Merge pull request #48050 from JFonS/occlusion_culling

1 files changed, 692 insertions, 0 deletions

diff --git a/thirdparty/embree-aarch64/kernels/builders/bvh_builder_msmblur.h b/thirdparty/embree-aarch64/kernels/builders/bvh_builder_msmblur.h
new file mode 100644
index 0000000000..4c138dacdb
--- /dev/null
+++ b/thirdparty/embree-aarch64/kernels/builders/bvh_builder_msmblur.h
@@ -0,0 +1,692 @@
+// Copyright 2009-2020 Intel Corporation
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+
+#define MBLUR_NUM_TEMPORAL_BINS 2
+#define MBLUR_NUM_OBJECT_BINS   32
+
+#include "../bvh/bvh.h"
+#include "../common/primref_mb.h"
+#include "heuristic_binning_array_aligned.h"
+#include "heuristic_timesplit_array.h"
+
+namespace embree
+{
+  namespace isa
+  {
+    template<typename T>
+      struct SharedVector
+      {
+        __forceinline SharedVector() {}
+
+        __forceinline SharedVector(T* ptr, size_t refCount = 1)
+          : prims(ptr), refCount(refCount) {}
+
+        __forceinline void incRef() {
+          refCount++;
+        }
+
+        __forceinline void decRef()
+        {
+          if (--refCount == 0)
+            delete prims;
+        }
+
+        T* prims;
+        size_t refCount;
+      };
+
+    template<typename BuildRecord, int MAX_BRANCHING_FACTOR>
+      struct LocalChildListT
+      {
+        typedef SharedVector<mvector<PrimRefMB>> SharedPrimRefVector;
+
+        __forceinline LocalChildListT (const BuildRecord& record)
+          : numChildren(1), numSharedPrimVecs(1)
+        {
+          /* the local root will be freed in the ancestor where it was created (thus refCount is 2) */
+          children[0] = record;
+          primvecs[0] = new (&sharedPrimVecs[0]) SharedPrimRefVector(record.prims.prims, 2);
+        }
+
+        __forceinline ~LocalChildListT()
+        {
+          for (size_t i = 0; i < numChildren; i++)
+            primvecs[i]->decRef();
+        }
+
+        __forceinline BuildRecord& operator[] ( const size_t i ) {
+          return children[i];
+        }
+
+        __forceinline size_t size() const {
+          return numChildren;
+        }
+
+        __forceinline void split(ssize_t bestChild, const BuildRecord& lrecord, const BuildRecord& rrecord, std::unique_ptr<mvector<PrimRefMB>> new_vector)
+        {
+          SharedPrimRefVector* bsharedPrimVec = primvecs[bestChild];
+          if (lrecord.prims.prims == bsharedPrimVec->prims) {
+            primvecs[bestChild] = bsharedPrimVec;
+            bsharedPrimVec->incRef();
+          }
+          else {
+            primvecs[bestChild] = new (&sharedPrimVecs[numSharedPrimVecs++]) SharedPrimRefVector(lrecord.prims.prims);
+          }
+
+          if (rrecord.prims.prims == bsharedPrimVec->prims) {
+            primvecs[numChildren] = bsharedPrimVec;
+            bsharedPrimVec->incRef();
+          }
+          else {
+            primvecs[numChildren] = new (&sharedPrimVecs[numSharedPrimVecs++]) SharedPrimRefVector(rrecord.prims.prims);
+          }
+          bsharedPrimVec->decRef();
+          new_vector.release();
+
+          children[bestChild] = lrecord;
+          children[numChildren] = rrecord;
+          numChildren++;
+        }
+
+      public:
+        array_t<BuildRecord,MAX_BRANCHING_FACTOR> children;
+        array_t<SharedPrimRefVector*,MAX_BRANCHING_FACTOR> primvecs;
+        size_t numChildren;
+
+        array_t<SharedPrimRefVector,2*MAX_BRANCHING_FACTOR> sharedPrimVecs;
+        size_t numSharedPrimVecs;
+      };
+
+    template<typename Mesh>
+      struct RecalculatePrimRef
+      {
+        Scene* scene;
+
+        __forceinline RecalculatePrimRef (Scene* scene)
+          : scene(scene) {}
+
+        __forceinline PrimRefMB operator() (const PrimRefMB& prim, const BBox1f time_range) const
+        {
+          const unsigned geomID = prim.geomID();
+          const unsigned primID = prim.primID();
+          const Mesh* mesh = scene->get<Mesh>(geomID);
+          const LBBox3fa lbounds = mesh->linearBounds(primID, time_range);
+          const range<int> tbounds = mesh->timeSegmentRange(time_range);
+          return PrimRefMB (lbounds, tbounds.size(), mesh->time_range, mesh->numTimeSegments(), geomID, primID);
+        }
+
+        // __noinline is workaround for ICC16 bug under MacOSX
+        __noinline PrimRefMB operator() (const PrimRefMB& prim, const BBox1f time_range, const LinearSpace3fa& space) const
+        {
+          const unsigned geomID = prim.geomID();
+          const unsigned primID = prim.primID();
+          const Mesh* mesh = scene->get<Mesh>(geomID);
+          const LBBox3fa lbounds = mesh->linearBounds(space, primID, time_range);
+          const range<int> tbounds = mesh->timeSegmentRange(time_range);
+          return PrimRefMB (lbounds, tbounds.size(), mesh->time_range, mesh->numTimeSegments(), geomID, primID);
+        }
+
+        __forceinline LBBox3fa linearBounds(const PrimRefMB& prim, const BBox1f time_range) const {
+          return scene->get<Mesh>(prim.geomID())->linearBounds(prim.primID(), time_range);
+        }
+
+        // __noinline is workaround for ICC16 bug under MacOSX
+        __noinline LBBox3fa linearBounds(const PrimRefMB& prim, const BBox1f time_range, const LinearSpace3fa& space) const {
+          return scene->get<Mesh>(prim.geomID())->linearBounds(space, prim.primID(), time_range);
+        }
+      };
+
+    struct VirtualRecalculatePrimRef
+    {
+      Scene* scene;
+      
+      __forceinline VirtualRecalculatePrimRef (Scene* scene)
+        : scene(scene) {}
+      
+      __forceinline PrimRefMB operator() (const PrimRefMB& prim, const BBox1f time_range) const
+      {
+        const unsigned geomID = prim.geomID();
+        const unsigned primID = prim.primID();
+        const Geometry* mesh = scene->get(geomID);
+        const LBBox3fa lbounds = mesh->vlinearBounds(primID, time_range);
+        const range<int> tbounds = mesh->timeSegmentRange(time_range);
+        return PrimRefMB (lbounds, tbounds.size(), mesh->time_range, mesh->numTimeSegments(), geomID, primID);
+      }
+      
+      __forceinline PrimRefMB operator() (const PrimRefMB& prim, const BBox1f time_range, const LinearSpace3fa& space) const
+      {
+        const unsigned geomID = prim.geomID();
+        const unsigned primID = prim.primID();
+        const Geometry* mesh = scene->get(geomID);
+        const LBBox3fa lbounds = mesh->vlinearBounds(space, primID, time_range);
+        const range<int> tbounds = mesh->timeSegmentRange(time_range);
+        return PrimRefMB (lbounds, tbounds.size(), mesh->time_range, mesh->numTimeSegments(), geomID, primID);
+      }
+      
+      __forceinline LBBox3fa linearBounds(const PrimRefMB& prim, const BBox1f time_range) const {
+        return scene->get(prim.geomID())->vlinearBounds(prim.primID(), time_range);
+      }
+      
+      __forceinline LBBox3fa linearBounds(const PrimRefMB& prim, const BBox1f time_range, const LinearSpace3fa& space) const {
+        return scene->get(prim.geomID())->vlinearBounds(space, prim.primID(), time_range);
+      }
+    };
+
+    struct BVHBuilderMSMBlur
+    {
+      /*! settings for msmblur builder */
+      struct Settings
+      {
+        /*! default settings */
+        Settings ()
+        : branchingFactor(2), maxDepth(32), logBlockSize(0), minLeafSize(1), maxLeafSize(8),
+          travCost(1.0f), intCost(1.0f), singleLeafTimeSegment(false),
+          singleThreadThreshold(1024) {}
+
+
+        Settings (size_t sahBlockSize, size_t minLeafSize, size_t maxLeafSize, float travCost, float intCost, size_t singleThreadThreshold)
+        : branchingFactor(2), maxDepth(32), logBlockSize(bsr(sahBlockSize)), minLeafSize(minLeafSize), maxLeafSize(maxLeafSize),
+          travCost(travCost), intCost(intCost), singleThreadThreshold(singleThreadThreshold)
+        {
+          minLeafSize = min(minLeafSize,maxLeafSize);
+        }
+
+      public:
+        size_t branchingFactor;  //!< branching factor of BVH to build
+        size_t maxDepth;         //!< maximum depth of BVH to build
+        size_t logBlockSize;     //!< log2 of blocksize for SAH heuristic
+        size_t minLeafSize;      //!< minimum size of a leaf
+        size_t maxLeafSize;      //!< maximum size of a leaf
+        float travCost;          //!< estimated cost of one traversal step
+        float intCost;           //!< estimated cost of one primitive intersection
+        bool singleLeafTimeSegment; //!< split time to single time range
+        size_t singleThreadThreshold; //!< threshold when we switch to single threaded build
+      };
+
+      struct BuildRecord
+      {
+      public:
+	__forceinline BuildRecord () {}
+
+        __forceinline BuildRecord (size_t depth)
+          : depth(depth) {}
+
+        __forceinline BuildRecord (const SetMB& prims, size_t depth)
+          : depth(depth), prims(prims) {}
+
+        __forceinline friend bool operator< (const BuildRecord& a, const BuildRecord& b) {
+          return a.prims.size() < b.prims.size();
+        }
+
+        __forceinline size_t size() const {
+          return prims.size();
+        }
+
+      public:
+	size_t depth;                     //!< Depth of the root of this subtree.
+	SetMB prims;                      //!< The list of primitives.
+      };
+
+      struct BuildRecordSplit : public BuildRecord
+      {
+        __forceinline BuildRecordSplit () {}
+
+        __forceinline BuildRecordSplit (size_t depth) 
+          : BuildRecord(depth) {}
+
+        __forceinline BuildRecordSplit (const BuildRecord& record, const BinSplit<MBLUR_NUM_OBJECT_BINS>& split)
+          : BuildRecord(record), split(split) {}
+        
+        BinSplit<MBLUR_NUM_OBJECT_BINS> split;
+      };
+
+      template<
+        typename NodeRef,
+        typename RecalculatePrimRef,
+        typename Allocator,
+        typename CreateAllocFunc,
+        typename CreateNodeFunc,
+        typename SetNodeFunc,
+        typename CreateLeafFunc,
+        typename ProgressMonitor>
+
+        class BuilderT
+        {
+          ALIGNED_CLASS_(16);
+          static const size_t MAX_BRANCHING_FACTOR = 16;       //!< maximum supported BVH branching factor	  
+          static const size_t MIN_LARGE_LEAF_LEVELS = 8;        //!< create balanced tree if we are that many levels before the maximum tree depth
+
+          typedef BVHNodeRecordMB4D<NodeRef> NodeRecordMB4D;
+          typedef BinSplit<MBLUR_NUM_OBJECT_BINS> Split;
+          typedef mvector<PrimRefMB>* PrimRefVector;
+          typedef SharedVector<mvector<PrimRefMB>> SharedPrimRefVector;
+          typedef LocalChildListT<BuildRecord,MAX_BRANCHING_FACTOR> LocalChildList;
+          typedef LocalChildListT<BuildRecordSplit,MAX_BRANCHING_FACTOR> LocalChildListSplit;
+
+        public:
+
+          BuilderT (MemoryMonitorInterface* device,
+                    const RecalculatePrimRef recalculatePrimRef,
+                    const CreateAllocFunc createAlloc,
+                    const CreateNodeFunc createNode,
+                    const SetNodeFunc setNode,
+                    const CreateLeafFunc createLeaf,
+                    const ProgressMonitor progressMonitor,
+                    const Settings& settings)
+            : cfg(settings),
+            heuristicObjectSplit(),
+            heuristicTemporalSplit(device, recalculatePrimRef),
+            recalculatePrimRef(recalculatePrimRef), createAlloc(createAlloc), createNode(createNode), setNode(setNode), createLeaf(createLeaf),
+            progressMonitor(progressMonitor)
+          {
+            if (cfg.branchingFactor > MAX_BRANCHING_FACTOR)
+              throw_RTCError(RTC_ERROR_UNKNOWN,"bvh_builder: branching factor too large");
+          }
+
+          /*! finds the best split */
+          const Split find(const SetMB& set)
+          {
+            /* first try standard object split */
+            const Split object_split = heuristicObjectSplit.find(set,cfg.logBlockSize);
+            const float object_split_sah = object_split.splitSAH();
+
+            /* test temporal splits only when object split was bad */
+            const float leaf_sah = set.leafSAH(cfg.logBlockSize);
+            if (object_split_sah < 0.50f*leaf_sah)
+              return object_split;
+
+            /* do temporal splits only if the the time range is big enough */
+            if (set.time_range.size() > 1.01f/float(set.max_num_time_segments))
+            {
+              const Split temporal_split = heuristicTemporalSplit.find(set,cfg.logBlockSize);
+              const float temporal_split_sah = temporal_split.splitSAH();
+
+              /* take temporal split if it improved SAH */
+              if (temporal_split_sah < object_split_sah)
+                return temporal_split;
+            }
+
+            return object_split;
+          }
+
+          /*! array partitioning */
+          __forceinline std::unique_ptr<mvector<PrimRefMB>> split(const Split& split, const SetMB& set, SetMB& lset, SetMB& rset)
+          {
+            /* perform object split */
+            if (likely(split.data == Split::SPLIT_OBJECT)) {
+              heuristicObjectSplit.split(split,set,lset,rset);
+            }
+            /* perform temporal split */
+            else if (likely(split.data == Split::SPLIT_TEMPORAL)) {
+              return heuristicTemporalSplit.split(split,set,lset,rset);
+            }
+            /* perform fallback split */
+            else if (unlikely(split.data == Split::SPLIT_FALLBACK)) {
+              set.deterministic_order();
+              splitFallback(set,lset,rset);
+            }
+            /* split by geometry */
+            else if (unlikely(split.data == Split::SPLIT_GEOMID)) {
+              set.deterministic_order();
+              splitByGeometry(set,lset,rset);
+            }
+            else
+              assert(false);
+
+            return std::unique_ptr<mvector<PrimRefMB>>();
+          }
+
+          /*! finds the best fallback split */
+          __noinline Split findFallback(const SetMB& set)
+          {
+            /* split if primitives are not from same geometry */
+            if (!sameGeometry(set))
+              return Split(0.0f,Split::SPLIT_GEOMID);
+            
+            /* if a leaf can only hold a single time-segment, we might have to do additional temporal splits */
+            if (cfg.singleLeafTimeSegment)
+            {
+              /* test if one primitive has more than one time segment in time range, if so split time */
+              for (size_t i=set.begin(); i<set.end(); i++)
+              {
+                const PrimRefMB& prim = (*set.prims)[i];
+                const range<int> itime_range = prim.timeSegmentRange(set.time_range);
+                const int localTimeSegments = itime_range.size();
+                assert(localTimeSegments > 0);
+                if (localTimeSegments > 1) {
+                  const int icenter = (itime_range.begin() + itime_range.end())/2;
+                  const float splitTime = prim.timeStep(icenter);
+                  return Split(0.0f,(unsigned)Split::SPLIT_TEMPORAL,0,splitTime);
+                }
+              }
+            }        
+
+            /* otherwise return fallback split */
+            return Split(0.0f,Split::SPLIT_FALLBACK);
+          }
+
+          /*! performs fallback split */
+          void splitFallback(const SetMB& set, SetMB& lset, SetMB& rset)
+          {
+            mvector<PrimRefMB>& prims = *set.prims;
+
+            const size_t begin = set.begin();
+            const size_t end   = set.end();
+            const size_t center = (begin + end)/2;
+
+            PrimInfoMB linfo = empty;
+            for (size_t i=begin; i<center; i++)
+              linfo.add_primref(prims[i]);
+
+            PrimInfoMB rinfo = empty;
+            for (size_t i=center; i<end; i++)
+              rinfo.add_primref(prims[i]);
+
+            new (&lset) SetMB(linfo,set.prims,range<size_t>(begin,center),set.time_range);
+            new (&rset) SetMB(rinfo,set.prims,range<size_t>(center,end  ),set.time_range);
+          }
+
+          /*! checks if all primitives are from the same geometry */
+          __forceinline bool sameGeometry(const SetMB& set)
+          {
+            if (set.size() == 0) return true;
+            mvector<PrimRefMB>& prims = *set.prims;
+            const size_t begin = set.begin();
+            const size_t end   = set.end();
+            unsigned int firstGeomID = prims[begin].geomID();
+            for (size_t i=begin+1; i<end; i++) {
+              if (prims[i].geomID() != firstGeomID){
+                return false;
+              }
+            }
+            return true;
+          }
+
+          /* split by geometry ID */
+          void splitByGeometry(const SetMB& set, SetMB& lset, SetMB& rset)
+          {
+            assert(set.size() > 1);
+
+            mvector<PrimRefMB>& prims = *set.prims;
+            const size_t begin = set.begin();
+            const size_t end   = set.end();
+            
+            PrimInfoMB left(empty);
+            PrimInfoMB right(empty);
+            unsigned int geomID = prims[begin].geomID();
+            size_t center = serial_partitioning(prims.data(),begin,end,left,right,
+                                                [&] ( const PrimRefMB& prim ) { return prim.geomID() == geomID; },
+                                                [ ] ( PrimInfoMB& dst, const PrimRefMB& prim ) { dst.add_primref(prim); });
+            
+            new (&lset) SetMB(left, set.prims,range<size_t>(begin,center),set.time_range);
+            new (&rset) SetMB(right,set.prims,range<size_t>(center,end  ),set.time_range);
+          }
+
+          const NodeRecordMB4D createLargeLeaf(const BuildRecord& in, Allocator alloc)
+          {
+            /* this should never occur but is a fatal error */
+            if (in.depth > cfg.maxDepth)
+              throw_RTCError(RTC_ERROR_UNKNOWN,"depth limit reached");
+
+            /* replace already found split by fallback split */
+            const BuildRecordSplit current(BuildRecord(in.prims,in.depth),findFallback(in.prims));
+
+            /* special case when directly creating leaf without any splits that could shrink time_range */
+            bool force_split = false;
+            if (current.depth == 1 && current.size() > 0)
+            {
+              BBox1f c = empty;
+              BBox1f p = current.prims.time_range;
+              for (size_t i=current.prims.begin(); i<current.prims.end(); i++) {
+                mvector<PrimRefMB>& prims = *current.prims.prims;
+                c.extend(prims[i].time_range);
+              }
+              
+              force_split = c.lower > p.lower || c.upper < p.upper;
+            }
+	    
+            /* create leaf for few primitives */
+            if (current.size() <= cfg.maxLeafSize && current.split.data < Split::SPLIT_ENFORCE && !force_split)
+              return createLeaf(current,alloc);
+	  
+            /* fill all children by always splitting the largest one */
+            bool hasTimeSplits = false;
+            NodeRecordMB4D values[MAX_BRANCHING_FACTOR];
+            LocalChildListSplit children(current);
+
+            do {
+              /* find best child with largest bounding box area */
+              size_t bestChild = -1;
+              size_t bestSize = 0;
+              for (size_t i=0; i<children.size(); i++)
+              {
+                /* ignore leaves as they cannot get split */
+                if (children[i].size() <= cfg.maxLeafSize && children[i].split.data < Split::SPLIT_ENFORCE && !force_split)
+                  continue;
+
+                force_split = false;
+                
+                /* remember child with largest size */
+                if (children[i].size() > bestSize) {
+                  bestSize = children[i].size();
+                  bestChild = i;
+                }
+              }
+              if (bestChild == -1) break;
+
+              /* perform best found split */
+              BuildRecordSplit& brecord = children[bestChild];
+              BuildRecordSplit lrecord(current.depth+1);
+              BuildRecordSplit rrecord(current.depth+1);
+              std::unique_ptr<mvector<PrimRefMB>> new_vector = split(brecord.split,brecord.prims,lrecord.prims,rrecord.prims);
+              hasTimeSplits |= new_vector != nullptr;
+
+              /* find new splits */
+              lrecord.split = findFallback(lrecord.prims);
+              rrecord.split = findFallback(rrecord.prims);
+              children.split(bestChild,lrecord,rrecord,std::move(new_vector));
+
+            } while (children.size() < cfg.branchingFactor);
+
+            /* detect time_ranges that have shrunken */
+            for (size_t i=0; i<children.size(); i++) {
+              const BBox1f c = children[i].prims.time_range;
+              const BBox1f p = in.prims.time_range;
+              hasTimeSplits |= c.lower > p.lower || c.upper < p.upper;
+            }
+
+            /* create node */
+            auto node = createNode(children.children.data(),children.numChildren,alloc,hasTimeSplits);
+
+            /* recurse into each child and perform reduction */
+            LBBox3fa gbounds = empty;
+            for (size_t i=0; i<children.size(); i++) {
+              values[i] = createLargeLeaf(children[i],alloc);
+              gbounds.extend(values[i].lbounds);
+            }
+
+            setNode(current,children.children.data(),node,values,children.numChildren);
+
+            /* calculate geometry bounds of this node */
+            if (hasTimeSplits)
+              return NodeRecordMB4D(node,current.prims.linearBounds(recalculatePrimRef),current.prims.time_range);
+            else
+              return NodeRecordMB4D(node,gbounds,current.prims.time_range);
+          }
+
+          const NodeRecordMB4D recurse(const BuildRecord& current, Allocator alloc, bool toplevel)
+          {
+            /* get thread local allocator */
+            if (!alloc)
+              alloc = createAlloc();
+
+            /* call memory monitor function to signal progress */
+            if (toplevel && current.size() <= cfg.singleThreadThreshold)
+              progressMonitor(current.size());
+
+            /*! find best split */
+            const Split csplit = find(current.prims);
+
+            /*! compute leaf and split cost */
+            const float leafSAH  = cfg.intCost*current.prims.leafSAH(cfg.logBlockSize);
+            const float splitSAH = cfg.travCost*current.prims.halfArea()+cfg.intCost*csplit.splitSAH();
+            assert((current.size() == 0) || ((leafSAH >= 0) && (splitSAH >= 0)));
+
+            /*! create a leaf node when threshold reached or SAH tells us to stop */
+            if (current.size() <= cfg.minLeafSize || current.depth+MIN_LARGE_LEAF_LEVELS >= cfg.maxDepth || (current.size() <= cfg.maxLeafSize && leafSAH <= splitSAH)) {
+              current.prims.deterministic_order();
+              return createLargeLeaf(current,alloc);
+            }
+
+            /*! perform initial split */
+            SetMB lprims,rprims;
+            std::unique_ptr<mvector<PrimRefMB>> new_vector = split(csplit,current.prims,lprims,rprims);
+            bool hasTimeSplits = new_vector != nullptr;
+            NodeRecordMB4D values[MAX_BRANCHING_FACTOR];
+            LocalChildList children(current);
+            {
+              BuildRecord lrecord(lprims,current.depth+1);
+              BuildRecord rrecord(rprims,current.depth+1);
+              children.split(0,lrecord,rrecord,std::move(new_vector));
+            }
+
+            /*! split until node is full or SAH tells us to stop */
+            while (children.size() < cfg.branchingFactor) 
+            {
+              /*! find best child to split */
+              float bestArea = neg_inf;
+              ssize_t bestChild = -1;
+              for (size_t i=0; i<children.size(); i++)
+              {
+                if (children[i].size() <= cfg.minLeafSize) continue;
+                if (expectedApproxHalfArea(children[i].prims.geomBounds) > bestArea) {
+                  bestChild = i; bestArea = expectedApproxHalfArea(children[i].prims.geomBounds);
+                }
+              }
+              if (bestChild == -1) break;
+
+              /* perform split */
+              BuildRecord& brecord = children[bestChild];
+              BuildRecord lrecord(current.depth+1);
+              BuildRecord rrecord(current.depth+1);
+              Split csplit = find(brecord.prims);
+              std::unique_ptr<mvector<PrimRefMB>> new_vector = split(csplit,brecord.prims,lrecord.prims,rrecord.prims);
+              hasTimeSplits |= new_vector != nullptr;
+              children.split(bestChild,lrecord,rrecord,std::move(new_vector));
+            }
+
+            /* detect time_ranges that have shrunken */
+            for (size_t i=0; i<children.size(); i++) {
+              const BBox1f c = children[i].prims.time_range;
+              const BBox1f p = current.prims.time_range;
+              hasTimeSplits |= c.lower > p.lower || c.upper < p.upper;
+            }
+
+            /* sort buildrecords for simpler shadow ray traversal */
+            //std::sort(&children[0],&children[children.size()],std::greater<BuildRecord>()); // FIXME: reduces traversal performance of bvh8.triangle4 (need to verified) !!
+
+            /*! create an inner node */
+            auto node = createNode(children.children.data(), children.numChildren, alloc, hasTimeSplits);
+            LBBox3fa gbounds = empty;
+
+            /* spawn tasks */
+            if (unlikely(current.size() > cfg.singleThreadThreshold))
+            {
+              /*! parallel_for is faster than spawing sub-tasks */
+              parallel_for(size_t(0), children.size(), [&] (const range<size_t>& r) {
+                  for (size_t i=r.begin(); i<r.end(); i++) {
+                    values[i] = recurse(children[i],nullptr,true);
+                    _mm_mfence(); // to allow non-temporal stores during build
+                  }
+                });
+
+              /*! merge bounding boxes */
+              for (size_t i=0; i<children.size(); i++)
+                gbounds.extend(values[i].lbounds);
+            }
+            /* recurse into each child */
+            else
+            {
+              //for (size_t i=0; i<children.size(); i++)
+              for (ssize_t i=children.size()-1; i>=0; i--) {
+                values[i] = recurse(children[i],alloc,false);
+                gbounds.extend(values[i].lbounds);
+              }
+            }
+
+            setNode(current,children.children.data(),node,values,children.numChildren);
+
+            /* calculate geometry bounds of this node */
+            if (unlikely(hasTimeSplits))
+              return NodeRecordMB4D(node,current.prims.linearBounds(recalculatePrimRef),current.prims.time_range);
+            else
+              return NodeRecordMB4D(node,gbounds,current.prims.time_range);
+          }
+
+          /*! builder entry function */
+          __forceinline const NodeRecordMB4D operator() (mvector<PrimRefMB>& prims, const PrimInfoMB& pinfo)
+          {
+            const SetMB set(pinfo,&prims);
+            auto ret = recurse(BuildRecord(set,1),nullptr,true);
+            _mm_mfence(); // to allow non-temporal stores during build
+            return ret;
+          }
+
+        private:
+          Settings cfg;
+          HeuristicArrayBinningMB<PrimRefMB,MBLUR_NUM_OBJECT_BINS> heuristicObjectSplit;
+          HeuristicMBlurTemporalSplit<PrimRefMB,RecalculatePrimRef,MBLUR_NUM_TEMPORAL_BINS> heuristicTemporalSplit;
+          const RecalculatePrimRef recalculatePrimRef;
+          const CreateAllocFunc createAlloc;
+          const CreateNodeFunc createNode;
+          const SetNodeFunc setNode;
+          const CreateLeafFunc createLeaf;
+          const ProgressMonitor progressMonitor;
+        };
+
+      template<typename NodeRef,
+        typename RecalculatePrimRef,
+        typename CreateAllocFunc,
+        typename CreateNodeFunc,
+        typename SetNodeFunc,
+        typename CreateLeafFunc,
+        typename ProgressMonitorFunc>
+
+        static const BVHNodeRecordMB4D<NodeRef> build(mvector<PrimRefMB>& prims,
+                                                      const PrimInfoMB& pinfo,
+                                                      MemoryMonitorInterface* device,
+                                                      const RecalculatePrimRef recalculatePrimRef,
+                                                      const CreateAllocFunc createAlloc,
+                                                      const CreateNodeFunc createNode,
+                                                      const SetNodeFunc setNode,
+                                                      const CreateLeafFunc createLeaf,
+                                                      const ProgressMonitorFunc progressMonitor,
+                                                      const Settings& settings)
+      {
+          typedef BuilderT<
+            NodeRef,
+            RecalculatePrimRef,
+            decltype(createAlloc()),
+            CreateAllocFunc,
+            CreateNodeFunc,
+            SetNodeFunc,
+            CreateLeafFunc,
+            ProgressMonitorFunc> Builder;
+
+          Builder builder(device,
+                          recalculatePrimRef,
+                          createAlloc,
+                          createNode,
+                          setNode,
+                          createLeaf,
+                          progressMonitor,
+                          settings);
+
+
+          return builder(prims,pinfo);
+        }
+    };
+  }
+}