; a++) {
+            pMesh->mVertices[a] = uniqueVertices[a].position;
+        }
+    }
+
+    // Normals, if present
+    if (pMesh->mNormals)
+    {
+        delete [] pMesh->mNormals;
+        pMesh->mNormals = new aiVector3D[pMesh->mNumVertices];
+        for( unsigned int a = 0; a < pMesh->mNumVertices; a++) {
+            pMesh->mNormals[a] = uniqueVertices[a].normal;
+        }
+    }
+    // Tangents, if present
+    if (pMesh->mTangents)
+    {
+        delete [] pMesh->mTangents;
+        pMesh->mTangents = new aiVector3D[pMesh->mNumVertices];
+        for (unsigned int a = 0; a < pMesh->mNumVertices; a++) {
+            pMesh->mTangents[a] = uniqueVertices[a].tangent;
+        }
+    }
+    // Bitangents as well
+    if (pMesh->mBitangents)
+    {
+        delete [] pMesh->mBitangents;
+        pMesh->mBitangents = new aiVector3D[pMesh->mNumVertices];
+        for (unsigned int a = 0; a < pMesh->mNumVertices; a++) {
+            pMesh->mBitangents[a] = uniqueVertices[a].bitangent;
+        }
+    }
+    // Vertex colors
+    for (unsigned int a = 0; pMesh->HasVertexColors(a); a++)
+    {
+        delete [] pMesh->mColors[a];
+        pMesh->mColors[a] = new aiColor4D[pMesh->mNumVertices];
+        for( unsigned int b = 0; b < pMesh->mNumVertices; b++) {
+            pMesh->mColors[a][b] = uniqueVertices[b].colors[a];
+        }
+    }
+    // Texture coords
+    for (unsigned int a = 0; pMesh->HasTextureCoords(a); a++)
+    {
+        delete [] pMesh->mTextureCoords[a];
+        pMesh->mTextureCoords[a] = new aiVector3D[pMesh->mNumVertices];
+        for (unsigned int b = 0; b < pMesh->mNumVertices; b++) {
+            pMesh->mTextureCoords[a][b] = uniqueVertices[b].texcoords[a];
+        }
+    }
+}
+} // namespace
+
+// ------------------------------------------------------------------------------------------------
+// Unites identical vertices in the given mesh
+int JoinVerticesProcess::ProcessMesh( aiMesh* pMesh, unsigned int meshIndex)
+{
+    static_assert( AI_MAX_NUMBER_OF_COLOR_SETS    == 8, "AI_MAX_NUMBER_OF_COLOR_SETS    == 8");
+	static_assert( AI_MAX_NUMBER_OF_TEXTURECOORDS == 8, "AI_MAX_NUMBER_OF_TEXTURECOORDS == 8");
+
+    // Return early if we don't have any positions
+    if (!pMesh->HasPositions() || !pMesh->HasFaces()) {
+        return 0;
+    }
+
+    // We should care only about used vertices, not all of them
+    // (this can happen due to original file vertices buffer being used by
+    // multiple meshes)
+    std::unordered_set<unsigned int> usedVertexIndices;
+    usedVertexIndices.reserve(pMesh->mNumVertices);
+    for( unsigned int a = 0; a < pMesh->mNumFaces; a++)
+    {
+        aiFace& face = pMesh->mFaces[a];
+        for( unsigned int b = 0; b < face.mNumIndices; b++) {
+            usedVertexIndices.insert(face.mIndices[b]);
+        }
+    }
+
+    // We'll never have more vertices afterwards.
+    std::vector<Vertex> uniqueVertices;
+    uniqueVertices.reserve( pMesh->mNumVertices);
+
+    // For each vertex the index of the vertex it was replaced by.
+    // Since the maximal number of vertices is 2^31-1, the most significand bit can be used to mark
+    //  whether a new vertex was created for the index (true) or if it was replaced by an existing
+    //  unique vertex (false). This saves an additional std::vector<bool> and greatly enhances
+    //  branching performance.
+    static_assert(AI_MAX_VERTICES == 0x7fffffff, "AI_MAX_VERTICES == 0x7fffffff");
+    std::vector<unsigned int> replaceIndex( pMesh->mNumVertices, 0xffffffff);
+
+    // float posEpsilonSqr;
+    SpatialSort* vertexFinder = NULL;
+    SpatialSort _vertexFinder;
+
+    typedef std::pair<SpatialSort,float> SpatPair;
+    if (shared) {
+        std::vector<SpatPair >* avf;
+        shared->GetProperty(AI_SPP_SPATIAL_SORT,avf);
+        if (avf)    {
+            SpatPair& blubb = (*avf)[meshIndex];
+            vertexFinder  = &blubb.first;
+            // posEpsilonSqr = blubb.second;
+        }
+    }
+    if (!vertexFinder)  {
+        // bad, need to compute it.
+        _vertexFinder.Fill(pMesh->mVertices, pMesh->mNumVertices, sizeof( aiVector3D));
+        vertexFinder = &_vertexFinder;
+        // posEpsilonSqr = ComputePositionEpsilon(pMesh);
+    }
+
+    // Again, better waste some bytes than a realloc ...
+    std::vector<unsigned int> verticesFound;
+    verticesFound.reserve(10);
+
+    // Run an optimized code path if we don't have multiple UVs or vertex colors.
+    // This should yield false in more than 99% of all imports ...
+    const bool complex = ( pMesh->GetNumColorChannels() > 0 || pMesh->GetNumUVChannels() > 1);
+    const bool hasAnimMeshes = pMesh->mNumAnimMeshes > 0;
+
+    // We'll never have more vertices afterwards.
+    std::vector<std::vector<Vertex>> uniqueAnimatedVertices;
+    if (hasAnimMeshes) {
+        uniqueAnimatedVertices.resize(pMesh->mNumAnimMeshes);
+        for (unsigned int animMeshIndex = 0; animMeshIndex < pMesh->mNumAnimMeshes; animMeshIndex++) {
+            uniqueAnimatedVertices[animMeshIndex].reserve(pMesh->mNumVertices);
+        }
+    }
+
+    // Now check each vertex if it brings something new to the table
+    for( unsigned int a = 0; a < pMesh->mNumVertices; a++)  {
+        if (usedVertexIndices.find(a) == usedVertexIndices.end()) {
+            continue;
+        }
+
+        // collect the vertex data
+        Vertex v(pMesh,a);
+
+        // collect all vertices that are close enough to the given position
+        vertexFinder->FindIdenticalPositions( v.position, verticesFound);
+        unsigned int matchIndex = 0xffffffff;
+
+        // check all unique vertices close to the position if this vertex is already present among them
+        for( unsigned int b = 0; b < verticesFound.size(); b++) {
+            const unsigned int vidx = verticesFound[b];
+            const unsigned int uidx = replaceIndex[ vidx];
+            if( uidx & 0x80000000)
+                continue;
+
+            const Vertex& uv = uniqueVertices[ uidx];
+
+            if (!areVerticesEqual(v, uv, complex)) {
+                continue;
+            }
+
+            if (hasAnimMeshes) {
+                // If given vertex is animated, then it has to be preserver 1 to 1 (base mesh and animated mesh require same topology)
+                // NOTE: not doing this totaly breaks anim meshes as they don't have their own faces (they use pMesh->mFaces)
+                bool breaksAnimMesh = false;
+                for (unsigned int animMeshIndex = 0; animMeshIndex < pMesh->mNumAnimMeshes; animMeshIndex++) {
+                    const Vertex& animatedUV = uniqueAnimatedVertices[animMeshIndex][ uidx];
+                    Vertex aniMeshVertex(pMesh->mAnimMeshes[animMeshIndex], a);
+                    if (!areVerticesEqual(aniMeshVertex, animatedUV, complex)) {
+                        breaksAnimMesh = true;
+                        break;
+                    }
+                }
+                if (breaksAnimMesh) {
+                    continue;
+                }
+            }
+
+            // we're still here -> this vertex perfectly matches our given vertex
+            matchIndex = uidx;
+            break;
+        }
+
+        // found a replacement vertex among the uniques?
+        if( matchIndex != 0xffffffff)
+        {
+            // store where to found the matching unique vertex
+            replaceIndex[a] = matchIndex | 0x80000000;
+        }
+        else
+        {
+            // no unique vertex matches it up to now -> so add it
+            replaceIndex[a] = (unsigned int)uniqueVertices.size();
+            uniqueVertices.push_back( v);
+            if (hasAnimMeshes) {
+                for (unsigned int animMeshIndex = 0; animMeshIndex < pMesh->mNumAnimMeshes; animMeshIndex++) {
+                    Vertex aniMeshVertex(pMesh->mAnimMeshes[animMeshIndex], a);
+                    uniqueAnimatedVertices[animMeshIndex].push_back(aniMeshVertex);
+                }
+            }
+        }
+    }
+
+    if (!DefaultLogger::isNullLogger() && DefaultLogger::get()->getLogSeverity() == Logger::VERBOSE)    {
+        ASSIMP_LOG_DEBUG_F(
+            "Mesh ",meshIndex,
+            " (",
+            (pMesh->mName.length ? pMesh->mName.data : "unnamed"),
+            ") | Verts in: ",pMesh->mNumVertices,
+            " out: ",
+            uniqueVertices.size(),
+            " | ~",
+            ((pMesh->mNumVertices - uniqueVertices.size()) / (float)pMesh->mNumVertices) * 100.f,
+            "%"
+        );
+    }
+
+    updateXMeshVertices(pMesh, uniqueVertices);
+    if (hasAnimMeshes) {
+        for (unsigned int animMeshIndex = 0; animMeshIndex < pMesh->mNumAnimMeshes; animMeshIndex++) {
+            updateXMeshVertices(pMesh->mAnimMeshes[animMeshIndex], uniqueAnimatedVertices[animMeshIndex]);
+        }
+    }
+
+    // adjust the indices in all faces
+    for( unsigned int a = 0; a < pMesh->mNumFaces; a++)
+    {
+        aiFace& face = pMesh->mFaces[a];
+        for( unsigned int b = 0; b < face.mNumIndices; b++) {
+            face.mIndices[b] = replaceIndex[face.mIndices[b]] & ~0x80000000;
+        }
+    }
+
+    // adjust bone vertex weights.
+    for( int a = 0; a < (int)pMesh->mNumBones; a++) {
+        aiBone* bone = pMesh->mBones[a];
+        std::vector<aiVertexWeight> newWeights;
+        newWeights.reserve( bone->mNumWeights);
+
+        if ( NULL != bone->mWeights ) {
+            for ( unsigned int b = 0; b < bone->mNumWeights; b++ ) {
+                const aiVertexWeight& ow = bone->mWeights[ b ];
+                // if the vertex is a unique one, translate it
+                if ( !( replaceIndex[ ow.mVertexId ] & 0x80000000 ) ) {
+                    aiVertexWeight nw;
+                    nw.mVertexId = replaceIndex[ ow.mVertexId ];
+                    nw.mWeight = ow.mWeight;
+                    newWeights.push_back( nw );
+                }
+            }
+        } else {
+            ASSIMP_LOG_ERROR( "X-Export: aiBone shall contain weights, but pointer to them is NULL." );
+        }
+
+        if (newWeights.size() > 0) {
+            // kill the old and replace them with the translated weights
+            delete [] bone->mWeights;
+            bone->mNumWeights = (unsigned int)newWeights.size();
+
+            bone->mWeights = new aiVertexWeight[bone->mNumWeights];
+            memcpy( bone->mWeights, &newWeights[0], bone->mNumWeights * sizeof( aiVertexWeight));
+        }
+        else {
+
+            /*  NOTE:
+             *
+             *  In the algorithm above we're assuming that there are no vertices
+             *  with a different bone weight setup at the same position. That wouldn't
+             *  make sense, but it is not absolutely impossible. SkeletonMeshBuilder
+             *  for example generates such input data if two skeleton points
+             *  share the same position. Again this doesn't make sense but is
+             *  reality for some model formats (MD5 for example uses these special
+             *  nodes as attachment tags for its weapons).
+             *
+             *  Then it is possible that a bone has no weights anymore .... as a quick
+             *  workaround, we're just removing these bones. If they're animated,
+             *  model geometry might be modified but at least there's no risk of a crash.
+             */
+            delete bone;
+            --pMesh->mNumBones;
+            for (unsigned int n = a; n < pMesh->mNumBones; ++n)  {
+                pMesh->mBones[n] = pMesh->mBones[n+1];
+            }
+
+            --a;
+            ASSIMP_LOG_WARN("Removing bone -> no weights remaining");
+        }
+    }
+    return pMesh->mNumVertices;
+}
+
+#endif // !! ASSIMP_BUILD_NO_JOINVERTICES_PROCESS
diff --git a/thirdparty/assimp/code/PostProcessing/JoinVerticesProcess.h b/thirdparty/assimp/code/PostProcessing/JoinVerticesProcess.h
new file mode 100644
index 0000000000..e017ae62db
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/JoinVerticesProcess.h
@@ -0,0 +1,95 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file Defines a post processing step to join identical vertices
+    on all imported meshes.*/
+#ifndef AI_JOINVERTICESPROCESS_H_INC
+#define AI_JOINVERTICESPROCESS_H_INC
+
+#include "Common/BaseProcess.h"
+
+#include <assimp/types.h>
+
+struct aiMesh;
+
+namespace Assimp
+{
+
+// ---------------------------------------------------------------------------
+/** The JoinVerticesProcess unites identical vertices in all imported meshes.
+ * By default the importer returns meshes where each face addressed its own
+ * set of vertices even if that means that identical vertices are stored multiple
+ * times. The JoinVerticesProcess finds these identical vertices and
+ * erases all but one of the copies. This usually reduces the number of vertices
+ * in a mesh by a serious amount and is the standard form to render a mesh.
+ */
+class ASSIMP_API JoinVerticesProcess : public BaseProcess {
+public:
+    JoinVerticesProcess();
+    ~JoinVerticesProcess();
+
+    // -------------------------------------------------------------------
+    /** Returns whether the processing step is present in the given flag field.
+     * @param pFlags The processing flags the importer was called with. A bitwise
+     *   combination of #aiPostProcessSteps.
+     * @return true if the process is present in this flag fields, false if not.
+    */
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    /** Executes the post processing step on the given imported data.
+    * At the moment a process is not supposed to fail.
+    * @param pScene The imported data to work at.
+    */
+    void Execute( aiScene* pScene);
+
+    // -------------------------------------------------------------------
+    /** Unites identical vertices in the given mesh.
+     * @param pMesh The mesh to process.
+     * @param meshIndex Index of the mesh to process
+     */
+    int ProcessMesh( aiMesh* pMesh, unsigned int meshIndex);
+};
+
+} // end of namespace Assimp
+
+#endif // AI_CALCTANGENTSPROCESS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/LimitBoneWeightsProcess.cpp b/thirdparty/assimp/code/PostProcessing/LimitBoneWeightsProcess.cpp
new file mode 100644
index 0000000000..d560f19287
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/LimitBoneWeightsProcess.cpp
@@ -0,0 +1,201 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** Implementation of the LimitBoneWeightsProcess post processing step */
+
+
+#include "LimitBoneWeightsProcess.h"
+#include <assimp/StringUtils.h>
+#include <assimp/postprocess.h>
+#include <assimp/DefaultLogger.hpp>
+#include <assimp/scene.h>
+#include <stdio.h>
+
+using namespace Assimp;
+
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+LimitBoneWeightsProcess::LimitBoneWeightsProcess()
+{
+    mMaxWeights = AI_LMW_MAX_WEIGHTS;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+LimitBoneWeightsProcess::~LimitBoneWeightsProcess()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool LimitBoneWeightsProcess::IsActive( unsigned int pFlags) const
+{
+    return (pFlags & aiProcess_LimitBoneWeights) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void LimitBoneWeightsProcess::Execute( aiScene* pScene) {
+    ASSIMP_LOG_DEBUG("LimitBoneWeightsProcess begin");
+    for (unsigned int a = 0; a < pScene->mNumMeshes; ++a ) {
+        ProcessMesh(pScene->mMeshes[a]);
+    }
+
+    ASSIMP_LOG_DEBUG("LimitBoneWeightsProcess end");
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void LimitBoneWeightsProcess::SetupProperties(const Importer* pImp)
+{
+    // get the current value of the property
+    this->mMaxWeights = pImp->GetPropertyInteger(AI_CONFIG_PP_LBW_MAX_WEIGHTS,AI_LMW_MAX_WEIGHTS);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Unites identical vertices in the given mesh
+void LimitBoneWeightsProcess::ProcessMesh( aiMesh* pMesh)
+{
+    if( !pMesh->HasBones())
+        return;
+
+    // collect all bone weights per vertex
+    typedef std::vector< std::vector< Weight > > WeightsPerVertex;
+    WeightsPerVertex vertexWeights( pMesh->mNumVertices);
+
+    // collect all weights per vertex
+    for( unsigned int a = 0; a < pMesh->mNumBones; a++)
+    {
+        const aiBone* bone = pMesh->mBones[a];
+        for( unsigned int b = 0; b < bone->mNumWeights; b++)
+        {
+            const aiVertexWeight& w = bone->mWeights[b];
+            vertexWeights[w.mVertexId].push_back( Weight( a, w.mWeight));
+        }
+    }
+
+    unsigned int removed = 0, old_bones = pMesh->mNumBones;
+
+    // now cut the weight count if it exceeds the maximum
+    bool bChanged = false;
+    for( WeightsPerVertex::iterator vit = vertexWeights.begin(); vit != vertexWeights.end(); ++vit)
+    {
+        if( vit->size() <= mMaxWeights)
+            continue;
+
+        bChanged = true;
+
+        // more than the defined maximum -> first sort by weight in descending order. That's
+        // why we defined the < operator in such a weird way.
+        std::sort( vit->begin(), vit->end());
+
+        // now kill everything beyond the maximum count
+        unsigned int m = static_cast<unsigned int>(vit->size());
+        vit->erase( vit->begin() + mMaxWeights, vit->end());
+        removed += static_cast<unsigned int>(m-vit->size());
+
+        // and renormalize the weights
+        float sum = 0.0f;
+        for( std::vector<Weight>::const_iterator it = vit->begin(); it != vit->end(); ++it ) {
+            sum += it->mWeight;
+        }
+        if( 0.0f != sum ) {
+            const float invSum = 1.0f / sum;
+            for( std::vector<Weight>::iterator it = vit->begin(); it != vit->end(); ++it ) {
+                it->mWeight *= invSum;
+            }
+        }
+    }
+
+    if (bChanged)   {
+        // rebuild the vertex weight array for all bones
+        typedef std::vector< std::vector< aiVertexWeight > > WeightsPerBone;
+        WeightsPerBone boneWeights( pMesh->mNumBones);
+        for( unsigned int a = 0; a < vertexWeights.size(); a++)
+        {
+            const std::vector<Weight>& vw = vertexWeights[a];
+            for( std::vector<Weight>::const_iterator it = vw.begin(); it != vw.end(); ++it)
+                boneWeights[it->mBone].push_back( aiVertexWeight( a, it->mWeight));
+        }
+
+        // and finally copy the vertex weight list over to the mesh's bones
+        std::vector<bool> abNoNeed(pMesh->mNumBones,false);
+        bChanged = false;
+
+        for( unsigned int a = 0; a < pMesh->mNumBones; a++)
+        {
+            const std::vector<aiVertexWeight>& bw = boneWeights[a];
+            aiBone* bone = pMesh->mBones[a];
+
+            if ( bw.empty() )
+            {
+                abNoNeed[a] = bChanged = true;
+                continue;
+            }
+
+            // copy the weight list. should always be less weights than before, so we don't need a new allocation
+            ai_assert( bw.size() <= bone->mNumWeights);
+            bone->mNumWeights = static_cast<unsigned int>( bw.size() );
+            ::memcpy( bone->mWeights, &bw[0], bw.size() * sizeof( aiVertexWeight));
+        }
+
+        if (bChanged)   {
+            // the number of new bones is smaller than before, so we can reuse the old array
+            aiBone** ppcCur = pMesh->mBones;aiBone** ppcSrc = ppcCur;
+
+            for (std::vector<bool>::const_iterator iter  = abNoNeed.begin();iter != abNoNeed.end()  ;++iter)    {
+                if (*iter)  {
+                    delete *ppcSrc;
+                    --pMesh->mNumBones;
+                }
+                else *ppcCur++ = *ppcSrc;
+                ++ppcSrc;
+            }
+        }
+
+        if (!DefaultLogger::isNullLogger()) {
+            ASSIMP_LOG_INFO_F("Removed ", removed, " weights. Input bones: ", old_bones, ". Output bones: ", pMesh->mNumBones );
+        }
+    }
+}
diff --git a/thirdparty/assimp/code/PostProcessing/LimitBoneWeightsProcess.h b/thirdparty/assimp/code/PostProcessing/LimitBoneWeightsProcess.h
new file mode 100644
index 0000000000..73c2a68d53
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/LimitBoneWeightsProcess.h
@@ -0,0 +1,138 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** Defines a post processing step to limit the number of bones affecting a single vertex. */
+#ifndef AI_LIMITBONEWEIGHTSPROCESS_H_INC
+#define AI_LIMITBONEWEIGHTSPROCESS_H_INC
+
+#include "Common/BaseProcess.h"
+
+// Forward declarations
+struct aiMesh;
+
+class LimitBoneWeightsTest;
+
+namespace Assimp {
+
+// NOTE: If you change these limits, don't forget to change the
+// corresponding values in all Assimp ports
+
+// **********************************************************
+// Java: ConfigProperty.java,
+//  ConfigProperty.DEFAULT_BONE_WEIGHT_LIMIT
+// **********************************************************
+
+#if (!defined AI_LMW_MAX_WEIGHTS)
+#   define AI_LMW_MAX_WEIGHTS   0x4
+#endif // !! AI_LMW_MAX_WEIGHTS
+
+// ---------------------------------------------------------------------------
+/** This post processing step limits the number of bones affecting a vertex
+* to a certain maximum value. If a vertex is affected by more than that number
+* of bones, the bone weight with the least influence on this vertex are removed.
+* The other weights on this bone are then renormalized to assure the sum weight
+* to be 1.
+*/
+class ASSIMP_API LimitBoneWeightsProcess : public BaseProcess {
+public:
+    LimitBoneWeightsProcess();
+    ~LimitBoneWeightsProcess();
+
+    // -------------------------------------------------------------------
+    /** Returns whether the processing step is present in the given flag.
+    * @param pFlags The processing flags the importer was called with.
+    *   A bitwise combination of #aiPostProcessSteps.
+    * @return true if the process is present in this flag fields,
+    *   false if not.
+    */
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    /** Called prior to ExecuteOnScene().
+    * The function is a request to the process to update its configuration
+    * basing on the Importer's configuration property list.
+    */
+    void SetupProperties(const Importer* pImp);
+
+    // -------------------------------------------------------------------
+    /** Limits the bone weight count for all vertices in the given mesh.
+    * @param pMesh The mesh to process.
+    */
+    void ProcessMesh( aiMesh* pMesh);
+
+    // -------------------------------------------------------------------
+    /** Executes the post processing step on the given imported data.
+    * At the moment a process is not supposed to fail.
+    * @param pScene The imported data to work at.
+    */
+    void Execute( aiScene* pScene);
+
+    // -------------------------------------------------------------------
+    /** Describes a bone weight on a vertex */
+    struct Weight {
+        unsigned int mBone; ///< Index of the bone
+        float mWeight;      ///< Weight of that bone on this vertex
+        Weight() AI_NO_EXCEPT
+        : mBone(0)
+        , mWeight(0.0f) {
+            // empty
+        }
+
+        Weight( unsigned int pBone, float pWeight)
+        : mBone(pBone)
+        , mWeight(pWeight) {
+            // empty
+        }
+
+        /** Comparison operator to sort bone weights by descending weight */
+        bool operator < (const Weight& pWeight) const {
+            return mWeight > pWeight.mWeight;
+        }
+    };
+
+    /** Maximum number of bones influencing any single vertex. */
+    unsigned int mMaxWeights;
+};
+
+} // end of namespace Assimp
+
+#endif // AI_LIMITBONEWEIGHTSPROCESS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/MakeVerboseFormat.cpp b/thirdparty/assimp/code/PostProcessing/MakeVerboseFormat.cpp
new file mode 100644
index 0000000000..50ff5ed93d
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/MakeVerboseFormat.cpp
@@ -0,0 +1,226 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+/** @file Implementation of the post processing step "MakeVerboseFormat"
+*/
+
+
+#include "MakeVerboseFormat.h"
+#include <assimp/scene.h>
+#include <assimp/DefaultLogger.hpp>
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+MakeVerboseFormatProcess::MakeVerboseFormatProcess()
+{
+    // nothing to do here
+}
+// ------------------------------------------------------------------------------------------------
+MakeVerboseFormatProcess::~MakeVerboseFormatProcess()
+{
+    // nothing to do here
+}
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void MakeVerboseFormatProcess::Execute( aiScene* pScene)
+{
+    ai_assert(NULL != pScene);
+    ASSIMP_LOG_DEBUG("MakeVerboseFormatProcess begin");
+
+    bool bHas = false;
+    for( unsigned int a = 0; a < pScene->mNumMeshes; a++)
+    {
+        if( MakeVerboseFormat( pScene->mMeshes[a]))
+            bHas = true;
+    }
+    if (bHas) {
+        ASSIMP_LOG_INFO("MakeVerboseFormatProcess finished. There was much work to do ...");
+    } else {
+        ASSIMP_LOG_DEBUG("MakeVerboseFormatProcess. There was nothing to do.");
+    }
+
+    pScene->mFlags &= ~AI_SCENE_FLAGS_NON_VERBOSE_FORMAT;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+bool MakeVerboseFormatProcess::MakeVerboseFormat(aiMesh* pcMesh)
+{
+    ai_assert(NULL != pcMesh);
+
+    unsigned int iOldNumVertices = pcMesh->mNumVertices;
+    const unsigned int iNumVerts = pcMesh->mNumFaces*3;
+
+    aiVector3D* pvPositions = new aiVector3D[ iNumVerts ];
+
+    aiVector3D* pvNormals = NULL;
+    if (pcMesh->HasNormals())
+    {
+        pvNormals = new aiVector3D[iNumVerts];
+    }
+    aiVector3D* pvTangents = NULL, *pvBitangents = NULL;
+    if (pcMesh->HasTangentsAndBitangents())
+    {
+        pvTangents = new aiVector3D[iNumVerts];
+        pvBitangents = new aiVector3D[iNumVerts];
+    }
+
+    aiVector3D* apvTextureCoords[AI_MAX_NUMBER_OF_TEXTURECOORDS] = {0};
+    aiColor4D* apvColorSets[AI_MAX_NUMBER_OF_COLOR_SETS] = {0};
+
+    unsigned int p = 0;
+    while (pcMesh->HasTextureCoords(p))
+        apvTextureCoords[p++] = new aiVector3D[iNumVerts];
+
+    p = 0;
+    while (pcMesh->HasVertexColors(p))
+        apvColorSets[p++] = new aiColor4D[iNumVerts];
+
+    // allocate enough memory to hold output bones and vertex weights ...
+    std::vector<aiVertexWeight>* newWeights = new std::vector<aiVertexWeight>[pcMesh->mNumBones];
+    for (unsigned int i = 0;i < pcMesh->mNumBones;++i) {
+        newWeights[i].reserve(pcMesh->mBones[i]->mNumWeights*3);
+    }
+
+    // iterate through all faces and build a clean list
+    unsigned int iIndex = 0;
+    for (unsigned int a = 0; a< pcMesh->mNumFaces;++a)
+    {
+        aiFace* pcFace = &pcMesh->mFaces[a];
+        for (unsigned int q = 0; q < pcFace->mNumIndices;++q,++iIndex)
+        {
+            // need to build a clean list of bones, too
+            for (unsigned int i = 0;i < pcMesh->mNumBones;++i)
+            {
+                for (unsigned int a = 0;  a < pcMesh->mBones[i]->mNumWeights;a++)
+                {
+                    const aiVertexWeight& w = pcMesh->mBones[i]->mWeights[a];
+                    if(pcFace->mIndices[q] == w.mVertexId)
+                    {
+                        aiVertexWeight wNew;
+                        wNew.mVertexId = iIndex;
+                        wNew.mWeight = w.mWeight;
+                        newWeights[i].push_back(wNew);
+                    }
+                }
+            }
+
+            pvPositions[iIndex] = pcMesh->mVertices[pcFace->mIndices[q]];
+
+            if (pcMesh->HasNormals())
+            {
+                pvNormals[iIndex] = pcMesh->mNormals[pcFace->mIndices[q]];
+            }
+            if (pcMesh->HasTangentsAndBitangents())
+            {
+                pvTangents[iIndex] = pcMesh->mTangents[pcFace->mIndices[q]];
+                pvBitangents[iIndex] = pcMesh->mBitangents[pcFace->mIndices[q]];
+            }
+
+            unsigned int p = 0;
+            while (pcMesh->HasTextureCoords(p))
+            {
+                apvTextureCoords[p][iIndex] = pcMesh->mTextureCoords[p][pcFace->mIndices[q]];
+                ++p;
+            }
+            p = 0;
+            while (pcMesh->HasVertexColors(p))
+            {
+                apvColorSets[p][iIndex] = pcMesh->mColors[p][pcFace->mIndices[q]];
+                ++p;
+            }
+            pcFace->mIndices[q] = iIndex;
+        }
+    }
+
+
+
+    // build output vertex weights
+    for (unsigned int i = 0;i < pcMesh->mNumBones;++i)
+    {
+        delete [] pcMesh->mBones[i]->mWeights;
+        if (!newWeights[i].empty()) {
+            pcMesh->mBones[i]->mWeights = new aiVertexWeight[newWeights[i].size()];
+            aiVertexWeight *weightToCopy = &( newWeights[i][0] );
+            memcpy(pcMesh->mBones[i]->mWeights, weightToCopy,
+                sizeof(aiVertexWeight) * newWeights[i].size());
+        } else {
+            pcMesh->mBones[i]->mWeights = NULL;
+        }
+    }
+    delete[] newWeights;
+
+    // delete the old members
+    delete[] pcMesh->mVertices;
+    pcMesh->mVertices = pvPositions;
+
+    p = 0;
+    while (pcMesh->HasTextureCoords(p))
+    {
+        delete[] pcMesh->mTextureCoords[p];
+        pcMesh->mTextureCoords[p] = apvTextureCoords[p];
+        ++p;
+    }
+    p = 0;
+    while (pcMesh->HasVertexColors(p))
+    {
+        delete[] pcMesh->mColors[p];
+        pcMesh->mColors[p] = apvColorSets[p];
+        ++p;
+    }
+    pcMesh->mNumVertices = iNumVerts;
+
+    if (pcMesh->HasNormals())
+    {
+        delete[] pcMesh->mNormals;
+        pcMesh->mNormals = pvNormals;
+    }
+    if (pcMesh->HasTangentsAndBitangents())
+    {
+        delete[] pcMesh->mTangents;
+        pcMesh->mTangents = pvTangents;
+        delete[] pcMesh->mBitangents;
+        pcMesh->mBitangents = pvBitangents;
+    }
+    return (pcMesh->mNumVertices != iOldNumVertices);
+}
diff --git a/thirdparty/assimp/code/PostProcessing/MakeVerboseFormat.h b/thirdparty/assimp/code/PostProcessing/MakeVerboseFormat.h
new file mode 100644
index 0000000000..1adf8e2f69
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/MakeVerboseFormat.h
@@ -0,0 +1,106 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file Defines a post processing step to bring a given scene
+ into the verbose format that is expected by most postprocess steps.
+ This is the inverse of the "JoinIdenticalVertices" step. */
+#ifndef AI_MAKEVERBOSEFORMAT_H_INC
+#define AI_MAKEVERBOSEFORMAT_H_INC
+
+#include "Common/BaseProcess.h"
+
+struct aiMesh;
+
+namespace Assimp    {
+
+// ---------------------------------------------------------------------------
+/** MakeVerboseFormatProcess: Class to convert an asset to the verbose
+ *  format which is expected by most postprocess steps.
+ *
+ * This is the inverse of what the "JoinIdenticalVertices" step is doing.
+ * This step has no official flag (since it wouldn't make sense to run it
+ * during import). It is intended for applications intending to modify the
+ * returned aiScene. After this step has been executed, they can execute
+ * other postprocess steps on the data. The code might also be useful to
+ * quickly adapt code that doesn't result in a verbose representation of
+ * the scene data.
+ * The step has been added because it was required by the viewer, however
+ * it has been moved to the main library since others might find it
+ * useful, too. */
+class ASSIMP_API_WINONLY MakeVerboseFormatProcess : public BaseProcess
+{
+public:
+
+
+    MakeVerboseFormatProcess();
+    ~MakeVerboseFormatProcess();
+
+public:
+
+    // -------------------------------------------------------------------
+    /** Returns whether the processing step is present in the given flag field.
+    * @param pFlags The processing flags the importer was called with. A bitwise
+    *   combination of #aiPostProcessSteps.
+    * @return true if the process is present in this flag fields, false if not */
+    bool IsActive( unsigned int /*pFlags*/ ) const
+    {
+        // NOTE: There is no direct flag that corresponds to
+        // this postprocess step.
+        return false;
+    }
+
+    // -------------------------------------------------------------------
+    /** Executes the post processing step on the given imported data.
+    * At the moment a process is not supposed to fail.
+    * @param pScene The imported data to work at. */
+    void Execute( aiScene* pScene);
+
+
+private:
+
+    //! Apply the postprocess step to a given submesh
+    bool MakeVerboseFormat (aiMesh* pcMesh);
+};
+
+} // end of namespace Assimp
+
+#endif // !!AI_KILLNORMALPROCESS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/OptimizeGraph.cpp b/thirdparty/assimp/code/PostProcessing/OptimizeGraph.cpp
new file mode 100644
index 0000000000..5db51f58b6
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/OptimizeGraph.cpp
@@ -0,0 +1,351 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file  OptimizeGraph.cpp
+ *  @brief Implementation of the aiProcess_OptimizGraph step
+ */
+
+
+#ifndef ASSIMP_BUILD_NO_OPTIMIZEGRAPH_PROCESS
+
+#include "OptimizeGraph.h"
+#include "ProcessHelper.h"
+#include <assimp/SceneCombiner.h>
+#include <assimp/Exceptional.h>
+#include <stdio.h>
+
+using namespace Assimp;
+
+#define AI_RESERVED_NODE_NAME "$Reserved_And_Evil"
+
+/* AI_OG_USE_HASHING enables the use of hashing to speed-up std::set lookups.
+ * The unhashed variant should be faster, except for *very* large data sets
+ */
+#ifdef AI_OG_USE_HASHING
+    // Use our standard hashing function to compute the hash
+#   define AI_OG_GETKEY(str) SuperFastHash(str.data,str.length)
+#else
+    // Otherwise hope that std::string will utilize a static buffer
+    // for shorter node names. This would avoid endless heap copying.
+#   define AI_OG_GETKEY(str) std::string(str.data)
+#endif
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+OptimizeGraphProcess::OptimizeGraphProcess()
+: mScene()
+, nodes_in()
+, nodes_out()
+, count_merged() {
+    // empty
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+OptimizeGraphProcess::~OptimizeGraphProcess() {
+    // empty
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool OptimizeGraphProcess::IsActive( unsigned int pFlags) const {
+    return (0 != (pFlags & aiProcess_OptimizeGraph));
+}
+
+// ------------------------------------------------------------------------------------------------
+// Setup properties for the post-processing step
+void OptimizeGraphProcess::SetupProperties(const Importer* pImp) {
+    // Get value of AI_CONFIG_PP_OG_EXCLUDE_LIST
+    std::string tmp = pImp->GetPropertyString(AI_CONFIG_PP_OG_EXCLUDE_LIST,"");
+    AddLockedNodeList(tmp);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Collect new children
+void OptimizeGraphProcess::CollectNewChildren(aiNode* nd, std::list<aiNode*>& nodes) {
+    nodes_in += nd->mNumChildren;
+
+    // Process children
+    std::list<aiNode*> child_nodes;
+    for (unsigned int i = 0; i < nd->mNumChildren; ++i) {
+        CollectNewChildren(nd->mChildren[i],child_nodes);
+        nd->mChildren[i] = nullptr;
+    }
+
+    // Check whether we need this node; if not we can replace it by our own children (warn, danger of incest).
+    if (locked.find(AI_OG_GETKEY(nd->mName)) == locked.end() ) {
+        for (std::list<aiNode*>::iterator it = child_nodes.begin(); it != child_nodes.end();) {
+
+            if (locked.find(AI_OG_GETKEY((*it)->mName)) == locked.end()) {
+                (*it)->mTransformation = nd->mTransformation * (*it)->mTransformation;
+                nodes.push_back(*it);
+
+                it = child_nodes.erase(it);
+                continue;
+            }
+            ++it;
+        }
+
+        if (nd->mNumMeshes || !child_nodes.empty()) {
+            nodes.push_back(nd);
+        } else {
+            delete nd; /* bye, node */
+            return;
+        }
+    } else {
+
+        // Retain our current position in the hierarchy
+        nodes.push_back(nd);
+
+        // Now check for possible optimizations in our list of child nodes. join as many as possible
+        aiNode* join_master = NULL;
+        aiMatrix4x4 inv;
+
+        const LockedSetType::const_iterator end = locked.end();
+
+        std::list<aiNode*> join;
+        for (std::list<aiNode*>::iterator it = child_nodes.begin(); it != child_nodes.end();)   {
+            aiNode* child = *it;
+            if (child->mNumChildren == 0 && locked.find(AI_OG_GETKEY(child->mName)) == end) {
+
+                // There may be no instanced meshes
+                unsigned int n = 0;
+                for (; n < child->mNumMeshes;++n) {
+                    if (meshes[child->mMeshes[n]] > 1) {
+                        break;
+                    }
+                }
+                if (n == child->mNumMeshes) {
+                    if (!join_master) {
+                        join_master = child;
+                        inv = join_master->mTransformation;
+                        inv.Inverse();
+                    } else {
+                        child->mTransformation = inv * child->mTransformation ;
+
+                        join.push_back(child);
+                        it = child_nodes.erase(it);
+                        continue;
+                    }
+                }
+            }
+            ++it;
+        }
+        if (join_master && !join.empty()) {
+            join_master->mName.length = ::ai_snprintf(join_master->mName.data, MAXLEN, "$MergedNode_%i",count_merged++);
+
+            unsigned int out_meshes = 0;
+            for (std::list<aiNode*>::iterator it = join.begin(); it != join.end(); ++it) {
+                out_meshes += (*it)->mNumMeshes;
+            }
+
+            // copy all mesh references in one array
+            if (out_meshes) {
+                unsigned int* meshes = new unsigned int[out_meshes+join_master->mNumMeshes], *tmp = meshes;
+                for (unsigned int n = 0; n < join_master->mNumMeshes;++n) {
+                    *tmp++ = join_master->mMeshes[n];
+                }
+
+                for (std::list<aiNode*>::iterator it = join.begin(); it != join.end(); ++it) {
+                    for (unsigned int n = 0; n < (*it)->mNumMeshes; ++n) {
+
+                        *tmp = (*it)->mMeshes[n];
+                        aiMesh* mesh = mScene->mMeshes[*tmp++];
+
+                        // manually move the mesh into the right coordinate system
+                        const aiMatrix3x3 IT = aiMatrix3x3( (*it)->mTransformation ).Inverse().Transpose();
+                        for (unsigned int a = 0; a < mesh->mNumVertices; ++a) {
+
+                            mesh->mVertices[a] *= (*it)->mTransformation;
+
+                            if (mesh->HasNormals())
+                                mesh->mNormals[a] *= IT;
+
+                            if (mesh->HasTangentsAndBitangents()) {
+                                mesh->mTangents[a] *= IT;
+                                mesh->mBitangents[a] *= IT;
+                            }
+                        }
+                    }
+                    delete *it; // bye, node
+                }
+                delete[] join_master->mMeshes;
+                join_master->mMeshes = meshes;
+                join_master->mNumMeshes += out_meshes;
+            }
+        }
+    }
+    // reassign children if something changed
+    if (child_nodes.empty() || child_nodes.size() > nd->mNumChildren) {
+
+        delete[] nd->mChildren;
+
+        if (!child_nodes.empty()) {
+            nd->mChildren = new aiNode*[child_nodes.size()];
+        }
+        else nd->mChildren = nullptr;
+    }
+
+    nd->mNumChildren = static_cast<unsigned int>(child_nodes.size());
+
+    if (nd->mChildren) {
+        aiNode** tmp = nd->mChildren;
+        for (std::list<aiNode*>::iterator it = child_nodes.begin(); it != child_nodes.end(); ++it) {
+            aiNode* node = *tmp++ = *it;
+            node->mParent = nd;
+        }
+    }
+
+    nodes_out += static_cast<unsigned int>(child_nodes.size());
+}
+
+// ------------------------------------------------------------------------------------------------
+// Execute the post-processing step on the given scene
+void OptimizeGraphProcess::Execute( aiScene* pScene) {
+    ASSIMP_LOG_DEBUG("OptimizeGraphProcess begin");
+    nodes_in = nodes_out = count_merged = 0;
+    mScene = pScene;
+
+    meshes.resize(pScene->mNumMeshes,0);
+    FindInstancedMeshes(pScene->mRootNode);
+
+    // build a blacklist of identifiers. If the name of a node matches one of these, we won't touch it
+    locked.clear();
+    for (std::list<std::string>::const_iterator it = locked_nodes.begin(); it != locked_nodes.end(); ++it) {
+#ifdef AI_OG_USE_HASHING
+        locked.insert(SuperFastHash((*it).c_str()));
+#else
+        locked.insert(*it);
+#endif
+    }
+
+    for (unsigned int i = 0; i < pScene->mNumAnimations; ++i) {
+        for (unsigned int a = 0; a < pScene->mAnimations[i]->mNumChannels; ++a) {
+            aiNodeAnim* anim = pScene->mAnimations[i]->mChannels[a];
+            locked.insert(AI_OG_GETKEY(anim->mNodeName));
+        }
+    }
+
+    for (unsigned int i = 0; i < pScene->mNumMeshes; ++i) {
+        for (unsigned int a = 0; a < pScene->mMeshes[i]->mNumBones; ++a) {
+
+            aiBone* bone = pScene->mMeshes[i]->mBones[a];
+            locked.insert(AI_OG_GETKEY(bone->mName));
+
+            // HACK: Meshes referencing bones may not be transformed; we need to look them.
+            // The easiest way to do this is to increase their reference counters ...
+            meshes[i] += 2;
+        }
+    }
+
+    for (unsigned int i = 0; i < pScene->mNumCameras; ++i) {
+        aiCamera* cam = pScene->mCameras[i];
+        locked.insert(AI_OG_GETKEY(cam->mName));
+    }
+
+    for (unsigned int i = 0; i < pScene->mNumLights; ++i) {
+        aiLight* lgh = pScene->mLights[i];
+        locked.insert(AI_OG_GETKEY(lgh->mName));
+    }
+
+    // Insert a dummy master node and make it read-only
+    aiNode* dummy_root = new aiNode(AI_RESERVED_NODE_NAME);
+    locked.insert(AI_OG_GETKEY(dummy_root->mName));
+
+    const aiString prev = pScene->mRootNode->mName;
+    pScene->mRootNode->mParent = dummy_root;
+
+    dummy_root->mChildren = new aiNode*[dummy_root->mNumChildren = 1];
+    dummy_root->mChildren[0] = pScene->mRootNode;
+
+    // Do our recursive processing of scenegraph nodes. For each node collect
+    // a fully new list of children and allow their children to place themselves
+    // on the same hierarchy layer as their parents.
+    std::list<aiNode*> nodes;
+    CollectNewChildren (dummy_root,nodes);
+
+    ai_assert(nodes.size() == 1);
+
+    if (dummy_root->mNumChildren == 0) {
+        pScene->mRootNode = NULL;
+        throw DeadlyImportError("After optimizing the scene graph, no data remains");
+    }
+
+    if (dummy_root->mNumChildren > 1) {
+        pScene->mRootNode = dummy_root;
+
+        // Keep the dummy node but assign the name of the old root node to it
+        pScene->mRootNode->mName = prev;
+    }
+    else {
+
+        // Remove the dummy root node again.
+        pScene->mRootNode = dummy_root->mChildren[0];
+
+        dummy_root->mChildren[0] = NULL;
+        delete dummy_root;
+    }
+
+    pScene->mRootNode->mParent = NULL;
+    if (!DefaultLogger::isNullLogger()) {
+        if ( nodes_in != nodes_out) {
+            ASSIMP_LOG_INFO_F("OptimizeGraphProcess finished; Input nodes: ", nodes_in, ", Output nodes: ", nodes_out);
+        } else {
+            ASSIMP_LOG_DEBUG("OptimizeGraphProcess finished");
+        }
+    }
+    meshes.clear();
+    locked.clear();
+}
+
+// ------------------------------------------------------------------------------------------------
+// Build a LUT of all instanced meshes
+void OptimizeGraphProcess::FindInstancedMeshes (aiNode* pNode)
+{
+    for (unsigned int i = 0; i < pNode->mNumMeshes;++i) {
+        ++meshes[pNode->mMeshes[i]];
+    }
+
+    for (unsigned int i = 0; i < pNode->mNumChildren; ++i)
+        FindInstancedMeshes(pNode->mChildren[i]);
+}
+
+#endif // !! ASSIMP_BUILD_NO_OPTIMIZEGRAPH_PROCESS
diff --git a/thirdparty/assimp/code/PostProcessing/OptimizeGraph.h b/thirdparty/assimp/code/PostProcessing/OptimizeGraph.h
new file mode 100644
index 0000000000..82cc5db3fe
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/OptimizeGraph.h
@@ -0,0 +1,140 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file  OptimizeGraph.h
+ *  @brief Declares a post processing step to optimize the scenegraph
+ */
+#ifndef AI_OPTIMIZEGRAPHPROCESS_H_INC
+#define AI_OPTIMIZEGRAPHPROCESS_H_INC
+
+#include "Common/BaseProcess.h"
+#include "PostProcessing/ProcessHelper.h"
+
+#include <assimp/types.h>
+
+#include <set>
+
+// Forward declarations
+struct aiMesh;
+
+class OptimizeGraphProcessTest;
+
+namespace Assimp    {
+
+// -----------------------------------------------------------------------------
+/** @brief Postprocessing step to optimize the scenegraph
+ *
+ *  The implementation tries to merge nodes, even if they use different
+ *  transformations. Animations are preserved.
+ *
+ *  @see aiProcess_OptimizeGraph for a detailed description of the
+ *  algorithm being applied.
+ */
+class OptimizeGraphProcess : public BaseProcess {
+public:
+    OptimizeGraphProcess();
+    ~OptimizeGraphProcess();
+
+    // -------------------------------------------------------------------
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    void Execute( aiScene* pScene);
+
+    // -------------------------------------------------------------------
+    void SetupProperties(const Importer* pImp);
+
+    // -------------------------------------------------------------------
+    /** @brief Add a list of node names to be locked and not modified.
+     *  @param in List of nodes. See #AI_CONFIG_PP_OG_EXCLUDE_LIST for
+     *    format explanations.
+     */
+    inline void AddLockedNodeList(std::string& in) {
+        ConvertListToStrings (in,locked_nodes);
+    }
+
+    // -------------------------------------------------------------------
+    /** @brief Add another node to be locked and not modified.
+     *  @param name Name to be locked
+     */
+    inline void AddLockedNode(std::string& name) {
+        locked_nodes.push_back(name);
+    }
+
+    // -------------------------------------------------------------------
+    /** @brief Remove a node from the list of locked nodes.
+     *  @param name Name to be unlocked
+     */
+    inline void RemoveLockedNode(std::string& name) {
+        locked_nodes.remove(name);
+    }
+
+protected:
+    void CollectNewChildren(aiNode* nd, std::list<aiNode*>& nodes);
+    void FindInstancedMeshes (aiNode* pNode);
+
+private:
+#ifdef AI_OG_USE_HASHING
+    typedef std::set<unsigned int> LockedSetType;
+#else
+    typedef std::set<std::string> LockedSetType;
+#endif
+
+    //! Scene we're working with
+    aiScene* mScene;
+
+    //! List of locked names. Stored is the hash of the name
+    LockedSetType locked;
+
+    //! List of nodes to be locked in addition to those with animations, lights or cameras assigned.
+    std::list<std::string> locked_nodes;
+
+    //! Node counters for logging purposes
+    unsigned int nodes_in,nodes_out, count_merged;
+
+    //! Reference counters for meshes
+    std::vector<unsigned int> meshes;
+};
+
+} // end of namespace Assimp
+
+#endif // AI_OPTIMIZEGRAPHPROCESS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/OptimizeMeshes.cpp b/thirdparty/assimp/code/PostProcessing/OptimizeMeshes.cpp
new file mode 100644
index 0000000000..3f6765f6ca
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/OptimizeMeshes.cpp
@@ -0,0 +1,256 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file  OptimizeMeshes.cpp
+ *  @brief Implementation of the aiProcess_OptimizeMeshes step
+ */
+
+
+#ifndef ASSIMP_BUILD_NO_OPTIMIZEMESHES_PROCESS
+
+
+#include "OptimizeMeshes.h"
+#include "ProcessHelper.h"
+#include <assimp/SceneCombiner.h>
+#include <assimp/Exceptional.h>
+
+using namespace Assimp;
+
+static const unsigned int NotSet   = 0xffffffff;
+static const unsigned int DeadBeef = 0xdeadbeef;
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+OptimizeMeshesProcess::OptimizeMeshesProcess()
+    : mScene()
+    , pts(false)
+    , max_verts( NotSet )
+    , max_faces( NotSet ) {
+    // empty
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+OptimizeMeshesProcess::~OptimizeMeshesProcess() {
+    // empty
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool OptimizeMeshesProcess::IsActive( unsigned int pFlags) const
+{
+    // Our behaviour needs to be different if the SortByPType or SplitLargeMeshes
+    // steps are active. Thus we need to query their flags here and store the
+    // information, although we're breaking const-correctness.
+    // That's a serious design flaw, consider redesign.
+    if( 0 != (pFlags & aiProcess_OptimizeMeshes) ) {
+        pts = (0 != (pFlags & aiProcess_SortByPType));
+        max_verts = ( 0 != ( pFlags & aiProcess_SplitLargeMeshes ) ) ? DeadBeef : max_verts;
+        return true;
+    }
+    return false;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Setup properties for the post-processing step
+void OptimizeMeshesProcess::SetupProperties(const Importer* pImp)
+{
+    if( max_verts == DeadBeef /* magic hack */ ) {
+        max_faces = pImp->GetPropertyInteger(AI_CONFIG_PP_SLM_TRIANGLE_LIMIT,AI_SLM_DEFAULT_MAX_TRIANGLES);
+        max_verts = pImp->GetPropertyInteger(AI_CONFIG_PP_SLM_VERTEX_LIMIT,AI_SLM_DEFAULT_MAX_VERTICES);
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Execute step
+void OptimizeMeshesProcess::Execute( aiScene* pScene)
+{
+    const unsigned int num_old = pScene->mNumMeshes;
+    if (num_old <= 1) {
+        ASSIMP_LOG_DEBUG("Skipping OptimizeMeshesProcess");
+        return;
+    }
+
+    ASSIMP_LOG_DEBUG("OptimizeMeshesProcess begin");
+    mScene = pScene;
+
+    // need to clear persistent members from previous runs
+    merge_list.resize( 0 );
+    output.resize( 0 );
+
+    // ensure we have the right sizes
+    merge_list.reserve(pScene->mNumMeshes);
+    output.reserve(pScene->mNumMeshes);
+
+    // Prepare lookup tables
+    meshes.resize(pScene->mNumMeshes);
+    FindInstancedMeshes(pScene->mRootNode);
+    if( max_verts == DeadBeef ) /* undo the magic hack */
+        max_verts = NotSet;
+
+    // ... instanced meshes are immediately processed and added to the output list
+    for (unsigned int i = 0, n = 0; i < pScene->mNumMeshes;++i) {
+        meshes[i].vertex_format = GetMeshVFormatUnique(pScene->mMeshes[i]);
+
+        if (meshes[i].instance_cnt > 1 && meshes[i].output_id == NotSet ) {
+            meshes[i].output_id = n++;
+            output.push_back(mScene->mMeshes[i]);
+        }
+    }
+
+    // and process all nodes in the scenegraph recursively
+    ProcessNode(pScene->mRootNode);
+    if (!output.size()) {
+        throw DeadlyImportError("OptimizeMeshes: No meshes remaining; there's definitely something wrong");
+    }
+
+    meshes.resize( 0 );
+    ai_assert(output.size() <= num_old);
+
+    mScene->mNumMeshes = static_cast<unsigned int>(output.size());
+    std::copy(output.begin(),output.end(),mScene->mMeshes);
+
+    if (output.size() != num_old) {
+        ASSIMP_LOG_DEBUG_F("OptimizeMeshesProcess finished. Input meshes: ", num_old, ", Output meshes: ", pScene->mNumMeshes);
+    } else {
+        ASSIMP_LOG_DEBUG( "OptimizeMeshesProcess finished" );
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Process meshes for a single node
+void OptimizeMeshesProcess::ProcessNode( aiNode* pNode)
+{
+    for (unsigned int i = 0; i < pNode->mNumMeshes;++i) {
+        unsigned int& im = pNode->mMeshes[i];
+
+        if (meshes[im].instance_cnt > 1) {
+            im = meshes[im].output_id;
+        }
+        else  {
+            merge_list.resize( 0 );
+            unsigned int verts = 0, faces = 0;
+
+            // Find meshes to merge with us
+            for (unsigned int a = i+1; a < pNode->mNumMeshes;++a) {
+                unsigned int am = pNode->mMeshes[a];
+                if (meshes[am].instance_cnt == 1 && CanJoin(im,am,verts,faces)) {
+
+                    merge_list.push_back(mScene->mMeshes[am]);
+                    verts += mScene->mMeshes[am]->mNumVertices;
+                    faces += mScene->mMeshes[am]->mNumFaces;
+
+                    pNode->mMeshes[a] = pNode->mMeshes[pNode->mNumMeshes - 1];
+                    --pNode->mNumMeshes;
+                    --a;
+                }
+            }
+
+            // and merge all meshes which we found, replace the old ones
+            if (!merge_list.empty()) {
+                merge_list.push_back(mScene->mMeshes[im]);
+
+                aiMesh* out;
+                SceneCombiner::MergeMeshes(&out,0,merge_list.begin(),merge_list.end());
+                output.push_back(out);
+            } else {
+                output.push_back(mScene->mMeshes[im]);
+            }
+            im = static_cast<unsigned int>(output.size()-1);
+        }
+    }
+
+
+    for( unsigned int i = 0; i < pNode->mNumChildren; ++i ) {
+        ProcessNode( pNode->mChildren[ i ] );
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Check whether two meshes can be joined
+bool OptimizeMeshesProcess::CanJoin ( unsigned int a, unsigned int b, unsigned int verts, unsigned int faces )
+{
+    if (meshes[a].vertex_format != meshes[b].vertex_format)
+        return false;
+
+    aiMesh* ma = mScene->mMeshes[a], *mb = mScene->mMeshes[b];
+
+    if ((NotSet != max_verts && verts+mb->mNumVertices > max_verts) ||
+        (NotSet != max_faces && faces+mb->mNumFaces    > max_faces)) {
+        return false;
+    }
+
+    // Never merge unskinned meshes with skinned meshes
+    if (ma->mMaterialIndex != mb->mMaterialIndex || ma->HasBones() != mb->HasBones())
+        return false;
+
+    // Never merge meshes with different kinds of primitives if SortByPType did already
+    // do its work. We would destroy everything again ...
+    if (pts && ma->mPrimitiveTypes != mb->mPrimitiveTypes)
+        return false;
+
+    // If both meshes are skinned, check whether we have many bones defined in both meshes.
+    // If yes, we can join them.
+    if (ma->HasBones()) {
+        // TODO
+        return false;
+    }
+    return true;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Build a LUT of all instanced meshes
+void OptimizeMeshesProcess::FindInstancedMeshes (aiNode* pNode)
+{
+    for( unsigned int i = 0; i < pNode->mNumMeshes; ++i ) {
+        ++meshes[ pNode->mMeshes[ i ] ].instance_cnt;
+    }
+
+    for( unsigned int i = 0; i < pNode->mNumChildren; ++i ) {
+        FindInstancedMeshes( pNode->mChildren[ i ] );
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+
+#endif // !! ASSIMP_BUILD_NO_OPTIMIZEMESHES_PROCESS
diff --git a/thirdparty/assimp/code/PostProcessing/OptimizeMeshes.h b/thirdparty/assimp/code/PostProcessing/OptimizeMeshes.h
new file mode 100644
index 0000000000..dec4ab52de
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/OptimizeMeshes.h
@@ -0,0 +1,186 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file  OptimizeMeshes.h
+ *  @brief Declares a post processing step to join meshes, if possible
+ */
+#ifndef AI_OPTIMIZEMESHESPROCESS_H_INC
+#define AI_OPTIMIZEMESHESPROCESS_H_INC
+
+#include "Common/BaseProcess.h"
+
+#include <assimp/types.h>
+
+#include <vector>
+
+struct aiMesh;
+struct aiNode;
+class OptimizeMeshesProcessTest;
+
+namespace Assimp    {
+
+// ---------------------------------------------------------------------------
+/** @brief Postprocessing step to optimize mesh usage
+ *
+ *  The implementation looks for meshes that could be joined and joins them.
+ *  Usually this will reduce the number of drawcalls.
+ *
+ *  @note Instanced meshes are currently not processed.
+ */
+class OptimizeMeshesProcess : public BaseProcess {
+public:
+    /// @brief  The class constructor.
+    OptimizeMeshesProcess();
+
+    /// @brief  The class destructor.
+    ~OptimizeMeshesProcess();
+
+    /** @brief Internal utility to store additional mesh info
+     */
+    struct MeshInfo {
+        MeshInfo() AI_NO_EXCEPT
+        : instance_cnt(0)
+        , vertex_format(0)
+        , output_id(0xffffffff) {
+            // empty
+        }
+
+        //! Number of times this mesh is referenced
+        unsigned int instance_cnt;
+
+        //! Vertex format id
+        unsigned int vertex_format;
+
+        //! Output ID
+        unsigned int output_id;
+    };
+
+public:
+    // -------------------------------------------------------------------
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    void Execute( aiScene* pScene);
+
+    // -------------------------------------------------------------------
+    void SetupProperties(const Importer* pImp);
+
+
+    // -------------------------------------------------------------------
+    /** @brief Specify whether you want meshes with different
+     *   primitive types to be merged as well.
+     *
+     *  IsActive() sets this property automatically to true if the
+     *  aiProcess_SortByPType flag is found.
+     */
+    void EnablePrimitiveTypeSorting(bool enable) {
+        pts = enable;
+    }
+
+    // Getter
+    bool IsPrimitiveTypeSortingEnabled () const {
+        return pts;
+    }
+
+
+    // -------------------------------------------------------------------
+    /** @brief Specify a maximum size of a single output mesh.
+     *
+     *  If a single input mesh already exceeds this limit, it won't
+     *  be split.
+     *  @param verts Maximum number of vertices per mesh
+     *  @param faces Maximum number of faces per mesh
+     */
+    void SetPreferredMeshSizeLimit (unsigned int verts, unsigned int faces)
+    {
+        max_verts = verts;
+        max_faces = faces;
+    }
+
+
+protected:
+
+    // -------------------------------------------------------------------
+    /** @brief Do the actual optimization on all meshes of this node
+     *  @param pNode Node we're working with
+     */
+    void ProcessNode( aiNode* pNode);
+
+    // -------------------------------------------------------------------
+    /** @brief Returns true if b can be joined with a
+     *
+     *  @param verts Number of output verts up to now
+     *  @param faces Number of output faces up to now
+     */
+    bool CanJoin ( unsigned int a, unsigned int b,
+        unsigned int verts, unsigned int faces );
+
+    // -------------------------------------------------------------------
+    /** @brief Find instanced meshes, for the moment we're excluding
+     *   them from all optimizations
+     */
+    void FindInstancedMeshes (aiNode* pNode);
+
+private:
+
+    //! Scene we're working with
+    aiScene* mScene;
+
+    //! Per mesh info
+    std::vector<MeshInfo> meshes;
+
+    //! Output meshes
+    std::vector<aiMesh*> output;
+
+    //! @see EnablePrimitiveTypeSorting
+    mutable bool pts;
+
+    //! @see SetPreferredMeshSizeLimit
+    mutable unsigned int max_verts,max_faces;
+
+    //! Temporary storage
+    std::vector<aiMesh*> merge_list;
+};
+
+} // end of namespace Assimp
+
+#endif // AI_CALCTANGENTSPROCESS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/PretransformVertices.cpp b/thirdparty/assimp/code/PostProcessing/PretransformVertices.cpp
new file mode 100644
index 0000000000..52001a0578
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/PretransformVertices.cpp
@@ -0,0 +1,728 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file PretransformVertices.cpp
+ *  @brief Implementation of the "PretransformVertices" post processing step
+*/
+
+
+#include "PretransformVertices.h"
+#include "ProcessHelper.h"
+#include <assimp/SceneCombiner.h>
+#include <assimp/Exceptional.h>
+
+using namespace Assimp;
+
+// some array offsets
+#define AI_PTVS_VERTEX 0x0
+#define AI_PTVS_FACE 0x1
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+PretransformVertices::PretransformVertices()
+: configKeepHierarchy (false)
+, configNormalize(false)
+, configTransform(false)
+, configTransformation()
+, mConfigPointCloud( false ) {
+    // empty
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+PretransformVertices::~PretransformVertices() {
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool PretransformVertices::IsActive( unsigned int pFlags) const
+{
+    return  (pFlags & aiProcess_PreTransformVertices) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Setup import configuration
+void PretransformVertices::SetupProperties(const Importer* pImp)
+{
+    // Get the current value of AI_CONFIG_PP_PTV_KEEP_HIERARCHY, AI_CONFIG_PP_PTV_NORMALIZE,
+    // AI_CONFIG_PP_PTV_ADD_ROOT_TRANSFORMATION and AI_CONFIG_PP_PTV_ROOT_TRANSFORMATION
+    configKeepHierarchy = (0 != pImp->GetPropertyInteger(AI_CONFIG_PP_PTV_KEEP_HIERARCHY,0));
+    configNormalize = (0 != pImp->GetPropertyInteger(AI_CONFIG_PP_PTV_NORMALIZE,0));
+    configTransform = (0 != pImp->GetPropertyInteger(AI_CONFIG_PP_PTV_ADD_ROOT_TRANSFORMATION,0));
+
+    configTransformation = pImp->GetPropertyMatrix(AI_CONFIG_PP_PTV_ROOT_TRANSFORMATION, aiMatrix4x4());
+
+    mConfigPointCloud = pImp->GetPropertyBool(AI_CONFIG_EXPORT_POINT_CLOUDS);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Count the number of nodes
+unsigned int PretransformVertices::CountNodes( aiNode* pcNode )
+{
+    unsigned int iRet = 1;
+    for (unsigned int i = 0;i < pcNode->mNumChildren;++i)
+    {
+        iRet += CountNodes(pcNode->mChildren[i]);
+    }
+    return iRet;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Get a bitwise combination identifying the vertex format of a mesh
+unsigned int PretransformVertices::GetMeshVFormat( aiMesh* pcMesh )
+{
+    // the vertex format is stored in aiMesh::mBones for later retrieval.
+    // there isn't a good reason to compute it a few hundred times
+    // from scratch. The pointer is unused as animations are lost
+    // during PretransformVertices.
+    if (pcMesh->mBones)
+        return (unsigned int)(uint64_t)pcMesh->mBones;
+
+
+    const unsigned int iRet = GetMeshVFormatUnique(pcMesh);
+
+    // store the value for later use
+    pcMesh->mBones = (aiBone**)(uint64_t)iRet;
+    return iRet;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Count the number of vertices in the whole scene and a given
+// material index
+void PretransformVertices::CountVerticesAndFaces( aiScene* pcScene, aiNode* pcNode, unsigned int iMat,
+    unsigned int iVFormat, unsigned int* piFaces, unsigned int* piVertices)
+{
+    for (unsigned int i = 0; i < pcNode->mNumMeshes;++i)
+    {
+        aiMesh* pcMesh = pcScene->mMeshes[ pcNode->mMeshes[i] ];
+        if (iMat == pcMesh->mMaterialIndex && iVFormat == GetMeshVFormat(pcMesh))
+        {
+            *piVertices += pcMesh->mNumVertices;
+            *piFaces += pcMesh->mNumFaces;
+        }
+    }
+    for (unsigned int i = 0;i < pcNode->mNumChildren;++i)
+    {
+        CountVerticesAndFaces(pcScene,pcNode->mChildren[i],iMat,
+            iVFormat,piFaces,piVertices);
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Collect vertex/face data
+void PretransformVertices::CollectData( aiScene* pcScene, aiNode* pcNode, unsigned int iMat,
+    unsigned int iVFormat, aiMesh* pcMeshOut,
+    unsigned int aiCurrent[2], unsigned int* num_refs)
+{
+    // No need to multiply if there's no transformation
+    const bool identity = pcNode->mTransformation.IsIdentity();
+    for (unsigned int i = 0; i < pcNode->mNumMeshes;++i)
+    {
+        aiMesh* pcMesh = pcScene->mMeshes[ pcNode->mMeshes[i] ];
+        if (iMat == pcMesh->mMaterialIndex && iVFormat == GetMeshVFormat(pcMesh))
+        {
+            // Decrement mesh reference counter
+            unsigned int& num_ref = num_refs[pcNode->mMeshes[i]];
+            ai_assert(0 != num_ref);
+            --num_ref;
+            // Save the name of the last mesh
+            if (num_ref==0)
+            {
+                pcMeshOut->mName = pcMesh->mName;
+            }
+
+            if (identity)   {
+                // copy positions without modifying them
+                ::memcpy(pcMeshOut->mVertices + aiCurrent[AI_PTVS_VERTEX],
+                    pcMesh->mVertices,
+                    pcMesh->mNumVertices * sizeof(aiVector3D));
+
+                if (iVFormat & 0x2) {
+                    // copy normals without modifying them
+                    ::memcpy(pcMeshOut->mNormals + aiCurrent[AI_PTVS_VERTEX],
+                        pcMesh->mNormals,
+                        pcMesh->mNumVertices * sizeof(aiVector3D));
+                }
+                if (iVFormat & 0x4)
+                {
+                    // copy tangents without modifying them
+                    ::memcpy(pcMeshOut->mTangents + aiCurrent[AI_PTVS_VERTEX],
+                        pcMesh->mTangents,
+                        pcMesh->mNumVertices * sizeof(aiVector3D));
+                    // copy bitangents without modifying them
+                    ::memcpy(pcMeshOut->mBitangents + aiCurrent[AI_PTVS_VERTEX],
+                        pcMesh->mBitangents,
+                        pcMesh->mNumVertices * sizeof(aiVector3D));
+                }
+            }
+            else
+            {
+                // copy positions, transform them to worldspace
+                for (unsigned int n = 0; n < pcMesh->mNumVertices;++n)  {
+                    pcMeshOut->mVertices[aiCurrent[AI_PTVS_VERTEX]+n] = pcNode->mTransformation * pcMesh->mVertices[n];
+                }
+                aiMatrix4x4 mWorldIT = pcNode->mTransformation;
+                mWorldIT.Inverse().Transpose();
+
+                // TODO: implement Inverse() for aiMatrix3x3
+                aiMatrix3x3 m = aiMatrix3x3(mWorldIT);
+
+                if (iVFormat & 0x2)
+                {
+                    // copy normals, transform them to worldspace
+                    for (unsigned int n = 0; n < pcMesh->mNumVertices;++n)  {
+                        pcMeshOut->mNormals[aiCurrent[AI_PTVS_VERTEX]+n] =
+                            (m * pcMesh->mNormals[n]).Normalize();
+                    }
+                }
+                if (iVFormat & 0x4)
+                {
+                    // copy tangents and bitangents, transform them to worldspace
+                    for (unsigned int n = 0; n < pcMesh->mNumVertices;++n)  {
+                        pcMeshOut->mTangents  [aiCurrent[AI_PTVS_VERTEX]+n] = (m * pcMesh->mTangents[n]).Normalize();
+                        pcMeshOut->mBitangents[aiCurrent[AI_PTVS_VERTEX]+n] = (m * pcMesh->mBitangents[n]).Normalize();
+                    }
+                }
+            }
+            unsigned int p = 0;
+            while (iVFormat & (0x100 << p))
+            {
+                // copy texture coordinates
+                memcpy(pcMeshOut->mTextureCoords[p] + aiCurrent[AI_PTVS_VERTEX],
+                    pcMesh->mTextureCoords[p],
+                    pcMesh->mNumVertices * sizeof(aiVector3D));
+                ++p;
+            }
+            p = 0;
+            while (iVFormat & (0x1000000 << p))
+            {
+                // copy vertex colors
+                memcpy(pcMeshOut->mColors[p] + aiCurrent[AI_PTVS_VERTEX],
+                    pcMesh->mColors[p],
+                    pcMesh->mNumVertices * sizeof(aiColor4D));
+                ++p;
+            }
+            // now we need to copy all faces. since we will delete the source mesh afterwards,
+            // we don't need to reallocate the array of indices except if this mesh is
+            // referenced multiple times.
+            for (unsigned int planck = 0;planck < pcMesh->mNumFaces;++planck)
+            {
+                aiFace& f_src = pcMesh->mFaces[planck];
+                aiFace& f_dst = pcMeshOut->mFaces[aiCurrent[AI_PTVS_FACE]+planck];
+
+                const unsigned int num_idx = f_src.mNumIndices;
+
+                f_dst.mNumIndices = num_idx;
+
+                unsigned int* pi;
+                if (!num_ref) { /* if last time the mesh is referenced -> no reallocation */
+                    pi = f_dst.mIndices = f_src.mIndices;
+
+                    // offset all vertex indices
+                    for (unsigned int hahn = 0; hahn < num_idx;++hahn){
+                        pi[hahn] += aiCurrent[AI_PTVS_VERTEX];
+                    }
+                }
+                else {
+                    pi = f_dst.mIndices = new unsigned int[num_idx];
+
+                    // copy and offset all vertex indices
+                    for (unsigned int hahn = 0; hahn < num_idx;++hahn){
+                        pi[hahn] = f_src.mIndices[hahn] + aiCurrent[AI_PTVS_VERTEX];
+                    }
+                }
+
+                // Update the mPrimitiveTypes member of the mesh
+                switch (pcMesh->mFaces[planck].mNumIndices)
+                {
+                case 0x1:
+                    pcMeshOut->mPrimitiveTypes |= aiPrimitiveType_POINT;
+                    break;
+                case 0x2:
+                    pcMeshOut->mPrimitiveTypes |= aiPrimitiveType_LINE;
+                    break;
+                case 0x3:
+                    pcMeshOut->mPrimitiveTypes |= aiPrimitiveType_TRIANGLE;
+                    break;
+                default:
+                    pcMeshOut->mPrimitiveTypes |= aiPrimitiveType_POLYGON;
+                    break;
+                };
+            }
+            aiCurrent[AI_PTVS_VERTEX] += pcMesh->mNumVertices;
+            aiCurrent[AI_PTVS_FACE]   += pcMesh->mNumFaces;
+        }
+    }
+
+    // append all children of us
+    for (unsigned int i = 0;i < pcNode->mNumChildren;++i) {
+        CollectData(pcScene,pcNode->mChildren[i],iMat,
+            iVFormat,pcMeshOut,aiCurrent,num_refs);
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Get a list of all vertex formats that occur for a given material index
+// The output list contains duplicate elements
+void PretransformVertices::GetVFormatList( aiScene* pcScene, unsigned int iMat,
+    std::list<unsigned int>& aiOut)
+{
+    for (unsigned int i = 0; i < pcScene->mNumMeshes;++i)
+    {
+        aiMesh* pcMesh = pcScene->mMeshes[ i ];
+        if (iMat == pcMesh->mMaterialIndex) {
+            aiOut.push_back(GetMeshVFormat(pcMesh));
+        }
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Compute the absolute transformation matrices of each node
+void PretransformVertices::ComputeAbsoluteTransform( aiNode* pcNode )
+{
+    if (pcNode->mParent)    {
+        pcNode->mTransformation = pcNode->mParent->mTransformation*pcNode->mTransformation;
+    }
+
+    for (unsigned int i = 0;i < pcNode->mNumChildren;++i)   {
+        ComputeAbsoluteTransform(pcNode->mChildren[i]);
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Apply the node transformation to a mesh
+void PretransformVertices::ApplyTransform(aiMesh* mesh, const aiMatrix4x4& mat)
+{
+    // Check whether we need to transform the coordinates at all
+    if (!mat.IsIdentity()) {
+
+        if (mesh->HasPositions()) {
+            for (unsigned int i = 0; i < mesh->mNumVertices; ++i) {
+                mesh->mVertices[i] = mat * mesh->mVertices[i];
+            }
+        }
+        if (mesh->HasNormals() || mesh->HasTangentsAndBitangents()) {
+            aiMatrix4x4 mWorldIT = mat;
+            mWorldIT.Inverse().Transpose();
+
+            // TODO: implement Inverse() for aiMatrix3x3
+            aiMatrix3x3 m = aiMatrix3x3(mWorldIT);
+
+            if (mesh->HasNormals()) {
+                for (unsigned int i = 0; i < mesh->mNumVertices; ++i) {
+                    mesh->mNormals[i] = (m * mesh->mNormals[i]).Normalize();
+                }
+            }
+            if (mesh->HasTangentsAndBitangents()) {
+                for (unsigned int i = 0; i < mesh->mNumVertices; ++i) {
+                    mesh->mTangents[i]   = (m * mesh->mTangents[i]).Normalize();
+                    mesh->mBitangents[i] = (m * mesh->mBitangents[i]).Normalize();
+                }
+            }
+        }
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Simple routine to build meshes in worldspace, no further optimization
+void PretransformVertices::BuildWCSMeshes(std::vector<aiMesh*>& out, aiMesh** in,
+    unsigned int numIn, aiNode* node)
+{
+    // NOTE:
+    //  aiMesh::mNumBones store original source mesh, or UINT_MAX if not a copy
+    //  aiMesh::mBones store reference to abs. transform we multiplied with
+
+    // process meshes
+    for (unsigned int i = 0; i < node->mNumMeshes;++i) {
+        aiMesh* mesh = in[node->mMeshes[i]];
+
+        // check whether we can operate on this mesh
+        if (!mesh->mBones || *reinterpret_cast<aiMatrix4x4*>(mesh->mBones) == node->mTransformation) {
+            // yes, we can.
+            mesh->mBones = reinterpret_cast<aiBone**> (&node->mTransformation);
+            mesh->mNumBones = UINT_MAX;
+        }
+        else {
+
+            // try to find us in the list of newly created meshes
+            for (unsigned int n = 0; n < out.size(); ++n) {
+                aiMesh* ctz = out[n];
+                if (ctz->mNumBones == node->mMeshes[i] && *reinterpret_cast<aiMatrix4x4*>(ctz->mBones) ==  node->mTransformation) {
+
+                    // ok, use this one. Update node mesh index
+                    node->mMeshes[i] = numIn + n;
+                }
+            }
+            if (node->mMeshes[i] < numIn) {
+                // Worst case. Need to operate on a full copy of the mesh
+                ASSIMP_LOG_INFO("PretransformVertices: Copying mesh due to mismatching transforms");
+                aiMesh* ntz;
+
+                const unsigned int tmp = mesh->mNumBones; //
+                mesh->mNumBones = 0;
+                SceneCombiner::Copy(&ntz,mesh);
+                mesh->mNumBones = tmp;
+
+                ntz->mNumBones = node->mMeshes[i];
+                ntz->mBones = reinterpret_cast<aiBone**> (&node->mTransformation);
+
+                out.push_back(ntz);
+
+                node->mMeshes[i] = static_cast<unsigned int>(numIn + out.size() - 1);
+            }
+        }
+    }
+
+    // call children
+    for (unsigned int i = 0; i < node->mNumChildren;++i)
+        BuildWCSMeshes(out,in,numIn,node->mChildren[i]);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Reset transformation matrices to identity
+void PretransformVertices::MakeIdentityTransform(aiNode* nd)
+{
+    nd->mTransformation = aiMatrix4x4();
+
+    // call children
+    for (unsigned int i = 0; i < nd->mNumChildren;++i)
+        MakeIdentityTransform(nd->mChildren[i]);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Build reference counters for all meshes
+void PretransformVertices::BuildMeshRefCountArray(aiNode* nd, unsigned int * refs)
+{
+    for (unsigned int i = 0; i< nd->mNumMeshes;++i)
+        refs[nd->mMeshes[i]]++;
+
+    // call children
+    for (unsigned int i = 0; i < nd->mNumChildren;++i)
+        BuildMeshRefCountArray(nd->mChildren[i],refs);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void PretransformVertices::Execute( aiScene* pScene)
+{
+    ASSIMP_LOG_DEBUG("PretransformVerticesProcess begin");
+
+    // Return immediately if we have no meshes
+    if (!pScene->mNumMeshes)
+        return;
+
+    const unsigned int iOldMeshes = pScene->mNumMeshes;
+    const unsigned int iOldAnimationChannels = pScene->mNumAnimations;
+    const unsigned int iOldNodes = CountNodes(pScene->mRootNode);
+
+    if(configTransform) {
+        pScene->mRootNode->mTransformation = configTransformation;
+    }
+
+    // first compute absolute transformation matrices for all nodes
+    ComputeAbsoluteTransform(pScene->mRootNode);
+
+    // Delete aiMesh::mBones for all meshes. The bones are
+    // removed during this step and we need the pointer as
+    // temporary storage
+    for (unsigned int i = 0; i < pScene->mNumMeshes;++i)    {
+        aiMesh* mesh = pScene->mMeshes[i];
+
+        for (unsigned int a = 0; a < mesh->mNumBones;++a)
+            delete mesh->mBones[a];
+
+        delete[] mesh->mBones;
+        mesh->mBones = NULL;
+    }
+
+    // now build a list of output meshes
+    std::vector<aiMesh*> apcOutMeshes;
+
+    // Keep scene hierarchy? It's an easy job in this case ...
+    // we go on and transform all meshes, if one is referenced by nodes
+    // with different absolute transformations a depth copy of the mesh
+    // is required.
+    if( configKeepHierarchy ) {
+
+        // Hack: store the matrix we're transforming a mesh with in aiMesh::mBones
+        BuildWCSMeshes(apcOutMeshes,pScene->mMeshes,pScene->mNumMeshes, pScene->mRootNode);
+
+        // ... if new meshes have been generated, append them to the end of the scene
+        if (apcOutMeshes.size() > 0) {
+            aiMesh** npp = new aiMesh*[pScene->mNumMeshes + apcOutMeshes.size()];
+
+            memcpy(npp,pScene->mMeshes,sizeof(aiMesh*)*pScene->mNumMeshes);
+            memcpy(npp+pScene->mNumMeshes,&apcOutMeshes[0],sizeof(aiMesh*)*apcOutMeshes.size());
+
+            pScene->mNumMeshes  += static_cast<unsigned int>(apcOutMeshes.size());
+            delete[] pScene->mMeshes; pScene->mMeshes = npp;
+        }
+
+        // now iterate through all meshes and transform them to worldspace
+        for (unsigned int i = 0; i < pScene->mNumMeshes; ++i) {
+            ApplyTransform(pScene->mMeshes[i],*reinterpret_cast<aiMatrix4x4*>( pScene->mMeshes[i]->mBones ));
+
+            // prevent improper destruction
+            pScene->mMeshes[i]->mBones    = NULL;
+            pScene->mMeshes[i]->mNumBones = 0;
+        }
+    } else {
+        apcOutMeshes.reserve(pScene->mNumMaterials<<1u);
+        std::list<unsigned int> aiVFormats;
+
+        std::vector<unsigned int> s(pScene->mNumMeshes,0);
+        BuildMeshRefCountArray(pScene->mRootNode,&s[0]);
+
+        for (unsigned int i = 0; i < pScene->mNumMaterials;++i)     {
+            // get the list of all vertex formats for this material
+            aiVFormats.clear();
+            GetVFormatList(pScene,i,aiVFormats);
+            aiVFormats.sort();
+            aiVFormats.unique();
+            for (std::list<unsigned int>::const_iterator j =  aiVFormats.begin();j != aiVFormats.end();++j) {
+                unsigned int iVertices = 0;
+                unsigned int iFaces = 0;
+                CountVerticesAndFaces(pScene,pScene->mRootNode,i,*j,&iFaces,&iVertices);
+                if (0 != iFaces && 0 != iVertices)
+                {
+                    apcOutMeshes.push_back(new aiMesh());
+                    aiMesh* pcMesh = apcOutMeshes.back();
+                    pcMesh->mNumFaces = iFaces;
+                    pcMesh->mNumVertices = iVertices;
+                    pcMesh->mFaces = new aiFace[iFaces];
+                    pcMesh->mVertices = new aiVector3D[iVertices];
+                    pcMesh->mMaterialIndex = i;
+                    if ((*j) & 0x2)pcMesh->mNormals = new aiVector3D[iVertices];
+                    if ((*j) & 0x4)
+                    {
+                        pcMesh->mTangents    = new aiVector3D[iVertices];
+                        pcMesh->mBitangents  = new aiVector3D[iVertices];
+                    }
+                    iFaces = 0;
+                    while ((*j) & (0x100 << iFaces))
+                    {
+                        pcMesh->mTextureCoords[iFaces] = new aiVector3D[iVertices];
+                        if ((*j) & (0x10000 << iFaces))pcMesh->mNumUVComponents[iFaces] = 3;
+                        else pcMesh->mNumUVComponents[iFaces] = 2;
+                        iFaces++;
+                    }
+                    iFaces = 0;
+                    while ((*j) & (0x1000000 << iFaces))
+                        pcMesh->mColors[iFaces++] = new aiColor4D[iVertices];
+
+                    // fill the mesh ...
+                    unsigned int aiTemp[2] = {0,0};
+                    CollectData(pScene,pScene->mRootNode,i,*j,pcMesh,aiTemp,&s[0]);
+                }
+            }
+        }
+
+        // If no meshes are referenced in the node graph it is possible that we get no output meshes.
+        if (apcOutMeshes.empty()) {
+            
+            throw DeadlyImportError("No output meshes: all meshes are orphaned and are not referenced by any nodes");
+        }
+        else
+        {
+            // now delete all meshes in the scene and build a new mesh list
+            for (unsigned int i = 0; i < pScene->mNumMeshes;++i)
+            {
+                aiMesh* mesh = pScene->mMeshes[i];
+                mesh->mNumBones = 0;
+                mesh->mBones    = NULL;
+
+                // we're reusing the face index arrays. avoid destruction
+                for (unsigned int a = 0; a < mesh->mNumFaces; ++a) {
+                    mesh->mFaces[a].mNumIndices = 0;
+                    mesh->mFaces[a].mIndices = NULL;
+                }
+
+                delete mesh;
+
+                // Invalidate the contents of the old mesh array. We will most
+                // likely have less output meshes now, so the last entries of
+                // the mesh array are not overridden. We set them to NULL to
+                // make sure the developer gets notified when his application
+                // attempts to access these fields ...
+                mesh = NULL;
+            }
+
+            // It is impossible that we have more output meshes than
+            // input meshes, so we can easily reuse the old mesh array
+            pScene->mNumMeshes = (unsigned int)apcOutMeshes.size();
+            for (unsigned int i = 0; i < pScene->mNumMeshes;++i) {
+                pScene->mMeshes[i] = apcOutMeshes[i];
+            }
+        }
+    }
+
+    // remove all animations from the scene
+    for (unsigned int i = 0; i < pScene->mNumAnimations;++i)
+        delete pScene->mAnimations[i];
+    delete[] pScene->mAnimations;
+
+    pScene->mAnimations    = NULL;
+    pScene->mNumAnimations = 0;
+
+    // --- we need to keep all cameras and lights
+    for (unsigned int i = 0; i < pScene->mNumCameras;++i)
+    {
+        aiCamera* cam = pScene->mCameras[i];
+        const aiNode* nd = pScene->mRootNode->FindNode(cam->mName);
+        ai_assert(NULL != nd);
+
+        // multiply all properties of the camera with the absolute
+        // transformation of the corresponding node
+        cam->mPosition = nd->mTransformation * cam->mPosition;
+        cam->mLookAt   = aiMatrix3x3( nd->mTransformation ) * cam->mLookAt;
+        cam->mUp       = aiMatrix3x3( nd->mTransformation ) * cam->mUp;
+    }
+
+    for (unsigned int i = 0; i < pScene->mNumLights;++i)
+    {
+        aiLight* l = pScene->mLights[i];
+        const aiNode* nd = pScene->mRootNode->FindNode(l->mName);
+        ai_assert(NULL != nd);
+
+        // multiply all properties of the camera with the absolute
+        // transformation of the corresponding node
+        l->mPosition   = nd->mTransformation * l->mPosition;
+        l->mDirection  = aiMatrix3x3( nd->mTransformation ) * l->mDirection;
+        l->mUp         = aiMatrix3x3( nd->mTransformation ) * l->mUp;
+    }
+
+    if( !configKeepHierarchy ) {
+
+        // now delete all nodes in the scene and build a new
+        // flat node graph with a root node and some level 1 children
+        aiNode* newRoot = new aiNode();
+        newRoot->mName = pScene->mRootNode->mName;
+        delete pScene->mRootNode;
+        pScene->mRootNode = newRoot;
+
+        if (1 == pScene->mNumMeshes && !pScene->mNumLights && !pScene->mNumCameras)
+        {
+            pScene->mRootNode->mNumMeshes = 1;
+            pScene->mRootNode->mMeshes = new unsigned int[1];
+            pScene->mRootNode->mMeshes[0] = 0;
+        }
+        else
+        {
+            pScene->mRootNode->mNumChildren = pScene->mNumMeshes+pScene->mNumLights+pScene->mNumCameras;
+            aiNode** nodes = pScene->mRootNode->mChildren = new aiNode*[pScene->mRootNode->mNumChildren];
+
+            // generate mesh nodes
+            for (unsigned int i = 0; i < pScene->mNumMeshes;++i,++nodes)
+            {
+                aiNode* pcNode = new aiNode();
+                *nodes = pcNode;
+                pcNode->mParent = pScene->mRootNode;
+                pcNode->mName = pScene->mMeshes[i]->mName;
+
+                // setup mesh indices
+                pcNode->mNumMeshes = 1;
+                pcNode->mMeshes = new unsigned int[1];
+                pcNode->mMeshes[0] = i;
+            }
+            // generate light nodes
+            for (unsigned int i = 0; i < pScene->mNumLights;++i,++nodes)
+            {
+                aiNode* pcNode = new aiNode();
+                *nodes = pcNode;
+                pcNode->mParent = pScene->mRootNode;
+                pcNode->mName.length = ai_snprintf(pcNode->mName.data, MAXLEN, "light_%u",i);
+                pScene->mLights[i]->mName = pcNode->mName;
+            }
+            // generate camera nodes
+            for (unsigned int i = 0; i < pScene->mNumCameras;++i,++nodes)
+            {
+                aiNode* pcNode = new aiNode();
+                *nodes = pcNode;
+                pcNode->mParent = pScene->mRootNode;
+                pcNode->mName.length = ::ai_snprintf(pcNode->mName.data,MAXLEN,"cam_%u",i);
+                pScene->mCameras[i]->mName = pcNode->mName;
+            }
+        }
+    }
+    else {
+        // ... and finally set the transformation matrix of all nodes to identity
+        MakeIdentityTransform(pScene->mRootNode);
+    }
+
+    if (configNormalize) {
+        // compute the boundary of all meshes
+        aiVector3D min,max;
+        MinMaxChooser<aiVector3D> ()(min,max);
+
+        for (unsigned int a = 0; a <  pScene->mNumMeshes; ++a) {
+            aiMesh* m = pScene->mMeshes[a];
+            for (unsigned int i = 0; i < m->mNumVertices;++i) {
+                min = std::min(m->mVertices[i],min);
+                max = std::max(m->mVertices[i],max);
+            }
+        }
+
+        // find the dominant axis
+        aiVector3D d = max-min;
+        const ai_real div = std::max(d.x,std::max(d.y,d.z))*ai_real( 0.5);
+
+        d = min + d * (ai_real)0.5;
+        for (unsigned int a = 0; a <  pScene->mNumMeshes; ++a) {
+            aiMesh* m = pScene->mMeshes[a];
+            for (unsigned int i = 0; i < m->mNumVertices;++i) {
+                m->mVertices[i] = (m->mVertices[i]-d)/div;
+            }
+        }
+    }
+
+    // print statistics
+    if (!DefaultLogger::isNullLogger()) {
+        ASSIMP_LOG_DEBUG("PretransformVerticesProcess finished");
+
+        ASSIMP_LOG_INFO_F("Removed ", iOldNodes, " nodes and ", iOldAnimationChannels, " animation channels (", 
+            CountNodes(pScene->mRootNode) ," output nodes)" );
+        ASSIMP_LOG_INFO_F("Kept ", pScene->mNumLights, " lights and ", pScene->mNumCameras, " cameras." );
+        ASSIMP_LOG_INFO_F("Moved ", iOldMeshes, " meshes to WCS (number of output meshes: ", pScene->mNumMeshes, ")");
+    }
+}
diff --git a/thirdparty/assimp/code/PostProcessing/PretransformVertices.h b/thirdparty/assimp/code/PostProcessing/PretransformVertices.h
new file mode 100644
index 0000000000..b2982951e0
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/PretransformVertices.h
@@ -0,0 +1,166 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file PretransformVertices.h
+ *  @brief Defines a post processing step to pretransform all
+ *    vertices in the scenegraph
+ */
+#ifndef AI_PRETRANSFORMVERTICES_H_INC
+#define AI_PRETRANSFORMVERTICES_H_INC
+
+#include "Common/BaseProcess.h"
+
+#include <assimp/mesh.h>
+
+#include <list>
+#include <vector>
+
+// Forward declarations
+struct aiNode;
+
+class PretransformVerticesTest;
+
+namespace Assimp    {
+
+// ---------------------------------------------------------------------------
+/** The PretransformVertices pre-transforms all vertices in the node tree
+ *  and removes the whole graph. The output is a list of meshes, one for
+ *  each material.
+*/
+class ASSIMP_API PretransformVertices : public BaseProcess {
+public:
+    PretransformVertices ();
+    ~PretransformVertices ();
+
+    // -------------------------------------------------------------------
+    // Check whether step is active
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    // Execute step on a given scene
+    void Execute( aiScene* pScene);
+
+    // -------------------------------------------------------------------
+    // Setup import settings
+    void SetupProperties(const Importer* pImp);
+
+    // -------------------------------------------------------------------
+    /** @brief Toggle the 'keep hierarchy' option
+     *  @param keep    true for keep configuration.
+     */
+    void KeepHierarchy(bool keep) {
+        configKeepHierarchy = keep;
+    }
+
+    // -------------------------------------------------------------------
+    /** @brief Check whether 'keep hierarchy' is currently enabled.
+     *  @return ...
+     */
+    bool IsHierarchyKept() const {
+        return configKeepHierarchy;
+    }
+
+private:
+    // -------------------------------------------------------------------
+    // Count the number of nodes
+    unsigned int CountNodes( aiNode* pcNode );
+
+    // -------------------------------------------------------------------
+    // Get a bitwise combination identifying the vertex format of a mesh
+    unsigned int GetMeshVFormat(aiMesh* pcMesh);
+
+    // -------------------------------------------------------------------
+    // Count the number of vertices in the whole scene and a given
+    // material index
+    void CountVerticesAndFaces( aiScene* pcScene, aiNode* pcNode,
+        unsigned int iMat,
+        unsigned int iVFormat,
+        unsigned int* piFaces,
+        unsigned int* piVertices);
+
+    // -------------------------------------------------------------------
+    // Collect vertex/face data
+    void CollectData( aiScene* pcScene, aiNode* pcNode,
+        unsigned int iMat,
+        unsigned int iVFormat,
+        aiMesh* pcMeshOut,
+        unsigned int aiCurrent[2],
+        unsigned int* num_refs);
+
+    // -------------------------------------------------------------------
+    // Get a list of all vertex formats that occur for a given material
+    // The output list contains duplicate elements
+    void GetVFormatList( aiScene* pcScene, unsigned int iMat,
+        std::list<unsigned int>& aiOut);
+
+    // -------------------------------------------------------------------
+    // Compute the absolute transformation matrices of each node
+    void ComputeAbsoluteTransform( aiNode* pcNode );
+
+    // -------------------------------------------------------------------
+    // Simple routine to build meshes in worldspace, no further optimization
+    void BuildWCSMeshes(std::vector<aiMesh*>& out, aiMesh** in,
+        unsigned int numIn, aiNode* node);
+
+    // -------------------------------------------------------------------
+    // Apply the node transformation to a mesh
+    void ApplyTransform(aiMesh* mesh, const aiMatrix4x4& mat);
+
+    // -------------------------------------------------------------------
+    // Reset transformation matrices to identity
+    void MakeIdentityTransform(aiNode* nd);
+
+    // -------------------------------------------------------------------
+    // Build reference counters for all meshes
+    void BuildMeshRefCountArray(aiNode* nd, unsigned int * refs);
+
+    //! Configuration option: keep scene hierarchy as long as possible
+    bool configKeepHierarchy;
+    bool configNormalize;
+    bool configTransform;
+    aiMatrix4x4 configTransformation;
+    bool mConfigPointCloud;
+};
+
+} // end of namespace Assimp
+
+#endif // !!AI_GENFACENORMALPROCESS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/ProcessHelper.cpp b/thirdparty/assimp/code/PostProcessing/ProcessHelper.cpp
new file mode 100644
index 0000000000..59869fdff7
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/ProcessHelper.cpp
@@ -0,0 +1,443 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/// @file ProcessHelper.cpp
+/** Implement shared utility functions for postprocessing steps */
+
+
+#include "ProcessHelper.h"
+
+
+#include <limits>
+
+namespace Assimp {
+
+// -------------------------------------------------------------------------------
+void ConvertListToStrings(const std::string& in, std::list<std::string>& out)
+{
+    const char* s = in.c_str();
+    while (*s) {
+        SkipSpacesAndLineEnd(&s);
+        if (*s == '\'') {
+            const char* base = ++s;
+            while (*s != '\'') {
+                ++s;
+                if (*s == '\0') {
+                    ASSIMP_LOG_ERROR("ConvertListToString: String list is ill-formatted");
+                    return;
+                }
+            }
+            out.push_back(std::string(base,(size_t)(s-base)));
+            ++s;
+        }
+        else {
+            out.push_back(GetNextToken(s));
+        }
+    }
+}
+
+// -------------------------------------------------------------------------------
+void FindAABBTransformed (const aiMesh* mesh, aiVector3D& min, aiVector3D& max,
+    const aiMatrix4x4& m)
+{
+    min = aiVector3D ( ai_real( 10e10 ), ai_real( 10e10 ), ai_real( 10e10 ) );
+    max = aiVector3D ( ai_real( -10e10 ), ai_real( -10e10 ), ai_real( -10e10 ) );
+    for (unsigned int i = 0;i < mesh->mNumVertices;++i)
+    {
+        const aiVector3D v = m * mesh->mVertices[i];
+        min = std::min(v,min);
+        max = std::max(v,max);
+    }
+}
+
+// -------------------------------------------------------------------------------
+void FindMeshCenter (aiMesh* mesh, aiVector3D& out, aiVector3D& min, aiVector3D& max)
+{
+    ArrayBounds(mesh->mVertices,mesh->mNumVertices, min,max);
+    out = min + (max-min)*(ai_real)0.5;
+}
+
+// -------------------------------------------------------------------------------
+void FindSceneCenter (aiScene* scene, aiVector3D& out, aiVector3D& min, aiVector3D& max) {
+    if ( NULL == scene ) {
+        return;
+    }
+
+    if ( 0 == scene->mNumMeshes ) {
+        return;
+    }
+    FindMeshCenter(scene->mMeshes[0], out, min, max);
+    for (unsigned int i = 1; i < scene->mNumMeshes; ++i) {
+        aiVector3D tout, tmin, tmax;
+        FindMeshCenter(scene->mMeshes[i], tout, tmin, tmax);
+        if (min[0] > tmin[0]) min[0] = tmin[0];
+        if (min[1] > tmin[1]) min[1] = tmin[1];
+        if (min[2] > tmin[2]) min[2] = tmin[2];
+        if (max[0] < tmax[0]) max[0] = tmax[0];
+        if (max[1] < tmax[1]) max[1] = tmax[1];
+        if (max[2] < tmax[2]) max[2] = tmax[2];
+    }
+    out = min + (max-min)*(ai_real)0.5;
+}
+
+
+// -------------------------------------------------------------------------------
+void FindMeshCenterTransformed (aiMesh* mesh, aiVector3D& out, aiVector3D& min,
+    aiVector3D& max, const aiMatrix4x4& m)
+{
+    FindAABBTransformed(mesh,min,max,m);
+    out = min + (max-min)*(ai_real)0.5;
+}
+
+// -------------------------------------------------------------------------------
+void FindMeshCenter (aiMesh* mesh, aiVector3D& out)
+{
+    aiVector3D min,max;
+    FindMeshCenter(mesh,out,min,max);
+}
+
+// -------------------------------------------------------------------------------
+void FindMeshCenterTransformed (aiMesh* mesh, aiVector3D& out,
+    const aiMatrix4x4& m)
+{
+    aiVector3D min,max;
+    FindMeshCenterTransformed(mesh,out,min,max,m);
+}
+
+// -------------------------------------------------------------------------------
+ai_real ComputePositionEpsilon(const aiMesh* pMesh)
+{
+    const ai_real epsilon = ai_real( 1e-4 );
+
+    // calculate the position bounds so we have a reliable epsilon to check position differences against
+    aiVector3D minVec, maxVec;
+    ArrayBounds(pMesh->mVertices,pMesh->mNumVertices,minVec,maxVec);
+    return (maxVec - minVec).Length() * epsilon;
+}
+
+// -------------------------------------------------------------------------------
+ai_real ComputePositionEpsilon(const aiMesh* const* pMeshes, size_t num)
+{
+    ai_assert( NULL != pMeshes );
+
+    const ai_real epsilon = ai_real( 1e-4 );
+
+    // calculate the position bounds so we have a reliable epsilon to check position differences against
+    aiVector3D minVec, maxVec, mi, ma;
+    MinMaxChooser<aiVector3D>()(minVec,maxVec);
+
+    for (size_t a = 0; a < num; ++a) {
+        const aiMesh* pMesh = pMeshes[a];
+        ArrayBounds(pMesh->mVertices,pMesh->mNumVertices,mi,ma);
+
+        minVec = std::min(minVec,mi);
+        maxVec = std::max(maxVec,ma);
+    }
+    return (maxVec - minVec).Length() * epsilon;
+}
+
+
+// -------------------------------------------------------------------------------
+unsigned int GetMeshVFormatUnique(const aiMesh* pcMesh)
+{
+    ai_assert(NULL != pcMesh);
+
+    // FIX: the hash may never be 0. Otherwise a comparison against
+    // nullptr could be successful
+    unsigned int iRet = 1;
+
+    // normals
+    if (pcMesh->HasNormals())iRet |= 0x2;
+    // tangents and bitangents
+    if (pcMesh->HasTangentsAndBitangents())iRet |= 0x4;
+
+#ifdef BOOST_STATIC_ASSERT
+    BOOST_STATIC_ASSERT(8 >= AI_MAX_NUMBER_OF_COLOR_SETS);
+    BOOST_STATIC_ASSERT(8 >= AI_MAX_NUMBER_OF_TEXTURECOORDS);
+#endif
+
+    // texture coordinates
+    unsigned int p = 0;
+    while (pcMesh->HasTextureCoords(p))
+    {
+        iRet |= (0x100 << p);
+        if (3 == pcMesh->mNumUVComponents[p])
+            iRet |= (0x10000 << p);
+
+        ++p;
+    }
+    // vertex colors
+    p = 0;
+    while (pcMesh->HasVertexColors(p))iRet |= (0x1000000 << p++);
+    return iRet;
+}
+
+// -------------------------------------------------------------------------------
+VertexWeightTable* ComputeVertexBoneWeightTable(const aiMesh* pMesh)
+{
+    if (!pMesh || !pMesh->mNumVertices || !pMesh->mNumBones) {
+        return NULL;
+    }
+
+    VertexWeightTable* avPerVertexWeights = new VertexWeightTable[pMesh->mNumVertices];
+    for (unsigned int i = 0; i < pMesh->mNumBones;++i)  {
+
+        aiBone* bone = pMesh->mBones[i];
+        for (unsigned int a = 0; a < bone->mNumWeights;++a) {
+            const aiVertexWeight& weight = bone->mWeights[a];
+            avPerVertexWeights[weight.mVertexId].push_back( std::pair<unsigned int,float>(i,weight.mWeight) );
+        }
+    }
+    return avPerVertexWeights;
+}
+
+
+// -------------------------------------------------------------------------------
+const char* TextureTypeToString(aiTextureType in)
+{
+    switch (in)
+    {
+    case aiTextureType_NONE:
+        return "n/a";
+    case aiTextureType_DIFFUSE:
+        return "Diffuse";
+    case aiTextureType_SPECULAR:
+        return "Specular";
+    case aiTextureType_AMBIENT:
+        return "Ambient";
+    case aiTextureType_EMISSIVE:
+        return "Emissive";
+    case aiTextureType_OPACITY:
+        return "Opacity";
+    case aiTextureType_NORMALS:
+        return "Normals";
+    case aiTextureType_HEIGHT:
+        return "Height";
+    case aiTextureType_SHININESS:
+        return "Shininess";
+    case aiTextureType_DISPLACEMENT:
+        return "Displacement";
+    case aiTextureType_LIGHTMAP:
+        return "Lightmap";
+    case aiTextureType_REFLECTION:
+        return "Reflection";
+    case aiTextureType_UNKNOWN:
+        return "Unknown";
+    default:
+        break;
+    }
+
+    ai_assert(false);
+    return  "BUG";
+}
+
+// -------------------------------------------------------------------------------
+const char* MappingTypeToString(aiTextureMapping in)
+{
+    switch (in)
+    {
+    case aiTextureMapping_UV:
+        return "UV";
+    case aiTextureMapping_BOX:
+        return "Box";
+    case aiTextureMapping_SPHERE:
+        return "Sphere";
+    case aiTextureMapping_CYLINDER:
+        return "Cylinder";
+    case aiTextureMapping_PLANE:
+        return "Plane";
+    case aiTextureMapping_OTHER:
+        return "Other";
+    default:
+        break;
+    }
+
+    ai_assert(false);
+    return  "BUG";
+}
+
+
+// -------------------------------------------------------------------------------
+aiMesh* MakeSubmesh(const aiMesh *pMesh, const std::vector<unsigned int> &subMeshFaces, unsigned int subFlags)
+{
+    aiMesh *oMesh = new aiMesh();
+    std::vector<unsigned int> vMap(pMesh->mNumVertices,UINT_MAX);
+
+    size_t numSubVerts = 0;
+    size_t numSubFaces = subMeshFaces.size();
+
+    for(unsigned int i=0;i<numSubFaces;i++) {
+        const aiFace &f = pMesh->mFaces[subMeshFaces[i]];
+
+        for(unsigned int j=0;j<f.mNumIndices;j++)   {
+            if(vMap[f.mIndices[j]]==UINT_MAX)   {
+                vMap[f.mIndices[j]] = static_cast<unsigned int>(numSubVerts++);
+            }
+        }
+    }
+
+    oMesh->mName = pMesh->mName;
+
+    oMesh->mMaterialIndex = pMesh->mMaterialIndex;
+    oMesh->mPrimitiveTypes = pMesh->mPrimitiveTypes;
+
+    // create all the arrays for this mesh if the old mesh contained them
+
+    oMesh->mNumFaces = static_cast<unsigned int>(subMeshFaces.size());
+    oMesh->mNumVertices = static_cast<unsigned int>(numSubVerts);
+    oMesh->mVertices = new aiVector3D[numSubVerts];
+    if( pMesh->HasNormals() ) {
+        oMesh->mNormals = new aiVector3D[numSubVerts];
+    }
+
+    if( pMesh->HasTangentsAndBitangents() ) {
+        oMesh->mTangents = new aiVector3D[numSubVerts];
+        oMesh->mBitangents = new aiVector3D[numSubVerts];
+    }
+
+    for( size_t a = 0;  pMesh->HasTextureCoords(static_cast<unsigned int>(a)) ; ++a ) {
+        oMesh->mTextureCoords[a] = new aiVector3D[numSubVerts];
+        oMesh->mNumUVComponents[a] = pMesh->mNumUVComponents[a];
+    }
+
+    for( size_t a = 0; pMesh->HasVertexColors( static_cast<unsigned int>(a)); ++a )    {
+        oMesh->mColors[a] = new aiColor4D[numSubVerts];
+    }
+
+    // and copy over the data, generating faces with linear indices along the way
+    oMesh->mFaces = new aiFace[numSubFaces];
+
+    for(unsigned int a = 0; a < numSubFaces; ++a )  {
+
+        const aiFace& srcFace = pMesh->mFaces[subMeshFaces[a]];
+        aiFace& dstFace = oMesh->mFaces[a];
+        dstFace.mNumIndices = srcFace.mNumIndices;
+        dstFace.mIndices = new unsigned int[dstFace.mNumIndices];
+
+        // accumulate linearly all the vertices of the source face
+        for( size_t b = 0; b < dstFace.mNumIndices; ++b )   {
+            dstFace.mIndices[b] = vMap[srcFace.mIndices[b]];
+        }
+    }
+
+    for(unsigned int srcIndex = 0; srcIndex < pMesh->mNumVertices; ++srcIndex ) {
+        unsigned int nvi = vMap[srcIndex];
+        if(nvi==UINT_MAX) {
+            continue;
+        }
+
+        oMesh->mVertices[nvi] = pMesh->mVertices[srcIndex];
+        if( pMesh->HasNormals() ) {
+            oMesh->mNormals[nvi] = pMesh->mNormals[srcIndex];
+        }
+
+        if( pMesh->HasTangentsAndBitangents() ) {
+            oMesh->mTangents[nvi] = pMesh->mTangents[srcIndex];
+            oMesh->mBitangents[nvi] = pMesh->mBitangents[srcIndex];
+        }
+        for( size_t c = 0, cc = pMesh->GetNumUVChannels(); c < cc; ++c )    {
+                oMesh->mTextureCoords[c][nvi] = pMesh->mTextureCoords[c][srcIndex];
+        }
+        for( size_t c = 0, cc = pMesh->GetNumColorChannels(); c < cc; ++c ) {
+            oMesh->mColors[c][nvi] = pMesh->mColors[c][srcIndex];
+        }
+    }
+
+    if(~subFlags&AI_SUBMESH_FLAGS_SANS_BONES)   {
+        std::vector<unsigned int> subBones(pMesh->mNumBones,0);
+
+        for(unsigned int a=0;a<pMesh->mNumBones;++a)    {
+            const aiBone* bone = pMesh->mBones[a];
+
+            for(unsigned int b=0;b<bone->mNumWeights;b++)   {
+                unsigned int v = vMap[bone->mWeights[b].mVertexId];
+
+                if(v!=UINT_MAX) {
+                    subBones[a]++;
+                }
+            }
+        }
+
+        for(unsigned int a=0;a<pMesh->mNumBones;++a)    {
+            if(subBones[a]>0) {
+                oMesh->mNumBones++;
+            }
+        }
+
+        if(oMesh->mNumBones) {
+            oMesh->mBones = new aiBone*[oMesh->mNumBones]();
+            unsigned int nbParanoia = oMesh->mNumBones;
+
+            oMesh->mNumBones = 0; //rewind
+
+            for(unsigned int a=0;a<pMesh->mNumBones;++a)    {
+                if(subBones[a]==0) {
+                    continue;
+                }
+                aiBone *newBone = new aiBone;
+                oMesh->mBones[oMesh->mNumBones++] = newBone;
+
+                const aiBone* bone = pMesh->mBones[a];
+
+                newBone->mName = bone->mName;
+                newBone->mOffsetMatrix = bone->mOffsetMatrix;
+                newBone->mWeights = new aiVertexWeight[subBones[a]];
+
+                for(unsigned int b=0;b<bone->mNumWeights;b++)   {
+                    const unsigned int v = vMap[bone->mWeights[b].mVertexId];
+
+                    if(v!=UINT_MAX) {
+                        aiVertexWeight w(v,bone->mWeights[b].mWeight);
+                        newBone->mWeights[newBone->mNumWeights++] = w;
+                    }
+                }
+            }
+
+            ai_assert(nbParanoia==oMesh->mNumBones);
+            (void)nbParanoia; // remove compiler warning on release build
+        }
+    }
+
+    return oMesh;
+}
+
+} // namespace Assimp
diff --git a/thirdparty/assimp/code/PostProcessing/ProcessHelper.h b/thirdparty/assimp/code/PostProcessing/ProcessHelper.h
new file mode 100644
index 0000000000..0afcc41420
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/ProcessHelper.h
@@ -0,0 +1,386 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+#ifndef AI_PROCESS_HELPER_H_INCLUDED
+#define AI_PROCESS_HELPER_H_INCLUDED
+
+#include <assimp/postprocess.h>
+#include <assimp/anim.h>
+#include <assimp/mesh.h>
+#include <assimp/material.h>
+#include <assimp/DefaultLogger.hpp>
+#include <assimp/scene.h>
+
+#include <assimp/SpatialSort.h>
+#include "Common/BaseProcess.h"
+#include <assimp/ParsingUtils.h>
+
+#include <list>
+
+// -------------------------------------------------------------------------------
+// Some extensions to std namespace. Mainly std::min and std::max for all
+// flat data types in the aiScene. They're used to quickly determine the
+// min/max bounds of data arrays.
+#ifdef __cplusplus
+namespace std {
+
+    // std::min for aiVector3D
+    template <typename TReal>
+    inline ::aiVector3t<TReal> min (const ::aiVector3t<TReal>& a, const ::aiVector3t<TReal>& b) {
+        return ::aiVector3t<TReal> (min(a.x,b.x),min(a.y,b.y),min(a.z,b.z));
+    }
+
+    // std::max for aiVector3t<TReal>
+    template <typename TReal>
+    inline ::aiVector3t<TReal> max (const ::aiVector3t<TReal>& a, const ::aiVector3t<TReal>& b) {
+        return ::aiVector3t<TReal> (max(a.x,b.x),max(a.y,b.y),max(a.z,b.z));
+    }
+
+    // std::min for aiVector2t<TReal>
+    template <typename TReal>
+    inline ::aiVector2t<TReal> min (const ::aiVector2t<TReal>& a, const ::aiVector2t<TReal>& b) {
+        return ::aiVector2t<TReal> (min(a.x,b.x),min(a.y,b.y));
+    }
+
+    // std::max for aiVector2t<TReal>
+    template <typename TReal>
+    inline ::aiVector2t<TReal> max (const ::aiVector2t<TReal>& a, const ::aiVector2t<TReal>& b) {
+        return ::aiVector2t<TReal> (max(a.x,b.x),max(a.y,b.y));
+    }
+
+    // std::min for aiColor4D
+    template <typename TReal>
+    inline ::aiColor4t<TReal> min (const ::aiColor4t<TReal>& a, const ::aiColor4t<TReal>& b)    {
+        return ::aiColor4t<TReal> (min(a.r,b.r),min(a.g,b.g),min(a.b,b.b),min(a.a,b.a));
+    }
+
+    // std::max for aiColor4D
+    template <typename TReal>
+    inline ::aiColor4t<TReal> max (const ::aiColor4t<TReal>& a, const ::aiColor4t<TReal>& b)    {
+        return ::aiColor4t<TReal> (max(a.r,b.r),max(a.g,b.g),max(a.b,b.b),max(a.a,b.a));
+    }
+
+
+    // std::min for aiQuaterniont<TReal>
+    template <typename TReal>
+    inline ::aiQuaterniont<TReal> min (const ::aiQuaterniont<TReal>& a, const ::aiQuaterniont<TReal>& b)    {
+        return ::aiQuaterniont<TReal> (min(a.w,b.w),min(a.x,b.x),min(a.y,b.y),min(a.z,b.z));
+    }
+
+    // std::max for aiQuaterniont<TReal>
+    template <typename TReal>
+    inline ::aiQuaterniont<TReal> max (const ::aiQuaterniont<TReal>& a, const ::aiQuaterniont<TReal>& b)    {
+        return ::aiQuaterniont<TReal> (max(a.w,b.w),max(a.x,b.x),max(a.y,b.y),max(a.z,b.z));
+    }
+
+
+
+    // std::min for aiVectorKey
+    inline ::aiVectorKey min (const ::aiVectorKey& a, const ::aiVectorKey& b)   {
+        return ::aiVectorKey (min(a.mTime,b.mTime),min(a.mValue,b.mValue));
+    }
+
+    // std::max for aiVectorKey
+    inline ::aiVectorKey max (const ::aiVectorKey& a, const ::aiVectorKey& b)   {
+        return ::aiVectorKey (max(a.mTime,b.mTime),max(a.mValue,b.mValue));
+    }
+
+    // std::min for aiQuatKey
+    inline ::aiQuatKey min (const ::aiQuatKey& a, const ::aiQuatKey& b) {
+        return ::aiQuatKey (min(a.mTime,b.mTime),min(a.mValue,b.mValue));
+    }
+
+    // std::max for aiQuatKey
+    inline ::aiQuatKey max (const ::aiQuatKey& a, const ::aiQuatKey& b) {
+        return ::aiQuatKey (max(a.mTime,b.mTime),max(a.mValue,b.mValue));
+    }
+
+    // std::min for aiVertexWeight
+    inline ::aiVertexWeight min (const ::aiVertexWeight& a, const ::aiVertexWeight& b)  {
+        return ::aiVertexWeight (min(a.mVertexId,b.mVertexId),min(a.mWeight,b.mWeight));
+    }
+
+    // std::max for aiVertexWeight
+    inline ::aiVertexWeight max (const ::aiVertexWeight& a, const ::aiVertexWeight& b)  {
+        return ::aiVertexWeight (max(a.mVertexId,b.mVertexId),max(a.mWeight,b.mWeight));
+    }
+
+} // end namespace std
+#endif // !! C++
+
+namespace Assimp {
+
+// -------------------------------------------------------------------------------
+// Start points for ArrayBounds<T> for all supported Ts
+template <typename T>
+struct MinMaxChooser;
+
+template <> struct MinMaxChooser<float> {
+    void operator ()(float& min,float& max) {
+        max = -1e10f;
+        min =  1e10f;
+}};
+template <> struct MinMaxChooser<double> {
+    void operator ()(double& min,double& max) {
+        max = -1e10;
+        min =  1e10;
+}};
+template <> struct MinMaxChooser<unsigned int> {
+    void operator ()(unsigned int& min,unsigned int& max) {
+        max = 0;
+        min = (1u<<(sizeof(unsigned int)*8-1));
+}};
+
+template <typename T> struct MinMaxChooser< aiVector3t<T> > {
+    void operator ()(aiVector3t<T>& min,aiVector3t<T>& max) {
+        max = aiVector3t<T>(-1e10f,-1e10f,-1e10f);
+        min = aiVector3t<T>( 1e10f, 1e10f, 1e10f);
+}};
+template <typename T> struct MinMaxChooser< aiVector2t<T> > {
+    void operator ()(aiVector2t<T>& min,aiVector2t<T>& max) {
+        max = aiVector2t<T>(-1e10f,-1e10f);
+        min = aiVector2t<T>( 1e10f, 1e10f);
+    }};
+template <typename T> struct MinMaxChooser< aiColor4t<T> > {
+    void operator ()(aiColor4t<T>& min,aiColor4t<T>& max) {
+        max = aiColor4t<T>(-1e10f,-1e10f,-1e10f,-1e10f);
+        min = aiColor4t<T>( 1e10f, 1e10f, 1e10f, 1e10f);
+}};
+
+template <typename T> struct MinMaxChooser< aiQuaterniont<T> > {
+    void operator ()(aiQuaterniont<T>& min,aiQuaterniont<T>& max) {
+        max = aiQuaterniont<T>(-1e10f,-1e10f,-1e10f,-1e10f);
+        min = aiQuaterniont<T>( 1e10f, 1e10f, 1e10f, 1e10f);
+}};
+
+template <> struct MinMaxChooser<aiVectorKey> {
+    void operator ()(aiVectorKey& min,aiVectorKey& max) {
+        MinMaxChooser<double>()(min.mTime,max.mTime);
+        MinMaxChooser<aiVector3D>()(min.mValue,max.mValue);
+}};
+template <> struct MinMaxChooser<aiQuatKey> {
+    void operator ()(aiQuatKey& min,aiQuatKey& max) {
+        MinMaxChooser<double>()(min.mTime,max.mTime);
+        MinMaxChooser<aiQuaternion>()(min.mValue,max.mValue);
+}};
+
+template <> struct MinMaxChooser<aiVertexWeight> {
+    void operator ()(aiVertexWeight& min,aiVertexWeight& max) {
+        MinMaxChooser<unsigned int>()(min.mVertexId,max.mVertexId);
+        MinMaxChooser<float>()(min.mWeight,max.mWeight);
+}};
+
+// -------------------------------------------------------------------------------
+/** @brief Find the min/max values of an array of Ts
+ *  @param in Input array
+ *  @param size Number of elements to process
+ *  @param[out] min minimum value
+ *  @param[out] max maximum value
+ */
+template <typename T>
+inline void ArrayBounds(const T* in, unsigned int size, T& min, T& max)
+{
+    MinMaxChooser<T> ()(min,max);
+    for (unsigned int i = 0; i < size;++i) {
+        min = std::min(in[i],min);
+        max = std::max(in[i],max);
+    }
+}
+
+
+// -------------------------------------------------------------------------------
+/** Little helper function to calculate the quadratic difference
+ * of two colours.
+ * @param pColor1 First color
+ * @param pColor2 second color
+ * @return Quadratic color difference */
+inline ai_real GetColorDifference( const aiColor4D& pColor1, const aiColor4D& pColor2)
+{
+    const aiColor4D c (pColor1.r - pColor2.r, pColor1.g - pColor2.g, pColor1.b - pColor2.b, pColor1.a - pColor2.a);
+    return c.r*c.r + c.g*c.g + c.b*c.b + c.a*c.a;
+}
+
+
+// -------------------------------------------------------------------------------
+/** @brief Extract single strings from a list of identifiers
+ *  @param in Input string list.
+ *  @param out Receives a list of clean output strings
+ *  @sdee #AI_CONFIG_PP_OG_EXCLUDE_LIST */
+void ConvertListToStrings(const std::string& in, std::list<std::string>& out);
+
+
+// -------------------------------------------------------------------------------
+/** @brief Compute the AABB of a mesh after applying a given transform
+ *  @param mesh Input mesh
+ *  @param[out] min Receives minimum transformed vertex
+ *  @param[out] max Receives maximum transformed vertex
+ *  @param m Transformation matrix to be applied */
+void FindAABBTransformed (const aiMesh* mesh, aiVector3D& min, aiVector3D& max, const aiMatrix4x4& m);
+
+
+// -------------------------------------------------------------------------------
+/** @brief Helper function to determine the 'real' center of a mesh
+ *
+ *  That is the center of its axis-aligned bounding box.
+ *  @param mesh Input mesh
+ *  @param[out] min Minimum vertex of the mesh
+ *  @param[out] max maximum vertex of the mesh
+ *  @param[out] out Center point */
+void FindMeshCenter (aiMesh* mesh, aiVector3D& out, aiVector3D& min, aiVector3D& max);
+
+// -------------------------------------------------------------------------------
+/** @brief Helper function to determine the 'real' center of a scene
+ *
+ *  That is the center of its axis-aligned bounding box.
+ *  @param scene Input scene
+ *  @param[out] min Minimum vertex of the scene
+ *  @param[out] max maximum vertex of the scene
+ *  @param[out] out Center point */
+void FindSceneCenter (aiScene* scene, aiVector3D& out, aiVector3D& min, aiVector3D& max);
+
+
+// -------------------------------------------------------------------------------
+// Helper function to determine the 'real' center of a mesh after applying a given transform
+void FindMeshCenterTransformed (aiMesh* mesh, aiVector3D& out, aiVector3D& min,aiVector3D& max, const aiMatrix4x4& m);
+
+
+// -------------------------------------------------------------------------------
+// Helper function to determine the 'real' center of a mesh
+void FindMeshCenter (aiMesh* mesh, aiVector3D& out);
+
+
+// -------------------------------------------------------------------------------
+// Helper function to determine the 'real' center of a mesh after applying a given transform
+void FindMeshCenterTransformed (aiMesh* mesh, aiVector3D& out,const aiMatrix4x4& m);
+
+
+// -------------------------------------------------------------------------------
+// Compute a good epsilon value for position comparisons on a mesh
+ai_real ComputePositionEpsilon(const aiMesh* pMesh);
+
+
+// -------------------------------------------------------------------------------
+// Compute a good epsilon value for position comparisons on a array of meshes
+ai_real ComputePositionEpsilon(const aiMesh* const* pMeshes, size_t num);
+
+
+// -------------------------------------------------------------------------------
+// Compute an unique value for the vertex format of a mesh
+unsigned int GetMeshVFormatUnique(const aiMesh* pcMesh);
+
+
+// defs for ComputeVertexBoneWeightTable()
+typedef std::pair <unsigned int,float> PerVertexWeight;
+typedef std::vector <PerVertexWeight> VertexWeightTable;
+
+// -------------------------------------------------------------------------------
+// Compute a per-vertex bone weight table
+VertexWeightTable* ComputeVertexBoneWeightTable(const aiMesh* pMesh);
+
+
+// -------------------------------------------------------------------------------
+// Get a string for a given aiTextureType
+const char* TextureTypeToString(aiTextureType in);
+
+
+// -------------------------------------------------------------------------------
+// Get a string for a given aiTextureMapping
+const char* MappingTypeToString(aiTextureMapping in);
+
+
+// flags for MakeSubmesh()
+#define AI_SUBMESH_FLAGS_SANS_BONES 0x1
+
+// -------------------------------------------------------------------------------
+// Split a mesh given a list of faces to be contained in the sub mesh
+aiMesh* MakeSubmesh(const aiMesh *superMesh, const std::vector<unsigned int> &subMeshFaces, unsigned int subFlags);
+
+// -------------------------------------------------------------------------------
+// Utility postprocess step to share the spatial sort tree between
+// all steps which use it to speedup its computations.
+class ComputeSpatialSortProcess : public BaseProcess
+{
+    bool IsActive( unsigned int pFlags) const
+    {
+        return NULL != shared && 0 != (pFlags & (aiProcess_CalcTangentSpace |
+            aiProcess_GenNormals | aiProcess_JoinIdenticalVertices));
+    }
+
+    void Execute( aiScene* pScene)
+    {
+        typedef std::pair<SpatialSort, ai_real> _Type;
+        ASSIMP_LOG_DEBUG("Generate spatially-sorted vertex cache");
+
+        std::vector<_Type>* p = new std::vector<_Type>(pScene->mNumMeshes);
+        std::vector<_Type>::iterator it = p->begin();
+
+        for (unsigned int i = 0; i < pScene->mNumMeshes; ++i, ++it) {
+            aiMesh* mesh = pScene->mMeshes[i];
+            _Type& blubb = *it;
+            blubb.first.Fill(mesh->mVertices,mesh->mNumVertices,sizeof(aiVector3D));
+            blubb.second = ComputePositionEpsilon(mesh);
+        }
+
+        shared->AddProperty(AI_SPP_SPATIAL_SORT,p);
+    }
+};
+
+// -------------------------------------------------------------------------------
+// ... and the same again to cleanup the whole stuff
+class DestroySpatialSortProcess : public BaseProcess
+{
+    bool IsActive( unsigned int pFlags) const
+    {
+        return NULL != shared && 0 != (pFlags & (aiProcess_CalcTangentSpace |
+            aiProcess_GenNormals | aiProcess_JoinIdenticalVertices));
+    }
+
+    void Execute( aiScene* /*pScene*/)
+    {
+        shared->RemoveProperty(AI_SPP_SPATIAL_SORT);
+    }
+};
+
+
+
+} // ! namespace Assimp
+#endif // !! AI_PROCESS_HELPER_H_INCLUDED
diff --git a/thirdparty/assimp/code/PostProcessing/RemoveRedundantMaterials.cpp b/thirdparty/assimp/code/PostProcessing/RemoveRedundantMaterials.cpp
new file mode 100644
index 0000000000..49ec8f5c47
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/RemoveRedundantMaterials.cpp
@@ -0,0 +1,221 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+/** @file RemoveRedundantMaterials.cpp
+ *  @brief Implementation of the "RemoveRedundantMaterials" post processing step
+*/
+
+// internal headers
+
+#include "RemoveRedundantMaterials.h"
+#include <assimp/ParsingUtils.h>
+#include "ProcessHelper.h"
+#include "Material/MaterialSystem.h"
+#include <stdio.h>
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+RemoveRedundantMatsProcess::RemoveRedundantMatsProcess()
+: mConfigFixedMaterials() {
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+RemoveRedundantMatsProcess::~RemoveRedundantMatsProcess()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool RemoveRedundantMatsProcess::IsActive( unsigned int pFlags) const
+{
+    return (pFlags & aiProcess_RemoveRedundantMaterials) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Setup import properties
+void RemoveRedundantMatsProcess::SetupProperties(const Importer* pImp)
+{
+    // Get value of AI_CONFIG_PP_RRM_EXCLUDE_LIST
+    mConfigFixedMaterials = pImp->GetPropertyString(AI_CONFIG_PP_RRM_EXCLUDE_LIST,"");
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void RemoveRedundantMatsProcess::Execute( aiScene* pScene)
+{
+    ASSIMP_LOG_DEBUG("RemoveRedundantMatsProcess begin");
+
+    unsigned int redundantRemoved = 0, unreferencedRemoved = 0;
+    if (pScene->mNumMaterials)
+    {
+        // Find out which materials are referenced by meshes
+        std::vector<bool> abReferenced(pScene->mNumMaterials,false);
+        for (unsigned int i = 0;i < pScene->mNumMeshes;++i)
+            abReferenced[pScene->mMeshes[i]->mMaterialIndex] = true;
+
+        // If a list of materials to be excluded was given, match the list with
+        // our imported materials and 'salt' all positive matches to ensure that
+        // we get unique hashes later.
+        if (mConfigFixedMaterials.length()) {
+
+            std::list<std::string> strings;
+            ConvertListToStrings(mConfigFixedMaterials,strings);
+
+            for (unsigned int i = 0; i < pScene->mNumMaterials;++i) {
+                aiMaterial* mat = pScene->mMaterials[i];
+
+                aiString name;
+                mat->Get(AI_MATKEY_NAME,name);
+
+                if (name.length) {
+                    std::list<std::string>::const_iterator it = std::find(strings.begin(), strings.end(), name.data);
+                    if (it != strings.end()) {
+
+                        // Our brilliant 'salt': A single material property with ~ as first
+                        // character to mark it as internal and temporary.
+                        const int dummy = 1;
+                        ((aiMaterial*)mat)->AddProperty(&dummy,1,"~RRM.UniqueMaterial",0,0);
+
+                        // Keep this material even if no mesh references it
+                        abReferenced[i] = true;
+                        ASSIMP_LOG_DEBUG_F( "Found positive match in exclusion list: \'", name.data, "\'");
+                    }
+                }
+            }
+        }
+
+        // TODO: re-implement this algorithm to work in-place
+        unsigned int *aiMappingTable = new unsigned int[pScene->mNumMaterials];
+        for ( unsigned int i=0; i<pScene->mNumMaterials; i++ ) {
+            aiMappingTable[ i ] = 0;
+        }
+        unsigned int iNewNum = 0;
+
+        // Iterate through all materials and calculate a hash for them
+        // store all hashes in a list and so a quick search whether
+        // we do already have a specific hash. This allows us to
+        // determine which materials are identical.
+        uint32_t *aiHashes = new uint32_t[ pScene->mNumMaterials ];;
+        for (unsigned int i = 0; i < pScene->mNumMaterials;++i)
+        {
+            // No mesh is referencing this material, remove it.
+            if (!abReferenced[i]) {
+                ++unreferencedRemoved;
+                delete pScene->mMaterials[i];
+                pScene->mMaterials[i] = nullptr;
+                continue;
+            }
+
+            // Check all previously mapped materials for a matching hash.
+            // On a match we can delete this material and just make it ref to the same index.
+            uint32_t me = aiHashes[i] = ComputeMaterialHash(pScene->mMaterials[i]);
+            for (unsigned int a = 0; a < i;++a)
+            {
+                if (abReferenced[a] && me == aiHashes[a]) {
+                    ++redundantRemoved;
+                    me = 0;
+                    aiMappingTable[i] = aiMappingTable[a];
+                    delete pScene->mMaterials[i];
+                    pScene->mMaterials[i] = nullptr;
+                    break;
+                }
+            }
+            // This is a new material that is referenced, add to the map.
+            if (me) {
+                aiMappingTable[i] = iNewNum++;
+            }
+        }
+        // If the new material count differs from the original,
+        // we need to rebuild the material list and remap mesh material indexes.
+        if (iNewNum != pScene->mNumMaterials) {
+            ai_assert(iNewNum > 0);
+            aiMaterial** ppcMaterials = new aiMaterial*[iNewNum];
+            ::memset(ppcMaterials,0,sizeof(void*)*iNewNum);
+            for (unsigned int p = 0; p < pScene->mNumMaterials;++p)
+            {
+                // if the material is not referenced ... remove it
+                if (!abReferenced[p]) {
+                    continue;
+                }
+
+                // generate new names for modified materials that had no names
+                const unsigned int idx = aiMappingTable[p];
+                if (ppcMaterials[idx]) {
+                    aiString sz;
+                    if( ppcMaterials[idx]->Get(AI_MATKEY_NAME, sz) != AI_SUCCESS ) {
+                        sz.length = ::ai_snprintf(sz.data,MAXLEN,"JoinedMaterial_#%u",p);
+                        ((aiMaterial*)ppcMaterials[idx])->AddProperty(&sz,AI_MATKEY_NAME);
+                    }
+                } else {
+                    ppcMaterials[idx] = pScene->mMaterials[p];
+                }
+            }
+            // update all material indices
+            for (unsigned int p = 0; p < pScene->mNumMeshes;++p) {
+                aiMesh* mesh = pScene->mMeshes[p];
+                ai_assert( NULL!=mesh );
+                mesh->mMaterialIndex = aiMappingTable[mesh->mMaterialIndex];
+            }
+            // delete the old material list
+            delete[] pScene->mMaterials;
+            pScene->mMaterials = ppcMaterials;
+            pScene->mNumMaterials = iNewNum;
+        }
+        // delete temporary storage
+        delete[] aiHashes;
+        delete[] aiMappingTable;
+    }
+    if (redundantRemoved == 0 && unreferencedRemoved == 0)
+    {
+        ASSIMP_LOG_DEBUG("RemoveRedundantMatsProcess finished ");
+    }
+    else
+    {
+        ASSIMP_LOG_INFO_F("RemoveRedundantMatsProcess finished. Removed ", redundantRemoved, " redundant and ", 
+            unreferencedRemoved, " unused materials.");
+    }
+}
diff --git a/thirdparty/assimp/code/PostProcessing/RemoveRedundantMaterials.h b/thirdparty/assimp/code/PostProcessing/RemoveRedundantMaterials.h
new file mode 100644
index 0000000000..1f32a0abfb
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/RemoveRedundantMaterials.h
@@ -0,0 +1,103 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file RemoveRedundantMaterials.h
+ *  @brief Defines a post processing step to remove redundant materials
+ */
+#ifndef AI_REMOVEREDUNDANTMATERIALS_H_INC
+#define AI_REMOVEREDUNDANTMATERIALS_H_INC
+
+#include "Common/BaseProcess.h"
+#include <assimp/mesh.h>
+
+class RemoveRedundantMatsTest;
+
+namespace Assimp    {
+
+// ---------------------------------------------------------------------------
+/** RemoveRedundantMatsProcess: Post-processing step to remove redundant
+ *  materials from the imported scene.
+ */
+class ASSIMP_API RemoveRedundantMatsProcess : public BaseProcess {
+public:
+    /// The default class constructor.
+    RemoveRedundantMatsProcess();
+
+    /// The class destructor.
+    ~RemoveRedundantMatsProcess();
+
+    // -------------------------------------------------------------------
+    // Check whether step is active
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    // Execute step on a given scene
+    void Execute( aiScene* pScene);
+
+    // -------------------------------------------------------------------
+    // Setup import settings
+    void SetupProperties(const Importer* pImp);
+
+    // -------------------------------------------------------------------
+    /** @brief Set list of fixed (inmutable) materials
+     *  @param fixed See #AI_CONFIG_PP_RRM_EXCLUDE_LIST
+     */
+    void SetFixedMaterialsString(const std::string& fixed = "") {
+        mConfigFixedMaterials = fixed;
+    }
+
+    // -------------------------------------------------------------------
+    /** @brief Get list of fixed (inmutable) materials
+     *  @return See #AI_CONFIG_PP_RRM_EXCLUDE_LIST
+     */
+    const std::string& GetFixedMaterialsString() const {
+        return mConfigFixedMaterials;
+    }
+
+private:
+    //! Configuration option: list of all fixed materials
+    std::string mConfigFixedMaterials;
+};
+
+} // end of namespace Assimp
+
+#endif // !!AI_REMOVEREDUNDANTMATERIALS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/RemoveVCProcess.cpp b/thirdparty/assimp/code/PostProcessing/RemoveVCProcess.cpp
new file mode 100644
index 0000000000..99fd47a3aa
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/RemoveVCProcess.cpp
@@ -0,0 +1,337 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+/** @file Implementation of the post processing step to remove
+ *        any parts of the mesh structure from the imported data.
+*/
+
+
+#include "RemoveVCProcess.h"
+#include <assimp/postprocess.h>
+#include <assimp/DefaultLogger.hpp>
+#include <assimp/scene.h>
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+RemoveVCProcess::RemoveVCProcess() :
+    configDeleteFlags()
+  , mScene()
+{}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+RemoveVCProcess::~RemoveVCProcess()
+{}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool RemoveVCProcess::IsActive( unsigned int pFlags) const
+{
+    return (pFlags & aiProcess_RemoveComponent) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Small helper function to delete all elements in a T** aray using delete
+template <typename T>
+inline void ArrayDelete(T**& in, unsigned int& num)
+{
+    for (unsigned int i = 0; i < num; ++i)
+        delete in[i];
+
+    delete[] in;
+    in = NULL;
+    num = 0;
+}
+
+#if 0
+// ------------------------------------------------------------------------------------------------
+// Updates the node graph - removes all nodes which have the "remove" flag set and the
+// "don't remove" flag not set. Nodes with meshes are never deleted.
+bool UpdateNodeGraph(aiNode* node,std::list<aiNode*>& childsOfParent,bool root)
+{
+    bool b = false;
+
+    std::list<aiNode*> mine;
+    for (unsigned int i = 0; i < node->mNumChildren;++i)
+    {
+        if(UpdateNodeGraph(node->mChildren[i],mine,false))
+            b = true;
+    }
+
+    // somewhat tricky ... mNumMeshes must be originally 0 and MSB2 may not be set,
+    // so we can do a simple comparison against MSB here
+    if (!root && AI_RC_UINT_MSB == node->mNumMeshes )
+    {
+        // this node needs to be removed
+        if(node->mNumChildren)
+        {
+            childsOfParent.insert(childsOfParent.end(),mine.begin(),mine.end());
+
+            // set all children to NULL to make sure they are not deleted when we delete ourself
+            for (unsigned int i = 0; i < node->mNumChildren;++i)
+                node->mChildren[i] = NULL;
+        }
+        b = true;
+        delete node;
+    }
+    else
+    {
+        AI_RC_UNMASK(node->mNumMeshes);
+        childsOfParent.push_back(node);
+
+        if (b)
+        {
+            // reallocate the array of our children here
+            node->mNumChildren = (unsigned int)mine.size();
+            aiNode** const children = new aiNode*[mine.size()];
+            aiNode** ptr = children;
+
+            for (std::list<aiNode*>::iterator it = mine.begin(), end = mine.end();
+                 it != end; ++it)
+            {
+                *ptr++ = *it;
+            }
+            delete[] node->mChildren;
+            node->mChildren = children;
+            return false;
+        }
+    }
+    return b;
+}
+#endif
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void RemoveVCProcess::Execute( aiScene* pScene)
+{
+    ASSIMP_LOG_DEBUG("RemoveVCProcess begin");
+    bool bHas = false; //,bMasked = false;
+
+    mScene = pScene;
+
+    // handle animations
+    if ( configDeleteFlags & aiComponent_ANIMATIONS)
+    {
+
+        bHas = true;
+        ArrayDelete(pScene->mAnimations,pScene->mNumAnimations);
+    }
+
+    // handle textures
+    if ( configDeleteFlags & aiComponent_TEXTURES)
+    {
+        bHas = true;
+        ArrayDelete(pScene->mTextures,pScene->mNumTextures);
+    }
+
+    // handle materials
+    if ( configDeleteFlags & aiComponent_MATERIALS && pScene->mNumMaterials)
+    {
+        bHas = true;
+        for (unsigned int i = 1;i < pScene->mNumMaterials;++i)
+            delete pScene->mMaterials[i];
+
+        pScene->mNumMaterials = 1;
+        aiMaterial* helper = (aiMaterial*) pScene->mMaterials[0];
+        ai_assert(NULL != helper);
+        helper->Clear();
+
+        // gray
+        aiColor3D clr(0.6f,0.6f,0.6f);
+        helper->AddProperty(&clr,1,AI_MATKEY_COLOR_DIFFUSE);
+
+        // add a small ambient color value
+        clr = aiColor3D(0.05f,0.05f,0.05f);
+        helper->AddProperty(&clr,1,AI_MATKEY_COLOR_AMBIENT);
+
+        aiString s;
+        s.Set("Dummy_MaterialsRemoved");
+        helper->AddProperty(&s,AI_MATKEY_NAME);
+    }
+
+    // handle light sources
+    if ( configDeleteFlags & aiComponent_LIGHTS)
+    {
+        bHas =  true;
+        ArrayDelete(pScene->mLights,pScene->mNumLights);
+    }
+
+    // handle camneras
+    if ( configDeleteFlags & aiComponent_CAMERAS)
+    {
+        bHas = true;
+        ArrayDelete(pScene->mCameras,pScene->mNumCameras);
+    }
+
+    // handle meshes
+    if (configDeleteFlags & aiComponent_MESHES)
+    {
+        bHas = true;
+        ArrayDelete(pScene->mMeshes,pScene->mNumMeshes);
+    }
+    else
+    {
+        for( unsigned int a = 0; a < pScene->mNumMeshes; a++)
+        {
+            if( ProcessMesh( pScene->mMeshes[a]))
+                bHas = true;
+        }
+    }
+
+
+    // now check whether the result is still a full scene
+    if (!pScene->mNumMeshes || !pScene->mNumMaterials)
+    {
+        pScene->mFlags |= AI_SCENE_FLAGS_INCOMPLETE;
+        ASSIMP_LOG_DEBUG("Setting AI_SCENE_FLAGS_INCOMPLETE flag");
+
+        // If we have no meshes anymore we should also clear another flag ...
+        if (!pScene->mNumMeshes)
+            pScene->mFlags &= ~AI_SCENE_FLAGS_NON_VERBOSE_FORMAT;
+    }
+
+    if (bHas) {
+        ASSIMP_LOG_INFO("RemoveVCProcess finished. Data structure cleanup has been done.");
+    } else {
+        ASSIMP_LOG_DEBUG("RemoveVCProcess finished. Nothing to be done ...");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Setup configuration properties for the step
+void RemoveVCProcess::SetupProperties(const Importer* pImp)
+{
+    configDeleteFlags = pImp->GetPropertyInteger(AI_CONFIG_PP_RVC_FLAGS,0x0);
+    if (!configDeleteFlags)
+    {
+        ASSIMP_LOG_WARN("RemoveVCProcess: AI_CONFIG_PP_RVC_FLAGS is zero.");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+bool RemoveVCProcess::ProcessMesh(aiMesh* pMesh)
+{
+    bool ret = false;
+
+    // if all materials have been deleted let the material
+    // index of the mesh point to the created default material
+    if ( configDeleteFlags & aiComponent_MATERIALS)
+        pMesh->mMaterialIndex = 0;
+
+    // handle normals
+    if (configDeleteFlags & aiComponent_NORMALS && pMesh->mNormals)
+    {
+        delete[] pMesh->mNormals;
+        pMesh->mNormals = NULL;
+        ret = true;
+    }
+
+    // handle tangents and bitangents
+    if (configDeleteFlags & aiComponent_TANGENTS_AND_BITANGENTS && pMesh->mTangents)
+    {
+        delete[] pMesh->mTangents;
+        pMesh->mTangents = NULL;
+
+        delete[] pMesh->mBitangents;
+        pMesh->mBitangents = NULL;
+        ret = true;
+    }
+
+    // handle texture coordinates
+    bool b = (0 != (configDeleteFlags & aiComponent_TEXCOORDS));
+    for (unsigned int i = 0, real = 0; real < AI_MAX_NUMBER_OF_TEXTURECOORDS; ++real)
+    {
+        if (!pMesh->mTextureCoords[i])break;
+        if (configDeleteFlags & aiComponent_TEXCOORDSn(real) || b)
+        {
+            delete [] pMesh->mTextureCoords[i];
+            pMesh->mTextureCoords[i] = NULL;
+            ret = true;
+
+            if (!b)
+            {
+                // collapse the rest of the array
+                for (unsigned int a = i+1; a < AI_MAX_NUMBER_OF_TEXTURECOORDS;++a)
+                    pMesh->mTextureCoords[a-1] = pMesh->mTextureCoords[a];
+
+                pMesh->mTextureCoords[AI_MAX_NUMBER_OF_TEXTURECOORDS-1] = NULL;
+                continue;
+            }
+        }
+        ++i;
+    }
+
+    // handle vertex colors
+    b = (0 != (configDeleteFlags & aiComponent_COLORS));
+    for (unsigned int i = 0, real = 0; real < AI_MAX_NUMBER_OF_COLOR_SETS; ++real)
+    {
+        if (!pMesh->mColors[i])break;
+        if (configDeleteFlags & aiComponent_COLORSn(i) || b)
+        {
+            delete [] pMesh->mColors[i];
+            pMesh->mColors[i] = NULL;
+            ret = true;
+
+            if (!b)
+            {
+                // collapse the rest of the array
+                for (unsigned int a = i+1; a < AI_MAX_NUMBER_OF_COLOR_SETS;++a)
+                    pMesh->mColors[a-1] = pMesh->mColors[a];
+
+                pMesh->mColors[AI_MAX_NUMBER_OF_COLOR_SETS-1] = NULL;
+                continue;
+            }
+        }
+        ++i;
+    }
+
+    // handle bones
+    if (configDeleteFlags & aiComponent_BONEWEIGHTS && pMesh->mBones)
+    {
+        ArrayDelete(pMesh->mBones,pMesh->mNumBones);
+        ret = true;
+    }
+    return ret;
+}
diff --git a/thirdparty/assimp/code/PostProcessing/RemoveVCProcess.h b/thirdparty/assimp/code/PostProcessing/RemoveVCProcess.h
new file mode 100644
index 0000000000..7bb21a8330
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/RemoveVCProcess.h
@@ -0,0 +1,124 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file Defines a post processing step to remove specific parts of the scene */
+#ifndef AI_REMOVEVCPROCESS_H_INCLUDED
+#define AI_REMOVEVCPROCESS_H_INCLUDED
+
+#include "Common/BaseProcess.h"
+
+#include <assimp/mesh.h>
+
+class RemoveVCProcessTest;
+
+namespace Assimp {
+
+// ---------------------------------------------------------------------------
+/** RemoveVCProcess: Class to exclude specific parts of the data structure
+ *  from further processing by removing them,
+*/
+class ASSIMP_API RemoveVCProcess : public BaseProcess {
+public:
+    /// The default class constructor.
+    RemoveVCProcess();
+
+    /// The class destructor.
+    ~RemoveVCProcess();
+
+    // -------------------------------------------------------------------
+    /** Returns whether the processing step is present in the given flag field.
+    * @param pFlags The processing flags the importer was called with. A bitwise
+    *   combination of #aiPostProcessSteps.
+    * @return true if the process is present in this flag fields, false if not.
+    */
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    /** Executes the post processing step on the given imported data.
+    * At the moment a process is not supposed to fail.
+    * @param pScene The imported data to work at.
+    */
+    void Execute( aiScene* pScene);
+
+    // -------------------------------------------------------------------
+    /** Called prior to ExecuteOnScene().
+    * The function is a request to the process to update its configuration
+    * basing on the Importer's configuration property list.
+    */
+    virtual void SetupProperties(const Importer* pImp);
+
+    // -------------------------------------------------------------------
+    /** Manually setup the configuration flags for the step
+     *
+     *  @param Bitwise combination of the #aiComponent enumerated values.
+    */
+    void SetDeleteFlags(unsigned int f)
+    {
+        configDeleteFlags = f;
+    }
+
+    // -------------------------------------------------------------------
+    /** Query the current configuration.
+    */
+    unsigned int GetDeleteFlags() const
+    {
+        return configDeleteFlags;
+    }
+
+private:
+
+    bool ProcessMesh (aiMesh* pcMesh);
+
+    /** Configuration flag
+     */
+    unsigned int configDeleteFlags;
+
+    /** The scene we're working with
+     */
+    aiScene* mScene;
+};
+
+// ---------------------------------------------------------------------------
+
+} // end of namespace Assimp
+
+#endif // !!AI_REMOVEVCPROCESS_H_INCLUDED
diff --git a/thirdparty/assimp/code/PostProcessing/ScaleProcess.cpp b/thirdparty/assimp/code/PostProcessing/ScaleProcess.cpp
new file mode 100644
index 0000000000..6d458c4b11
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/ScaleProcess.cpp
@@ -0,0 +1,103 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+copyright notice, this list of conditions and the
+following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the
+following disclaimer in the documentation and/or other
+materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+contributors may be used to endorse or promote products
+derived from this software without specific prior
+written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+#ifndef ASSIMP_BUILD_NO_GLOBALSCALE_PROCESS
+
+#include "ScaleProcess.h"
+
+#include <assimp/scene.h>
+#include <assimp/postprocess.h>
+
+namespace Assimp {
+
+ScaleProcess::ScaleProcess()
+: BaseProcess()
+, mScale( AI_CONFIG_GLOBAL_SCALE_FACTOR_DEFAULT ) {
+    // empty
+}
+
+ScaleProcess::~ScaleProcess() {
+    // empty
+}
+
+void ScaleProcess::setScale( ai_real scale ) {
+    mScale = scale;
+}
+
+ai_real ScaleProcess::getScale() const {
+    return mScale;
+}
+
+bool ScaleProcess::IsActive( unsigned int pFlags ) const {
+    return ( pFlags & aiProcess_GlobalScale ) != 0;
+}
+
+void ScaleProcess::SetupProperties( const Importer* pImp ) {
+    mScale = pImp->GetPropertyFloat( AI_CONFIG_GLOBAL_SCALE_FACTOR_KEY, 0 );
+}
+
+void ScaleProcess::Execute( aiScene* pScene ) {
+    if ( nullptr == pScene ) {
+        return;
+    }
+
+    if ( nullptr == pScene->mRootNode ) {
+        return;
+    }
+
+    traverseNodes( pScene->mRootNode );
+}
+
+void ScaleProcess::traverseNodes( aiNode *node ) {
+    applyScaling( node );
+}
+
+void ScaleProcess::applyScaling( aiNode *currentNode ) {
+    if ( nullptr != currentNode ) {
+        currentNode->mTransformation.a1 = currentNode->mTransformation.a1 * mScale;
+        currentNode->mTransformation.b2 = currentNode->mTransformation.b2 * mScale;
+        currentNode->mTransformation.c3 = currentNode->mTransformation.c3 * mScale;
+    }
+}
+
+} // Namespace Assimp
+
+#endif // !! ASSIMP_BUILD_NO_GLOBALSCALE_PROCESS
diff --git a/thirdparty/assimp/code/PostProcessing/ScaleProcess.h b/thirdparty/assimp/code/PostProcessing/ScaleProcess.h
new file mode 100644
index 0000000000..2567378759
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/ScaleProcess.h
@@ -0,0 +1,88 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+copyright notice, this list of conditions and the
+following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the
+following disclaimer in the documentation and/or other
+materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+contributors may be used to endorse or promote products
+derived from this software without specific prior
+written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+#pragma once
+
+#include "Common/BaseProcess.h"
+
+struct aiNode;
+
+#if (!defined AI_CONFIG_GLOBAL_SCALE_FACTOR_DEFAULT)
+#   define AI_CONFIG_GLOBAL_SCALE_FACTOR_DEFAULT  1.0f
+#endif // !! AI_DEBONE_THRESHOLD
+
+namespace Assimp {
+
+// ---------------------------------------------------------------------------
+/** ScaleProcess: Class to rescale the whole model.
+*/
+class ASSIMP_API ScaleProcess : public BaseProcess {
+public:
+    /// The default class constructor.
+    ScaleProcess();
+
+    /// The class destructor.
+    virtual ~ScaleProcess();
+
+    /// Will set the scale manually.
+    void setScale( ai_real scale );
+
+    /// Returns the current scaling value.
+    ai_real getScale() const;
+
+    /// Overwritten, @see BaseProcess
+    virtual bool IsActive( unsigned int pFlags ) const;
+
+    /// Overwritten, @see BaseProcess
+    virtual void SetupProperties( const Importer* pImp );
+
+    /// Overwritten, @see BaseProcess
+    virtual void Execute( aiScene* pScene );
+
+private:
+    void traverseNodes( aiNode *currentNode );
+    void applyScaling( aiNode *currentNode );
+
+private:
+    ai_real mScale;
+};
+
+} // Namespace Assimp
diff --git a/thirdparty/assimp/code/PostProcessing/SortByPTypeProcess.cpp b/thirdparty/assimp/code/PostProcessing/SortByPTypeProcess.cpp
new file mode 100644
index 0000000000..be8405a17b
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/SortByPTypeProcess.cpp
@@ -0,0 +1,403 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file Implementation of the DeterminePTypeHelperProcess and
+ *  SortByPTypeProcess post-process steps.
+*/
+
+
+
+// internal headers
+#include "ProcessHelper.h"
+#include "SortByPTypeProcess.h"
+#include <assimp/Exceptional.h>
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+SortByPTypeProcess::SortByPTypeProcess()
+: mConfigRemoveMeshes( 0 ) {
+    // empty
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+SortByPTypeProcess::~SortByPTypeProcess()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool SortByPTypeProcess::IsActive( unsigned int pFlags) const
+{
+    return  (pFlags & aiProcess_SortByPType) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+void SortByPTypeProcess::SetupProperties(const Importer* pImp)
+{
+    mConfigRemoveMeshes = pImp->GetPropertyInteger(AI_CONFIG_PP_SBP_REMOVE,0);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Update changed meshes in all nodes
+void UpdateNodes(const std::vector<unsigned int>& replaceMeshIndex, aiNode* node)
+{
+    if (node->mNumMeshes)
+    {
+        unsigned int newSize = 0;
+        for (unsigned int m = 0; m< node->mNumMeshes; ++m)
+        {
+            unsigned int add = node->mMeshes[m]<<2;
+            for (unsigned int i = 0; i < 4;++i)
+            {
+                if (UINT_MAX != replaceMeshIndex[add+i])++newSize;
+            }
+        }
+        if (!newSize)
+        {
+            delete[] node->mMeshes;
+            node->mNumMeshes = 0;
+            node->mMeshes    = NULL;
+        }
+        else
+        {
+            // Try to reuse the old array if possible
+            unsigned int* newMeshes = (newSize > node->mNumMeshes
+                ? new unsigned int[newSize] : node->mMeshes);
+
+            for (unsigned int m = 0; m< node->mNumMeshes; ++m)
+            {
+                unsigned int add = node->mMeshes[m]<<2;
+                for (unsigned int i = 0; i < 4;++i)
+                {
+                    if (UINT_MAX != replaceMeshIndex[add+i])
+                        *newMeshes++ = replaceMeshIndex[add+i];
+                }
+            }
+            if (newSize > node->mNumMeshes)
+                delete[] node->mMeshes;
+
+            node->mMeshes = newMeshes-(node->mNumMeshes = newSize);
+        }
+    }
+
+    // call all subnodes recursively
+    for (unsigned int m = 0; m < node->mNumChildren; ++m)
+        UpdateNodes(replaceMeshIndex,node->mChildren[m]);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void SortByPTypeProcess::Execute( aiScene* pScene) {
+    if ( 0 == pScene->mNumMeshes) {
+        ASSIMP_LOG_DEBUG("SortByPTypeProcess skipped, there are no meshes");
+        return;
+    }
+
+    ASSIMP_LOG_DEBUG("SortByPTypeProcess begin");
+
+    unsigned int aiNumMeshesPerPType[4] = {0,0,0,0};
+
+    std::vector<aiMesh*> outMeshes;
+    outMeshes.reserve(pScene->mNumMeshes<<1u);
+
+    bool bAnyChanges = false;
+
+    std::vector<unsigned int> replaceMeshIndex(pScene->mNumMeshes*4,UINT_MAX);
+    std::vector<unsigned int>::iterator meshIdx = replaceMeshIndex.begin();
+    for (unsigned int i = 0; i < pScene->mNumMeshes; ++i) {
+        aiMesh* const mesh = pScene->mMeshes[i];
+        ai_assert(0 != mesh->mPrimitiveTypes);
+
+        // if there's just one primitive type in the mesh there's nothing to do for us
+        unsigned int num = 0;
+        if (mesh->mPrimitiveTypes & aiPrimitiveType_POINT) {
+            ++aiNumMeshesPerPType[0];
+            ++num;
+        }
+        if (mesh->mPrimitiveTypes & aiPrimitiveType_LINE) {
+            ++aiNumMeshesPerPType[1];
+            ++num;
+        }
+        if (mesh->mPrimitiveTypes & aiPrimitiveType_TRIANGLE) {
+            ++aiNumMeshesPerPType[2];
+            ++num;
+        }
+        if (mesh->mPrimitiveTypes & aiPrimitiveType_POLYGON) {
+            ++aiNumMeshesPerPType[3];
+            ++num;
+        }
+
+        if (1 == num) {
+            if (!(mConfigRemoveMeshes & mesh->mPrimitiveTypes)) {
+                *meshIdx = static_cast<unsigned int>( outMeshes.size() );
+                outMeshes.push_back(mesh);
+            } else {
+                delete mesh;
+                pScene->mMeshes[ i ] = nullptr;
+                bAnyChanges = true;
+            }
+
+            meshIdx += 4;
+            continue;
+        }
+        bAnyChanges = true;
+
+        // reuse our current mesh arrays for the submesh
+        // with the largest number of primitives
+        unsigned int aiNumPerPType[4] = {0,0,0,0};
+        aiFace* pFirstFace = mesh->mFaces;
+        aiFace* const pLastFace = pFirstFace + mesh->mNumFaces;
+
+        unsigned int numPolyVerts = 0;
+        for (;pFirstFace != pLastFace; ++pFirstFace) {
+            if (pFirstFace->mNumIndices <= 3)
+                ++aiNumPerPType[pFirstFace->mNumIndices-1];
+            else
+            {
+                ++aiNumPerPType[3];
+                numPolyVerts += pFirstFace-> mNumIndices;
+            }
+        }
+
+        VertexWeightTable* avw = ComputeVertexBoneWeightTable(mesh);
+        for (unsigned int real = 0; real < 4; ++real,++meshIdx)
+        {
+            if ( !aiNumPerPType[real] || mConfigRemoveMeshes & (1u << real))
+            {
+                continue;
+            }
+
+            *meshIdx = (unsigned int) outMeshes.size();
+            outMeshes.push_back(new aiMesh());
+            aiMesh* out = outMeshes.back();
+
+            // the name carries the adjacency information between the meshes
+            out->mName = mesh->mName;
+
+            // copy data members
+            out->mPrimitiveTypes = 1u << real;
+            out->mMaterialIndex = mesh->mMaterialIndex;
+
+            // allocate output storage
+            out->mNumFaces = aiNumPerPType[real];
+            aiFace* outFaces = out->mFaces = new aiFace[out->mNumFaces];
+
+            out->mNumVertices = (3 == real ? numPolyVerts : out->mNumFaces * (real+1));
+
+            aiVector3D *vert(nullptr), *nor(nullptr), *tan(nullptr), *bit(nullptr);
+            aiVector3D *uv   [AI_MAX_NUMBER_OF_TEXTURECOORDS];
+            aiColor4D  *cols [AI_MAX_NUMBER_OF_COLOR_SETS];
+
+            if (mesh->mVertices) {
+                vert = out->mVertices = new aiVector3D[out->mNumVertices];
+            }
+
+            if (mesh->mNormals) {
+                nor = out->mNormals = new aiVector3D[out->mNumVertices];
+            }
+
+            if (mesh->mTangents) {
+                tan = out->mTangents   = new aiVector3D[out->mNumVertices];
+                bit = out->mBitangents = new aiVector3D[out->mNumVertices];
+            }
+
+            for (unsigned int j = 0; j < AI_MAX_NUMBER_OF_TEXTURECOORDS;++j) {
+                uv[j] = nullptr;
+                if (mesh->mTextureCoords[j]) {
+                    uv[j] = out->mTextureCoords[j] = new aiVector3D[out->mNumVertices];
+                }
+
+                out->mNumUVComponents[j] = mesh->mNumUVComponents[j];
+            }
+
+            for (unsigned int j = 0; j < AI_MAX_NUMBER_OF_COLOR_SETS;++j) {
+                cols[j] = nullptr;
+                if (mesh->mColors[j]) {
+                    cols[j] = out->mColors[j] = new aiColor4D[out->mNumVertices];
+                }
+            }
+
+            typedef std::vector< aiVertexWeight > TempBoneInfo;
+            std::vector< TempBoneInfo > tempBones(mesh->mNumBones);
+
+            // try to guess how much storage we'll need
+            for (unsigned int q = 0; q < mesh->mNumBones;++q)
+            {
+                tempBones[q].reserve(mesh->mBones[q]->mNumWeights / (num-1));
+            }
+
+            unsigned int outIdx = 0;
+            for (unsigned int m = 0; m < mesh->mNumFaces; ++m)
+            {
+                aiFace& in = mesh->mFaces[m];
+                if ((real == 3  && in.mNumIndices <= 3) || (real != 3 && in.mNumIndices != real+1))
+                {
+                    continue;
+                }
+
+                outFaces->mNumIndices = in.mNumIndices;
+                outFaces->mIndices    = in.mIndices;
+
+                for (unsigned int q = 0; q < in.mNumIndices; ++q)
+                {
+                    unsigned int idx = in.mIndices[q];
+
+                    // process all bones of this index
+                    if (avw)
+                    {
+                        VertexWeightTable& tbl = avw[idx];
+                        for (VertexWeightTable::const_iterator it = tbl.begin(), end = tbl.end();
+                             it != end; ++it)
+                        {
+                            tempBones[ (*it).first ].push_back( aiVertexWeight(outIdx, (*it).second) );
+                        }
+                    }
+
+                    if (vert)
+                    {
+                        *vert++ = mesh->mVertices[idx];
+                        //mesh->mVertices[idx].x = get_qnan();
+                    }
+                    if (nor )*nor++  = mesh->mNormals[idx];
+                    if (tan )
+                    {
+                        *tan++  = mesh->mTangents[idx];
+                        *bit++  = mesh->mBitangents[idx];
+                    }
+
+                    for (unsigned int pp = 0; pp < AI_MAX_NUMBER_OF_TEXTURECOORDS; ++pp)
+                    {
+                        if (!uv[pp])break;
+                        *uv[pp]++ = mesh->mTextureCoords[pp][idx];
+                    }
+
+                    for (unsigned int pp = 0; pp < AI_MAX_NUMBER_OF_COLOR_SETS; ++pp)
+                    {
+                        if (!cols[pp])break;
+                        *cols[pp]++ = mesh->mColors[pp][idx];
+                    }
+
+                    in.mIndices[q] = outIdx++;
+                }
+
+                in.mIndices = nullptr;
+                ++outFaces;
+            }
+            ai_assert(outFaces == out->mFaces + out->mNumFaces);
+
+            // now generate output bones
+            for (unsigned int q = 0; q < mesh->mNumBones;++q)
+                if (!tempBones[q].empty())++out->mNumBones;
+
+            if (out->mNumBones)
+            {
+                out->mBones = new aiBone*[out->mNumBones];
+                for (unsigned int q = 0, real = 0; q < mesh->mNumBones;++q)
+                {
+                    TempBoneInfo& in = tempBones[q];
+                    if (in.empty())continue;
+
+                    aiBone* srcBone = mesh->mBones[q];
+                    aiBone* bone = out->mBones[real] = new aiBone();
+
+                    bone->mName = srcBone->mName;
+                    bone->mOffsetMatrix = srcBone->mOffsetMatrix;
+
+                    bone->mNumWeights = (unsigned int)in.size();
+                    bone->mWeights = new aiVertexWeight[bone->mNumWeights];
+
+                    ::memcpy(bone->mWeights,&in[0],bone->mNumWeights*sizeof(aiVertexWeight));
+
+                    ++real;
+                }
+            }
+        }
+
+        // delete the per-vertex bone weights table
+        delete[] avw;
+
+        // delete the input mesh
+        delete mesh;
+
+        // avoid invalid pointer
+        pScene->mMeshes[i] = NULL;
+    }
+
+    if (outMeshes.empty())
+    {
+        // This should not occur
+        throw DeadlyImportError("No meshes remaining");
+    }
+
+    // If we added at least one mesh process all nodes in the node
+    // graph and update their respective mesh indices.
+    if (bAnyChanges)
+    {
+        UpdateNodes(replaceMeshIndex,pScene->mRootNode);
+    }
+
+    if (outMeshes.size() != pScene->mNumMeshes)
+    {
+        delete[] pScene->mMeshes;
+        pScene->mNumMeshes = (unsigned int)outMeshes.size();
+        pScene->mMeshes = new aiMesh*[pScene->mNumMeshes];
+    }
+    ::memcpy(pScene->mMeshes,&outMeshes[0],pScene->mNumMeshes*sizeof(void*));
+
+    if (!DefaultLogger::isNullLogger())
+    {
+        char buffer[1024];
+        ::ai_snprintf(buffer,1024,"Points: %u%s, Lines: %u%s, Triangles: %u%s, Polygons: %u%s (Meshes, X = removed)",
+            aiNumMeshesPerPType[0], ((mConfigRemoveMeshes & aiPrimitiveType_POINT)     ? "X" : ""),
+            aiNumMeshesPerPType[1], ((mConfigRemoveMeshes & aiPrimitiveType_LINE)      ? "X" : ""),
+            aiNumMeshesPerPType[2], ((mConfigRemoveMeshes & aiPrimitiveType_TRIANGLE)  ? "X" : ""),
+            aiNumMeshesPerPType[3], ((mConfigRemoveMeshes & aiPrimitiveType_POLYGON)   ? "X" : ""));
+        ASSIMP_LOG_INFO(buffer);
+        ASSIMP_LOG_DEBUG("SortByPTypeProcess finished");
+    }
+}
+
diff --git a/thirdparty/assimp/code/PostProcessing/SortByPTypeProcess.h b/thirdparty/assimp/code/PostProcessing/SortByPTypeProcess.h
new file mode 100644
index 0000000000..1d7ccfc152
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/SortByPTypeProcess.h
@@ -0,0 +1,82 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file Defines a post processing step to sort meshes by the types
+    of primitives they contain */
+#ifndef AI_SORTBYPTYPEPROCESS_H_INC
+#define AI_SORTBYPTYPEPROCESS_H_INC
+
+#include "Common/BaseProcess.h"
+#include <assimp/mesh.h>
+
+class SortByPTypeProcessTest;
+
+namespace Assimp    {
+
+
+// ---------------------------------------------------------------------------
+/** SortByPTypeProcess: Sorts meshes by the types of primitives they contain.
+ *  A mesh with 5 lines, 3 points and 145 triangles would be split in 3
+ * submeshes.
+*/
+class ASSIMP_API SortByPTypeProcess : public BaseProcess {
+public:
+    SortByPTypeProcess();
+    ~SortByPTypeProcess();
+
+    // -------------------------------------------------------------------
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    void Execute( aiScene* pScene);
+
+    // -------------------------------------------------------------------
+    void SetupProperties(const Importer* pImp);
+
+private:
+    int mConfigRemoveMeshes;
+};
+
+
+} // end of namespace Assimp
+
+#endif // !!AI_SORTBYPTYPEPROCESS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/SplitLargeMeshes.cpp b/thirdparty/assimp/code/PostProcessing/SplitLargeMeshes.cpp
new file mode 100644
index 0000000000..1797b28d5a
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/SplitLargeMeshes.cpp
@@ -0,0 +1,623 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** 
+ *  @file Implementation of the SplitLargeMeshes postprocessing step
+ */
+
+// internal headers of the post-processing framework
+#include "SplitLargeMeshes.h"
+#include "ProcessHelper.h"
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+SplitLargeMeshesProcess_Triangle::SplitLargeMeshesProcess_Triangle() {
+    LIMIT = AI_SLM_DEFAULT_MAX_TRIANGLES;
+}
+
+// ------------------------------------------------------------------------------------------------
+SplitLargeMeshesProcess_Triangle::~SplitLargeMeshesProcess_Triangle() {
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool SplitLargeMeshesProcess_Triangle::IsActive( unsigned int pFlags) const {
+    return (pFlags & aiProcess_SplitLargeMeshes) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void SplitLargeMeshesProcess_Triangle::Execute( aiScene* pScene) {
+    if (0xffffffff == this->LIMIT || nullptr == pScene ) {
+        return;
+    }
+
+    ASSIMP_LOG_DEBUG("SplitLargeMeshesProcess_Triangle begin");
+    std::vector<std::pair<aiMesh*, unsigned int> > avList;
+
+    for( unsigned int a = 0; a < pScene->mNumMeshes; ++a) {
+        this->SplitMesh(a, pScene->mMeshes[a],avList);
+    }
+
+    if (avList.size() != pScene->mNumMeshes) {
+        // it seems something has been split. rebuild the mesh list
+        delete[] pScene->mMeshes;
+        pScene->mNumMeshes = (unsigned int)avList.size();
+        pScene->mMeshes = new aiMesh*[avList.size()];
+
+        for (unsigned int i = 0; i < avList.size();++i) {
+            pScene->mMeshes[i] = avList[i].first;
+        }
+
+        // now we need to update all nodes
+        this->UpdateNode(pScene->mRootNode,avList);
+        ASSIMP_LOG_INFO("SplitLargeMeshesProcess_Triangle finished. Meshes have been split");
+    } else {
+        ASSIMP_LOG_DEBUG("SplitLargeMeshesProcess_Triangle finished. There was nothing to do");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Setup properties
+void SplitLargeMeshesProcess_Triangle::SetupProperties( const Importer* pImp) {
+    // get the current value of the split property
+    this->LIMIT = pImp->GetPropertyInteger(AI_CONFIG_PP_SLM_TRIANGLE_LIMIT,AI_SLM_DEFAULT_MAX_TRIANGLES);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Update a node after some meshes have been split
+void SplitLargeMeshesProcess_Triangle::UpdateNode(aiNode* pcNode,
+        const std::vector<std::pair<aiMesh*, unsigned int> >& avList) {
+    // for every index in out list build a new entry
+    std::vector<unsigned int> aiEntries;
+    aiEntries.reserve(pcNode->mNumMeshes + 1);
+    for (unsigned int i = 0; i < pcNode->mNumMeshes;++i) {
+        for (unsigned int a = 0; a < avList.size();++a) {
+            if (avList[a].second == pcNode->mMeshes[i]) {
+                aiEntries.push_back(a);
+            }
+        }
+    }
+
+    // now build the new list
+    delete[] pcNode->mMeshes;
+    pcNode->mNumMeshes = (unsigned int)aiEntries.size();
+    pcNode->mMeshes = new unsigned int[pcNode->mNumMeshes];
+
+    for (unsigned int b = 0; b < pcNode->mNumMeshes;++b) {
+        pcNode->mMeshes[b] = aiEntries[b];
+    }
+
+    // recusively update all other nodes
+    for (unsigned int i = 0; i < pcNode->mNumChildren;++i) {
+        UpdateNode ( pcNode->mChildren[i], avList );
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void SplitLargeMeshesProcess_Triangle::SplitMesh(
+        unsigned int a,
+        aiMesh* pMesh,
+        std::vector<std::pair<aiMesh*, unsigned int> >& avList) {
+    if (pMesh->mNumFaces > SplitLargeMeshesProcess_Triangle::LIMIT) {
+        ASSIMP_LOG_INFO("Mesh exceeds the triangle limit. It will be split ...");
+
+        // we need to split this mesh into sub meshes
+        // determine the size of a submesh
+        const unsigned int iSubMeshes = (pMesh->mNumFaces / LIMIT) + 1;
+
+        const unsigned int iOutFaceNum = pMesh->mNumFaces / iSubMeshes;
+        const unsigned int iOutVertexNum = iOutFaceNum * 3;
+
+        // now generate all submeshes
+        for (unsigned int i = 0; i < iSubMeshes;++i) {
+            aiMesh* pcMesh          = new aiMesh;
+            pcMesh->mNumFaces       = iOutFaceNum;
+            pcMesh->mMaterialIndex  = pMesh->mMaterialIndex;
+
+            // the name carries the adjacency information between the meshes
+            pcMesh->mName = pMesh->mName;
+
+            if (i == iSubMeshes-1) {
+                pcMesh->mNumFaces = iOutFaceNum + (
+                    pMesh->mNumFaces - iOutFaceNum * iSubMeshes);
+            }
+            // copy the list of faces
+            pcMesh->mFaces = new aiFace[pcMesh->mNumFaces];
+
+            const unsigned int iBase = iOutFaceNum * i;
+
+            // get the total number of indices
+            unsigned int iCnt = 0;
+            for (unsigned int p = iBase; p < pcMesh->mNumFaces + iBase;++p) {
+                iCnt += pMesh->mFaces[p].mNumIndices;
+            }
+            pcMesh->mNumVertices = iCnt;
+
+            // allocate storage
+            if (pMesh->mVertices != nullptr) {
+                pcMesh->mVertices = new aiVector3D[iCnt];
+            }
+
+            if (pMesh->HasNormals()) {
+                pcMesh->mNormals = new aiVector3D[iCnt];
+            }
+
+            if (pMesh->HasTangentsAndBitangents()) {
+                pcMesh->mTangents = new aiVector3D[iCnt];
+                pcMesh->mBitangents = new aiVector3D[iCnt];
+            }
+
+            // texture coordinates
+            for (unsigned int c = 0;  c < AI_MAX_NUMBER_OF_TEXTURECOORDS;++c) {
+                pcMesh->mNumUVComponents[c] = pMesh->mNumUVComponents[c];
+                if (pMesh->HasTextureCoords( c)) {
+                    pcMesh->mTextureCoords[c] = new aiVector3D[iCnt];
+                }
+            }
+
+            // vertex colors
+            for (unsigned int c = 0;  c < AI_MAX_NUMBER_OF_COLOR_SETS;++c) {
+                if (pMesh->HasVertexColors( c)) {
+                    pcMesh->mColors[c] = new aiColor4D[iCnt];
+                }
+            }
+
+            if (pMesh->HasBones()) {
+                // assume the number of bones won't change in most cases
+                pcMesh->mBones = new aiBone*[pMesh->mNumBones];
+
+                // iterate through all bones of the mesh and find those which
+                // need to be copied to the split mesh
+                std::vector<aiVertexWeight> avTempWeights;
+                for (unsigned int p = 0; p < pcMesh->mNumBones;++p) {
+                    aiBone* const bone = pcMesh->mBones[p];
+                    avTempWeights.clear();
+                    avTempWeights.reserve(bone->mNumWeights / iSubMeshes);
+
+                    for (unsigned int q = 0; q < bone->mNumWeights;++q) {
+                        aiVertexWeight& weight = bone->mWeights[q];
+                        if(weight.mVertexId >= iBase && weight.mVertexId < iBase + iOutVertexNum) {
+                            avTempWeights.push_back(weight);
+                            weight = avTempWeights.back();
+                            weight.mVertexId -= iBase;
+                        }
+                    }
+
+                    if (!avTempWeights.empty()) {
+                        // we'll need this bone. Copy it ...
+                        aiBone* pc = new aiBone();
+                        pcMesh->mBones[pcMesh->mNumBones++] = pc;
+                        pc->mName = aiString(bone->mName);
+                        pc->mNumWeights = (unsigned int)avTempWeights.size();
+                        pc->mOffsetMatrix = bone->mOffsetMatrix;
+
+                        // no need to reallocate the array for the last submesh.
+                        // Here we can reuse the (large) source array, although
+                        // we'll waste some memory
+                        if (iSubMeshes-1 == i) {
+                            pc->mWeights = bone->mWeights;
+                            bone->mWeights = nullptr;
+                        } else {
+                            pc->mWeights = new aiVertexWeight[pc->mNumWeights];
+                        }
+
+                        // copy the weights
+                        ::memcpy(pc->mWeights,&avTempWeights[0],sizeof(aiVertexWeight)*pc->mNumWeights);
+                    }
+                }
+            }
+
+            // (we will also need to copy the array of indices)
+            unsigned int iCurrent = 0;
+            for (unsigned int p = 0; p < pcMesh->mNumFaces;++p) {
+                pcMesh->mFaces[p].mNumIndices = 3;
+                // allocate a new array
+                const unsigned int iTemp = p + iBase;
+                const unsigned int iNumIndices = pMesh->mFaces[iTemp].mNumIndices;
+
+                // setup face type and number of indices
+                pcMesh->mFaces[p].mNumIndices = iNumIndices;
+                unsigned int* pi = pMesh->mFaces[iTemp].mIndices;
+                unsigned int* piOut = pcMesh->mFaces[p].mIndices = new unsigned int[iNumIndices];
+
+                // need to update the output primitive types
+                switch (iNumIndices) {
+                case 1:
+                    pcMesh->mPrimitiveTypes |= aiPrimitiveType_POINT;
+                    break;
+                case 2:
+                    pcMesh->mPrimitiveTypes |= aiPrimitiveType_LINE;
+                    break;
+                case 3:
+                    pcMesh->mPrimitiveTypes |= aiPrimitiveType_TRIANGLE;
+                    break;
+                default:
+                    pcMesh->mPrimitiveTypes |= aiPrimitiveType_POLYGON;
+                }
+
+                // and copy the contents of the old array, offset by current base
+                for (unsigned int v = 0; v < iNumIndices;++v) {
+                    unsigned int iIndex = pi[v];
+                    unsigned int iIndexOut = iCurrent++;
+                    piOut[v] = iIndexOut;
+
+                    // copy positions
+                    if (pMesh->mVertices != nullptr) {
+                        pcMesh->mVertices[iIndexOut] = pMesh->mVertices[iIndex];
+                    }
+
+                    // copy normals
+                    if (pMesh->HasNormals()) {
+                        pcMesh->mNormals[iIndexOut] = pMesh->mNormals[iIndex];
+                    }
+
+                    // copy tangents/bitangents
+                    if (pMesh->HasTangentsAndBitangents()) {
+                        pcMesh->mTangents[iIndexOut] = pMesh->mTangents[iIndex];
+                        pcMesh->mBitangents[iIndexOut] = pMesh->mBitangents[iIndex];
+                    }
+
+                    // texture coordinates
+                    for (unsigned int c = 0;  c < AI_MAX_NUMBER_OF_TEXTURECOORDS;++c) {
+                        if (pMesh->HasTextureCoords( c ) ) {
+                            pcMesh->mTextureCoords[c][iIndexOut] = pMesh->mTextureCoords[c][iIndex];
+                        }
+                    }
+                    // vertex colors
+                    for (unsigned int c = 0;  c < AI_MAX_NUMBER_OF_COLOR_SETS;++c) {
+                        if (pMesh->HasVertexColors( c)) {
+                            pcMesh->mColors[c][iIndexOut] = pMesh->mColors[c][iIndex];
+                        }
+                    }
+                }
+            }
+
+            // add the newly created mesh to the list
+            avList.push_back(std::pair<aiMesh*, unsigned int>(pcMesh,a));
+        }
+
+        // now delete the old mesh data
+        delete pMesh;
+    } else {
+        avList.push_back(std::pair<aiMesh*, unsigned int>(pMesh,a));
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+SplitLargeMeshesProcess_Vertex::SplitLargeMeshesProcess_Vertex() {
+    LIMIT = AI_SLM_DEFAULT_MAX_VERTICES;
+}
+
+// ------------------------------------------------------------------------------------------------
+SplitLargeMeshesProcess_Vertex::~SplitLargeMeshesProcess_Vertex() {
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool SplitLargeMeshesProcess_Vertex::IsActive( unsigned int pFlags) const {
+    return (pFlags & aiProcess_SplitLargeMeshes) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void SplitLargeMeshesProcess_Vertex::Execute( aiScene* pScene) {
+    if (0xffffffff == this->LIMIT || nullptr == pScene ) {
+        return;
+    }
+
+    ASSIMP_LOG_DEBUG("SplitLargeMeshesProcess_Vertex begin");
+
+    std::vector<std::pair<aiMesh*, unsigned int> > avList;
+
+    //Check for point cloud first, 
+    //Do not process point cloud, splitMesh works only with faces data
+    for (unsigned int a = 0; a < pScene->mNumMeshes; a++) {
+        if ( pScene->mMeshes[a]->mPrimitiveTypes == aiPrimitiveType_POINT ) {
+            return;
+        }
+    }
+
+    for( unsigned int a = 0; a < pScene->mNumMeshes; ++a ) {
+        this->SplitMesh(a, pScene->mMeshes[a], avList);
+    }
+
+    if (avList.size() != pScene->mNumMeshes) {
+        // it seems something has been split. rebuild the mesh list
+        delete[] pScene->mMeshes;
+        pScene->mNumMeshes = (unsigned int)avList.size();
+        pScene->mMeshes = new aiMesh*[avList.size()];
+
+        for (unsigned int i = 0; i < avList.size();++i) {
+            pScene->mMeshes[i] = avList[i].first;
+        }
+
+        // now we need to update all nodes
+        SplitLargeMeshesProcess_Triangle::UpdateNode(pScene->mRootNode,avList);
+        ASSIMP_LOG_INFO("SplitLargeMeshesProcess_Vertex finished. Meshes have been split");
+    } else {
+        ASSIMP_LOG_DEBUG("SplitLargeMeshesProcess_Vertex finished. There was nothing to do");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Setup properties
+void SplitLargeMeshesProcess_Vertex::SetupProperties( const Importer* pImp) {
+    this->LIMIT = pImp->GetPropertyInteger(AI_CONFIG_PP_SLM_VERTEX_LIMIT,AI_SLM_DEFAULT_MAX_VERTICES);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void SplitLargeMeshesProcess_Vertex::SplitMesh(
+        unsigned int a,
+        aiMesh* pMesh,
+        std::vector<std::pair<aiMesh*, unsigned int> >& avList) {
+    if (pMesh->mNumVertices > SplitLargeMeshesProcess_Vertex::LIMIT) {
+        typedef std::vector< std::pair<unsigned int,float> > VertexWeightTable;
+
+        // build a per-vertex weight list if necessary
+        VertexWeightTable* avPerVertexWeights = ComputeVertexBoneWeightTable(pMesh);
+
+        // we need to split this mesh into sub meshes
+        // determine the estimated size of a submesh
+        // (this could be too large. Max waste is a single digit percentage)
+        const unsigned int iSubMeshes = (pMesh->mNumVertices / SplitLargeMeshesProcess_Vertex::LIMIT) + 1;
+
+        // create a std::vector<unsigned int> to indicate which vertices
+        // have already been copied
+        std::vector<unsigned int> avWasCopied;
+        avWasCopied.resize(pMesh->mNumVertices,0xFFFFFFFF);
+
+        // try to find a good estimate for the number of output faces
+        // per mesh. Add 12.5% as buffer
+        unsigned int iEstimatedSize = pMesh->mNumFaces / iSubMeshes;
+        iEstimatedSize += iEstimatedSize >> 3;
+
+        // now generate all submeshes
+        unsigned int iBase( 0 );
+        while (true) {
+            const unsigned int iOutVertexNum = SplitLargeMeshesProcess_Vertex::LIMIT;
+            aiMesh* pcMesh          = new aiMesh;
+            pcMesh->mNumVertices    = 0;
+            pcMesh->mMaterialIndex  = pMesh->mMaterialIndex;
+
+            // the name carries the adjacency information between the meshes
+            pcMesh->mName = pMesh->mName;
+
+            typedef std::vector<aiVertexWeight> BoneWeightList;
+            if (pMesh->HasBones()) {
+                pcMesh->mBones = new aiBone*[pMesh->mNumBones];
+                ::memset(pcMesh->mBones,0,sizeof(void*)*pMesh->mNumBones);
+            }
+
+            // clear the temporary helper array
+            if (iBase) {
+                // we can't use memset here we unsigned int needn' be 32 bits
+                for (auto &elem : avWasCopied) {
+                    elem = 0xffffffff;
+                }
+            }
+
+            // output vectors
+            std::vector<aiFace> vFaces;
+
+            // reserve enough storage for most cases
+            if (pMesh->HasPositions()) {
+                pcMesh->mVertices = new aiVector3D[iOutVertexNum];
+            }
+            if (pMesh->HasNormals()) {
+                pcMesh->mNormals = new aiVector3D[iOutVertexNum];
+            }
+            if (pMesh->HasTangentsAndBitangents()) {
+                pcMesh->mTangents = new aiVector3D[iOutVertexNum];
+                pcMesh->mBitangents = new aiVector3D[iOutVertexNum];
+            }
+            for (unsigned int c = 0; pMesh->HasVertexColors(c);++c) {
+                pcMesh->mColors[c] = new aiColor4D[iOutVertexNum];
+            }
+            for (unsigned int c = 0; pMesh->HasTextureCoords(c);++c) {
+                pcMesh->mNumUVComponents[c] = pMesh->mNumUVComponents[c];
+                pcMesh->mTextureCoords[c] = new aiVector3D[iOutVertexNum];
+            }
+            vFaces.reserve(iEstimatedSize);
+
+            // (we will also need to copy the array of indices)
+            while (iBase < pMesh->mNumFaces) {
+                // allocate a new array
+                const unsigned int iNumIndices = pMesh->mFaces[iBase].mNumIndices;
+
+                // doesn't catch degenerates but is quite fast
+                unsigned int iNeed = 0;
+                for (unsigned int v = 0; v < iNumIndices;++v) {
+                    unsigned int iIndex = pMesh->mFaces[iBase].mIndices[v];
+
+                    // check whether we do already have this vertex
+                    if (0xFFFFFFFF == avWasCopied[iIndex]) {
+                        iNeed++;
+                    }
+                }
+                if (pcMesh->mNumVertices + iNeed > iOutVertexNum) {
+                    // don't use this face
+                    break;
+                }
+
+                vFaces.push_back(aiFace());
+                aiFace& rFace = vFaces.back();
+
+                // setup face type and number of indices
+                rFace.mNumIndices = iNumIndices;
+                rFace.mIndices = new unsigned int[iNumIndices];
+
+                // need to update the output primitive types
+                switch (rFace.mNumIndices) {
+                case 1:
+                    pcMesh->mPrimitiveTypes |= aiPrimitiveType_POINT;
+                    break;
+                case 2:
+                    pcMesh->mPrimitiveTypes |= aiPrimitiveType_LINE;
+                    break;
+                case 3:
+                    pcMesh->mPrimitiveTypes |= aiPrimitiveType_TRIANGLE;
+                    break;
+                default:
+                    pcMesh->mPrimitiveTypes |= aiPrimitiveType_POLYGON;
+                }
+
+                // and copy the contents of the old array, offset by current base
+                for (unsigned int v = 0; v < iNumIndices;++v) {
+                    unsigned int iIndex = pMesh->mFaces[iBase].mIndices[v];
+
+                    // check whether we do already have this vertex
+                    if (0xFFFFFFFF != avWasCopied[iIndex]) {
+                        rFace.mIndices[v] = avWasCopied[iIndex];
+                        continue;
+                    }
+
+                    // copy positions
+                    pcMesh->mVertices[pcMesh->mNumVertices] = (pMesh->mVertices[iIndex]);
+
+                    // copy normals
+                    if (pMesh->HasNormals()) {
+                        pcMesh->mNormals[pcMesh->mNumVertices] = (pMesh->mNormals[iIndex]);
+                    }
+
+                    // copy tangents/bitangents
+                    if (pMesh->HasTangentsAndBitangents()) {
+                        pcMesh->mTangents[pcMesh->mNumVertices] = (pMesh->mTangents[iIndex]);
+                        pcMesh->mBitangents[pcMesh->mNumVertices] = (pMesh->mBitangents[iIndex]);
+                    }
+
+                    // texture coordinates
+                    for (unsigned int c = 0;  c < AI_MAX_NUMBER_OF_TEXTURECOORDS;++c) {
+                        if (pMesh->HasTextureCoords( c)) {
+                            pcMesh->mTextureCoords[c][pcMesh->mNumVertices] = pMesh->mTextureCoords[c][iIndex];
+                        }
+                    }
+                    // vertex colors
+                    for (unsigned int c = 0;  c < AI_MAX_NUMBER_OF_COLOR_SETS;++c) {
+                        if (pMesh->HasVertexColors( c)) {
+                            pcMesh->mColors[c][pcMesh->mNumVertices] = pMesh->mColors[c][iIndex];
+                        }
+                    }
+                    // check whether we have bone weights assigned to this vertex
+                    rFace.mIndices[v] = pcMesh->mNumVertices;
+                    if (avPerVertexWeights) {
+                        VertexWeightTable& table = avPerVertexWeights[ pcMesh->mNumVertices ];
+                        if( !table.empty() ) {
+                            for (VertexWeightTable::const_iterator iter =  table.begin();
+                                    iter != table.end();++iter) {
+                                // allocate the bone weight array if necessary
+                                BoneWeightList* pcWeightList = (BoneWeightList*)pcMesh->mBones[(*iter).first];
+                                if (nullptr == pcWeightList) {
+                                    pcMesh->mBones[(*iter).first] = (aiBone*)(pcWeightList = new BoneWeightList());
+                                }
+                                pcWeightList->push_back(aiVertexWeight(pcMesh->mNumVertices,(*iter).second));
+                            }
+                        }
+                    }
+
+                    avWasCopied[iIndex] = pcMesh->mNumVertices;
+                    pcMesh->mNumVertices++;
+                }
+                ++iBase;
+                if(pcMesh->mNumVertices == iOutVertexNum) {
+                    // break here. The face is only added if it was complete
+                    break;
+                }
+            }
+
+            // check which bones we'll need to create for this submesh
+            if (pMesh->HasBones()) {
+                aiBone** ppCurrent = pcMesh->mBones;
+                for (unsigned int k = 0; k < pMesh->mNumBones;++k) {
+                    // check whether the bone is existing
+                    BoneWeightList* pcWeightList;
+                    if ((pcWeightList = (BoneWeightList*)pcMesh->mBones[k])) {
+                        aiBone* pcOldBone = pMesh->mBones[k];
+                        aiBone* pcOut( nullptr );
+                        *ppCurrent++ = pcOut = new aiBone();
+                        pcOut->mName = aiString(pcOldBone->mName);
+                        pcOut->mOffsetMatrix = pcOldBone->mOffsetMatrix;
+                        pcOut->mNumWeights = (unsigned int)pcWeightList->size();
+                        pcOut->mWeights = new aiVertexWeight[pcOut->mNumWeights];
+
+                        // copy the vertex weights
+                        ::memcpy(pcOut->mWeights,&pcWeightList->operator[](0),
+                            pcOut->mNumWeights * sizeof(aiVertexWeight));
+
+                        // delete the temporary bone weight list
+                        delete pcWeightList;
+                        pcMesh->mNumBones++;
+                    }
+                }
+            }
+
+            // copy the face list to the mesh
+            pcMesh->mFaces = new aiFace[vFaces.size()];
+            pcMesh->mNumFaces = (unsigned int)vFaces.size();
+
+            for (unsigned int p = 0; p < pcMesh->mNumFaces;++p) {
+                pcMesh->mFaces[p] = vFaces[p];
+            }
+
+            // add the newly created mesh to the list
+            avList.push_back(std::pair<aiMesh*, unsigned int>(pcMesh,a));
+
+            if (iBase == pMesh->mNumFaces) {
+                // have all faces ... finish the outer loop, too
+                break;
+            }
+        }
+
+        // delete the per-vertex weight list again
+        delete[] avPerVertexWeights;
+
+        // now delete the old mesh data
+        delete pMesh;
+        return;
+    }
+    avList.push_back(std::pair<aiMesh*, unsigned int>(pMesh,a));
+}
diff --git a/thirdparty/assimp/code/PostProcessing/SplitLargeMeshes.h b/thirdparty/assimp/code/PostProcessing/SplitLargeMeshes.h
new file mode 100644
index 0000000000..3f90576ea9
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/SplitLargeMeshes.h
@@ -0,0 +1,209 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file Defines a post processing step to split large meshes into sub-meshes
+ */
+#ifndef AI_SPLITLARGEMESHES_H_INC
+#define AI_SPLITLARGEMESHES_H_INC
+
+#include <vector>
+#include "Common/BaseProcess.h"
+
+#include <assimp/mesh.h>
+#include <assimp/scene.h>
+
+// Forward declarations
+class SplitLargeMeshesTest;
+
+namespace Assimp {
+
+class SplitLargeMeshesProcess_Triangle;
+class SplitLargeMeshesProcess_Vertex;
+
+// NOTE: If you change these limits, don't forget to change the
+// corresponding values in all Assimp ports
+
+// **********************************************************
+// Java: ConfigProperty.java,
+//  ConfigProperty.DEFAULT_VERTEX_SPLIT_LIMIT
+//  ConfigProperty.DEFAULT_TRIANGLE_SPLIT_LIMIT
+// **********************************************************
+
+// default limit for vertices
+#if (!defined AI_SLM_DEFAULT_MAX_VERTICES)
+#   define AI_SLM_DEFAULT_MAX_VERTICES      1000000
+#endif
+
+// default limit for triangles
+#if (!defined AI_SLM_DEFAULT_MAX_TRIANGLES)
+#   define AI_SLM_DEFAULT_MAX_TRIANGLES     1000000
+#endif
+
+// ---------------------------------------------------------------------------
+/** Post-processing filter to split large meshes into sub-meshes
+ *
+ * Applied BEFORE the JoinVertices-Step occurs.
+ * Returns NON-UNIQUE vertices, splits by triangle number.
+*/
+class ASSIMP_API SplitLargeMeshesProcess_Triangle : public BaseProcess
+{
+    friend class SplitLargeMeshesProcess_Vertex;
+
+public:
+
+    SplitLargeMeshesProcess_Triangle();
+    ~SplitLargeMeshesProcess_Triangle();
+
+public:
+    // -------------------------------------------------------------------
+    /** Returns whether the processing step is present in the given flag.
+    * @param pFlags The processing flags the importer was called with. A
+    *   bitwise combination of #aiPostProcessSteps.
+    * @return true if the process is present in this flag fields,
+    *   false if not.
+    */
+    bool IsActive( unsigned int pFlags) const;
+
+
+    // -------------------------------------------------------------------
+    /** Called prior to ExecuteOnScene().
+    * The function is a request to the process to update its configuration
+    * basing on the Importer's configuration property list.
+    */
+    virtual void SetupProperties(const Importer* pImp);
+
+
+    //! Set the split limit - needed for unit testing
+    inline void SetLimit(unsigned int l)
+        {LIMIT = l;}
+
+    //! Get the split limit
+    inline unsigned int GetLimit() const
+        {return LIMIT;}
+
+public:
+
+    // -------------------------------------------------------------------
+    /** Executes the post processing step on the given imported data.
+    * At the moment a process is not supposed to fail.
+    * @param pScene The imported data to work at.
+    */
+    void Execute( aiScene* pScene);
+
+    // -------------------------------------------------------------------
+    //! Apply the algorithm to a given mesh
+    void SplitMesh (unsigned int a, aiMesh* pcMesh,
+        std::vector<std::pair<aiMesh*, unsigned int> >& avList);
+
+    // -------------------------------------------------------------------
+    //! Update a node in the asset after a few of its meshes
+    //! have been split
+    static void UpdateNode(aiNode* pcNode,
+        const std::vector<std::pair<aiMesh*, unsigned int> >& avList);
+
+public:
+    //! Triangle limit
+    unsigned int LIMIT;
+};
+
+
+// ---------------------------------------------------------------------------
+/** Post-processing filter to split large meshes into sub-meshes
+ *
+ * Applied AFTER the JoinVertices-Step occurs.
+ * Returns UNIQUE vertices, splits by vertex number.
+*/
+class ASSIMP_API SplitLargeMeshesProcess_Vertex : public BaseProcess
+{
+public:
+
+    SplitLargeMeshesProcess_Vertex();
+    ~SplitLargeMeshesProcess_Vertex();
+
+public:
+    // -------------------------------------------------------------------
+    /** Returns whether the processing step is present in the given flag field.
+    * @param pFlags The processing flags the importer was called with. A bitwise
+    *   combination of #aiPostProcessSteps.
+    * @return true if the process is present in this flag fields, false if not.
+    */
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    /** Called prior to ExecuteOnScene().
+    * The function is a request to the process to update its configuration
+    * basing on the Importer's configuration property list.
+    */
+    virtual void SetupProperties(const Importer* pImp);
+
+
+    //! Set the split limit - needed for unit testing
+    inline void SetLimit(unsigned int l)
+        {LIMIT = l;}
+
+    //! Get the split limit
+    inline unsigned int GetLimit() const
+        {return LIMIT;}
+
+public:
+
+    // -------------------------------------------------------------------
+    /** Executes the post processing step on the given imported data.
+    * At the moment a process is not supposed to fail.
+    * @param pScene The imported data to work at.
+    */
+    void Execute( aiScene* pScene);
+
+    // -------------------------------------------------------------------
+    //! Apply the algorithm to a given mesh
+    void SplitMesh (unsigned int a, aiMesh* pcMesh,
+        std::vector<std::pair<aiMesh*, unsigned int> >& avList);
+
+    // NOTE: Reuse SplitLargeMeshesProcess_Triangle::UpdateNode()
+
+public:
+    //! Triangle limit
+    unsigned int LIMIT;
+};
+
+} // end of namespace Assimp
+
+#endif // !!AI_SPLITLARGEMESHES_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/TextureTransform.cpp b/thirdparty/assimp/code/PostProcessing/TextureTransform.cpp
new file mode 100644
index 0000000000..8ae2ba7218
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/TextureTransform.cpp
@@ -0,0 +1,566 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file A helper class that processes texture transformations */
+
+
+
+#include <assimp/Importer.hpp>
+#include <assimp/postprocess.h>
+#include <assimp/DefaultLogger.hpp>
+#include <assimp/scene.h>
+
+#include "TextureTransform.h"
+#include <assimp/StringUtils.h>
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+TextureTransformStep::TextureTransformStep() :
+    configFlags()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+TextureTransformStep::~TextureTransformStep()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool TextureTransformStep::IsActive( unsigned int pFlags) const
+{
+    return  (pFlags & aiProcess_TransformUVCoords) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Setup properties
+void TextureTransformStep::SetupProperties(const Importer* pImp)
+{
+    configFlags = pImp->GetPropertyInteger(AI_CONFIG_PP_TUV_EVALUATE,AI_UVTRAFO_ALL);
+}
+
+// ------------------------------------------------------------------------------------------------
+void TextureTransformStep::PreProcessUVTransform(STransformVecInfo& info)
+{
+    /*  This function tries to simplify the input UV transformation.
+     *  That's very important as it allows us to reduce the number
+     *  of output UV channels. The order in which the transformations
+     *  are applied is - as always - scaling, rotation, translation.
+     */
+
+    char szTemp[512];
+    int rounded = 0;
+
+
+    /* Optimize the rotation angle. That's slightly difficult as
+     * we have an inprecise floating-point number (when comparing
+     * UV transformations we'll take that into account by using
+     * an epsilon of 5 degrees). If there is a rotation value, we can't
+     * perform any further optimizations.
+     */
+    if (info.mRotation)
+    {
+        float out = info.mRotation;
+        if ((rounded = static_cast<int>((info.mRotation / static_cast<float>(AI_MATH_TWO_PI)))))
+        {
+            out -= rounded * static_cast<float>(AI_MATH_PI);
+            ASSIMP_LOG_INFO_F("Texture coordinate rotation ", info.mRotation, " can be simplified to ", out);
+        }
+
+        // Next step - convert negative rotation angles to positives
+        if (out < 0.f)
+            out = (float)AI_MATH_TWO_PI * 2 + out;
+
+        info.mRotation = out;
+        return;
+    }
+
+
+    /* Optimize UV translation in the U direction. To determine whether
+     * or not we can optimize we need to look at the requested mapping
+     * type (e.g. if mirroring is active there IS a difference between
+     * offset 2 and 3)
+     */
+    if ((rounded  = (int)info.mTranslation.x))  {
+        float out = 0.0f;
+        szTemp[0] = 0;
+        if (aiTextureMapMode_Wrap == info.mapU) {
+            // Wrap - simple take the fraction of the field
+            out = info.mTranslation.x-(float)rounded;
+			ai_snprintf(szTemp, 512, "[w] UV U offset %f can be simplified to %f", info.mTranslation.x, out);
+        }
+        else if (aiTextureMapMode_Mirror == info.mapU && 1 != rounded)  {
+            // Mirror
+            if (rounded % 2)
+                rounded--;
+            out = info.mTranslation.x-(float)rounded;
+
+            ai_snprintf(szTemp,512,"[m/d] UV U offset %f can be simplified to %f",info.mTranslation.x,out);
+        }
+        else if (aiTextureMapMode_Clamp == info.mapU || aiTextureMapMode_Decal == info.mapU)    {
+            // Clamp - translations beyond 1,1 are senseless
+            ai_snprintf(szTemp,512,"[c] UV U offset %f can be clamped to 1.0f",info.mTranslation.x);
+
+            out = 1.f;
+        }
+        if (szTemp[0])      {
+            ASSIMP_LOG_INFO(szTemp);
+            info.mTranslation.x = out;
+        }
+    }
+
+    /* Optimize UV translation in the V direction. To determine whether
+     * or not we can optimize we need to look at the requested mapping
+     * type (e.g. if mirroring is active there IS a difference between
+     * offset 2 and 3)
+     */
+    if ((rounded  = (int)info.mTranslation.y))  {
+        float out = 0.0f;
+        szTemp[0] = 0;
+        if (aiTextureMapMode_Wrap == info.mapV) {
+            // Wrap - simple take the fraction of the field
+            out = info.mTranslation.y-(float)rounded;
+            ::ai_snprintf(szTemp,512,"[w] UV V offset %f can be simplified to %f",info.mTranslation.y,out);
+        }
+        else if (aiTextureMapMode_Mirror == info.mapV  && 1 != rounded) {
+            // Mirror
+            if (rounded % 2)
+                rounded--;
+            out = info.mTranslation.x-(float)rounded;
+
+            ::ai_snprintf(szTemp,512,"[m/d] UV V offset %f can be simplified to %f",info.mTranslation.y,out);
+        }
+        else if (aiTextureMapMode_Clamp == info.mapV || aiTextureMapMode_Decal == info.mapV)    {
+            // Clamp - translations beyond 1,1 are senseless
+            ::ai_snprintf(szTemp,512,"[c] UV V offset %f canbe clamped to 1.0f",info.mTranslation.y);
+
+            out = 1.f;
+        }
+        if (szTemp[0])  {
+            ASSIMP_LOG_INFO(szTemp);
+            info.mTranslation.y = out;
+        }
+    }
+    return;
+}
+
+// ------------------------------------------------------------------------------------------------
+void UpdateUVIndex(const std::list<TTUpdateInfo>& l, unsigned int n)
+{
+    // Don't set if == 0 && wasn't set before
+    for (std::list<TTUpdateInfo>::const_iterator it = l.begin();it != l.end(); ++it) {
+        const TTUpdateInfo& info = *it;
+
+        if (info.directShortcut)
+            *info.directShortcut = n;
+        else if (!n)
+        {
+            info.mat->AddProperty<int>((int*)&n,1,AI_MATKEY_UVWSRC(info.semantic,info.index));
+        }
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+inline const char* MappingModeToChar(aiTextureMapMode map)
+{
+    if (aiTextureMapMode_Wrap == map)
+        return "-w";
+
+    if (aiTextureMapMode_Mirror == map)
+        return "-m";
+
+    return "-c";
+}
+
+// ------------------------------------------------------------------------------------------------
+void TextureTransformStep::Execute( aiScene* pScene)
+{
+    ASSIMP_LOG_DEBUG("TransformUVCoordsProcess begin");
+
+
+    /*  We build a per-mesh list of texture transformations we'll need
+     *  to apply. To achieve this, we iterate through all materials,
+     *  find all textures and get their transformations and UV indices.
+     *  Then we search for all meshes using this material.
+     */
+    typedef std::list<STransformVecInfo> MeshTrafoList;
+    std::vector<MeshTrafoList> meshLists(pScene->mNumMeshes);
+
+    for (unsigned int i = 0; i < pScene->mNumMaterials;++i) {
+
+        aiMaterial* mat = pScene->mMaterials[i];
+        for (unsigned int a = 0; a < mat->mNumProperties;++a)   {
+
+            aiMaterialProperty* prop = mat->mProperties[a];
+            if (!::strcmp( prop->mKey.data, "$tex.file"))   {
+                STransformVecInfo info;
+
+                // Setup a shortcut structure to allow for a fast updating
+                // of the UV index later
+                TTUpdateInfo update;
+                update.mat = (aiMaterial*) mat;
+                update.semantic = prop->mSemantic;
+                update.index = prop->mIndex;
+
+                // Get textured properties and transform
+                for (unsigned int a2 = 0; a2 < mat->mNumProperties;++a2)  {
+                    aiMaterialProperty* prop2 = mat->mProperties[a2];
+                    if (prop2->mSemantic != prop->mSemantic || prop2->mIndex != prop->mIndex) {
+                        continue;
+                    }
+
+                    if ( !::strcmp( prop2->mKey.data, "$tex.uvwsrc")) {
+                        info.uvIndex = *((int*)prop2->mData);
+
+                        // Store a direct pointer for later use
+                        update.directShortcut = (unsigned int*) prop2->mData;
+                    }
+
+                    else if ( !::strcmp( prop2->mKey.data, "$tex.mapmodeu")) {
+                        info.mapU = *((aiTextureMapMode*)prop2->mData);
+                    }
+                    else if ( !::strcmp( prop2->mKey.data, "$tex.mapmodev")) {
+                        info.mapV = *((aiTextureMapMode*)prop2->mData);
+                    }
+                    else if ( !::strcmp( prop2->mKey.data, "$tex.uvtrafo"))  {
+                        // ValidateDS should check this
+                        ai_assert(prop2->mDataLength >= 20);
+                        ::memcpy(&info.mTranslation.x,prop2->mData,sizeof(float)*5);
+
+                        // Directly remove this property from the list
+                        mat->mNumProperties--;
+                        for (unsigned int a3 = a2; a3 < mat->mNumProperties;++a3) {
+                            mat->mProperties[a3] = mat->mProperties[a3+1];
+                        }
+
+                        delete prop2;
+
+                        // Warn: could be an underflow, but this does not invoke undefined behaviour
+                        --a2;
+                    }
+                }
+
+                // Find out which transformations are to be evaluated
+                if (!(configFlags & AI_UVTRAFO_ROTATION)) {
+                    info.mRotation = 0.f;
+                }
+                if (!(configFlags & AI_UVTRAFO_SCALING)) {
+                    info.mScaling = aiVector2D(1.f,1.f);
+                }
+                if (!(configFlags & AI_UVTRAFO_TRANSLATION)) {
+                    info.mTranslation = aiVector2D(0.f,0.f);
+                }
+
+                // Do some preprocessing
+                PreProcessUVTransform(info);
+                info.uvIndex = std::min(info.uvIndex,AI_MAX_NUMBER_OF_TEXTURECOORDS -1u);
+
+                // Find out whether this material is used by more than
+                // one mesh. This will make our task much, much more difficult!
+                unsigned int cnt = 0;
+                for (unsigned int n = 0; n < pScene->mNumMeshes;++n)    {
+                    if (pScene->mMeshes[n]->mMaterialIndex == i)
+                        ++cnt;
+                }
+
+                if (!cnt)
+                    continue;
+                else if (1 != cnt)  {
+                    // This material is referenced by more than one mesh!
+                    // So we need to make sure the UV index for the texture
+                    // is identical for each of it ...
+                    info.lockedPos = AI_TT_UV_IDX_LOCK_TBD;
+                }
+
+                // Get all corresponding meshes
+                for (unsigned int n = 0; n < pScene->mNumMeshes;++n)    {
+                    aiMesh* mesh = pScene->mMeshes[n];
+                    if (mesh->mMaterialIndex != i || !mesh->mTextureCoords[0])
+                        continue;
+
+                    unsigned int uv = info.uvIndex;
+                    if (!mesh->mTextureCoords[uv])  {
+                        // If the requested UV index is not available, take the first one instead.
+                        uv = 0;
+                    }
+
+                    if (mesh->mNumUVComponents[info.uvIndex] >= 3){
+                        ASSIMP_LOG_WARN("UV transformations on 3D mapping channels are not supported");
+                        continue;
+                    }
+
+                    MeshTrafoList::iterator it;
+
+                    // Check whether we have this transform setup already
+                    for (it = meshLists[n].begin();it != meshLists[n].end(); ++it)  {
+
+                        if ((*it) == info && (*it).uvIndex == uv)   {
+                            (*it).updateList.push_back(update);
+                            break;
+                        }
+                    }
+
+                    if (it == meshLists[n].end())   {
+                        meshLists[n].push_back(info);
+                        meshLists[n].back().uvIndex = uv;
+                        meshLists[n].back().updateList.push_back(update);
+                    }
+                }
+            }
+        }
+    }
+
+    char buffer[1024]; // should be sufficiently large
+    unsigned int outChannels = 0, inChannels = 0, transformedChannels = 0;
+
+    // Now process all meshes. Important: we don't remove unreferenced UV channels.
+    // This is a job for the RemoveUnreferencedData-Step.
+    for (unsigned int q = 0; q < pScene->mNumMeshes;++q)    {
+
+        aiMesh* mesh = pScene->mMeshes[q];
+        MeshTrafoList& trafo =  meshLists[q];
+
+        inChannels += mesh->GetNumUVChannels();
+
+        if (!mesh->mTextureCoords[0] || trafo.empty() ||  (trafo.size() == 1 && trafo.begin()->IsUntransformed())) {
+            outChannels += mesh->GetNumUVChannels();
+            continue;
+        }
+
+        // Move untransformed UV channels to the first position in the list ....
+        // except if we need a new locked index which should be as small as possible
+        bool veto = false, need = false;
+        unsigned int cnt = 0;
+        unsigned int untransformed = 0;
+
+        MeshTrafoList::iterator it,it2;
+        for (it = trafo.begin();it != trafo.end(); ++it,++cnt)  {
+
+            if (!(*it).IsUntransformed()) {
+                need = true;
+            }
+
+            if ((*it).lockedPos == AI_TT_UV_IDX_LOCK_TBD)   {
+                // Lock this index and make sure it won't be changed
+                (*it).lockedPos = cnt;
+                veto = true;
+                continue;
+            }
+
+            if (!veto && it != trafo.begin() && (*it).IsUntransformed())    {
+                for (it2 = trafo.begin();it2 != it; ++it2) {
+                    if (!(*it2).IsUntransformed())
+                        break;
+                }
+                trafo.insert(it2,*it);
+                trafo.erase(it);
+                break;
+            }
+        }
+        if (!need)
+            continue;
+
+        // Find all that are not at their 'locked' position and move them to it.
+        // Conflicts are possible but quite unlikely.
+        cnt = 0;
+        for (it = trafo.begin();it != trafo.end(); ++it,++cnt) {
+            if ((*it).lockedPos != AI_TT_UV_IDX_LOCK_NONE && (*it).lockedPos != cnt) {
+                it2 = trafo.begin();unsigned int t = 0;
+                while (t != (*it).lockedPos)
+                    ++it2;
+
+                if ((*it2).lockedPos != AI_TT_UV_IDX_LOCK_NONE) {
+                    ASSIMP_LOG_ERROR("Channel mismatch, can't compute all transformations properly [design bug]");
+                    continue;
+                }
+
+                std::swap(*it2,*it);
+                if ((*it).lockedPos == untransformed)
+                    untransformed = cnt;
+            }
+        }
+
+        // ... and add dummies for all unreferenced channels
+        // at the end of the list
+        bool ref[AI_MAX_NUMBER_OF_TEXTURECOORDS];
+        for (unsigned int n = 0; n < AI_MAX_NUMBER_OF_TEXTURECOORDS;++n)
+            ref[n] = (!mesh->mTextureCoords[n] ? true : false);
+
+        for (it = trafo.begin();it != trafo.end(); ++it)
+            ref[(*it).uvIndex] = true;
+
+        for (unsigned int n = 0; n < AI_MAX_NUMBER_OF_TEXTURECOORDS;++n) {
+            if (ref[n])
+                continue;
+            trafo.push_back(STransformVecInfo());
+            trafo.back().uvIndex = n;
+        }
+
+        // Then check whether this list breaks the channel limit.
+        // The unimportant ones are at the end of the list, so
+        // it shouldn't be too worse if we remove them.
+        unsigned int size = (unsigned int)trafo.size();
+        if (size > AI_MAX_NUMBER_OF_TEXTURECOORDS) {
+
+            if (!DefaultLogger::isNullLogger()) {
+                ASSIMP_LOG_ERROR_F(static_cast<unsigned int>(trafo.size()), " UV channels required but just ", 
+                    AI_MAX_NUMBER_OF_TEXTURECOORDS, " available");
+            }
+            size = AI_MAX_NUMBER_OF_TEXTURECOORDS;
+        }
+
+
+        aiVector3D* old[AI_MAX_NUMBER_OF_TEXTURECOORDS];
+        for (unsigned int n = 0; n < AI_MAX_NUMBER_OF_TEXTURECOORDS;++n)
+            old[n] = mesh->mTextureCoords[n];
+
+        // Now continue and generate the output channels. Channels
+        // that we're not going to need later can be overridden.
+        it = trafo.begin();
+        for (unsigned int n = 0; n < trafo.size();++n,++it) {
+
+            if (n >= size)  {
+                // Try to use an untransformed channel for all channels we threw over board
+                UpdateUVIndex((*it).updateList,untransformed);
+                continue;
+            }
+
+            outChannels++;
+
+            // Write to the log
+            if (!DefaultLogger::isNullLogger()) {
+                ::ai_snprintf(buffer,1024,"Mesh %u, channel %u: t(%.3f,%.3f), s(%.3f,%.3f), r(%.3f), %s%s",
+                    q,n,
+                    (*it).mTranslation.x,
+                    (*it).mTranslation.y,
+                    (*it).mScaling.x,
+                    (*it).mScaling.y,
+                    AI_RAD_TO_DEG( (*it).mRotation),
+                    MappingModeToChar ((*it).mapU),
+                    MappingModeToChar ((*it).mapV));
+
+                ASSIMP_LOG_INFO(buffer);
+            }
+
+            // Check whether we need a new buffer here
+            if (mesh->mTextureCoords[n])    {
+
+                it2 = it;++it2;
+                for (unsigned int m = n+1; m < size;++m, ++it2) {
+
+                    if ((*it2).uvIndex == n){
+                        it2 = trafo.begin();
+                        break;
+                    }
+                }
+                if (it2 == trafo.begin()){
+                    mesh->mTextureCoords[n] = new aiVector3D[mesh->mNumVertices];
+                }
+            }
+            else mesh->mTextureCoords[n] = new aiVector3D[mesh->mNumVertices];
+
+            aiVector3D* src = old[(*it).uvIndex];
+            aiVector3D* dest, *end;
+            dest = mesh->mTextureCoords[n];
+
+            ai_assert(NULL != src);
+
+            // Copy the data to the destination array
+            if (dest != src)
+                ::memcpy(dest,src,sizeof(aiVector3D)*mesh->mNumVertices);
+
+            end = dest + mesh->mNumVertices;
+
+            // Build a transformation matrix and transform all UV coords with it
+            if (!(*it).IsUntransformed()) {
+                const aiVector2D& trl = (*it).mTranslation;
+                const aiVector2D& scl = (*it).mScaling;
+
+                // fixme: simplify ..
+                ++transformedChannels;
+                aiMatrix3x3 matrix;
+
+                aiMatrix3x3 m2,m3,m4,m5;
+
+                m4.a1 = scl.x;
+                m4.b2 = scl.y;
+
+                m2.a3 = m2.b3 = 0.5f;
+                m3.a3 = m3.b3 = -0.5f;
+
+                if ((*it).mRotation > AI_TT_ROTATION_EPSILON )
+                    aiMatrix3x3::RotationZ((*it).mRotation,matrix);
+
+                m5.a3 += trl.x; m5.b3 += trl.y;
+                matrix = m2 * m4 * matrix * m3 * m5;
+
+                for (src = dest; src != end; ++src) { /* manual homogenious divide */
+                    src->z = 1.f;
+                    *src = matrix * *src;
+                    src->x /= src->z;
+                    src->y /= src->z;
+                    src->z = 0.f;
+                }
+            }
+
+            // Update all UV indices
+            UpdateUVIndex((*it).updateList,n);
+        }
+    }
+
+    // Print some detailed statistics into the log
+    if (!DefaultLogger::isNullLogger()) {
+
+        if (transformedChannels)    {
+            ASSIMP_LOG_INFO_F("TransformUVCoordsProcess end: ", outChannels, " output channels (in: ", inChannels, ", modified: ", transformedChannels,")");
+        } else {
+            ASSIMP_LOG_DEBUG("TransformUVCoordsProcess finished");
+        }
+    }
+}
+
+
diff --git a/thirdparty/assimp/code/PostProcessing/TextureTransform.h b/thirdparty/assimp/code/PostProcessing/TextureTransform.h
new file mode 100644
index 0000000000..2a5d623d7f
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/TextureTransform.h
@@ -0,0 +1,232 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file Definition of a helper step that processes texture transformations */
+#ifndef AI_TEXTURE_TRANSFORM_H_INCLUDED
+#define AI_TEXTURE_TRANSFORM_H_INCLUDED
+
+#include <assimp/BaseImporter.h>
+#include "Common/BaseProcess.h"
+
+#include <assimp/material.h>
+#include <list>
+
+struct aiNode;
+struct aiMaterial;
+
+namespace Assimp    {
+
+#define AI_TT_UV_IDX_LOCK_TBD   0xffffffff
+#define AI_TT_UV_IDX_LOCK_NONE  0xeeeeeeee
+
+
+#define AI_TT_ROTATION_EPSILON  ((float)AI_DEG_TO_RAD(0.5))
+
+// ---------------------------------------------------------------------------
+/** Small helper structure representing a shortcut into the material list
+ *  to be able to update some values quickly.
+*/
+struct TTUpdateInfo {
+    TTUpdateInfo() AI_NO_EXCEPT
+    : directShortcut(nullptr)
+    , mat(nullptr)
+    , semantic(0)
+    , index(0) {
+        // empty
+    }
+
+    //! Direct shortcut, if available
+    unsigned int* directShortcut;
+
+    //! Material
+    aiMaterial *mat;
+
+    //! Texture type and index
+    unsigned int semantic, index;
+};
+
+
+// ---------------------------------------------------------------------------
+/** Helper class representing texture coordinate transformations
+*/
+struct STransformVecInfo : public aiUVTransform {
+    STransformVecInfo() AI_NO_EXCEPT
+    : uvIndex(0)
+    , mapU(aiTextureMapMode_Wrap)
+    , mapV(aiTextureMapMode_Wrap)
+    , lockedPos(AI_TT_UV_IDX_LOCK_NONE) {
+        // empty
+    }
+
+    //! Source texture coordinate index
+    unsigned int uvIndex;
+
+    //! Texture mapping mode in the u, v direction
+    aiTextureMapMode mapU,mapV;
+
+    //! Locked destination UV index
+    //! AI_TT_UV_IDX_LOCK_TBD - to be determined
+    //! AI_TT_UV_IDX_LOCK_NONE - none (default)
+    unsigned int lockedPos;
+
+    //! Update info - shortcuts into all materials
+    //! that are referencing this transform setup
+    std::list<TTUpdateInfo> updateList;
+
+
+    // -------------------------------------------------------------------
+    /** Compare two transform setups
+    */
+    inline bool operator== (const STransformVecInfo& other) const
+    {
+        // We use a small epsilon here
+        const static float epsilon = 0.05f;
+
+        if (std::fabs( mTranslation.x - other.mTranslation.x ) > epsilon ||
+            std::fabs( mTranslation.y - other.mTranslation.y ) > epsilon)
+        {
+            return false;
+        }
+
+        if (std::fabs( mScaling.x - other.mScaling.x ) > epsilon ||
+            std::fabs( mScaling.y - other.mScaling.y ) > epsilon)
+        {
+            return false;
+        }
+
+        if (std::fabs( mRotation - other.mRotation) > epsilon)
+        {
+            return false;
+        }
+        return true;
+    }
+
+    inline bool operator!= (const STransformVecInfo& other) const
+    {
+            return !(*this == other);
+    }
+
+
+    // -------------------------------------------------------------------
+    /** Returns whether this is an untransformed texture coordinate set
+    */
+    inline bool IsUntransformed() const
+    {
+        return (1.0f == mScaling.x && 1.f == mScaling.y &&
+            !mTranslation.x && !mTranslation.y &&
+            mRotation < AI_TT_ROTATION_EPSILON);
+    }
+
+    // -------------------------------------------------------------------
+    /** Build a 3x3 matrix from the transformations
+    */
+    inline void GetMatrix(aiMatrix3x3& mOut)
+    {
+        mOut = aiMatrix3x3();
+
+        if (1.0f != mScaling.x || 1.0f != mScaling.y)
+        {
+            aiMatrix3x3 mScale;
+            mScale.a1 = mScaling.x;
+            mScale.b2 = mScaling.y;
+            mOut = mScale;
+        }
+        if (mRotation)
+        {
+            aiMatrix3x3 mRot;
+            mRot.a1 = mRot.b2 = std::cos(mRotation);
+            mRot.a2 = mRot.b1 = std::sin(mRotation);
+            mRot.a2 = -mRot.a2;
+            mOut *= mRot;
+        }
+        if (mTranslation.x || mTranslation.y)
+        {
+            aiMatrix3x3 mTrans;
+            mTrans.a3 = mTranslation.x;
+            mTrans.b3 = mTranslation.y;
+            mOut *= mTrans;
+        }
+    }
+};
+
+
+// ---------------------------------------------------------------------------
+/** Helper step to compute final UV coordinate sets if there are scalings
+ *  or rotations in the original data read from the file.
+*/
+class TextureTransformStep : public BaseProcess
+{
+public:
+
+    TextureTransformStep();
+    ~TextureTransformStep();
+
+public:
+
+    // -------------------------------------------------------------------
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    void Execute( aiScene* pScene);
+
+    // -------------------------------------------------------------------
+    void SetupProperties(const Importer* pImp);
+
+
+protected:
+
+
+    // -------------------------------------------------------------------
+    /** Preprocess a specific UV transformation setup
+     *
+     *  @param info Transformation setup to be preprocessed.
+    */
+    void PreProcessUVTransform(STransformVecInfo& info);
+
+private:
+
+    unsigned int configFlags;
+};
+
+}
+
+#endif //! AI_TEXTURE_TRANSFORM_H_INCLUDED
diff --git a/thirdparty/assimp/code/PostProcessing/TriangulateProcess.cpp b/thirdparty/assimp/code/PostProcessing/TriangulateProcess.cpp
new file mode 100644
index 0000000000..1040836bbe
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/TriangulateProcess.cpp
@@ -0,0 +1,530 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file  TriangulateProcess.cpp
+ *  @brief Implementation of the post processing step to split up
+ *    all faces with more than three indices into triangles.
+ *
+ *
+ *  The triangulation algorithm will handle concave or convex polygons.
+ *  Self-intersecting or non-planar polygons are not rejected, but
+ *  they're probably not triangulated correctly.
+ *
+ * DEBUG SWITCHES - do not enable any of them in release builds:
+ *
+ * AI_BUILD_TRIANGULATE_COLOR_FACE_WINDING
+ *   - generates vertex colors to represent the face winding order.
+ *     the first vertex of a polygon becomes red, the last blue.
+ * AI_BUILD_TRIANGULATE_DEBUG_POLYS
+ *   - dump all polygons and their triangulation sequences to
+ *     a file
+ */
+#ifndef ASSIMP_BUILD_NO_TRIANGULATE_PROCESS
+
+#include "PostProcessing/TriangulateProcess.h"
+#include "PostProcessing/ProcessHelper.h"
+#include "Common/PolyTools.h"
+
+#include <memory>
+
+//#define AI_BUILD_TRIANGULATE_COLOR_FACE_WINDING
+//#define AI_BUILD_TRIANGULATE_DEBUG_POLYS
+
+#define POLY_GRID_Y 40
+#define POLY_GRID_X 70
+#define POLY_GRID_XPAD 20
+#define POLY_OUTPUT_FILE "assimp_polygons_debug.txt"
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+TriangulateProcess::TriangulateProcess()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+TriangulateProcess::~TriangulateProcess()
+{
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool TriangulateProcess::IsActive( unsigned int pFlags) const
+{
+    return (pFlags & aiProcess_Triangulate) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void TriangulateProcess::Execute( aiScene* pScene)
+{
+    ASSIMP_LOG_DEBUG("TriangulateProcess begin");
+
+    bool bHas = false;
+    for( unsigned int a = 0; a < pScene->mNumMeshes; a++)
+    {
+        if (pScene->mMeshes[ a ]) {
+            if ( TriangulateMesh( pScene->mMeshes[ a ] ) ) {
+                bHas = true;
+            }
+        }
+    }
+    if ( bHas ) {
+        ASSIMP_LOG_INFO( "TriangulateProcess finished. All polygons have been triangulated." );
+    } else {
+        ASSIMP_LOG_DEBUG( "TriangulateProcess finished. There was nothing to be done." );
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Triangulates the given mesh.
+bool TriangulateProcess::TriangulateMesh( aiMesh* pMesh)
+{
+    // Now we have aiMesh::mPrimitiveTypes, so this is only here for test cases
+    if (!pMesh->mPrimitiveTypes)    {
+        bool bNeed = false;
+
+        for( unsigned int a = 0; a < pMesh->mNumFaces; a++) {
+            const aiFace& face = pMesh->mFaces[a];
+
+            if( face.mNumIndices != 3)  {
+                bNeed = true;
+            }
+        }
+        if (!bNeed)
+            return false;
+    }
+    else if (!(pMesh->mPrimitiveTypes & aiPrimitiveType_POLYGON)) {
+        return false;
+    }
+
+    // Find out how many output faces we'll get
+    unsigned int numOut = 0, max_out = 0;
+    bool get_normals = true;
+    for( unsigned int a = 0; a < pMesh->mNumFaces; a++) {
+        aiFace& face = pMesh->mFaces[a];
+        if (face.mNumIndices <= 4) {
+            get_normals = false;
+        }
+        if( face.mNumIndices <= 3) {
+            numOut++;
+
+        }
+        else {
+            numOut += face.mNumIndices-2;
+            max_out = std::max(max_out,face.mNumIndices);
+        }
+    }
+
+    // Just another check whether aiMesh::mPrimitiveTypes is correct
+    ai_assert(numOut != pMesh->mNumFaces);
+
+    aiVector3D* nor_out = NULL;
+
+    // if we don't have normals yet, but expect them to be a cheap side
+    // product of triangulation anyway, allocate storage for them.
+    if (!pMesh->mNormals && get_normals) {
+        // XXX need a mechanism to inform the GenVertexNormals process to treat these normals as preprocessed per-face normals
+    //  nor_out = pMesh->mNormals = new aiVector3D[pMesh->mNumVertices];
+    }
+
+    // the output mesh will contain triangles, but no polys anymore
+    pMesh->mPrimitiveTypes |= aiPrimitiveType_TRIANGLE;
+    pMesh->mPrimitiveTypes &= ~aiPrimitiveType_POLYGON;
+
+    aiFace* out = new aiFace[numOut](), *curOut = out;
+    std::vector<aiVector3D> temp_verts3d(max_out+2); /* temporary storage for vertices */
+    std::vector<aiVector2D> temp_verts(max_out+2);
+
+    // Apply vertex colors to represent the face winding?
+#ifdef AI_BUILD_TRIANGULATE_COLOR_FACE_WINDING
+    if (!pMesh->mColors[0])
+        pMesh->mColors[0] = new aiColor4D[pMesh->mNumVertices];
+    else
+        new(pMesh->mColors[0]) aiColor4D[pMesh->mNumVertices];
+
+    aiColor4D* clr = pMesh->mColors[0];
+#endif
+
+#ifdef AI_BUILD_TRIANGULATE_DEBUG_POLYS
+    FILE* fout = fopen(POLY_OUTPUT_FILE,"a");
+#endif
+
+    const aiVector3D* verts = pMesh->mVertices;
+
+    // use std::unique_ptr to avoid slow std::vector<bool> specialiations
+    std::unique_ptr<bool[]> done(new bool[max_out]);
+    for( unsigned int a = 0; a < pMesh->mNumFaces; a++) {
+        aiFace& face = pMesh->mFaces[a];
+
+        unsigned int* idx = face.mIndices;
+        int num = (int)face.mNumIndices, ear = 0, tmp, prev = num-1, next = 0, max = num;
+
+        // Apply vertex colors to represent the face winding?
+#ifdef AI_BUILD_TRIANGULATE_COLOR_FACE_WINDING
+        for (unsigned int i = 0; i < face.mNumIndices; ++i) {
+            aiColor4D& c = clr[idx[i]];
+            c.r = (i+1) / (float)max;
+            c.b = 1.f - c.r;
+        }
+#endif
+
+        aiFace* const last_face = curOut;
+
+        // if it's a simple point,line or triangle: just copy it
+        if( face.mNumIndices <= 3)
+        {
+            aiFace& nface = *curOut++;
+            nface.mNumIndices = face.mNumIndices;
+            nface.mIndices    = face.mIndices;
+
+            face.mIndices = NULL;
+            continue;
+        }
+        // optimized code for quadrilaterals
+        else if ( face.mNumIndices == 4) {
+
+            // quads can have at maximum one concave vertex. Determine
+            // this vertex (if it exists) and start tri-fanning from
+            // it.
+            unsigned int start_vertex = 0;
+            for (unsigned int i = 0; i < 4; ++i) {
+                const aiVector3D& v0 = verts[face.mIndices[(i+3) % 4]];
+                const aiVector3D& v1 = verts[face.mIndices[(i+2) % 4]];
+                const aiVector3D& v2 = verts[face.mIndices[(i+1) % 4]];
+
+                const aiVector3D& v = verts[face.mIndices[i]];
+
+                aiVector3D left = (v0-v);
+                aiVector3D diag = (v1-v);
+                aiVector3D right = (v2-v);
+
+                left.Normalize();
+                diag.Normalize();
+                right.Normalize();
+
+                const float angle = std::acos(left*diag) + std::acos(right*diag);
+                if (angle > AI_MATH_PI_F) {
+                    // this is the concave point
+                    start_vertex = i;
+                    break;
+                }
+            }
+
+            const unsigned int temp[] = {face.mIndices[0], face.mIndices[1], face.mIndices[2], face.mIndices[3]};
+
+            aiFace& nface = *curOut++;
+            nface.mNumIndices = 3;
+            nface.mIndices = face.mIndices;
+
+            nface.mIndices[0] = temp[start_vertex];
+            nface.mIndices[1] = temp[(start_vertex + 1) % 4];
+            nface.mIndices[2] = temp[(start_vertex + 2) % 4];
+
+            aiFace& sface = *curOut++;
+            sface.mNumIndices = 3;
+            sface.mIndices = new unsigned int[3];
+
+            sface.mIndices[0] = temp[start_vertex];
+            sface.mIndices[1] = temp[(start_vertex + 2) % 4];
+            sface.mIndices[2] = temp[(start_vertex + 3) % 4];
+
+            // prevent double deletion of the indices field
+            face.mIndices = NULL;
+            continue;
+        }
+        else
+        {
+            // A polygon with more than 3 vertices can be either concave or convex.
+            // Usually everything we're getting is convex and we could easily
+            // triangulate by tri-fanning. However, LightWave is probably the only
+            // modeling suite to make extensive use of highly concave, monster polygons ...
+            // so we need to apply the full 'ear cutting' algorithm to get it right.
+
+            // RERQUIREMENT: polygon is expected to be simple and *nearly* planar.
+            // We project it onto a plane to get a 2d triangle.
+
+            // Collect all vertices of of the polygon.
+           for (tmp = 0; tmp < max; ++tmp) {
+                temp_verts3d[tmp] = verts[idx[tmp]];
+            }
+
+            // Get newell normal of the polygon. Store it for future use if it's a polygon-only mesh
+            aiVector3D n;
+            NewellNormal<3,3,3>(n,max,&temp_verts3d.front().x,&temp_verts3d.front().y,&temp_verts3d.front().z);
+            if (nor_out) {
+                 for (tmp = 0; tmp < max; ++tmp)
+                     nor_out[idx[tmp]] = n;
+            }
+
+            // Select largest normal coordinate to ignore for projection
+            const float ax = (n.x>0 ? n.x : -n.x);
+            const float ay = (n.y>0 ? n.y : -n.y);
+            const float az = (n.z>0 ? n.z : -n.z);
+
+            unsigned int ac = 0, bc = 1; /* no z coord. projection to xy */
+            float inv = n.z;
+            if (ax > ay) {
+                if (ax > az) { /* no x coord. projection to yz */
+                    ac = 1; bc = 2;
+                    inv = n.x;
+                }
+            }
+            else if (ay > az) { /* no y coord. projection to zy */
+                ac = 2; bc = 0;
+                inv = n.y;
+            }
+
+            // Swap projection axes to take the negated projection vector into account
+            if (inv < 0.f) {
+                std::swap(ac,bc);
+            }
+
+            for (tmp =0; tmp < max; ++tmp) {
+                temp_verts[tmp].x = verts[idx[tmp]][ac];
+                temp_verts[tmp].y = verts[idx[tmp]][bc];
+                done[tmp] = false;
+            }
+
+#ifdef AI_BUILD_TRIANGULATE_DEBUG_POLYS
+            // plot the plane onto which we mapped the polygon to a 2D ASCII pic
+            aiVector2D bmin,bmax;
+            ArrayBounds(&temp_verts[0],max,bmin,bmax);
+
+            char grid[POLY_GRID_Y][POLY_GRID_X+POLY_GRID_XPAD];
+            std::fill_n((char*)grid,POLY_GRID_Y*(POLY_GRID_X+POLY_GRID_XPAD),' ');
+
+            for (int i =0; i < max; ++i) {
+                const aiVector2D& v = (temp_verts[i] - bmin) / (bmax-bmin);
+                const size_t x = static_cast<size_t>(v.x*(POLY_GRID_X-1)), y = static_cast<size_t>(v.y*(POLY_GRID_Y-1));
+                char* loc = grid[y]+x;
+                if (grid[y][x] != ' ') {
+                    for(;*loc != ' '; ++loc);
+                    *loc++ = '_';
+                }
+                *(loc+::ai_snprintf(loc, POLY_GRID_XPAD,"%i",i)) = ' ';
+            }
+
+
+            for(size_t y = 0; y < POLY_GRID_Y; ++y) {
+                grid[y][POLY_GRID_X+POLY_GRID_XPAD-1] = '\0';
+                fprintf(fout,"%s\n",grid[y]);
+            }
+
+            fprintf(fout,"\ntriangulation sequence: ");
+#endif
+
+            //
+            // FIXME: currently this is the slow O(kn) variant with a worst case
+            // complexity of O(n^2) (I think). Can be done in O(n).
+            while (num > 3) {
+
+                // Find the next ear of the polygon
+                int num_found = 0;
+                for (ear = next;;prev = ear,ear = next) {
+
+                    // break after we looped two times without a positive match
+                    for (next=ear+1;done[(next>=max?next=0:next)];++next);
+                    if (next < ear) {
+                        if (++num_found == 2) {
+                            break;
+                        }
+                    }
+                    const aiVector2D* pnt1 = &temp_verts[ear],
+                        *pnt0 = &temp_verts[prev],
+                        *pnt2 = &temp_verts[next];
+
+                    // Must be a convex point. Assuming ccw winding, it must be on the right of the line between p-1 and p+1.
+                    if (OnLeftSideOfLine2D(*pnt0,*pnt2,*pnt1)) {
+                        continue;
+                    }
+
+                    // and no other point may be contained in this triangle
+                    for ( tmp = 0; tmp < max; ++tmp) {
+
+                        // We need to compare the actual values because it's possible that multiple indexes in
+                        // the polygon are referring to the same position. concave_polygon.obj is a sample
+                        //
+                        // FIXME: Use 'epsiloned' comparisons instead? Due to numeric inaccuracies in
+                        // PointInTriangle() I'm guessing that it's actually possible to construct
+                        // input data that would cause us to end up with no ears. The problem is,
+                        // which epsilon? If we chose a too large value, we'd get wrong results
+                        const aiVector2D& vtmp = temp_verts[tmp];
+                        if ( vtmp != *pnt1 && vtmp != *pnt2 && vtmp != *pnt0 && PointInTriangle2D(*pnt0,*pnt1,*pnt2,vtmp)) {
+                            break;
+                        }
+                    }
+                    if (tmp != max) {
+                        continue;
+                    }
+
+                    // this vertex is an ear
+                    break;
+                }
+                if (num_found == 2) {
+
+                    // Due to the 'two ear theorem', every simple polygon with more than three points must
+                    // have 2 'ears'. Here's definitely something wrong ... but we don't give up yet.
+                    //
+
+                    // Instead we're continuing with the standard tri-fanning algorithm which we'd
+                    // use if we had only convex polygons. That's life.
+                    ASSIMP_LOG_ERROR("Failed to triangulate polygon (no ear found). Probably not a simple polygon?");
+
+#ifdef AI_BUILD_TRIANGULATE_DEBUG_POLYS
+                    fprintf(fout,"critical error here, no ear found! ");
+#endif
+                    num = 0;
+                    break;
+
+                    curOut -= (max-num); /* undo all previous work */
+                    for (tmp = 0; tmp < max-2; ++tmp) {
+                        aiFace& nface = *curOut++;
+
+                        nface.mNumIndices = 3;
+                        if (!nface.mIndices)
+                            nface.mIndices = new unsigned int[3];
+
+                        nface.mIndices[0] = 0;
+                        nface.mIndices[1] = tmp+1;
+                        nface.mIndices[2] = tmp+2;
+
+                    }
+                    num = 0;
+                    break;
+                }
+
+                aiFace& nface = *curOut++;
+                nface.mNumIndices = 3;
+
+                if (!nface.mIndices) {
+                    nface.mIndices = new unsigned int[3];
+                }
+
+                // setup indices for the new triangle ...
+                nface.mIndices[0] = prev;
+                nface.mIndices[1] = ear;
+                nface.mIndices[2] = next;
+
+                // exclude the ear from most further processing
+                done[ear] = true;
+                --num;
+            }
+            if (num > 0) {
+                // We have three indices forming the last 'ear' remaining. Collect them.
+                aiFace& nface = *curOut++;
+                nface.mNumIndices = 3;
+                if (!nface.mIndices) {
+                    nface.mIndices = new unsigned int[3];
+                }
+
+                for (tmp = 0; done[tmp]; ++tmp);
+                nface.mIndices[0] = tmp;
+
+                for (++tmp; done[tmp]; ++tmp);
+                nface.mIndices[1] = tmp;
+
+                for (++tmp; done[tmp]; ++tmp);
+                nface.mIndices[2] = tmp;
+
+            }
+        }
+
+#ifdef AI_BUILD_TRIANGULATE_DEBUG_POLYS
+
+        for(aiFace* f = last_face; f != curOut; ++f) {
+            unsigned int* i = f->mIndices;
+            fprintf(fout," (%i %i %i)",i[0],i[1],i[2]);
+        }
+
+        fprintf(fout,"\n*********************************************************************\n");
+        fflush(fout);
+
+#endif
+
+        for(aiFace* f = last_face; f != curOut; ) {
+            unsigned int* i = f->mIndices;
+
+            //  drop dumb 0-area triangles - deactivated for now:
+            //FindDegenerates post processing step can do the same thing
+            //if (std::fabs(GetArea2D(temp_verts[i[0]],temp_verts[i[1]],temp_verts[i[2]])) < 1e-5f) {
+            //    ASSIMP_LOG_DEBUG("Dropping triangle with area 0");
+            //    --curOut;
+
+            //    delete[] f->mIndices;
+            //    f->mIndices = nullptr;
+
+            //    for(aiFace* ff = f; ff != curOut; ++ff) {
+            //        ff->mNumIndices = (ff+1)->mNumIndices;
+            //        ff->mIndices = (ff+1)->mIndices;
+            //        (ff+1)->mIndices = nullptr;
+            //    }
+            //    continue;
+            //}
+
+            i[0] = idx[i[0]];
+            i[1] = idx[i[1]];
+            i[2] = idx[i[2]];
+            ++f;
+        }
+
+        delete[] face.mIndices;
+        face.mIndices = NULL;
+    }
+
+#ifdef AI_BUILD_TRIANGULATE_DEBUG_POLYS
+    fclose(fout);
+#endif
+
+    // kill the old faces
+    delete [] pMesh->mFaces;
+
+    // ... and store the new ones
+    pMesh->mFaces    = out;
+    pMesh->mNumFaces = (unsigned int)(curOut-out); /* not necessarily equal to numOut */
+    return true;
+}
+
+#endif // !! ASSIMP_BUILD_NO_TRIANGULATE_PROCESS
diff --git a/thirdparty/assimp/code/PostProcessing/TriangulateProcess.h b/thirdparty/assimp/code/PostProcessing/TriangulateProcess.h
new file mode 100644
index 0000000000..916b5103dd
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/TriangulateProcess.h
@@ -0,0 +1,91 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file Defines a post processing step to triangulate all faces
+          with more than three vertices.
+ */
+#ifndef AI_TRIANGULATEPROCESS_H_INC
+#define AI_TRIANGULATEPROCESS_H_INC
+
+#include "Common/BaseProcess.h"
+
+struct aiMesh;
+
+class TriangulateProcessTest;
+
+namespace Assimp {
+
+// ---------------------------------------------------------------------------
+/** The TriangulateProcess splits up all faces with more than three indices
+ * into triangles. You usually want this to happen because the graphics cards
+ * need their data as triangles.
+ */
+class ASSIMP_API TriangulateProcess : public BaseProcess {
+public:
+    TriangulateProcess();
+    ~TriangulateProcess();
+
+    // -------------------------------------------------------------------
+    /** Returns whether the processing step is present in the given flag field.
+     * @param pFlags The processing flags the importer was called with. A bitwise
+     *   combination of #aiPostProcessSteps.
+     * @return true if the process is present in this flag fields, false if not.
+    */
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    /** Executes the post processing step on the given imported data.
+    * At the moment a process is not supposed to fail.
+    * @param pScene The imported data to work at.
+    */
+    void Execute( aiScene* pScene);
+
+    // -------------------------------------------------------------------
+    /** Triangulates the given mesh.
+     * @param pMesh The mesh to triangulate.
+     */
+    bool TriangulateMesh( aiMesh* pMesh);
+};
+
+} // end of namespace Assimp
+
+#endif // AI_TRIANGULATEPROCESS_H_INC
diff --git a/thirdparty/assimp/code/PostProcessing/ValidateDataStructure.cpp b/thirdparty/assimp/code/PostProcessing/ValidateDataStructure.cpp
new file mode 100644
index 0000000000..712fd6943d
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/ValidateDataStructure.cpp
@@ -0,0 +1,979 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file  ValidateDataStructure.cpp
+ *  @brief Implementation of the post processing step to validate
+ *    the data structure returned by Assimp.
+ */
+
+// internal headers
+#include "ValidateDataStructure.h"
+#include <assimp/BaseImporter.h>
+#include <assimp/fast_atof.h>
+#include "ProcessHelper.h"
+#include <memory>
+
+// CRT headers
+#include <stdarg.h>
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+ValidateDSProcess::ValidateDSProcess() :
+    mScene()
+{}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+ValidateDSProcess::~ValidateDSProcess()
+{}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool ValidateDSProcess::IsActive( unsigned int pFlags) const
+{
+    return (pFlags & aiProcess_ValidateDataStructure) != 0;
+}
+// ------------------------------------------------------------------------------------------------
+AI_WONT_RETURN void ValidateDSProcess::ReportError(const char* msg,...)
+{
+    ai_assert(NULL != msg);
+
+    va_list args;
+    va_start(args,msg);
+
+    char szBuffer[3000];
+    const int iLen = vsprintf(szBuffer,msg,args);
+    ai_assert(iLen > 0);
+
+    va_end(args);
+
+    throw DeadlyImportError("Validation failed: " + std::string(szBuffer,iLen));
+}
+// ------------------------------------------------------------------------------------------------
+void ValidateDSProcess::ReportWarning(const char* msg,...)
+{
+    ai_assert(NULL != msg);
+
+    va_list args;
+    va_start(args,msg);
+
+    char szBuffer[3000];
+    const int iLen = vsprintf(szBuffer,msg,args);
+    ai_assert(iLen > 0);
+
+    va_end(args);
+    ASSIMP_LOG_WARN("Validation warning: " + std::string(szBuffer,iLen));
+}
+
+// ------------------------------------------------------------------------------------------------
+inline
+int HasNameMatch(const aiString& in, aiNode* node) {
+    int result = (node->mName == in ? 1 : 0 );
+    for (unsigned int i = 0; i < node->mNumChildren;++i)    {
+        result += HasNameMatch(in,node->mChildren[i]);
+    }
+    return result;
+}
+
+// ------------------------------------------------------------------------------------------------
+template <typename T>
+inline
+void ValidateDSProcess::DoValidation(T** parray, unsigned int size, const char* firstName, const char* secondName) {
+    // validate all entries
+    if (size)
+    {
+        if (!parray)
+        {
+            ReportError("aiScene::%s is NULL (aiScene::%s is %i)",
+                firstName, secondName, size);
+        }
+        for (unsigned int i = 0; i < size;++i)
+        {
+            if (!parray[i])
+            {
+                ReportError("aiScene::%s[%i] is NULL (aiScene::%s is %i)",
+                    firstName,i,secondName,size);
+            }
+            Validate(parray[i]);
+        }
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+template <typename T>
+inline void ValidateDSProcess::DoValidationEx(T** parray, unsigned int size,
+    const char* firstName, const char* secondName)
+{
+    // validate all entries
+    if (size)
+    {
+        if (!parray)    {
+            ReportError("aiScene::%s is NULL (aiScene::%s is %i)",
+                firstName, secondName, size);
+        }
+        for (unsigned int i = 0; i < size;++i)
+        {
+            if (!parray[i])
+            {
+                ReportError("aiScene::%s[%u] is NULL (aiScene::%s is %u)",
+                    firstName,i,secondName,size);
+            }
+            Validate(parray[i]);
+
+            // check whether there are duplicate names
+            for (unsigned int a = i+1; a < size;++a)
+            {
+                if (parray[i]->mName == parray[a]->mName)
+                {
+                	ReportError("aiScene::%s[%u] has the same name as "
+                        "aiScene::%s[%u]",firstName, i,secondName, a);
+                }
+            }
+        }
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+template <typename T>
+inline
+void ValidateDSProcess::DoValidationWithNameCheck(T** array, unsigned int size, const char* firstName,
+        const char* secondName) {
+    // validate all entries
+    DoValidationEx(array,size,firstName,secondName);
+
+    for (unsigned int i = 0; i < size;++i) {
+        int res = HasNameMatch(array[i]->mName,mScene->mRootNode);
+        if (0 == res)   {
+            const std::string name = static_cast<char*>(array[i]->mName.data);
+            ReportError("aiScene::%s[%i] has no corresponding node in the scene graph (%s)",
+                firstName,i, name.c_str());
+        } else if (1 != res)  {
+            const std::string name = static_cast<char*>(array[i]->mName.data);
+            ReportError("aiScene::%s[%i]: there are more than one nodes with %s as name",
+                firstName,i, name.c_str());
+        }
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void ValidateDSProcess::Execute( aiScene* pScene) {
+    mScene = pScene;
+    ASSIMP_LOG_DEBUG("ValidateDataStructureProcess begin");
+
+    // validate the node graph of the scene
+    Validate(pScene->mRootNode);
+
+    // validate all meshes
+    if (pScene->mNumMeshes) {
+        DoValidation(pScene->mMeshes,pScene->mNumMeshes,"mMeshes","mNumMeshes");
+    }
+    else if (!(mScene->mFlags & AI_SCENE_FLAGS_INCOMPLETE)) {
+        ReportError("aiScene::mNumMeshes is 0. At least one mesh must be there");
+    }
+    else if (pScene->mMeshes)   {
+        ReportError("aiScene::mMeshes is non-null although there are no meshes");
+    }
+
+    // validate all animations
+    if (pScene->mNumAnimations) {
+        DoValidation(pScene->mAnimations,pScene->mNumAnimations,
+            "mAnimations","mNumAnimations");
+    }
+    else if (pScene->mAnimations)   {
+        ReportError("aiScene::mAnimations is non-null although there are no animations");
+    }
+
+    // validate all cameras
+    if (pScene->mNumCameras) {
+        DoValidationWithNameCheck(pScene->mCameras,pScene->mNumCameras,
+            "mCameras","mNumCameras");
+    }
+    else if (pScene->mCameras)  {
+        ReportError("aiScene::mCameras is non-null although there are no cameras");
+    }
+
+    // validate all lights
+    if (pScene->mNumLights) {
+        DoValidationWithNameCheck(pScene->mLights,pScene->mNumLights,
+            "mLights","mNumLights");
+    }
+    else if (pScene->mLights)   {
+        ReportError("aiScene::mLights is non-null although there are no lights");
+    }
+
+    // validate all textures
+    if (pScene->mNumTextures) {
+        DoValidation(pScene->mTextures,pScene->mNumTextures,
+            "mTextures","mNumTextures");
+    }
+    else if (pScene->mTextures) {
+        ReportError("aiScene::mTextures is non-null although there are no textures");
+    }
+
+    // validate all materials
+    if (pScene->mNumMaterials) {
+        DoValidation(pScene->mMaterials,pScene->mNumMaterials,"mMaterials","mNumMaterials");
+    }
+#if 0
+    // NOTE: ScenePreprocessor generates a default material if none is there
+    else if (!(mScene->mFlags & AI_SCENE_FLAGS_INCOMPLETE)) {
+        ReportError("aiScene::mNumMaterials is 0. At least one material must be there");
+    }
+#endif
+    else if (pScene->mMaterials)    {
+        ReportError("aiScene::mMaterials is non-null although there are no materials");
+    }
+
+//  if (!has)ReportError("The aiScene data structure is empty");
+    ASSIMP_LOG_DEBUG("ValidateDataStructureProcess end");
+}
+
+// ------------------------------------------------------------------------------------------------
+void ValidateDSProcess::Validate( const aiLight* pLight)
+{
+    if (pLight->mType == aiLightSource_UNDEFINED)
+        ReportWarning("aiLight::mType is aiLightSource_UNDEFINED");
+
+    if (!pLight->mAttenuationConstant &&
+        !pLight->mAttenuationLinear   &&
+        !pLight->mAttenuationQuadratic) {
+        ReportWarning("aiLight::mAttenuationXXX - all are zero");
+    }
+
+    if (pLight->mAngleInnerCone > pLight->mAngleOuterCone)
+        ReportError("aiLight::mAngleInnerCone is larger than aiLight::mAngleOuterCone");
+
+    if (pLight->mColorDiffuse.IsBlack() && pLight->mColorAmbient.IsBlack()
+        && pLight->mColorSpecular.IsBlack())
+    {
+        ReportWarning("aiLight::mColorXXX - all are black and won't have any influence");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+void ValidateDSProcess::Validate( const aiCamera* pCamera)
+{
+    if (pCamera->mClipPlaneFar <= pCamera->mClipPlaneNear)
+        ReportError("aiCamera::mClipPlaneFar must be >= aiCamera::mClipPlaneNear");
+
+    // FIX: there are many 3ds files with invalid FOVs. No reason to
+    // reject them at all ... a warning is appropriate.
+    if (!pCamera->mHorizontalFOV || pCamera->mHorizontalFOV >= (float)AI_MATH_PI)
+        ReportWarning("%f is not a valid value for aiCamera::mHorizontalFOV",pCamera->mHorizontalFOV);
+}
+
+// ------------------------------------------------------------------------------------------------
+void ValidateDSProcess::Validate( const aiMesh* pMesh)
+{
+    // validate the material index of the mesh
+    if (mScene->mNumMaterials && pMesh->mMaterialIndex >= mScene->mNumMaterials)
+    {
+        ReportError("aiMesh::mMaterialIndex is invalid (value: %i maximum: %i)",
+            pMesh->mMaterialIndex,mScene->mNumMaterials-1);
+    }
+
+    Validate(&pMesh->mName);
+
+    for (unsigned int i = 0; i < pMesh->mNumFaces; ++i)
+    {
+        aiFace& face = pMesh->mFaces[i];
+
+        if (pMesh->mPrimitiveTypes)
+        {
+            switch (face.mNumIndices)
+            {
+            case 0:
+                ReportError("aiMesh::mFaces[%i].mNumIndices is 0",i);
+                break;
+            case 1:
+                if (0 == (pMesh->mPrimitiveTypes & aiPrimitiveType_POINT))
+                {
+                    ReportError("aiMesh::mFaces[%i] is a POINT but aiMesh::mPrimitiveTypes "
+                        "does not report the POINT flag",i);
+                }
+                break;
+            case 2:
+                if (0 == (pMesh->mPrimitiveTypes & aiPrimitiveType_LINE))
+                {
+                    ReportError("aiMesh::mFaces[%i] is a LINE but aiMesh::mPrimitiveTypes "
+                        "does not report the LINE flag",i);
+                }
+                break;
+            case 3:
+                if (0 == (pMesh->mPrimitiveTypes & aiPrimitiveType_TRIANGLE))
+                {
+                    ReportError("aiMesh::mFaces[%i] is a TRIANGLE but aiMesh::mPrimitiveTypes "
+                        "does not report the TRIANGLE flag",i);
+                }
+                break;
+            default:
+                if (0 == (pMesh->mPrimitiveTypes & aiPrimitiveType_POLYGON))
+                {
+                    this->ReportError("aiMesh::mFaces[%i] is a POLYGON but aiMesh::mPrimitiveTypes "
+                        "does not report the POLYGON flag",i);
+                }
+                break;
+            };
+        }
+
+        if (!face.mIndices)
+            ReportError("aiMesh::mFaces[%i].mIndices is NULL",i);
+    }
+
+    // positions must always be there ...
+    if (!pMesh->mNumVertices || (!pMesh->mVertices && !mScene->mFlags)) {
+        ReportError("The mesh %s contains no vertices", pMesh->mName.C_Str());
+    }
+
+    if (pMesh->mNumVertices > AI_MAX_VERTICES) {
+        ReportError("Mesh has too many vertices: %u, but the limit is %u",pMesh->mNumVertices,AI_MAX_VERTICES);
+    }
+    if (pMesh->mNumFaces > AI_MAX_FACES) {
+        ReportError("Mesh has too many faces: %u, but the limit is %u",pMesh->mNumFaces,AI_MAX_FACES);
+    }
+
+    // if tangents are there there must also be bitangent vectors ...
+    if ((pMesh->mTangents != NULL) != (pMesh->mBitangents != NULL)) {
+        ReportError("If there are tangents, bitangent vectors must be present as well");
+    }
+
+    // faces, too
+    if (!pMesh->mNumFaces || (!pMesh->mFaces && !mScene->mFlags))   {
+        ReportError("Mesh %s contains no faces", pMesh->mName.C_Str());
+    }
+
+    // now check whether the face indexing layout is correct:
+    // unique vertices, pseudo-indexed.
+    std::vector<bool> abRefList;
+    abRefList.resize(pMesh->mNumVertices,false);
+    for (unsigned int i = 0; i < pMesh->mNumFaces;++i)
+    {
+        aiFace& face = pMesh->mFaces[i];
+        if (face.mNumIndices > AI_MAX_FACE_INDICES) {
+            ReportError("Face %u has too many faces: %u, but the limit is %u",i,face.mNumIndices,AI_MAX_FACE_INDICES);
+        }
+
+        for (unsigned int a = 0; a < face.mNumIndices;++a)
+        {
+            if (face.mIndices[a] >= pMesh->mNumVertices)    {
+                ReportError("aiMesh::mFaces[%i]::mIndices[%i] is out of range",i,a);
+            }
+            // the MSB flag is temporarily used by the extra verbose
+            // mode to tell us that the JoinVerticesProcess might have
+            // been executed already.
+			/*if ( !(this->mScene->mFlags & AI_SCENE_FLAGS_NON_VERBOSE_FORMAT ) && !(this->mScene->mFlags & AI_SCENE_FLAGS_ALLOW_SHARED) &&
+				abRefList[face.mIndices[a]])
+            {
+                ReportError("aiMesh::mVertices[%i] is referenced twice - second "
+                    "time by aiMesh::mFaces[%i]::mIndices[%i]",face.mIndices[a],i,a);
+            }*/
+            abRefList[face.mIndices[a]] = true;
+        }
+    }
+
+    // check whether there are vertices that aren't referenced by a face
+    bool b = false;
+    for (unsigned int i = 0; i < pMesh->mNumVertices;++i)   {
+        if (!abRefList[i])b = true;
+    }
+    abRefList.clear();
+    if (b) {
+    	ReportWarning("There are unreferenced vertices");
+    }
+
+    // texture channel 2 may not be set if channel 1 is zero ...
+    {
+        unsigned int i = 0;
+        for (;i < AI_MAX_NUMBER_OF_TEXTURECOORDS;++i)
+        {
+            if (!pMesh->HasTextureCoords(i))break;
+        }
+        for (;i < AI_MAX_NUMBER_OF_TEXTURECOORDS;++i)
+            if (pMesh->HasTextureCoords(i))
+            {
+                ReportError("Texture coordinate channel %i exists "
+                    "although the previous channel was NULL.",i);
+            }
+    }
+    // the same for the vertex colors
+    {
+        unsigned int i = 0;
+        for (;i < AI_MAX_NUMBER_OF_COLOR_SETS;++i)
+        {
+            if (!pMesh->HasVertexColors(i))break;
+        }
+        for (;i < AI_MAX_NUMBER_OF_COLOR_SETS;++i)
+            if (pMesh->HasVertexColors(i))
+            {
+                ReportError("Vertex color channel %i is exists "
+                    "although the previous channel was NULL.",i);
+            }
+    }
+
+
+    // now validate all bones
+    if (pMesh->mNumBones)
+    {
+        if (!pMesh->mBones)
+        {
+            ReportError("aiMesh::mBones is NULL (aiMesh::mNumBones is %i)",
+                pMesh->mNumBones);
+        }
+        std::unique_ptr<float[]> afSum(nullptr);
+        if (pMesh->mNumVertices)
+        {
+            afSum.reset(new float[pMesh->mNumVertices]);
+            for (unsigned int i = 0; i < pMesh->mNumVertices;++i)
+                afSum[i] = 0.0f;
+        }
+
+        // check whether there are duplicate bone names
+        for (unsigned int i = 0; i < pMesh->mNumBones;++i)
+        {
+            const aiBone* bone = pMesh->mBones[i];
+            if (bone->mNumWeights > AI_MAX_BONE_WEIGHTS) {
+                ReportError("Bone %u has too many weights: %u, but the limit is %u",i,bone->mNumWeights,AI_MAX_BONE_WEIGHTS);
+            }
+
+            if (!pMesh->mBones[i])
+            {
+                ReportError("aiMesh::mBones[%i] is NULL (aiMesh::mNumBones is %i)",
+                    i,pMesh->mNumBones);
+            }
+            Validate(pMesh,pMesh->mBones[i],afSum.get());
+
+            for (unsigned int a = i+1; a < pMesh->mNumBones;++a)
+            {
+                if (pMesh->mBones[i]->mName == pMesh->mBones[a]->mName)
+                {
+                    const char *name = "unknown";
+                    if (nullptr != pMesh->mBones[ i ]->mName.C_Str()) {
+                        name = pMesh->mBones[ i ]->mName.C_Str();
+                    }
+                    ReportError("aiMesh::mBones[%i], name = \"%s\" has the same name as "
+                        "aiMesh::mBones[%i]", i, name, a );
+                }
+            }
+        }
+        // check whether all bone weights for a vertex sum to 1.0 ...
+        for (unsigned int i = 0; i < pMesh->mNumVertices;++i)
+        {
+            if (afSum[i] && (afSum[i] <= 0.94 || afSum[i] >= 1.05)) {
+                ReportWarning("aiMesh::mVertices[%i]: bone weight sum != 1.0 (sum is %f)",i,afSum[i]);
+            }
+        }
+    }
+    else if (pMesh->mBones)
+    {
+        ReportError("aiMesh::mBones is non-null although there are no bones");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+void ValidateDSProcess::Validate( const aiMesh* pMesh, const aiBone* pBone,float* afSum) {
+    this->Validate(&pBone->mName);
+
+    if (!pBone->mNumWeights)    {
+        //ReportError("aiBone::mNumWeights is zero");
+    }
+
+    // check whether all vertices affected by this bone are valid
+    for (unsigned int i = 0; i < pBone->mNumWeights;++i)
+    {
+        if (pBone->mWeights[i].mVertexId >= pMesh->mNumVertices)    {
+            ReportError("aiBone::mWeights[%i].mVertexId is out of range",i);
+        }
+        else if (!pBone->mWeights[i].mWeight || pBone->mWeights[i].mWeight > 1.0f)  {
+            ReportWarning("aiBone::mWeights[%i].mWeight has an invalid value",i);
+        }
+        afSum[pBone->mWeights[i].mVertexId] += pBone->mWeights[i].mWeight;
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+void ValidateDSProcess::Validate( const aiAnimation* pAnimation)
+{
+    Validate(&pAnimation->mName);
+
+    // validate all materials
+    if (pAnimation->mNumChannels)
+    {
+        if (!pAnimation->mChannels) {
+            ReportError("aiAnimation::mChannels is NULL (aiAnimation::mNumChannels is %i)",
+                pAnimation->mNumChannels);
+        }
+        for (unsigned int i = 0; i < pAnimation->mNumChannels;++i)
+        {
+            if (!pAnimation->mChannels[i])
+            {
+                ReportError("aiAnimation::mChannels[%i] is NULL (aiAnimation::mNumChannels is %i)",
+                    i, pAnimation->mNumChannels);
+            }
+            Validate(pAnimation, pAnimation->mChannels[i]);
+        }
+    }
+    else {
+    	ReportError("aiAnimation::mNumChannels is 0. At least one node animation channel must be there.");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+void ValidateDSProcess::SearchForInvalidTextures(const aiMaterial* pMaterial,
+    aiTextureType type)
+{
+    const char* szType = TextureTypeToString(type);
+
+    // ****************************************************************************
+    // Search all keys of the material ...
+    // textures must be specified with ascending indices
+    // (e.g. diffuse #2 may not be specified if diffuse #1 is not there ...)
+    // ****************************************************************************
+
+    int iNumIndices = 0;
+    int iIndex = -1;
+    for (unsigned int i = 0; i < pMaterial->mNumProperties;++i) {
+        aiMaterialProperty* prop = pMaterial->mProperties[ i ];
+        ai_assert(nullptr != prop);
+        if ( !::strcmp(prop->mKey.data,"$tex.file") && prop->mSemantic == static_cast<unsigned int>(type))  {
+            iIndex = std::max(iIndex, (int) prop->mIndex);
+            ++iNumIndices;
+
+            if (aiPTI_String != prop->mType) {
+                ReportError("Material property %s is expected to be a string", prop->mKey.data);
+            }
+        }
+    }
+    if (iIndex +1 != iNumIndices)   {
+        ReportError("%s #%i is set, but there are only %i %s textures",
+            szType,iIndex,iNumIndices,szType);
+    }
+    if (!iNumIndices)return;
+    std::vector<aiTextureMapping> mappings(iNumIndices);
+
+    // Now check whether all UV indices are valid ...
+    bool bNoSpecified = true;
+    for (unsigned int i = 0; i < pMaterial->mNumProperties;++i)
+    {
+        aiMaterialProperty* prop = pMaterial->mProperties[i];
+        if (prop->mSemantic != type)continue;
+
+        if ((int)prop->mIndex >= iNumIndices)
+        {
+            ReportError("Found texture property with index %i, although there "
+                "are only %i textures of type %s",
+                prop->mIndex, iNumIndices, szType);
+        }
+
+        if (!::strcmp(prop->mKey.data,"$tex.mapping"))  {
+            if (aiPTI_Integer != prop->mType || prop->mDataLength < sizeof(aiTextureMapping))
+            {
+                ReportError("Material property %s%i is expected to be an integer (size is %i)",
+                    prop->mKey.data,prop->mIndex,prop->mDataLength);
+            }
+            mappings[prop->mIndex] = *((aiTextureMapping*)prop->mData);
+        }
+        else if (!::strcmp(prop->mKey.data,"$tex.uvtrafo")) {
+            if (aiPTI_Float != prop->mType || prop->mDataLength < sizeof(aiUVTransform))
+            {
+                ReportError("Material property %s%i is expected to be 5 floats large (size is %i)",
+                    prop->mKey.data,prop->mIndex, prop->mDataLength);
+            }
+            mappings[prop->mIndex] = *((aiTextureMapping*)prop->mData);
+        }
+        else if (!::strcmp(prop->mKey.data,"$tex.uvwsrc")) {
+            if (aiPTI_Integer != prop->mType || sizeof(int) > prop->mDataLength)
+            {
+                ReportError("Material property %s%i is expected to be an integer (size is %i)",
+                    prop->mKey.data,prop->mIndex,prop->mDataLength);
+            }
+            bNoSpecified = false;
+
+            // Ignore UV indices for texture channels that are not there ...
+
+            // Get the value
+            iIndex = *((unsigned int*)prop->mData);
+
+            // Check whether there is a mesh using this material
+            // which has not enough UV channels ...
+            for (unsigned int a = 0; a < mScene->mNumMeshes;++a)
+            {
+                aiMesh* mesh = this->mScene->mMeshes[a];
+                if(mesh->mMaterialIndex == (unsigned int)i)
+                {
+                    int iChannels = 0;
+                    while (mesh->HasTextureCoords(iChannels))++iChannels;
+                    if (iIndex >= iChannels)
+                    {
+                        ReportWarning("Invalid UV index: %i (key %s). Mesh %i has only %i UV channels",
+                            iIndex,prop->mKey.data,a,iChannels);
+                    }
+                }
+            }
+        }
+    }
+    if (bNoSpecified)
+    {
+        // Assume that all textures are using the first UV channel
+        for (unsigned int a = 0; a < mScene->mNumMeshes;++a)
+        {
+            aiMesh* mesh = mScene->mMeshes[a];
+            if(mesh->mMaterialIndex == (unsigned int)iIndex && mappings[0] == aiTextureMapping_UV)
+            {
+                if (!mesh->mTextureCoords[0])
+                {
+                    // This is a special case ... it could be that the
+                    // original mesh format intended the use of a special
+                    // mapping here.
+                    ReportWarning("UV-mapped texture, but there are no UV coords");
+                }
+            }
+        }
+    }
+}
+// ------------------------------------------------------------------------------------------------
+void ValidateDSProcess::Validate( const aiMaterial* pMaterial)
+{
+    // check whether there are material keys that are obviously not legal
+    for (unsigned int i = 0; i < pMaterial->mNumProperties;++i)
+    {
+        const aiMaterialProperty* prop = pMaterial->mProperties[i];
+        if (!prop)  {
+            ReportError("aiMaterial::mProperties[%i] is NULL (aiMaterial::mNumProperties is %i)",
+                i,pMaterial->mNumProperties);
+        }
+        if (!prop->mDataLength || !prop->mData) {
+            ReportError("aiMaterial::mProperties[%i].mDataLength or "
+                "aiMaterial::mProperties[%i].mData is 0",i,i);
+        }
+        // check all predefined types
+        if (aiPTI_String == prop->mType)    {
+            // FIX: strings are now stored in a less expensive way, but we can't use the
+            // validation routine for 'normal' aiStrings
+            if (prop->mDataLength < 5 || prop->mDataLength < 4 + (*reinterpret_cast<uint32_t*>(prop->mData)) + 1)   {
+                ReportError("aiMaterial::mProperties[%i].mDataLength is "
+                    "too small to contain a string (%i, needed: %i)",
+                    i,prop->mDataLength,static_cast<int>(sizeof(aiString)));
+            }
+            if(prop->mData[prop->mDataLength-1]) {
+                ReportError("Missing null-terminator in string material property");
+            }
+        //  Validate((const aiString*)prop->mData);
+        }
+        else if (aiPTI_Float == prop->mType)    {
+            if (prop->mDataLength < sizeof(float))  {
+                ReportError("aiMaterial::mProperties[%i].mDataLength is "
+                    "too small to contain a float (%i, needed: %i)",
+                    i,prop->mDataLength, static_cast<int>(sizeof(float)));
+            }
+        }
+        else if (aiPTI_Integer == prop->mType)  {
+            if (prop->mDataLength < sizeof(int))    {
+                ReportError("aiMaterial::mProperties[%i].mDataLength is "
+                    "too small to contain an integer (%i, needed: %i)",
+                    i,prop->mDataLength, static_cast<int>(sizeof(int)));
+            }
+        }
+        // TODO: check whether there is a key with an unknown name ...
+    }
+
+    // make some more specific tests
+    ai_real fTemp;
+    int iShading;
+    if (AI_SUCCESS == aiGetMaterialInteger( pMaterial,AI_MATKEY_SHADING_MODEL,&iShading))   {
+        switch ((aiShadingMode)iShading)
+        {
+        case aiShadingMode_Blinn:
+        case aiShadingMode_CookTorrance:
+        case aiShadingMode_Phong:
+
+            if (AI_SUCCESS != aiGetMaterialFloat(pMaterial,AI_MATKEY_SHININESS,&fTemp)) {
+                ReportWarning("A specular shading model is specified but there is no "
+                    "AI_MATKEY_SHININESS key");
+            }
+            if (AI_SUCCESS == aiGetMaterialFloat(pMaterial,AI_MATKEY_SHININESS_STRENGTH,&fTemp) && !fTemp)  {
+                ReportWarning("A specular shading model is specified but the value of the "
+                    "AI_MATKEY_SHININESS_STRENGTH key is 0.0");
+            }
+            break;
+        default:
+            break;
+        }
+    }
+
+    if (AI_SUCCESS == aiGetMaterialFloat( pMaterial,AI_MATKEY_OPACITY,&fTemp) && (!fTemp || fTemp > 1.01)) {
+        ReportWarning("Invalid opacity value (must be 0 < opacity < 1.0)");
+    }
+
+    // Check whether there are invalid texture keys
+    // TODO: that's a relict of the past, where texture type and index were baked
+    // into the material string ... we could do that in one single pass.
+    SearchForInvalidTextures(pMaterial,aiTextureType_DIFFUSE);
+    SearchForInvalidTextures(pMaterial,aiTextureType_SPECULAR);
+    SearchForInvalidTextures(pMaterial,aiTextureType_AMBIENT);
+    SearchForInvalidTextures(pMaterial,aiTextureType_EMISSIVE);
+    SearchForInvalidTextures(pMaterial,aiTextureType_OPACITY);
+    SearchForInvalidTextures(pMaterial,aiTextureType_SHININESS);
+    SearchForInvalidTextures(pMaterial,aiTextureType_HEIGHT);
+    SearchForInvalidTextures(pMaterial,aiTextureType_NORMALS);
+    SearchForInvalidTextures(pMaterial,aiTextureType_DISPLACEMENT);
+    SearchForInvalidTextures(pMaterial,aiTextureType_LIGHTMAP);
+    SearchForInvalidTextures(pMaterial,aiTextureType_REFLECTION);
+}
+
+// ------------------------------------------------------------------------------------------------
+void ValidateDSProcess::Validate( const aiTexture* pTexture)
+{
+    // the data section may NEVER be NULL
+    if (!pTexture->pcData)  {
+        ReportError("aiTexture::pcData is NULL");
+    }
+    if (pTexture->mHeight)
+    {
+        if (!pTexture->mWidth){
+        	ReportError("aiTexture::mWidth is zero (aiTexture::mHeight is %i, uncompressed texture)",
+        			pTexture->mHeight);
+        }
+    }
+    else
+    {
+        if (!pTexture->mWidth) {
+            ReportError("aiTexture::mWidth is zero (compressed texture)");
+        }
+        if ('\0' != pTexture->achFormatHint[3]) {
+            ReportWarning("aiTexture::achFormatHint must be zero-terminated");
+        }
+        else if ('.'  == pTexture->achFormatHint[0])    {
+            ReportWarning("aiTexture::achFormatHint should contain a file extension "
+                "without a leading dot (format hint: %s).",pTexture->achFormatHint);
+        }
+    }
+
+    const char* sz = pTexture->achFormatHint;
+    if ((sz[0] >= 'A' && sz[0] <= 'Z') ||
+        (sz[1] >= 'A' && sz[1] <= 'Z') ||
+        (sz[2] >= 'A' && sz[2] <= 'Z') ||
+        (sz[3] >= 'A' && sz[3] <= 'Z')) {
+        ReportError("aiTexture::achFormatHint contains non-lowercase letters");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+void ValidateDSProcess::Validate( const aiAnimation* pAnimation,
+     const aiNodeAnim* pNodeAnim)
+{
+    Validate(&pNodeAnim->mNodeName);
+
+    if (!pNodeAnim->mNumPositionKeys && !pNodeAnim->mScalingKeys && !pNodeAnim->mNumRotationKeys) {
+        ReportError("Empty node animation channel");
+    }
+    // otherwise check whether one of the keys exceeds the total duration of the animation
+    if (pNodeAnim->mNumPositionKeys)
+    {
+        if (!pNodeAnim->mPositionKeys)
+        {
+        	ReportError("aiNodeAnim::mPositionKeys is NULL (aiNodeAnim::mNumPositionKeys is %i)",
+                pNodeAnim->mNumPositionKeys);
+        }
+        double dLast = -10e10;
+        for (unsigned int i = 0; i < pNodeAnim->mNumPositionKeys;++i)
+        {
+            // ScenePreprocessor will compute the duration if still the default value
+            // (Aramis) Add small epsilon, comparison tended to fail if max_time == duration,
+            //  seems to be due the compilers register usage/width.
+            if (pAnimation->mDuration > 0. && pNodeAnim->mPositionKeys[i].mTime > pAnimation->mDuration+0.001)
+            {
+                ReportError("aiNodeAnim::mPositionKeys[%i].mTime (%.5f) is larger "
+                    "than aiAnimation::mDuration (which is %.5f)",i,
+                    (float)pNodeAnim->mPositionKeys[i].mTime,
+                    (float)pAnimation->mDuration);
+            }
+            if (i && pNodeAnim->mPositionKeys[i].mTime <= dLast)
+            {
+                ReportWarning("aiNodeAnim::mPositionKeys[%i].mTime (%.5f) is smaller "
+                    "than aiAnimation::mPositionKeys[%i] (which is %.5f)",i,
+                    (float)pNodeAnim->mPositionKeys[i].mTime,
+                    i-1, (float)dLast);
+            }
+            dLast = pNodeAnim->mPositionKeys[i].mTime;
+        }
+    }
+    // rotation keys
+    if (pNodeAnim->mNumRotationKeys)
+    {
+        if (!pNodeAnim->mRotationKeys)
+        {
+            ReportError("aiNodeAnim::mRotationKeys is NULL (aiNodeAnim::mNumRotationKeys is %i)",
+                pNodeAnim->mNumRotationKeys);
+        }
+        double dLast = -10e10;
+        for (unsigned int i = 0; i < pNodeAnim->mNumRotationKeys;++i)
+        {
+            if (pAnimation->mDuration > 0. && pNodeAnim->mRotationKeys[i].mTime > pAnimation->mDuration+0.001)
+            {
+                ReportError("aiNodeAnim::mRotationKeys[%i].mTime (%.5f) is larger "
+                    "than aiAnimation::mDuration (which is %.5f)",i,
+                    (float)pNodeAnim->mRotationKeys[i].mTime,
+                    (float)pAnimation->mDuration);
+            }
+            if (i && pNodeAnim->mRotationKeys[i].mTime <= dLast)
+            {
+                ReportWarning("aiNodeAnim::mRotationKeys[%i].mTime (%.5f) is smaller "
+                    "than aiAnimation::mRotationKeys[%i] (which is %.5f)",i,
+                    (float)pNodeAnim->mRotationKeys[i].mTime,
+                    i-1, (float)dLast);
+            }
+            dLast = pNodeAnim->mRotationKeys[i].mTime;
+        }
+    }
+    // scaling keys
+    if (pNodeAnim->mNumScalingKeys)
+    {
+        if (!pNodeAnim->mScalingKeys)   {
+            ReportError("aiNodeAnim::mScalingKeys is NULL (aiNodeAnim::mNumScalingKeys is %i)",
+                pNodeAnim->mNumScalingKeys);
+        }
+        double dLast = -10e10;
+        for (unsigned int i = 0; i < pNodeAnim->mNumScalingKeys;++i)
+        {
+            if (pAnimation->mDuration > 0. && pNodeAnim->mScalingKeys[i].mTime > pAnimation->mDuration+0.001)
+            {
+                ReportError("aiNodeAnim::mScalingKeys[%i].mTime (%.5f) is larger "
+                    "than aiAnimation::mDuration (which is %.5f)",i,
+                    (float)pNodeAnim->mScalingKeys[i].mTime,
+                    (float)pAnimation->mDuration);
+            }
+            if (i && pNodeAnim->mScalingKeys[i].mTime <= dLast)
+            {
+                ReportWarning("aiNodeAnim::mScalingKeys[%i].mTime (%.5f) is smaller "
+                    "than aiAnimation::mScalingKeys[%i] (which is %.5f)",i,
+                    (float)pNodeAnim->mScalingKeys[i].mTime,
+                    i-1, (float)dLast);
+            }
+            dLast = pNodeAnim->mScalingKeys[i].mTime;
+        }
+    }
+
+    if (!pNodeAnim->mNumScalingKeys && !pNodeAnim->mNumRotationKeys &&
+        !pNodeAnim->mNumPositionKeys)
+    {
+        ReportError("A node animation channel must have at least one subtrack");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+void ValidateDSProcess::Validate( const aiNode* pNode)
+{
+    if (!pNode) {
+    	ReportError("A node of the scenegraph is NULL");
+    }
+    // Validate node name string first so that it's safe to use in below expressions
+    this->Validate(&pNode->mName);
+    const char* nodeName = (&pNode->mName)->C_Str();
+    if (pNode != mScene->mRootNode && !pNode->mParent){
+        ReportError("Non-root node %s lacks a valid parent (aiNode::mParent is NULL) ", nodeName);
+    }
+
+    // validate all meshes
+    if (pNode->mNumMeshes)
+    {
+        if (!pNode->mMeshes)
+        {
+            ReportError("aiNode::mMeshes is NULL for node %s (aiNode::mNumMeshes is %i)",
+            		  nodeName, pNode->mNumMeshes);
+        }
+        std::vector<bool> abHadMesh;
+        abHadMesh.resize(mScene->mNumMeshes,false);
+        for (unsigned int i = 0; i < pNode->mNumMeshes;++i)
+        {
+            if (pNode->mMeshes[i] >= mScene->mNumMeshes)
+            {
+                ReportError("aiNode::mMeshes[%i] is out of range for node %s (maximum is %i)",
+                    pNode->mMeshes[i], nodeName, mScene->mNumMeshes-1);
+            }
+            if (abHadMesh[pNode->mMeshes[i]])
+            {
+                ReportError("aiNode::mMeshes[%i] is already referenced by this node %s (value: %i)",
+                    i, nodeName, pNode->mMeshes[i]);
+            }
+            abHadMesh[pNode->mMeshes[i]] = true;
+        }
+    }
+    if (pNode->mNumChildren)
+    {
+        if (!pNode->mChildren)  {
+            ReportError("aiNode::mChildren is NULL for node %s (aiNode::mNumChildren is %i)",
+            		nodeName, pNode->mNumChildren);
+        }
+        for (unsigned int i = 0; i < pNode->mNumChildren;++i)   {
+            Validate(pNode->mChildren[i]);
+        }
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+void ValidateDSProcess::Validate( const aiString* pString)
+{
+    if (pString->length > MAXLEN)
+    {
+        ReportError("aiString::length is too large (%lu, maximum is %lu)",
+            pString->length,MAXLEN);
+    }
+    const char* sz = pString->data;
+    while (true)
+    {
+        if ('\0' == *sz)
+        {
+            if (pString->length != (unsigned int)(sz-pString->data)) {
+                ReportError("aiString::data is invalid: the terminal zero is at a wrong offset");
+            }
+            break;
+        }
+        else if (sz >= &pString->data[MAXLEN]) {
+            ReportError("aiString::data is invalid. There is no terminal character");
+        }
+        ++sz;
+    }
+}
diff --git a/thirdparty/assimp/code/PostProcessing/ValidateDataStructure.h b/thirdparty/assimp/code/PostProcessing/ValidateDataStructure.h
new file mode 100644
index 0000000000..0b891ef414
--- /dev/null
+++ b/thirdparty/assimp/code/PostProcessing/ValidateDataStructure.h
@@ -0,0 +1,189 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+/** @file Defines a (dummy) post processing step to validate the loader's
+ * output data structure (for debugging)
+ */
+#ifndef AI_VALIDATEPROCESS_H_INC
+#define AI_VALIDATEPROCESS_H_INC
+
+#include <assimp/types.h>
+#include <assimp/material.h>
+
+#include "Common/BaseProcess.h"
+
+struct aiBone;
+struct aiMesh;
+struct aiAnimation;
+struct aiNodeAnim;
+struct aiTexture;
+struct aiMaterial;
+struct aiNode;
+struct aiString;
+struct aiCamera;
+struct aiLight;
+
+namespace Assimp    {
+
+// --------------------------------------------------------------------------------------
+/** Validates the whole ASSIMP scene data structure for correctness.
+ *  ImportErrorException is thrown of the scene is corrupt.*/
+// --------------------------------------------------------------------------------------
+class ValidateDSProcess : public BaseProcess
+{
+public:
+
+    ValidateDSProcess();
+    ~ValidateDSProcess();
+
+public:
+    // -------------------------------------------------------------------
+    bool IsActive( unsigned int pFlags) const;
+
+    // -------------------------------------------------------------------
+    void Execute( aiScene* pScene);
+
+protected:
+
+    // -------------------------------------------------------------------
+    /** Report a validation error. This will throw an exception,
+     *  control won't return.
+     * @param msg Format string for sprintf().*/
+    AI_WONT_RETURN void ReportError(const char* msg,...) AI_WONT_RETURN_SUFFIX;
+
+
+    // -------------------------------------------------------------------
+    /** Report a validation warning. This won't throw an exception,
+     *  control will return to the caller.
+     * @param msg Format string for sprintf().*/
+    void ReportWarning(const char* msg,...);
+
+
+    // -------------------------------------------------------------------
+    /** Validates a mesh
+     * @param pMesh Input mesh*/
+    void Validate( const aiMesh* pMesh);
+
+    // -------------------------------------------------------------------
+    /** Validates a bone
+     * @param pMesh Input mesh
+     * @param pBone Input bone*/
+    void Validate( const aiMesh* pMesh,const aiBone* pBone,float* afSum);
+
+    // -------------------------------------------------------------------
+    /** Validates an animation
+     * @param pAnimation Input animation*/
+    void Validate( const aiAnimation* pAnimation);
+
+    // -------------------------------------------------------------------
+    /** Validates a material
+     * @param pMaterial Input material*/
+    void Validate( const aiMaterial* pMaterial);
+
+    // -------------------------------------------------------------------
+    /** Search the material data structure for invalid or corrupt
+     *  texture keys.
+     * @param pMaterial Input material
+     * @param type Type of the texture*/
+    void SearchForInvalidTextures(const aiMaterial* pMaterial,
+        aiTextureType type);
+
+    // -------------------------------------------------------------------
+    /** Validates a texture
+     * @param pTexture Input texture*/
+    void Validate( const aiTexture* pTexture);
+
+    // -------------------------------------------------------------------
+    /** Validates a light source
+     * @param pLight Input light
+     */
+    void Validate( const aiLight* pLight);
+
+    // -------------------------------------------------------------------
+    /** Validates a camera
+     * @param pCamera Input camera*/
+    void Validate( const aiCamera* pCamera);
+
+    // -------------------------------------------------------------------
+    /** Validates a bone animation channel
+     * @param pAnimation Animation channel.
+     * @param pBoneAnim Input bone animation */
+    void Validate( const aiAnimation* pAnimation,
+        const aiNodeAnim* pBoneAnim);
+
+    // -------------------------------------------------------------------
+    /** Validates a node and all of its subnodes
+     * @param Node Input node*/
+    void Validate( const aiNode* pNode);
+
+    // -------------------------------------------------------------------
+    /** Validates a string
+     * @param pString Input string*/
+    void Validate( const aiString* pString);
+
+private:
+
+    // template to validate one of the aiScene::mXXX arrays
+    template <typename T>
+    inline void DoValidation(T** array, unsigned int size,
+        const char* firstName, const char* secondName);
+
+    // extended version: checks whether T::mName occurs twice
+    template <typename T>
+    inline void DoValidationEx(T** array, unsigned int size,
+        const char* firstName, const char* secondName);
+
+    // extension to the first template which does also search
+    // the nodegraph for an item with the same name
+    template <typename T>
+    inline void DoValidationWithNameCheck(T** array, unsigned int size,
+        const char* firstName, const char* secondName);
+
+    aiScene* mScene;
+};
+
+
+
+
+} // end of namespace Assimp
+
+#endif // AI_VALIDATEPROCESS_H_INC