message: don't apply roughness remapping for solid refraction
  The thin roughness remapping only makes sense for thin surfaces, it was
  a mistake to apply it to solids. It assumes that a ray will go
  undisturbed though the thin surface with an ior of 1.
diff: @@ -337,6 +337,7 @@ void applyRefraction(const PixelParams pixel,
  const vec3 n0, vec3 E, vec3 Fd, vec3 Fr,
  inout vec3 color) {
  + float perceptualRoughness = pixel.perceptualRoughnessUnclamped;
  vec3 r = -shading_view;
  float eta0 = pixel.etaIR;
  @@ -378,13 +379,9 @@ void applyRefraction(const PixelParams pixel,
  #endif
  // Roughness remaping for thin layers, see Burley 2012, "Physically-Based Shading at Disney"
  - //
  - // We apply this remapping to solid objects too because we are handling both interfaces
  - // in one go for solids as well.
  - // Note: this remapping is valid only for realistic IORs.
  - // Note: it's unclear whether we should use perceptualRoughness or roughness here, using
  - // roughness seems to produce worse results.
  - float perceptualRoughness = saturate((0.65 * pixel.etaRI - 0.35) * pixel.perceptualRoughnessUnclamped);
  +#if REFRACTION_TYPE == REFRACTION_TYPE_THIN
  + perceptualRoughness = saturate((0.65 * pixel.etaRI - 0.35) * perceptualRoughness);
  +#endif
  /* sample the cubemap or screen-space */
  #if REFRACTION_MODE == REFRACTION_MODE_CUBEMAP
  