Fog should be calculated in the user's world coordinates

Fixes #6798

shaders/src/fog.fs

@@ -62,7 +62,7 @@ vec4 fog(vec4 color, highp vec3 view) {
         // Add sun colored fog when looking towards the sun
         vec3 sunColor = frameUniforms.lightColorIntensity.rgb * frameUniforms.lightColorIntensity.w;
 
-        float sunAmount = max(dot(-shading_view, frameUniforms.lightDirection), 0.0); // between 0 and 1
+        float sunAmount = max(dot(normalize(view), frameUniforms.lightDirection), 0.0); // between 0 and 1
         float sunInscattering = pow(sunAmount, frameUniforms.fogInscatteringSize);
 
         fogColor += sunColor * (sunInscattering * (1.0 - sunTransmittance));

shaders/src/main.fs

@@ -44,6 +44,13 @@ void main() {
 
 #if defined(VARIANT_HAS_FOG)
     highp vec3 view = getWorldPosition() - getWorldCameraPosition();
+
+    // fog should be calculated in the "user's world coordinates" so that it's not
+    // affected by the IBL rotation. We're transofrming a vector, so we should use the
+    // cofactor (or inverse-transpose), but since we know this matrix is a rigid transform,
+    // we can use it as is.
+    view = mulMat3x3Float3(frameUniforms.userWorldFromWorldMatrix, view);
+
     fragColor = fog(fragColor, view);
 #endif