FG files, Append new FG points & preset Tokens...

[adrencg]

So when using Final Gathering we have the option of storing the FG results in file cache for later use and thus faster render times.

When using the 'Append new FG points to file' option Mental Ray generates a FG file (if there isn't one to begin with) and will proceed to add additional FG points to this file if and when they get generated throughout subsequent frames.
I've noticed however that by default in the 'Map file' entry box (under the Final Gathering render options tab), the [Frame] Preset Token is used. The result of this is that MR will generate a new FG file for each frame.
My question is, does every subsequent FG file (beyond the first frame) contain an entirely new set of FG points relative to that frame, or do the subsequent FG files merely contain just the additional points?
I get the idea that with the [Frame] Preset token in place MR is confused by the frame-based file naming and thus generates a completely new FG point cache for each frame, thus negating any render speed-ups.

For now I've removed the [Frame] Preset token to ensure one large FG file cache. However I do see the advantage of having multiple files instead, should the FG cache grow too large on long shots.

Take out the frames token and just use pass. It will create one large file with the proper info for each frame. I've actually rendered a low antialised pass with a frame step of 5 to build my my map file, then set it to use file and render the whole scene.

[Lone Deranger]

Yeah... for now I've just removed [Frame]... Adding [Pass] is a good idea.
Still wondering wether having multiple frames would mean taking a FG generation hit.

On the issue of mapping the FG cache... I think you can do that without the need to render a low aa pass. By setting the 'Render Type' (under the Optimization tab) to 'Final Gathering Only', MR will do just that.... only FG cache file(s) will be generated. Saves the need for any additional rendering.

Take out the frames token and just use pass. It will create one large file with the proper info for each frame. I've actually rendered a low antialised pass with a frame step of 5 to build my my map file, then set it to use file and render the whole scene.

[adrencg]

Yeah... for now I've just removed [Frame]... Adding [Pass] is a good idea.
Still wondering wether having multiple frames would mean taking a FG generation hit.

On the issue of mapping the FG cache... I think you can do that without the need to render a low aa pass. By setting the 'Render Type' (under the Optimization tab) to 'Final Gathering Only', MR will do just that.... only FG cache file(s) will be generated. Saves the need for any additional rendering.

I just learned something new. Thank you. I had a feeling there was a better way to do that.

[Lone Deranger]

Glad to hear it! :)

I only just found that out myself when I was combing through the manual trying to figure out FG caching. It's a real time saver.
I wonder when they added that feature?

Gotta love XSI for stuff like this. :)

[Saturn]

it's a new set for every frame.

It's actually handy if you do character animation.
You have to recalculate it every frame.

For a camera fly, you don't need that so just remove the [Frame] token.

[Lone Deranger]

Thanks for clearing that up Saturn. I thought that might be the case.
My current scene is indeed just a camera fly through (a simple dolly track) with no geometry deformation. So single file FG cache it is then.

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