message: Kill specular AO at low roughness
  On metals (made only of specular light), specular AO can
  create large black spots. This change simply kills specular
  AO to avoid this artifact. In practice we should take into
  account multiple bounces but this is rasterization...
diff: @@ -50,7 +50,7 @@ void evaluateDirectionalLight(const MaterialInputs material,
  }
  }
  - visibility = visibility * (1.0 - ssContactShadowOcclusion);
  + visibility *= 1.0 - ssContactShadowOcclusion;
  #if defined(MATERIAL_HAS_AMBIENT_OCCLUSION)
  visibility *= computeMicroShadowing(light.NoL, material.ambientOcclusion);
  