Cycles: optimization for hair BVH build, allow max 2 hair curves per leaf.

This gives me 14% reduction in render time for koro_final.blend.

1 files changed, 26 insertions, 3 deletions

diff --git a/intern/cycles/bvh/bvh_build.cpp b/intern/cycles/bvh/bvh_build.cpp
index 9367e7b86b4..eb4cca92b6b 100644
--- a/intern/cycles/bvh/bvh_build.cpp
+++ b/intern/cycles/bvh/bvh_build.cpp
@@ -298,18 +298,41 @@ void BVHBuild::thread_build_node(InnerNode *inner, int child, BVHObjectBinning *
 	}
 }
 
+bool BVHBuild::range_within_max_leaf_size(const BVHRange& range)
+{
+	size_t size = range.size();
+	size_t max_leaf_size = max(params.max_triangle_leaf_size, params.max_curve_leaf_size);
+
+	if(size > max_leaf_size)
+		return false;
+	
+	size_t num_triangles = 0;
+	size_t num_curves = 0;
+
+	for(int i = 0; i < size; i++) {
+		BVHReference& ref = references[range.start() + i];
+
+		if(ref.prim_type() & PRIMITIVE_ALL_CURVE)
+			num_curves++;
+		else if(ref.prim_type() & PRIMITIVE_ALL_TRIANGLE)
+			num_triangles++;
+	}
+
+	return (num_triangles < params.max_triangle_leaf_size) && (num_curves < params.max_curve_leaf_size);
+}
+
 /* multithreaded binning builder */
 BVHNode* BVHBuild::build_node(const BVHObjectBinning& range, int level)
 {
 	size_t size = range.size();
-	float leafSAH = params.sah_triangle_cost * range.leafSAH;
-	float splitSAH = params.sah_node_cost * range.bounds().half_area() + params.sah_triangle_cost * range.splitSAH;
+	float leafSAH = params.sah_primitive_cost * range.leafSAH;
+	float splitSAH = params.sah_node_cost * range.bounds().half_area() + params.sah_primitive_cost * range.splitSAH;
 
 	/* have at least one inner node on top level, for performance and correct
 	 * visibility tests, since object instances do not check visibility flag */
 	if(!(range.size() > 0 && params.top_level && level == 0)) {
 		/* make leaf node when threshold reached or SAH tells us */
-		if(params.small_enough_for_leaf(size, level) || (size <= params.max_leaf_size && leafSAH < splitSAH))
+		if(params.small_enough_for_leaf(size, level) || (range_within_max_leaf_size(range) && leafSAH < splitSAH))
 			return create_leaf_node(range);
 	}