Cycles: Only sort indices when finding a best dimension to split

This reduces amount of data being moved back and forth, which should
have positive effect on the performance.

1 files changed, 14 insertions, 4 deletions

diff --git a/intern/cycles/bvh/bvh_split.cpp b/intern/cycles/bvh/bvh_split.cpp
index 037702c1d06..ff0142fa786 100644
--- a/intern/cycles/bvh/bvh_split.cpp
+++ b/intern/cycles/bvh/bvh_split.cpp
@@ -42,15 +42,25 @@ BVHObjectSplit::BVHObjectSplit(BVHBuild *builder,
 	const BVHReference *ref_ptr = &builder->references[range.start()];
 	float min_sah = FLT_MAX;
 
+	storage->spatial_indices.resize(range.size());
+	int *indices = &storage->spatial_indices[0];
+
 	for(int dim = 0; dim < 3; dim++) {
-		/* sort references */
-		bvh_reference_sort(range.start(), range.end(), &builder->references[0], dim);
+		/* Sort references.
+		 * We only sort indices, to save amount of memory being sent back
+		 * and forth.
+		 */
+		bvh_reference_sort_indices(range.start(),
+		                           range.end(),
+		                           &builder->references[0],
+		                           indices,
+		                           dim);
 
 		/* sweep right to left and determine bounds. */
 		BoundBox right_bounds = BoundBox::empty;
 
 		for(int i = range.size() - 1; i > 0; i--) {
-			right_bounds.grow(ref_ptr[i].bounds());
+			right_bounds.grow(ref_ptr[indices[i]].bounds());
 			storage_->spatial_right_bounds[i - 1] = right_bounds;
 		}
 
@@ -58,7 +68,7 @@ BVHObjectSplit::BVHObjectSplit(BVHBuild *builder,
 		BoundBox left_bounds = BoundBox::empty;
 
 		for(int i = 1; i < range.size(); i++) {
-			left_bounds.grow(ref_ptr[i - 1].bounds());
+			left_bounds.grow(ref_ptr[indices[i - 1]].bounds());
 			right_bounds = storage_->spatial_right_bounds[i - 1];
 
 			float sah = nodeSAH +