message: When IOR=1.0, there should be no transmission roughness
  * When IOR=1.0, there should be no transmission roughness
  See
  for details.
  * Use a smoothsteph instead
  * Don't modify roughness twice
diff: @@ -509,11 +509,11 @@ void applyRefraction(const PixelParams pixel,
  #endif
  #endif
  - float perceptualRoughness = pixel.perceptualRoughnessUnclamped;
  + // Roughness remapping so that an IOR of 1.0 means no microfacet refraction and an IOR
  + // of 1.5 has full microfacet refraction
  + float perceptualRoughness = mix(pixel.perceptualRoughnessUnclamped, 0.0,
  + saturate(pixel.etaIR * 3.0 - 2.0));
  #if REFRACTION_TYPE == REFRACTION_TYPE_THIN
  - // Roughness remaping for thin layers, see Burley 2012, "Physically-Based Shading at Disney"
  - perceptualRoughness = saturate((0.65 * pixel.etaRI - 0.35) * perceptualRoughness);
  -
  // For thin surfaces, the light will bounce off at the second interface in the direction of
  // the reflection, effectively adding to the specular, but this process will repeat itself.
  // Each time the ray exits the surface on the front side after the first bounce,
  