View Full Version : How to avoid this FG problem. (URGENT)

11 November 2009, 06:49 PM
Hello guys.

Check the photo I uploaded.

I don't know why I'm getting all that green ┐radiosity? in the walls. All materials in the scene are lamberts and I'm wondering why they are acting like that since I'm only using MR+FG with a physical sun & sky. BTW how would you iluminate something like this? Should I start with an ambient then go for spot lights with decay?

Sadly, I don't have time to make tests because I got the project yesterday and I have to finish it for tomorrow morning. Plus, I'm kinda new to Maya and it can be ovewhelming sometimes...

I don't have problems modeling but lighting and shading :banghead:

11 November 2009, 07:03 PM
What you are experiencing is color bleeding. When you do the Final Gather lookup it checks the color of objects near it and grabs a small portion of it. This does happen in the real world but rarely to the extent we see in CG images.

Not sure what the easiest way is to get rid of it as I rarely use MR for Arch Vis type setups.

Anyway, at least you know what you are up against. If it is still a problem I can fire up Maya and try to sort it out for you. Let me know.


11 November 2009, 07:45 PM
If you look at the atributes under the shape node for the object. You'll see a mental ray section , which will give you some options that should help.

11 November 2009, 07:51 PM
Well the fastest an probably (in your case) easiest way would be to calculate a final gather map with like a 50 % gray lambert on all your objects, save the fg-map. Fire up your original scene with the right materials and use final gather freeze, that means that mental ray only reads from your saved fg-map, therefore no color-bleed.


11 November 2009, 08:25 PM
Turning off Final Gather Casts in the shape node of all your green objects should remove the problem. This might make for a slightly unusual look around the green objects (slightly darker than they should be) but it will certainly solve your green tint problem.

Visua's solution with the Final Gather map should do the trick and you can use the brightness of the gray material as another way to play with how much the FG affects your scene. You can probably achieve this with render layers but I am not sure how good the reusing of FG maps is with render layers.

Good hunting,


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11 November 2009, 08:25 PM
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