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diff --git a/thirdparty/assimp/code/PostProcessing/CalcTangentsProcess.cpp b/thirdparty/assimp/code/PostProcessing/CalcTangentsProcess.cpp
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+/*
+---------------------------------------------------------------------------
+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;
+}