Fix #32904: strange pattern on subdivided cube with anistropic shader. Now

tangents from generated coordinates are computed per pixel on the fly, avoids
bad interpolation of singularities.

1 files changed, 27 insertions, 2 deletions

diff --git a/intern/cycles/kernel/svm/svm_geometry.h b/intern/cycles/kernel/svm/svm_geometry.h
index 30afd6322a7..e0f9e337652 100644
--- a/intern/cycles/kernel/svm/svm_geometry.h
+++ b/intern/cycles/kernel/svm/svm_geometry.h
@@ -20,6 +20,22 @@ CCL_NAMESPACE_BEGIN
 
 /* Geometry Node */
 
+__device_inline float3 svm_tangent_from_generated(float3 P)
+{
+	float length = len(P);
+
+	if(length == 0.0f)
+		return make_float3(0.0f, 0.0f, 0.0f);
+
+	float u = 0.0f;
+	if(!(P.x == 0.0f && P.y == 0.0f))
+		u = (1.0f - atan2f(P.x, P.y))/(2.0f*M_PI_F);
+	
+	float v = 1.0f - acosf(clamp(P.z/length, -1.0f, 1.0f))/M_PI_F;
+
+	return make_float3(u, v, 0.0f);
+}
+
 __device void svm_node_geometry(KernelGlobals *kg, ShaderData *sd, float *stack, uint type, uint out_offset)
 {
 	float3 data;
@@ -36,8 +52,17 @@ __device void svm_node_geometry(KernelGlobals *kg, ShaderData *sd, float *stack,
 					data = triangle_attribute_float3(kg, sd, ATTR_ELEMENT_VERTEX, attr_offset, NULL, NULL);
 					object_normal_transform(kg, sd, &data);
 				}
-				else
-					data = normalize(sd->dPdu);
+				else {
+					attr_offset = find_attribute(kg, sd, ATTR_STD_GENERATED);
+
+					if(attr_offset != ATTR_STD_NOT_FOUND) {
+						data = triangle_attribute_float3(kg, sd, ATTR_ELEMENT_VERTEX, attr_offset, NULL, NULL);
+						svm_tangent_from_generated(data);
+						object_normal_transform(kg, sd, &data);
+					}
+					else
+						data = normalize(sd->dPdu);
+				}
 			}
 			else
 				data = normalize(sd->dPdu);