Improved fix for issue that causes hair builder to be non-deterministic.

RenderKit · Jan 16, 2018 · f998ab2 · f998ab2
1 parent e4c2588
commit f998ab2
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Showing 2 changed files with 40 additions and 14 deletions.
diff --git a/kernels/builders/heuristic_binning_array_unaligned.h b/kernels/builders/heuristic_binning_array_unaligned.h
@@ -39,12 +39,18 @@ namespace embree
 
         const LinearSpace3fa computeAlignedSpace(const range<size_t>& set)
         {
-          /*! find first curve that defines valid direction */
           Vec3fa axis(0,0,1);
+          uint64_t bestGeomPrimID = -1;
+
+          /*! find curve with minimal ID that defines valid direction */
           for (size_t i=set.begin(); i<set.end(); i++)
           {
-            NativeCurves* mesh = (NativeCurves*) scene->get(prims[i].geomID());
-            const unsigned vtxID = mesh->curve(prims[i].primID());
+            const unsigned int geomID = prims[i].geomID();
+            const unsigned int primID = prims[i].primID();
+            const uint64_t geomprimID = prims[i].ID64();
+            if (geomprimID >= bestGeomPrimID) continue;
+            NativeCurves* mesh = (NativeCurves*) scene->get(geomID);
+            const unsigned vtxID = mesh->curve(primID);
             const Vec3fa v0 = mesh->vertex(vtxID+0);
             const Vec3fa v1 = mesh->vertex(vtxID+1);
             const Vec3fa v2 = mesh->vertex(vtxID+2);
@@ -55,12 +61,12 @@ namespace embree
             const Vec3fa axis1 = normalize(p3 - p0);
             if (sqr_length(p3-p0) > 1E-18f) {
               axis = axis1;
-              break;
+              bestGeomPrimID = geomprimID;
             }
           }
           return frame(axis).transposed();
         }
-
+        
         const PrimInfo computePrimInfo(const range<size_t>& set, const LinearSpace3fa& space)
         {
           auto computeBounds = [&](const range<size_t>& r) -> CentGeomBBox3fa
@@ -216,15 +222,18 @@ namespace embree
         const LinearSpace3fa computeAlignedSpaceMB(Scene* scene, const SetMB& set)
         {
           Vec3fa axis0(0,0,1);
+          uint64_t bestGeomPrimID = -1;
 
-          /*! find first curve that defines valid direction */
+          /*! find curve with minimal ID that defines valid direction */
           for (size_t i=set.object_range.begin(); i<set.object_range.end(); i++)
           {
             const PrimRefMB& prim = (*set.prims)[i];
-            const size_t geomID = prim.geomID();
-            const size_t primID = prim.primID();
+            const unsigned int geomID = prim.geomID();
+            const unsigned int primID = prim.primID();
+            const uint64_t geomprimID = prim.ID64();
+            if (geomprimID >= bestGeomPrimID) continue;
+
             const NativeCurves* mesh = scene->get<NativeCurves>(geomID);
-
             const unsigned num_time_segments = mesh->numTimeSegments();
             const range<int> tbounds = getTimeSegmentRange(set.time_range, (float)num_time_segments);
             if (tbounds.size() == 0) continue;
@@ -236,7 +245,7 @@ namespace embree
 
             if (sqr_length(a3 - a0) > 1E-18f) {
               axis0 = normalize(a3 - a0);
-              break;
+              bestGeomPrimID = geomprimID;
             }
           }
 

diff --git a/kernels/builders/heuristic_strand_array.h b/kernels/builders/heuristic_strand_array.h
@@ -85,20 +85,37 @@ namespace embree
       /*! finds the best split */
       const Split find(const range<size_t>& set)
       {
-        /* first curve determines first axis */
-        Vec3fa axis0 = normalize(direction(prims[set.begin()]));
+        Vec3fa axis0(0,0,1);
+        uint64_t bestGeomPrimID = -1;
+
+        /* curve with minimal 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 */
+        /* find 2nd axis that is most misaligned with first axis and has minimal 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) { bestCos = cos; axis1 = axisi; }
+          if ((cos == bestCos && (geomprimID < bestGeomPrimID)) || cos < bestCos) {
+            bestCos = cos; axis1 = axisi;
+            bestGeomPrimID = geomprimID;
+          }
         }
 
         /* partition the two strands */