Plane: Uber Coating set to reflect the cubes above
Cube 1: Uber shader with Transparency = 1
Cube 2: Simple Diffuse cube
Cube 3: Simple Diffuse cube with RPR Settings Casts Shadows + Camera Visibility turned off.
Cube 4: Same as Cube 3 only with another Sphere object dissecting the Cube - showing the "darkening effect" of the supposedly invisible cube.
Cube 1: Cuts a hole in the plane displaying the background colour of the scene. It should not do this.
Cube 2: Correct
Cube 3: Should not display a reflection or cast a shadow.
Cube 4: As Cube 3 but it is also darkening the sphere as if it is casting a shadow.
All of these issues above also exist on any Simulation Domain box.
It's a good test case.
1 and 4 seem like the might be core renderer bugs. But I'll mention workarounds:
1. Add a bit of distance between the cube and plane or use a smaller ray epsilon
2. Use a transparent shader
3. I think is a feature request that we should expose the "reflection visibility"
It would be awesome if you could expose the reflection visibility as a new feature. Combined with being able to turn off the camera visibility it enables some brilliant visual effects to be created.
There is also the problem that on Cube 4 somehow the cube's internal shadow is changing the colour of the sphere. That may well be fixed if the cube was truly transparent via the core renderer fix.
Thanks for the testing. I think most of these should be fixed with the upcoming bug fix release which will have a "reflection visibility" option on the object. #1 We're still investigating.