message: Expose backgroundRefraction param for Pathtracer
diff: @@ -34,6 +34,10 @@ PathTracer::PathTracer() : Renderer("pathtracer")
  "bool",
  "whether geometries with an emissive material illuminate the scene",
  true);
  + createChild("backgroundRefraction",
  + "bool",
  + "allow for alpha blending even if background is seen through refractive objects like glass",
  + false);
  child("lightSamples").setMinMax(-1, 1000);
  child("roulettePathLength").setMinMax(0, 1000);
  