View Full Version : FG & AO = FG + AO ?

06 June 2007, 10:13 PM
I was wondering if anyone could give me any advice on Final Gathering and Ambient Occlusion when rendered together, compared to a Final Gather pass and a seperate Ambient Occlusion pass that are composited together.

Is there a speed difference ? Is the final render the same ?
I love the look of FG & AO, but it seems to crank up rendertimes.
I'm wondering if it would be faster to render layers. But I don't want to sacrifice quality.

Thankyou !

06 June 2007, 11:21 AM
If you're working on maya 8.5 you should use mia_material with built in AO; you'll get good results with 10 or 16 samples in a faster & easier way than compositing different layers ;)
In compositing maybe you've got much more control on AO, but I find built in AO enough fine for me.

06 June 2007, 10:45 PM
yes I find the mia_material built in AO quite awesome as well. Just be sure to check 'details', thats what tells it to essentially fill in the details that the FG couldn't get with the AO. I think what it does exactly is multiply the AO pass by the FG intensity and also recolor the AO to match the FG coloring its on. But either way, the mia_material composites the AO in there as good as anyone could manually in post. As for render time difference, not too sure, prolly pretty close. But using the built in AO on the mia_material certainly speeds up workflow because then you dont have to make a seperate AO pass and then you dont have composite it. I use the built in mia_material AO on pretty much every still shot I make now.

06 June 2007, 06:17 AM
Thankyou so much for your insights. I will make sure to report back with my own findings.
I am excited to use the new mia_material. There is some superb literature about them at (
(direct link to pdf manual on architectural shaders)

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06 June 2007, 06:17 AM
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