Fix T100377: EEVEE: Regression 3.2 normalmap node broken

This was caused by un-wanted normalization. This is a requirement of
the MikkTspace. The issue is that g_data.N is expected to be normalized
by many other functions and overriden by bump displacement.

Adding a new global variable containing the interpolated normal fixes the
issue AND make it match cycles behavior better (mix between bump and
interpolated normal).

2 files changed, 6 insertions, 4 deletions

diff --git a/source/blender/gpu/shaders/gpu_shader_codegen_lib.glsl b/source/blender/gpu/shaders/gpu_shader_codegen_lib.glsl
index 6091a5c834a..c0821085c8d 100644
--- a/source/blender/gpu/shaders/gpu_shader_codegen_lib.glsl
+++ b/source/blender/gpu/shaders/gpu_shader_codegen_lib.glsl
@@ -187,8 +187,10 @@ struct ClosureTransparency {
 struct GlobalData {
   /** World position. */
   vec3 P;
-  /** Surface Normal. */
+  /** Surface Normal. Normalized, overriden by bump displacement. */
   vec3 N;
+  /** Raw interpolated normal (non-normalized) data. */
+  vec3 Ni;
   /** Geometric Normal. */
   vec3 Ng;
   /** Curve Tangent Space. */
diff --git a/source/blender/gpu/shaders/material/gpu_shader_material_normal_map.glsl b/source/blender/gpu/shaders/material/gpu_shader_material_normal_map.glsl
index a54dc59ddfe..3fc4992f7c4 100644
--- a/source/blender/gpu/shaders/material/gpu_shader_material_normal_map.glsl
+++ b/source/blender/gpu/shaders/material/gpu_shader_material_normal_map.glsl
@@ -3,13 +3,13 @@
 void node_normal_map(vec4 tangent, vec3 texnormal, out vec3 outnormal)
 {
   if (all(equal(tangent, vec4(0.0, 0.0, 0.0, 1.0)))) {
-    outnormal = g_data.N;
+    outnormal = g_data.Ni;
     return;
   }
   tangent *= (FrontFacing ? 1.0 : -1.0);
-  vec3 B = tangent.w * cross(g_data.N, tangent.xyz) * sign(ObjectInfo.w);
+  vec3 B = tangent.w * cross(g_data.Ni, tangent.xyz) * sign(ObjectInfo.w);
 
-  outnormal = texnormal.x * tangent.xyz + texnormal.y * B + texnormal.z * g_data.N;
+  outnormal = texnormal.x * tangent.xyz + texnormal.y * B + texnormal.z * g_data.Ni;
   outnormal = normalize(outnormal);
 }
 #endif