Upgrade Embree to the latest official release.

Since Embree v3.13.0 supports AARCH64, switch back to the
official repo instead of using Embree-aarch64.

`thirdparty/embree/patches/godot-changes.patch` should now contain
an accurate diff of the changes done to the library.

1 files changed, 546 insertions, 0 deletions

diff --git a/thirdparty/embree/kernels/builders/heuristic_spatial_array.h b/thirdparty/embree/kernels/builders/heuristic_spatial_array.h
new file mode 100644
index 0000000000..60d235f48d
--- /dev/null
+++ b/thirdparty/embree/kernels/builders/heuristic_spatial_array.h
@@ -0,0 +1,546 @@
+// Copyright 2009-2021 Intel Corporation
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+
+#include "heuristic_binning.h"
+#include "heuristic_spatial.h"
+
+namespace embree
+{
+  namespace isa
+  { 
+#if 0
+#define SPATIAL_ASPLIT_OVERLAP_THRESHOLD 0.2f
+#define SPATIAL_ASPLIT_SAH_THRESHOLD 0.95f
+#define SPATIAL_ASPLIT_AREA_THRESHOLD 0.0f
+#else
+#define SPATIAL_ASPLIT_OVERLAP_THRESHOLD 0.1f
+#define SPATIAL_ASPLIT_SAH_THRESHOLD 0.99f
+#define SPATIAL_ASPLIT_AREA_THRESHOLD 0.000005f
+#endif
+
+    struct PrimInfoExtRange : public CentGeomBBox3fa, public extended_range<size_t>
+    {
+      __forceinline PrimInfoExtRange() {
+      }
+
+      __forceinline PrimInfoExtRange(EmptyTy)
+        : CentGeomBBox3fa(EmptyTy()), extended_range<size_t>(0,0,0) {}
+
+      __forceinline PrimInfoExtRange(size_t begin, size_t end, size_t ext_end, const CentGeomBBox3fa& centGeomBounds) 
+        : CentGeomBBox3fa(centGeomBounds), extended_range<size_t>(begin,end,ext_end) {}
+      
+      __forceinline float leafSAH() const { 
+	return expectedApproxHalfArea(geomBounds)*float(size()); 
+      }
+      
+      __forceinline float leafSAH(size_t block_shift) const { 
+	return expectedApproxHalfArea(geomBounds)*float((size()+(size_t(1)<<block_shift)-1) >> block_shift);
+      }
+    };
+
+    template<typename ObjectSplit, typename SpatialSplit>
+      struct Split2
+      {
+        __forceinline Split2 () {}
+        
+        __forceinline Split2 (const Split2& other) 
+        {
+          spatial = other.spatial;
+          sah = other.sah;
+          if (spatial) spatialSplit() = other.spatialSplit();
+          else         objectSplit()  = other.objectSplit();
+        }
+        
+        __forceinline Split2& operator= (const Split2& other) 
+        {
+          spatial = other.spatial;
+          sah = other.sah;
+          if (spatial) spatialSplit() = other.spatialSplit();
+          else         objectSplit()  = other.objectSplit();
+          return *this;
+        }
+          
+          __forceinline     ObjectSplit&  objectSplit()        { return *(      ObjectSplit*)data; }
+        __forceinline const ObjectSplit&  objectSplit() const  { return *(const ObjectSplit*)data; }
+        
+        __forceinline       SpatialSplit& spatialSplit()       { return *(      SpatialSplit*)data; }
+        __forceinline const SpatialSplit& spatialSplit() const { return *(const SpatialSplit*)data; }
+        
+        __forceinline Split2 (const ObjectSplit& objectSplit, float sah)
+          : spatial(false), sah(sah) 
+        {
+          new (data) ObjectSplit(objectSplit);
+        }
+        
+        __forceinline Split2 (const SpatialSplit& spatialSplit, float sah)
+          : spatial(true), sah(sah) 
+        {
+          new (data) SpatialSplit(spatialSplit);
+        }
+        
+        __forceinline float splitSAH() const { 
+          return sah; 
+        }
+        
+        __forceinline bool valid() const {
+          return sah < float(inf);
+        }
+        
+      public:
+        __aligned(64) char data[sizeof(ObjectSplit) > sizeof(SpatialSplit) ? sizeof(ObjectSplit) : sizeof(SpatialSplit)];
+        bool spatial;
+        float sah;
+      };
+    
+    /*! Performs standard object binning */
+    template<typename PrimitiveSplitterFactory, typename PrimRef, size_t OBJECT_BINS, size_t SPATIAL_BINS>
+      struct HeuristicArraySpatialSAH
+      {
+        typedef BinSplit<OBJECT_BINS> ObjectSplit;
+        typedef BinInfoT<OBJECT_BINS,PrimRef,BBox3fa> ObjectBinner;
+
+        typedef SpatialBinSplit<SPATIAL_BINS> SpatialSplit;
+        typedef SpatialBinInfo<SPATIAL_BINS,PrimRef> SpatialBinner;
+
+        //typedef extended_range<size_t> Set;
+        typedef Split2<ObjectSplit,SpatialSplit> Split;
+        
+        static const size_t PARALLEL_THRESHOLD = 3*1024;
+        static const size_t PARALLEL_FIND_BLOCK_SIZE = 1024;
+        static const size_t PARALLEL_PARTITION_BLOCK_SIZE = 128;
+
+        static const size_t MOVE_STEP_SIZE = 64;
+        static const size_t CREATE_SPLITS_STEP_SIZE = 64;
+
+        __forceinline HeuristicArraySpatialSAH ()
+          : prims0(nullptr) {}
+        
+        /*! remember prim array */
+        __forceinline HeuristicArraySpatialSAH (const PrimitiveSplitterFactory& splitterFactory, PrimRef* prims0, const CentGeomBBox3fa& root_info)
+          : prims0(prims0), splitterFactory(splitterFactory), root_info(root_info) {}
+
+
+        /*! compute extended ranges */
+        __noinline void setExtentedRanges(const PrimInfoExtRange& set, PrimInfoExtRange& lset, PrimInfoExtRange& rset, const size_t lweight, const size_t rweight)
+        {
+          assert(set.ext_range_size() > 0);
+          const float left_factor           = (float)lweight / (lweight + rweight);
+          const size_t ext_range_size       = set.ext_range_size();
+          const size_t left_ext_range_size  = min((size_t)(floorf(left_factor * ext_range_size)),ext_range_size);
+          const size_t right_ext_range_size = ext_range_size - left_ext_range_size;
+          lset.set_ext_range(lset.end() + left_ext_range_size);
+          rset.set_ext_range(rset.end() + right_ext_range_size);
+        }
+
+        /*! move ranges */
+        __noinline void moveExtentedRange(const PrimInfoExtRange& set, const PrimInfoExtRange& lset, PrimInfoExtRange& rset)
+        {
+          const size_t left_ext_range_size = lset.ext_range_size();
+          const size_t right_size = rset.size();
+
+          /* has the left child an extended range? */
+          if (left_ext_range_size > 0)
+          {
+            /* left extended range smaller than right range ? */
+            if (left_ext_range_size < right_size)
+            {
+              /* only move a small part of the beginning of the right range to the end */
+              parallel_for( rset.begin(), rset.begin()+left_ext_range_size, MOVE_STEP_SIZE, [&](const range<size_t>& r) {                  
+                  for (size_t i=r.begin(); i<r.end(); i++)
+                    prims0[i+right_size] = prims0[i];
+                });
+            }
+            else
+            {
+              /* no overlap, move entire right range to new location, can be made fully parallel */
+              parallel_for( rset.begin(), rset.end(), MOVE_STEP_SIZE,  [&](const range<size_t>& r) {
+                  for (size_t i=r.begin(); i<r.end(); i++)
+                    prims0[i+left_ext_range_size] = prims0[i];
+                });
+            }
+            /* update right range */
+            assert(rset.ext_end() + left_ext_range_size == set.ext_end());
+            rset.move_right(left_ext_range_size);
+          }
+        }
+
+        /*! finds the best split */
+        const Split find(const PrimInfoExtRange& set, const size_t logBlockSize)
+        {
+          SplitInfo oinfo;
+          const ObjectSplit object_split = object_find(set,logBlockSize,oinfo);
+          const float object_split_sah = object_split.splitSAH();
+
+          if (unlikely(set.has_ext_range()))
+          {
+            const BBox3fa overlap = intersect(oinfo.leftBounds, oinfo.rightBounds);
+            
+            /* do only spatial splits if the child bounds overlap */
+            if (safeArea(overlap) >= SPATIAL_ASPLIT_AREA_THRESHOLD*safeArea(root_info.geomBounds) &&
+                safeArea(overlap) >= SPATIAL_ASPLIT_OVERLAP_THRESHOLD*safeArea(set.geomBounds))
+            {              
+              const SpatialSplit spatial_split = spatial_find(set, logBlockSize);
+              const float spatial_split_sah = spatial_split.splitSAH();
+
+              /* valid spatial split, better SAH and number of splits do not exceed extended range */
+              if (spatial_split_sah < SPATIAL_ASPLIT_SAH_THRESHOLD*object_split_sah &&
+                  spatial_split.left + spatial_split.right - set.size() <= set.ext_range_size())
+              {          
+                return Split(spatial_split,spatial_split_sah);
+              }
+            }
+          }
+
+          return Split(object_split,object_split_sah);
+        }
+
+        /*! finds the best object split */
+        __forceinline const ObjectSplit object_find(const PrimInfoExtRange& set, const size_t logBlockSize, SplitInfo &info)
+        {
+          if (set.size() < PARALLEL_THRESHOLD) return sequential_object_find(set,logBlockSize,info);
+          else                                 return parallel_object_find  (set,logBlockSize,info);
+        }
+
+        /*! finds the best object split */
+        __noinline const ObjectSplit sequential_object_find(const PrimInfoExtRange& set, const size_t logBlockSize, SplitInfo &info)
+        {
+          ObjectBinner binner(empty); 
+          const BinMapping<OBJECT_BINS> mapping(set);
+          binner.bin(prims0,set.begin(),set.end(),mapping);
+          ObjectSplit s = binner.best(mapping,logBlockSize);
+          binner.getSplitInfo(mapping, s, info);
+          return s;
+        }
+
+        /*! finds the best split */
+        __noinline const ObjectSplit parallel_object_find(const PrimInfoExtRange& set, const size_t logBlockSize, SplitInfo &info)
+        {
+          ObjectBinner binner(empty);
+          const BinMapping<OBJECT_BINS> mapping(set);
+          const BinMapping<OBJECT_BINS>& _mapping = mapping; // CLANG 3.4 parser bug workaround
+          binner = parallel_reduce(set.begin(),set.end(),PARALLEL_FIND_BLOCK_SIZE,binner,
+                                   [&] (const range<size_t>& r) -> ObjectBinner { ObjectBinner binner(empty); binner.bin(prims0+r.begin(),r.size(),_mapping); return binner; },
+                                   [&] (const ObjectBinner& b0, const ObjectBinner& b1) -> ObjectBinner { ObjectBinner r = b0; r.merge(b1,_mapping.size()); return r; });
+          ObjectSplit s = binner.best(mapping,logBlockSize);
+          binner.getSplitInfo(mapping, s, info);
+          return s;
+        }
+
+        /*! finds the best spatial split */
+        __forceinline const SpatialSplit spatial_find(const PrimInfoExtRange& set, const size_t logBlockSize)
+        {
+          if (set.size() < PARALLEL_THRESHOLD) return sequential_spatial_find(set, logBlockSize);
+          else                                 return parallel_spatial_find  (set, logBlockSize);
+        }
+
+        /*! finds the best spatial split */
+        __noinline const SpatialSplit sequential_spatial_find(const PrimInfoExtRange& set, const size_t logBlockSize)
+        {
+          SpatialBinner binner(empty); 
+          const SpatialBinMapping<SPATIAL_BINS> mapping(set);
+          binner.bin2(splitterFactory,prims0,set.begin(),set.end(),mapping);
+          /* todo: best spatial split not exeeding the extended range does not provide any benefit ?*/
+          return binner.best(mapping,logBlockSize); //,set.ext_size());
+        }
+
+        __noinline const SpatialSplit parallel_spatial_find(const PrimInfoExtRange& set, const size_t logBlockSize)
+        {
+          SpatialBinner binner(empty);
+          const SpatialBinMapping<SPATIAL_BINS> mapping(set);
+          const SpatialBinMapping<SPATIAL_BINS>& _mapping = mapping; // CLANG 3.4 parser bug workaround
+          binner = parallel_reduce(set.begin(),set.end(),PARALLEL_FIND_BLOCK_SIZE,binner,
+                                   [&] (const range<size_t>& r) -> SpatialBinner { 
+                                     SpatialBinner binner(empty); 
+                                     binner.bin2(splitterFactory,prims0,r.begin(),r.end(),_mapping);
+                                     return binner; },
+                                   [&] (const SpatialBinner& b0, const SpatialBinner& b1) -> SpatialBinner { return SpatialBinner::reduce(b0,b1); });
+          /* todo: best spatial split not exeeding the extended range does not provide any benefit ?*/
+          return binner.best(mapping,logBlockSize); //,set.ext_size());
+        }
+
+
+        /*! subdivides primitives based on a spatial split */
+        __noinline void create_spatial_splits(PrimInfoExtRange& set, const SpatialSplit& split, const SpatialBinMapping<SPATIAL_BINS> &mapping)
+        {
+          assert(set.has_ext_range());
+          const size_t max_ext_range_size = set.ext_range_size();
+          const size_t ext_range_start = set.end();
+
+          /* atomic counter for number of primref splits */
+          std::atomic<size_t> ext_elements;
+          ext_elements.store(0);
+          
+          const float fpos = split.mapping.pos(split.pos,split.dim);
+        
+          const unsigned int mask = 0xFFFFFFFF >> RESERVED_NUM_SPATIAL_SPLITS_GEOMID_BITS;
+
+          parallel_for( set.begin(), set.end(), CREATE_SPLITS_STEP_SIZE, [&](const range<size_t>& r) {
+              for (size_t i=r.begin();i<r.end();i++)
+              {
+                const unsigned int splits = prims0[i].geomID() >> (32-RESERVED_NUM_SPATIAL_SPLITS_GEOMID_BITS);
+
+                if (likely(splits <= 1)) continue; /* todo: does this ever happen ? */
+
+                //int bin0 = split.mapping.bin(prims0[i].lower)[split.dim];
+                //int bin1 = split.mapping.bin(prims0[i].upper)[split.dim];
+                //if (unlikely(bin0 < split.pos && bin1 >= split.pos))
+                if (unlikely(prims0[i].lower[split.dim] < fpos && prims0[i].upper[split.dim] > fpos))
+                {
+                  assert(splits > 1);
+
+                  PrimRef left,right;
+                  const auto splitter = splitterFactory(prims0[i]);
+                  splitter(prims0[i],split.dim,fpos,left,right);
+                
+                  // no empty splits
+                  if (unlikely(left.bounds().empty() || right.bounds().empty())) continue;
+                
+                  left.lower.u  = (left.lower.u  & mask) | ((splits-1) << (32-RESERVED_NUM_SPATIAL_SPLITS_GEOMID_BITS));
+                  right.lower.u = (right.lower.u & mask) | ((splits-1) << (32-RESERVED_NUM_SPATIAL_SPLITS_GEOMID_BITS));
+
+                  const size_t ID = ext_elements.fetch_add(1);
+
+                  /* break if the number of subdivided elements are greater than the maximum allowed size */
+                  if (unlikely(ID >= max_ext_range_size)) 
+                    break;
+
+                  /* only write within the correct bounds */
+                  assert(ID < max_ext_range_size);
+                  prims0[i] = left;
+                  prims0[ext_range_start+ID] = right;     
+                }
+              }
+            });
+
+          const size_t numExtElements = min(max_ext_range_size,ext_elements.load());          
+          assert(set.end()+numExtElements<=set.ext_end());
+          set._end += numExtElements;
+        }
+        
+        /*! array partitioning */
+        void split(const Split& split, const PrimInfoExtRange& set_i, PrimInfoExtRange& lset, PrimInfoExtRange& rset) 
+        {
+          PrimInfoExtRange set = set_i;
+          
+          /* valid split */
+          if (unlikely(!split.valid())) {
+            deterministic_order(set);
+            return splitFallback(set,lset,rset);
+          }
+
+          std::pair<size_t,size_t> ext_weights(0,0);
+
+          if (unlikely(split.spatial))
+          {
+            create_spatial_splits(set,split.spatialSplit(), split.spatialSplit().mapping); 
+
+            /* spatial split */
+            if (likely(set.size() < PARALLEL_THRESHOLD)) 
+              ext_weights = sequential_spatial_split(split.spatialSplit(),set,lset,rset);
+            else
+              ext_weights = parallel_spatial_split(split.spatialSplit(),set,lset,rset);
+          }
+          else
+          {
+            /* object split */
+            if (likely(set.size() < PARALLEL_THRESHOLD)) 
+              ext_weights = sequential_object_split(split.objectSplit(),set,lset,rset);
+            else
+              ext_weights = parallel_object_split(split.objectSplit(),set,lset,rset);
+          }
+
+          /* if we have an extended range, set extended child ranges and move right split range */
+          if (unlikely(set.has_ext_range())) 
+          {
+            setExtentedRanges(set,lset,rset,ext_weights.first,ext_weights.second);
+            moveExtentedRange(set,lset,rset);
+          }
+        }
+
+        /*! array partitioning */
+        std::pair<size_t,size_t> sequential_object_split(const ObjectSplit& split, const PrimInfoExtRange& set, PrimInfoExtRange& lset, PrimInfoExtRange& rset) 
+        {
+          const size_t begin = set.begin();
+          const size_t end   = set.end();
+          PrimInfo local_left(empty);
+          PrimInfo local_right(empty);
+          const unsigned int splitPos = split.pos;
+          const unsigned int splitDim = split.dim;
+          const unsigned int splitDimMask = (unsigned int)1 << splitDim; 
+
+          const typename ObjectBinner::vint vSplitPos(splitPos);
+          const typename ObjectBinner::vbool vSplitMask(splitDimMask);
+          size_t center = serial_partitioning(prims0,
+                                              begin,end,local_left,local_right,
+                                              [&] (const PrimRef& ref) { 
+                                                return split.mapping.bin_unsafe(ref,vSplitPos,vSplitMask);
+                                              },
+                                              [] (PrimInfo& pinfo,const PrimRef& ref) { pinfo.add_center2(ref,ref.lower.u >> (32-RESERVED_NUM_SPATIAL_SPLITS_GEOMID_BITS)); });          
+          const size_t left_weight  = local_left.end;
+          const size_t right_weight = local_right.end;
+
+          new (&lset) PrimInfoExtRange(begin,center,center,local_left);
+          new (&rset) PrimInfoExtRange(center,end,end,local_right);
+
+          assert(area(lset.geomBounds) >= 0.0f);
+          assert(area(rset.geomBounds) >= 0.0f);
+          return std::pair<size_t,size_t>(left_weight,right_weight);
+        }
+
+
+        /*! array partitioning */
+        __noinline std::pair<size_t,size_t> sequential_spatial_split(const SpatialSplit& split, const PrimInfoExtRange& set, PrimInfoExtRange& lset, PrimInfoExtRange& rset) 
+        {
+          const size_t begin = set.begin();
+          const size_t end   = set.end();
+          PrimInfo local_left(empty);
+          PrimInfo local_right(empty);
+          const unsigned int splitPos = split.pos;
+          const unsigned int splitDim = split.dim;
+          const unsigned int splitDimMask = (unsigned int)1 << splitDim; 
+
+          /* init spatial mapping */
+          const SpatialBinMapping<SPATIAL_BINS> &mapping = split.mapping;
+          const vint4 vSplitPos(splitPos);
+          const vbool4 vSplitMask( (int)splitDimMask );
+
+          size_t center = serial_partitioning(prims0,
+                                              begin,end,local_left,local_right,
+                                              [&] (const PrimRef& ref) {
+                                                const Vec3fa c = ref.bounds().center();
+                                                return any(((vint4)mapping.bin(c) < vSplitPos) & vSplitMask); 
+                                              },
+                                              [] (PrimInfo& pinfo,const PrimRef& ref) { pinfo.add_center2(ref,ref.lower.u >> (32-RESERVED_NUM_SPATIAL_SPLITS_GEOMID_BITS)); });
+
+          const size_t left_weight  = local_left.end;
+          const size_t right_weight = local_right.end;
+          
+          new (&lset) PrimInfoExtRange(begin,center,center,local_left);
+          new (&rset) PrimInfoExtRange(center,end,end,local_right);
+          assert(area(lset.geomBounds) >= 0.0f);
+          assert(area(rset.geomBounds) >= 0.0f);
+          return std::pair<size_t,size_t>(left_weight,right_weight);
+        }
+
+
+        
+        /*! array partitioning */
+        __noinline std::pair<size_t,size_t> parallel_object_split(const ObjectSplit& split, const PrimInfoExtRange& set, PrimInfoExtRange& lset, PrimInfoExtRange& rset)
+        {
+          const size_t begin = set.begin();
+          const size_t end   = set.end();
+          PrimInfo left(empty);
+          PrimInfo right(empty);
+          const unsigned int splitPos = split.pos;
+          const unsigned int splitDim = split.dim;
+          const unsigned int splitDimMask = (unsigned int)1 << splitDim;
+
+          const typename ObjectBinner::vint vSplitPos(splitPos);
+          const typename ObjectBinner::vbool vSplitMask(splitDimMask);
+          auto isLeft = [&] (const PrimRef &ref) { return split.mapping.bin_unsafe(ref,vSplitPos,vSplitMask); };
+
+          const size_t center = parallel_partitioning(
+            prims0,begin,end,EmptyTy(),left,right,isLeft,
+            [] (PrimInfo &pinfo,const PrimRef &ref) { pinfo.add_center2(ref,ref.lower.u >> (32-RESERVED_NUM_SPATIAL_SPLITS_GEOMID_BITS)); },
+            [] (PrimInfo &pinfo0,const PrimInfo &pinfo1) { pinfo0.merge(pinfo1); },
+            PARALLEL_PARTITION_BLOCK_SIZE);
+
+          const size_t left_weight  = left.end;
+          const size_t right_weight = right.end;
+          
+          left.begin  = begin;  left.end  = center; 
+          right.begin = center; right.end = end;
+          
+          new (&lset) PrimInfoExtRange(begin,center,center,left);
+          new (&rset) PrimInfoExtRange(center,end,end,right);
+
+          assert(area(left.geomBounds) >= 0.0f);
+          assert(area(right.geomBounds) >= 0.0f);
+          return std::pair<size_t,size_t>(left_weight,right_weight);
+        }
+
+        /*! array partitioning */
+        __noinline std::pair<size_t,size_t> parallel_spatial_split(const SpatialSplit& split, const PrimInfoExtRange& set, PrimInfoExtRange& lset, PrimInfoExtRange& rset)
+        {
+          const size_t begin = set.begin();
+          const size_t end   = set.end();
+          PrimInfo left(empty);
+          PrimInfo right(empty);
+          const unsigned int splitPos = split.pos;
+          const unsigned int splitDim = split.dim;
+          const unsigned int splitDimMask = (unsigned int)1 << splitDim;
+
+          /* init spatial mapping */
+          const SpatialBinMapping<SPATIAL_BINS>& mapping = split.mapping;
+          const vint4 vSplitPos(splitPos);
+          const vbool4 vSplitMask( (int)splitDimMask );
+
+          auto isLeft = [&] (const PrimRef &ref) { 
+            const Vec3fa c = ref.bounds().center();
+            return any(((vint4)mapping.bin(c) < vSplitPos) & vSplitMask); };
+
+          const size_t center = parallel_partitioning(
+            prims0,begin,end,EmptyTy(),left,right,isLeft,
+            [] (PrimInfo &pinfo,const PrimRef &ref) { pinfo.add_center2(ref,ref.lower.u >> (32-RESERVED_NUM_SPATIAL_SPLITS_GEOMID_BITS)); },
+            [] (PrimInfo &pinfo0,const PrimInfo &pinfo1) { pinfo0.merge(pinfo1); },
+            PARALLEL_PARTITION_BLOCK_SIZE);
+
+          const size_t left_weight  = left.end;
+          const size_t right_weight = right.end;
+          
+          left.begin  = begin;  left.end  = center; 
+          right.begin = center; right.end = end;
+          
+          new (&lset) PrimInfoExtRange(begin,center,center,left);
+          new (&rset) PrimInfoExtRange(center,end,end,right);
+
+          assert(area(left.geomBounds) >= 0.0f);
+          assert(area(right.geomBounds) >= 0.0f);
+          return std::pair<size_t,size_t>(left_weight,right_weight);
+        }
+
+        void deterministic_order(const PrimInfoExtRange& set) 
+        {
+          /* required as parallel partition destroys original primitive order */
+          std::sort(&prims0[set.begin()],&prims0[set.end()]);
+        }
+
+        void splitFallback(const PrimInfoExtRange& set, 
+                           PrimInfoExtRange& lset, 
+                           PrimInfoExtRange& rset)
+        {
+          const size_t begin = set.begin();
+          const size_t end   = set.end();
+          const size_t center = (begin + end)/2;
+
+          PrimInfo left(empty);
+          for (size_t i=begin; i<center; i++) {
+            left.add_center2(prims0[i],prims0[i].lower.u >> (32-RESERVED_NUM_SPATIAL_SPLITS_GEOMID_BITS));
+          }
+          const size_t lweight = left.end;
+          
+          PrimInfo right(empty);
+          for (size_t i=center; i<end; i++) {
+            right.add_center2(prims0[i],prims0[i].lower.u >> (32-RESERVED_NUM_SPATIAL_SPLITS_GEOMID_BITS));	
+          }
+          const size_t rweight = right.end;
+
+          new (&lset) PrimInfoExtRange(begin,center,center,left);
+          new (&rset) PrimInfoExtRange(center,end,end,right);
+
+          /* if we have an extended range */
+          if (set.has_ext_range()) {
+            setExtentedRanges(set,lset,rset,lweight,rweight);
+            moveExtentedRange(set,lset,rset);
+          }
+        }
+        
+      private:
+        PrimRef* const prims0;
+        const PrimitiveSplitterFactory& splitterFactory;
+        const CentGeomBBox3fa& root_info;
+      };
+  }
+}