Rendering an Animation using Final Gather in Maya?

Kyle_butler

Hi, guys!
I'm about to batch render my animation, but I've read that I may be facing flickering problems, once I'm using Final Gather in an animated scene (where both camera and charaters move).
In Maya, there is a option called "Optimize for animation" but after reading serveral threads, I think it might be useless.
Since I'm taking about 14 minutes for frame, I'd like to be sure it is going to work before getting started.
Any suggestions?

ZacD

This might not be the best forum for mental ray render issues, 90% of the work we do is with realtime engines. I only have mess with Final Gather for static scenes, and I know it has really bad flickering unless you tell it to not rebuild and only add new points. I think the main way to reduce flickering for an animation would be to turn up the settings and sampling, but this will make the render times increase as well.

AdmiralTex

Render out a handful of frames to try it out.

Kyle_butler

Thanks for the tips. I'm sorry for posting in the wrong forum.

Meteora

Animation is very tricky to do when dealing with final gathering points. I don't know how well it works, but normally for basic prop animation scenes (excluding simple camera movements) what I would normally do is this:

Frame 0 > Build On
Frame 1 > Freeze
Frame [X] > Build Off

Have build on at the first frame, then freeze it so it doesn't have to calculate every frame afterwards. This ensures that there won't be any flickering, since you're not recalculating every time. It'll just use the existing map (you may need to designate a FG map name, like default.fgmap). Frame X is when the camera or animation changes to such a significant point that the existing FG map doesn't work.

Having the build off simply means adding points on top of the existing final gathering map, you're not recalculating anything so the points will always be consistent.

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To make sense of the whole Build On/Off/Freeze:

Build On = Creating a new final gathering map, calculate all points in a given frame (slowest)
Build Off = Add points on top of existing final gathering map (faster)
Freeze = Don't make any changes to the final gathering map, read the map as a cache (fastest)

You can set keyframes on the builds, so it will automatically switch between each build type depending on which frame it is on. An example of how it would be set could be something like this:

Frame 0 > Build On (make map)
Frame 1 > Freeze
Frame 100 > Build Off (drastic change in scene)
Frame 101 > Freeze

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I guess I went on a bit of a tangent. Simply put, build it first, freeze it and then use off when there's a drastic change. Rinse and repeat throughout each shot. I hope I didn't confuse you and that it helped. I may have some things mixed up though, but this is my understanding of final gathering.

Kyle_butler

Meteora, thank you very much for this answer ( or should I call it a tutorial?! =D ).
I had lost hope on this thread and your answer may save my project from fake indirect ilumination.