View Full Version : Final Gather & animated objects

10 October 2005, 07:34 AM
i've tried to render out a small bouncing ball test animation with FG (maya 6.5), using the FG freeze option.

i did a single-frame render with FG rebuild on (specifying a FG map name), then turned rebuild off and rendered a few frames with the ball in different locations, then enabled freeze for the final animation render. this works for camera fly-throughs, but the problem is the ball's radiosity is being left behind on other objects, because the map is not being rebuilt :(

you can see the position on the ground plane where the bouncing ball came from. rebuilding every frame would take forever, and flickers like crazy, so what's a good method for rendering FG with animated objects...?

btw the scene file is attached if anyone wants my stupid lil' bouncing ball scene to play around with ;)

10 October 2005, 08:20 AM
You could try rendering an occlusion pass instead. Faster and no flicker.
I never use FG for animation, too much hazzle.

10 October 2005, 03:33 PM
When illumination changes, you should rebuild the FG map.

The animated ball changes the illumination.

I concur with the AO suggestion.

If you want to stick with FG, I would use higher density FG points to avoid flicker.
Use FG diagnostics to see how you are doing. Try to get most of the points to be colored green (pre-sample stage) instead of colored red (rendering stage).

Also, Maya 7 has the FG presample density option. It is a factor to increase FG sample density. I also suggest checking the view checkbox for easier understanding of the FG radii. With view, distances are in pixel units.

See LAmrUG resources for more information.

10 October 2005, 03:40 PM
Yes, FG in animations is a hassle. For static scenes with a moving camera Rebuild should be Off, this works well as it only adds FG when it's needed. For full animated scenes, where everything is moving you need Rebuild on an increase your FG rays significantly and play with the FG radius. You'll still get noise, but with post-processing it can be reduced. When I was testing FG in 6.5 I made a simple FG animation, you can find it on this geocities page (, you can see there is some flicker, but it rendered in less than a minute per frame (single AMD cpu), it was rendered with 1000 FG rays and was not post-processed.

10 October 2005, 09:53 PM
Backlund: thanks for your reply - i've just tried the mib_amb_occlusion shader and it looks pretty cool (havn't tried animation with it yet) - but if i render in seperate passes will i still be able to get the AO effect to show up in the mirror as shown in the image..? most presentations i do have mirrors or reflective glass, and i need to see shadows and radiosity effect in reflections...

bgawboy: thanks for that link :)

Sphere: cool animation there ;) most of my scenes are huge (at least a couple hundred thousand polys), and FG rebuild throughout animation is simply not an option. i'll experiment some more with AO and see how it goes.

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10 October 2005, 09:53 PM
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