OPTIM: shader optimization

shaders/background_env.frag

@@ -14,9 +14,10 @@ void main()
     // Avoid per-pixel matrix inverses. With a perspective projection, a view-space ray can be
     // reconstructed directly from the projection diagonal and then rotated to world space.
     vec3 viewDir = normalize(vec3(ndc.x / sceneData.proj[0][0], ndc.y / sceneData.proj[1][1], -1.0));
-    vec3 worldDir = normalize(transpose(mat3(sceneData.view)) * viewDir);
+    // view matrix is rigid-body => transpose(mat3(view)) preserves length for normalized vectors.
+    vec3 worldDir = transpose(mat3(sceneData.view)) * viewDir;
 
-    vec2 uv = dir_to_equirect(worldDir);
+    vec2 uv = dir_to_equirect_normalized(worldDir);
     // Sample a dedicated background environment map when available.
     // The engine binds iblBackground2D to a texture that may differ from the IBL specular map.
     vec3 col = textureLod(iblBackground2D, uv, 0.0).rgb;