- vray rt use default light when no light in the scene → too bright
- vray rt make luminous plan to “emit light on back side”
- vray rt can’t render “direct light” a multi sub object material
Can you explain this a bit more?
Best regards,
Vlado
oooopps sorry vlado, I don’t see your question… 
- vray rt can’t render “direct light” a multi sub object material
I mean, if you apply to a poly a luminous material part of a multi sub object material, it won’t generate light with “direct light”.
I make a test, and in fact it is reverse : rt do it not vray…
Grrrr
If I apply material or check option when vrayrt or vray is the renderer it seems to react differently…
Not sure,… grrr,… hope it can help :-)))
At present, V-Ray RT always calculates the light material with GI only, not as direct light (so the result might be a bit noisier, but should be the same otherwise).
The production V-Ray currently will not work properly if the light material with the “Direct light” option on is part of another material (e.g. a multi/subobject one). This will be implemented in the next builds.
Best regards,
Vlado
coooooooool