I have a GI/FG Issue


Hello All.

I’ve been using FG for a while and just starting to dabble with GI. I’ve been reading up on it and feel like I’m on the verge of getting Mental Ray to do what I want.

I have a simple scene. When I have a area light, with it’s MR attributes on and photons emitting. I would render the scene with GI only and got a nice layout of photons however whenever I turn final gather on my render turns out black.

The odd part of this to me is that when FG is gathering it’s point it appears like it’s going to render fine and then when the final pass is done everything turns very dark. See images.


i had the same problem…did you try to increase the photons Intestiy? or adding mor lights to the scene? lets say: more point lights with qubic Decay…and one more light that emmeitng photons…


Actually. All my lights are set to 0 intensity. Maybe that is the problem? I was thinking that I could just light the scene by emitting photons? As long as final gather is off the scene gets lit fairly well from 1 light source just emitting photons… 0 intensity on the light.


Not sure if this will help, but make sure ‘illuminates by default’ is checked on in at least one of your lights.


Yes this is your problem. Balance direct illumination (normal light) with indirect illumination (GI) and smooth/enhance the result with FG. This is a gross oversimplification of the GI/FG lighting.



Hey Guys, Thanks.

Yeah, that was the problem. I added a few more light and things are rendering much better.


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