message: revive somewhat the importance sampling mode
diff: @@ -224,9 +224,9 @@ float prefilteredImportanceSampling(float ipdf, float iblRoughnessOneLevel) {
  // Prefiltering doesn't work with anisotropy
  const float numSamples = float(IBL_INTEGRATION_IMPORTANCE_SAMPLING_COUNT);
  const float invNumSamples = 1.0 / float(numSamples);
  - const float dim = float(textureSize(light_iblSpecular, 0).x);
  - const float omegaP = (4.0 * PI) / (6.0 * dim * dim);
  - const float invOmegaP = 1.0 / omegaP;
  + float dim = float(textureSize(light_iblSpecular, 0).x);
  + float omegaP = (4.0 * PI) / (6.0 * dim * dim);
  + float invOmegaP = 1.0 / omegaP;
  const float K = 4.0;
  float omegaS = invNumSamples * ipdf;
  float mipLevel = clamp(log2(K * omegaS * invOmegaP) * 0.5, 0.0, iblRoughnessOneLevel);
  @@ -304,7 +304,9 @@ void isEvaluateClearCoatIBL(const PixelParams pixel, float specularAO, inout vec
  p.perceptualRoughness = pixel.clearCoatPerceptualRoughness;
  p.f0 = vec3(0.04);
  p.roughness = perceptualRoughnessToRoughness(p.perceptualRoughness);
  +#if defined(MATERIAL_HAS_ANISOTROPY)
  p.anisotropy = 0.0;
  +#endif
  vec3 clearCoatLobe = isEvaluateIBL(p, clearCoatNormal, shading_view, clearCoatNoV);
  Fr += clearCoatLobe * (specularAO * pixel.clearCoat);
  