initial commit, 4.5 stable

thirdparty/embree/kernels/builders/heuristic_strand_array.h

@@ -0,0 +1,188 @@
+// Copyright 2009-2021 Intel Corporation
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+
+#include "priminfo.h"
+#include "../../common/algorithms/parallel_reduce.h"
+#include "../../common/algorithms/parallel_partition.h"
+
+namespace embree
+{
+  namespace isa
+  { 
+    /*! Performs standard object binning */
+    struct HeuristicStrandSplit
+    {
+      typedef range<size_t> Set;
+  
+      static const size_t PARALLEL_THRESHOLD = 10000;
+      static const size_t PARALLEL_FIND_BLOCK_SIZE = 4096;
+      static const size_t PARALLEL_PARTITION_BLOCK_SIZE = 64;
+
+      /*! stores all information to perform some split */
+      struct Split
+      {    
+	/*! construct an invalid split by default */
+	__forceinline Split()
+	  : sah(inf), axis0(zero), axis1(zero) {}
+	
+	/*! constructs specified split */
+	__forceinline Split(const float sah, const Vec3fa& axis0, const Vec3fa& axis1)
+	  : sah(sah), axis0(axis0), axis1(axis1) {}
+	
+	/*! calculates standard surface area heuristic for the split */
+	__forceinline float splitSAH() const { return sah; }
+
+        /*! test if this split is valid */
+        __forceinline bool valid() const { return sah != float(inf); }
+		
+      public:
+	float sah;             //!< SAH cost of the split
+	Vec3fa axis0, axis1;   //!< axis the two strands are aligned into
+      };
+
+      __forceinline HeuristicStrandSplit () // FIXME: required?
+        : scene(nullptr), prims(nullptr) {}
+      
+      /*! remember prim array */
+      __forceinline HeuristicStrandSplit (Scene* scene, PrimRef* prims)
+        : scene(scene), prims(prims) {}
+      
+      __forceinline const Vec3fa direction(const PrimRef& prim) {
+        return scene->get(prim.geomID())->computeDirection(prim.primID());
+      }
+      
+      __forceinline const BBox3fa bounds(const PrimRef& prim) {
+        return scene->get(prim.geomID())->vbounds(prim.primID());
+      }
+
+      __forceinline const BBox3fa bounds(const LinearSpace3fa& space, const PrimRef& prim) {
+        return scene->get(prim.geomID())->vbounds(space,prim.primID());
+      }
+
+      /*! finds the best split */
+      const Split find(const range<size_t>& set, size_t logBlockSize)
+      {
+        Vec3fa axis0(0,0,1);
+        uint64_t bestGeomPrimID = -1;
+
+        /* curve with minimum ID determines first axis */
+        for (size_t i=set.begin(); i<set.end(); i++)
+        {
+          const uint64_t geomprimID = prims[i].ID64();
+          if (geomprimID >= bestGeomPrimID) continue;
+          const Vec3fa axis = direction(prims[i]);
+          if (sqr_length(axis) > 1E-18f) {
+            axis0 = normalize(axis);
+            bestGeomPrimID = geomprimID;
+          }
+        }
+      
+        /* find 2nd axis that is most misaligned with first axis and has minimum ID */
+        float bestCos = 1.0f;
+        Vec3fa axis1 = axis0;
+        bestGeomPrimID = -1;
+        for (size_t i=set.begin(); i<set.end(); i++) 
+        {
+          const uint64_t geomprimID = prims[i].ID64();
+          Vec3fa axisi = direction(prims[i]);
+          float leni = length(axisi);
+          if (leni == 0.0f) continue;
+          axisi /= leni;
+          float cos = abs(dot(axisi,axis0));
+          if ((cos == bestCos && (geomprimID < bestGeomPrimID)) || cos < bestCos) {
+            bestCos = cos; axis1 = axisi;
+            bestGeomPrimID = geomprimID;
+          }
+        }
+      
+        /* partition the two strands */
+        size_t lnum = 0, rnum = 0;
+        BBox3fa lbounds = empty, rbounds = empty;
+        const LinearSpace3fa space0 = frame(axis0).transposed();
+        const LinearSpace3fa space1 = frame(axis1).transposed();
+        
+        for (size_t i=set.begin(); i<set.end(); i++)
+        {
+          PrimRef& prim = prims[i];
+          const Vec3fa axisi = normalize(direction(prim));
+          const float cos0 = abs(dot(axisi,axis0));
+          const float cos1 = abs(dot(axisi,axis1));
+          
+          if (cos0 > cos1) { lnum++; lbounds.extend(bounds(space0,prim)); }
+          else             { rnum++; rbounds.extend(bounds(space1,prim)); }
+        }
+      
+        /*! return an invalid split if we do not partition */
+        if (lnum == 0 || rnum == 0) 
+          return Split(inf,axis0,axis1);
+      
+        /*! calculate sah for the split */
+        const size_t lblocks = (lnum+(1ull<<logBlockSize)-1ull) >> logBlockSize;
+        const size_t rblocks = (rnum+(1ull<<logBlockSize)-1ull) >> logBlockSize;
+        const float sah = madd(float(lblocks),halfArea(lbounds),float(rblocks)*halfArea(rbounds));
+        return Split(sah,axis0,axis1);
+      }
+
+      /*! array partitioning */
+      void split(const Split& split, const PrimInfoRange& set, PrimInfoRange& lset, PrimInfoRange& rset) 
+      {
+        if (!split.valid()) {
+          deterministic_order(set);
+          return splitFallback(set,lset,rset);
+        }
+        
+        const size_t begin = set.begin();
+        const size_t end   = set.end();
+        CentGeomBBox3fa local_left(empty);
+        CentGeomBBox3fa local_right(empty);
+
+        auto primOnLeftSide = [&] (const PrimRef& prim) -> bool { 
+          const Vec3fa axisi = normalize(direction(prim));
+          const float cos0 = abs(dot(axisi,split.axis0));
+          const float cos1 = abs(dot(axisi,split.axis1));
+          return cos0 > cos1;
+        };
+
+        auto mergePrimBounds = [this] (CentGeomBBox3fa& pinfo,const PrimRef& ref) { 
+          pinfo.extend(bounds(ref)); 
+        };
+        
+        size_t center = serial_partitioning(prims,begin,end,local_left,local_right,primOnLeftSide,mergePrimBounds);
+        
+        new (&lset) PrimInfoRange(begin,center,local_left);
+        new (&rset) PrimInfoRange(center,end,local_right);
+        assert(area(lset.geomBounds) >= 0.0f);
+        assert(area(rset.geomBounds) >= 0.0f);
+      }
+
+      void deterministic_order(const Set& set) 
+      {
+        /* required as parallel partition destroys original primitive order */
+        std::sort(&prims[set.begin()],&prims[set.end()]);
+      }
+      
+      void splitFallback(const Set& set, PrimInfoRange& lset, PrimInfoRange& rset)
+      {
+        const size_t begin = set.begin();
+        const size_t end   = set.end();
+        const size_t center = (begin + end)/2;
+        
+        CentGeomBBox3fa left(empty);
+        for (size_t i=begin; i<center; i++)
+          left.extend(bounds(prims[i]));
+        new (&lset) PrimInfoRange(begin,center,left);
+        
+        CentGeomBBox3fa right(empty);
+        for (size_t i=center; i<end; i++)
+          right.extend(bounds(prims[i]));	
+        new (&rset) PrimInfoRange(center,end,right);
+      }
+      
+    private:
+      Scene* const scene;
+      PrimRef* const prims;
+    };
+  }
+}