From 6de08f6cd1cb9e50736a0a43bf37d621c6eb2b87 Mon Sep 17 00:00:00 2001
From: Sergey Sharybin <sergey.vfx@gmail.com>
Date: Thu, 8 Sep 2016 15:08:35 +0200
Subject: [PATCH] Cycles: Fix regular BVH nodes refit

For proper indexing to work we need to use unaligned node with
identity transform instead of aligned nodes when doing refit.

To be backported to 2.78 release.
---
 intern/cycles/bvh/bvh.cpp | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/intern/cycles/bvh/bvh.cpp b/intern/cycles/bvh/bvh.cpp
index 5221aa506cc..09bd03cd0c9 100644
--- a/intern/cycles/bvh/bvh.cpp
+++ b/intern/cycles/bvh/bvh.cpp
@@ -633,9 +633,9 @@ void RegularBVH::refit_node(int idx, bool leaf, BoundBox& bbox, uint& visibility
 {
 	if(leaf) {
 		assert(idx + BVH_NODE_LEAF_SIZE <= pack.leaf_nodes.size());
-		int4 *data = &pack.leaf_nodes[idx];
-		int c0 = data[0].x;
-		int c1 = data[0].y;
+		const int4 *data = &pack.leaf_nodes[idx];
+		const int c0 = data[0].x;
+		const int c1 = data[0].y;
 		/* refit leaf node */
 		for(int prim = c0; prim < c1; prim++) {
 			int pidx = pack.prim_index[prim];
@@ -711,9 +711,11 @@ void RegularBVH::refit_node(int idx, bool leaf, BoundBox& bbox, uint& visibility
 	}
 	else {
 		assert(idx + BVH_NODE_SIZE <= pack.nodes.size());
-		int4 *data = &pack.nodes[idx];
-		int c0 = data[0].z;
-		int c1 = data[0].w;
+
+		const int4 *data = &pack.nodes[idx];
+		const bool is_unaligned = (data[0].x & PATH_RAY_NODE_UNALIGNED) != 0;
+		const int c0 = data[0].z;
+		const int c1 = data[0].w;
 		/* refit inner node, set bbox from children */
 		BoundBox bbox0 = BoundBox::empty, bbox1 = BoundBox::empty;
 		uint visibility0 = 0, visibility1 = 0;
@@ -721,7 +723,22 @@ void RegularBVH::refit_node(int idx, bool leaf, BoundBox& bbox, uint& visibility
 		refit_node((c0 < 0)? -c0-1: c0, (c0 < 0), bbox0, visibility0);
 		refit_node((c1 < 0)? -c1-1: c1, (c1 < 0), bbox1, visibility1);
 
-		pack_aligned_node(idx, bbox0, bbox1, c0, c1, visibility0, visibility1);
+		if(is_unaligned) {
+			Transform aligned_space = transform_identity();
+			pack_unaligned_node(idx,
+			                    aligned_space, aligned_space,
+			                    bbox0, bbox1,
+			                    c0, c1,
+			                    visibility0,
+			                    visibility1);
+		}
+		else {
+			pack_aligned_node(idx,
+			                  bbox0, bbox1,
+			                  c0, c1,
+			                  visibility0,
+			                  visibility1);
+		}
 
 		bbox.grow(bbox0);
 		bbox.grow(bbox1);