Cycles: Implement unaligned nodes BVH builder

This is a special builder type which is allowed to orient nodes to
strands direction, hence minimizing their surface area in comparison
with axis-aligned nodes. Such nodes are much more efficient for hair
rendering.

Implementation of BVH builder is based on Embree, and generally idea
there is to calculate axis-aligned SAH and oriented SAH and if SAH
of oriented node is smaller than axis-aligned SAH we create unaligned
node.

We store both aligned and unaligned nodes in the same tree (which
seems to be different from what Embree is doing) so we don't have
any any extra calculations needed to set up hair ray for BVH
traversal, hence avoiding any possible negative effect of this new
BVH nodes type.

This new builder is currently not in use, still need to make BVH
traversal code aware of unaligned nodes.

1 files changed, 34 insertions, 5 deletions

diff --git a/intern/cycles/bvh/bvh_binning.h b/intern/cycles/bvh/bvh_binning.h
index 60742157055..52955f70151 100644
--- a/intern/cycles/bvh/bvh_binning.h
+++ b/intern/cycles/bvh/bvh_binning.h
@@ -19,11 +19,14 @@
 #define __BVH_BINNING_H__
 
 #include "bvh_params.h"
+#include "bvh_unaligned.h"
 
 #include "util_types.h"
 
 CCL_NAMESPACE_BEGIN
 
+class BVHBuild;
+
 /* Single threaded object binner. Finds the split with the best SAH heuristic
  * by testing for each dimension multiple partitionings for regular spaced
  * partition locations. A partitioning for a partition location is computed,
@@ -34,10 +37,18 @@ CCL_NAMESPACE_BEGIN
 class BVHObjectBinning : public BVHRange
 {
 public:
-	__forceinline BVHObjectBinning() {}
-	BVHObjectBinning(const BVHRange& job, BVHReference *prims);
+	__forceinline BVHObjectBinning() : leafSAH(FLT_MAX) {}
+
+	BVHObjectBinning(const BVHRange& job,
+	                 BVHReference *prims,
+	                 const BVHUnaligned *unaligned_heuristic = NULL,
+	                 const Transform *aligned_space = NULL);
 
-	void split(BVHReference *prims, BVHObjectBinning& left_o, BVHObjectBinning& right_o) const;
+	void split(BVHReference *prims,
+	           BVHObjectBinning& left_o,
+	           BVHObjectBinning& right_o) const;
+
+	__forceinline const BoundBox& unaligned_bounds() { return bounds_; }
 
 	float splitSAH;	/* SAH cost of the best split */
 	float leafSAH;	/* SAH cost of creating a leaf */
@@ -48,13 +59,20 @@ protected:
 	size_t num_bins;	/* actual number of bins to use */
 	float3 scale;		/* scaling factor to compute bin */
 
+	/* Effective bounds and centroid bounds. */
+	BoundBox bounds_;
+	BoundBox cent_bounds_;
+
+	const BVHUnaligned *unaligned_heuristic_;
+	const Transform *aligned_space_;
+
 	enum { MAX_BINS = 32 };
 	enum { LOG_BLOCK_SIZE = 2 };
 
 	/* computes the bin numbers for each dimension for a box. */
 	__forceinline int4 get_bin(const BoundBox& box) const
 	{
-		int4 a = make_int4((box.center2() - cent_bounds().min)*scale - make_float3(0.5f));
+		int4 a = make_int4((box.center2() - cent_bounds_.min)*scale - make_float3(0.5f));
 		int4 mn = make_int4(0);
 		int4 mx = make_int4((int)num_bins-1);
 
@@ -64,7 +82,7 @@ protected:
 	/* computes the bin numbers for each dimension for a point. */
 	__forceinline int4 get_bin(const float3& c) const
 	{
-		return make_int4((c - cent_bounds().min)*scale - make_float3(0.5f));
+		return make_int4((c - cent_bounds_.min)*scale - make_float3(0.5f));
 	}
 
 	/* compute the number of blocks occupied for each dimension. */
@@ -78,6 +96,17 @@ protected:
 	{
 		return (int)((a+((1LL << LOG_BLOCK_SIZE)-1)) >> LOG_BLOCK_SIZE);
 	}
+
+	__forceinline BoundBox get_prim_bounds(const BVHReference& prim) const
+	{
+		if(aligned_space_ == NULL) {
+			return prim.bounds();
+		}
+		else {
+			return unaligned_heuristic_->compute_aligned_prim_boundbox(
+			        prim, *aligned_space_);
+		}
+	}
 };
 
 CCL_NAMESPACE_END