@N-drju:
Regarding the RTP turning black I noticed this:
- it turns black when you crank up the strength of for example the sunlight very high.
Reflections, white values or whatever in the preview explode so to speak and then it turns black.
You can try to "Reset view camera position" under the preview window left hand side
or (this works for me in most cases) click >Reset<
"Reset the 3D Preview to basic configuration" on top of the preview window - next to the RTP button.
CHeers, Klaus
Since I do not fully understand what the RTP shows me anyways I gave up on using it.
What it shows very often does not look like anything close to a final render.
It would be useful for my stuff if it was able to show geometry changes...