Fix T43484: Motion blur fails in certain circumstances

The issue was caused by mismatch in how aligned triangles storage was
filled in during BVH construction and how it was used during rendering.

Basically, i  was leaving uninitialized storage for triangles when
there was deformation motion blur detected for the mesh. Was likely
some sort of optimization, but in fact it's still possible that regular
triangles would be needed for rendering.

So now we're storing aligned storage for all triangle primitives and
only skipping motion triangles (the deformation motion blur flag from
mesh is now ignored).

1 files changed, 7 insertions, 5 deletions

diff --git a/intern/cycles/bvh/bvh.cpp b/intern/cycles/bvh/bvh.cpp
index 2152349ed49..9fa602f0952 100644
--- a/intern/cycles/bvh/bvh.cpp
+++ b/intern/cycles/bvh/bvh.cpp
@@ -268,9 +268,6 @@ void BVH::pack_triangle(int idx, float4 woop[3])
 	assert(tob >= 0 && tob < objects.size());
 	const Mesh *mesh = objects[tob]->mesh;
 
-	if(mesh->has_motion_blur())
-		return;
-
 	int tidx = pack.prim_index[idx];
 	const int *vidx = mesh->triangles[tidx].v;
 	const float3* vpos = &mesh->verts[0];
@@ -299,9 +296,14 @@ void BVH::pack_primitives()
 		if(pack.prim_index[i] != -1) {
 			float4 woop[3];
 
-			if(pack.prim_type[i] & PRIMITIVE_ALL_TRIANGLE)
+			if(pack.prim_type[i] & PRIMITIVE_TRIANGLE) {
 				pack_triangle(i, woop);
-			
+			}
+			else {
+				/* Avoid use of uninitialized memory. */
+				memset(&woop, 0, sizeof(woop));
+			}
+
 			memcpy(&pack.tri_woop[i * nsize], woop, sizeof(float4)*3);
 
 			int tob = pack.prim_object[i];