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View Full Version : final gather as a separate pass

mayaq
03-28-2005, 09:19 AM
hopefully someone can answer these questions:

1. is there a way to output final gather as a separate image pass (ie: separate from the direct illumination from my lights)?

2. is there a way to render part of my set (a layer of objects) with final gather contribution from other (invisible) parts of my set? is it as simple as turning off primary visiblility on the other objects in the scene?

3. what if i want the same as #2, but want the non-visible parts to be matted against the part of the set i'm rendering?

thanks in advance.
mayaq
04-08-2005, 05:24 PM
anyone?

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visjes
04-08-2005, 07:12 PM
I hope this can help a bit.

You need to be using Maya 6.5. If not, then you have to hack it, i.e. shower your scene with a white material and do it that way.. that's not really a final gather pass, but a pseudo-ambient occlusion pass.

In Maya 6.5, you select mentalrayGlobals (use the command like: select -r mentalrayGlobals; or just use the sel box at the top) and go into properties. Then you can select Render Mode to be Render Final Gather Maps. This is not necessarily a pass, but maps you apply to your shaders.. yum. It is possible that there is a way to separate your scene into a final gather pass, but I think maybe you have to use mental ray standalone? Check out http://www.lamrug.org/ and see if there is any info there on doing this. You could export your scene to a .mi file and edit it to be a fg pass.

If none of that is adequate I guess I can ask, what do you want out of a final gather pass. Final gathering uses so much information based on lights, colour bounced off of shaders, etc. I'm not sure what a pass by itself might look like, or how it would affect your overall scene if it were separated.
nojjy
04-08-2005, 10:22 PM
There is a way to extract a final gather only pass in post. Render your scene first with final gathering enabled, then without. In a compositing application (or photoshop) layer your two passes together and change the blending mode of the top layer to "Difference". It will show only the pixel value differences, which will be only the final gathering contribution. Check out the attached image.
bgawboy
04-10-2005, 02:32 AM
I think that the lambert included in the misss shaders has a way to get indirect illumination only. If you use FG and no caustics or GI, it gives you the FG only
bgawboy
04-10-2005, 02:35 AM
BTW, in 6.5 you also notice the FG scale in mental ray render globals, right?
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