Cycles: Fix wrong shading when some mesh triangle has non-finite coordinate

This is fully unpredictable for artists when one damaged object makes the whole
scene to render incorrectly. This involves two main changes:

- It is not enough to check triangle bounds to be valid when building BVH.
  This is because triangle might have some finite vertices and some non-finite.

- We shouldn't add non-finite triangle area to the overall area for MIS.

3 files changed, 12 insertions, 0 deletions

diff --git a/intern/cycles/render/light.cpp b/intern/cycles/render/light.cpp
index 6a7f985b756..bb73ebd7e41 100644
--- a/intern/cycles/render/light.cpp
+++ b/intern/cycles/render/light.cpp
@@ -345,6 +345,9 @@ void LightManager::device_update_distribution(Device *device, DeviceScene *dscen
 				offset++;
 
 				Mesh::Triangle t = mesh->get_triangle(i);
+				if(!t.valid(&mesh->verts[0])) {
+					continue;
+				}
 				float3 p1 = mesh->verts[t.v[0]];
 				float3 p2 = mesh->verts[t.v[1]];
 				float3 p3 = mesh->verts[t.v[2]];
diff --git a/intern/cycles/render/mesh.cpp b/intern/cycles/render/mesh.cpp
index c5eb3a0d3a8..6470b3b1075 100644
--- a/intern/cycles/render/mesh.cpp
+++ b/intern/cycles/render/mesh.cpp
@@ -120,6 +120,13 @@ float3 Mesh::Triangle::compute_normal(const float3 *verts) const
 	return norm / normlen;
 }
 
+bool Mesh::Triangle::valid(const float3 *verts) const
+{
+	return isfinite3_safe(verts[v[0]]) &&
+	       isfinite3_safe(verts[v[1]]) &&
+	       isfinite3_safe(verts[v[2]]);
+}
+
 /* Curve */
 
 void Mesh::Curve::bounds_grow(const int k, const float3 *curve_keys, const float *curve_radius, BoundBox& bounds) const
diff --git a/intern/cycles/render/mesh.h b/intern/cycles/render/mesh.h
index 3483ab4fd69..ed7cb881e91 100644
--- a/intern/cycles/render/mesh.h
+++ b/intern/cycles/render/mesh.h
@@ -72,6 +72,8 @@ public:
 		                    float3 r_verts[3]) const;
 
 		float3 compute_normal(const float3 *verts) const;
+
+		bool valid(const float3 *verts) const;
 	};
 
 	Triangle get_triangle(size_t i) const