Fix #33830: cycles normal mapping was not quite correct, was not correctly

respecting the assumption that normal and tangent are interpolated without
normalization.

2 files changed, 24 insertions, 13 deletions

diff --git a/intern/cycles/kernel/shaders/node_normal_map.osl b/intern/cycles/kernel/shaders/node_normal_map.osl
index dc25eb8539f..21382fab06f 100644
--- a/intern/cycles/kernel/shaders/node_normal_map.osl
+++ b/intern/cycles/kernel/shaders/node_normal_map.osl
@@ -31,15 +31,23 @@ shader node_normal_map(
 
 	if (space == "Tangent") {
 		vector tangent;
+		vector ninterp;
 		float tangent_sign;
 
-		getattribute(attr_name, tangent);
-		getattribute(attr_sign_name, tangent_sign);
+		// get _unnormalized_ interpolated normal and tangent
+		if(!getattribute(attr_name, tangent) ||
+		   !getattribute(attr_sign_name, tangent_sign) ||
+		   !getattribute("geom:N", ninterp)) {
+			Normal = normal(0, 0, 0);
+		}
+		else {
+			// apply normal map
+			vector B = tangent_sign * cross(ninterp, tangent);
+			Normal = normalize(mcolor[0] * tangent + mcolor[1] * B + mcolor[2] * ninterp);
 
-		tangent = transform("object", "world", tangent);
-
-		vector B = tangent_sign * cross(NormalIn, tangent);
-		Normal = normalize(mcolor[0] * tangent + mcolor[1] * B + mcolor[2] * NormalIn);
+			// transform to world space
+			Normal = normalize(transform("object", "world", Normal));
+		}
 	}
 	else if (space == "Object")
 		Normal = normalize(transform("object", "world", vector(mcolor)));
diff --git a/intern/cycles/kernel/svm/svm_tex_coord.h b/intern/cycles/kernel/svm/svm_tex_coord.h
index 7a1af43b625..d793169261d 100644
--- a/intern/cycles/kernel/svm/svm_tex_coord.h
+++ b/intern/cycles/kernel/svm/svm_tex_coord.h
@@ -248,24 +248,27 @@ __device void svm_node_normal_map(KernelGlobals *kg, ShaderData *sd, float *stac
 		}
 
 		/* first try to get tangent attribute */
-		AttributeElement attr_elem, attr_sign_elem;
+		AttributeElement attr_elem, attr_sign_elem, attr_normal_elem;
 		int attr_offset = find_attribute(kg, sd, node.z, &attr_elem);
 		int attr_sign_offset = find_attribute(kg, sd, node.w, &attr_sign_elem);
+		int attr_normal_offset = find_attribute(kg, sd, ATTR_STD_VERTEX_NORMAL, &attr_normal_elem);
 
-		if(attr_offset == ATTR_STD_NOT_FOUND || attr_sign_offset == ATTR_STD_NOT_FOUND) {
+		if(attr_offset == ATTR_STD_NOT_FOUND || attr_sign_offset == ATTR_STD_NOT_FOUND || attr_normal_offset == ATTR_STD_NOT_FOUND) {
 			stack_store_float3(stack, normal_offset, make_float3(0.0f, 0.0f, 0.0f));
 			return;
 		}
 
-		/* ensure orthogonal and normalized (interpolation breaks it) */
+		/* get _unnormalized_ interpolated normal and tangent */
 		float3 tangent = primitive_attribute_float3(kg, sd, attr_elem, attr_offset, NULL, NULL);
 		float sign = primitive_attribute_float(kg, sd, attr_sign_elem, attr_sign_offset, NULL, NULL);
+		float3 normal = primitive_attribute_float3(kg, sd, attr_normal_elem, attr_normal_offset, NULL, NULL);
 
-		object_normal_transform(kg, sd, &tangent);
-		tangent = cross(sd->N, normalize(cross(tangent, sd->N)));;
+		/* apply normal map */
+		float3 B = sign * cross(normal, tangent);
+		N = normalize(color.x * tangent + color.y * B + color.z * normal);
 
-		float3 B = sign * cross(sd->N, tangent);
-		N = normalize(color.x * tangent + color.y * B + color.z * sd->N);
+		/* transform to world space */
+		object_normal_transform(kg, sd, &N);
 	}
 	else {
 		/* object, world space */