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, 37 insertions, 3 deletions

diff --git a/intern/cycles/bvh/bvh.h b/intern/cycles/bvh/bvh.h
index da7c9f3834d..16752076f6a 100644
--- a/intern/cycles/bvh/bvh.h
+++ b/intern/cycles/bvh/bvh.h
@@ -40,6 +40,9 @@ class Progress;
 #define BVH_ALIGN		4096
 #define TRI_NODE_SIZE	3
 
+#define BVH_UNALIGNED_NODE_SIZE 7
+#define BVH_UNALIGNED_QNODE_SIZE 14
+
 /* Packed BVH
  *
  * BVH stored as it will be used for traversal on the rendering device. */
@@ -117,9 +120,32 @@ protected:
 
 	/* pack */
 	void pack_nodes(const BVHNode *root);
-	void pack_leaf(const BVHStackEntry& e, const LeafNode *leaf);
-	void pack_inner(const BVHStackEntry& e, const BVHStackEntry& e0, const BVHStackEntry& e1);
-	void pack_node(int idx, const BoundBox& b0, const BoundBox& b1, int c0, int c1, uint visibility0, uint visibility1);
+
+	void pack_leaf(const BVHStackEntry& e,
+	               const LeafNode *leaf);
+	void pack_inner(const BVHStackEntry& e,
+	                const BVHStackEntry& e0,
+	                const BVHStackEntry& e1);
+
+	void pack_aligned_inner(const BVHStackEntry& e,
+	                        const BVHStackEntry& e0,
+	                        const BVHStackEntry& e1);
+	void pack_aligned_node(int idx,
+	                       const BoundBox& b0,
+	                       const BoundBox& b1,
+	                       int c0, int c1,
+	                       uint visibility0, uint visibility1);
+
+	void pack_unaligned_inner(const BVHStackEntry& e,
+	                          const BVHStackEntry& e0,
+	                          const BVHStackEntry& e1);
+	void pack_unaligned_node(int idx,
+	                         const Transform& aligned_space0,
+	                         const Transform& aligned_space1,
+	                         const BoundBox& b0,
+	                         const BoundBox& b1,
+	                         int c0, int c1,
+	                         uint visibility0, uint visibility1);
 
 	/* refit */
 	void refit_nodes();
@@ -138,9 +164,17 @@ protected:
 
 	/* pack */
 	void pack_nodes(const BVHNode *root);
+
 	void pack_leaf(const BVHStackEntry& e, const LeafNode *leaf);
 	void pack_inner(const BVHStackEntry& e, const BVHStackEntry *en, int num);
 
+	void pack_aligned_inner(const BVHStackEntry& e,
+	                        const BVHStackEntry *en,
+	                        int num);
+	void pack_unaligned_inner(const BVHStackEntry& e,
+	                          const BVHStackEntry *en,
+	                          int num);
+
 	/* refit */
 	void refit_nodes();
 	void refit_node(int idx, bool leaf, BoundBox& bbox, uint& visibility);