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FG Saving. How often?


Peter M. Gruhn
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Hmm...

 

I was told/taught that once the FG Map is calculated and saved, as long as the lighting and geometry didn't change (i.e. you can move the camera, change textures, etc), you can re-use the FGM.

 

I've done test renders and test animations moving the camera around.

It wasn't an overly complicated scene, but it's surely a time-saver (especially if you're using multiple bounces in FG).

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FG is view dependant, however has the ability to interpolate between frames.

 

In other words it is possible (and recommended) to calculate FG for every nth frame of an animation. The frames that were not calculated are interpolated or avaeraged from the frames that were calculated.

 

Things to consider.

 

Length of the animation

motion of the camera path

geometry complexity

moving geometry

 

Used in combination with photons it is possible to use very few samples and frames.

 

jhv

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other things to consider,

 

If a fg sample exists then it will be skipped when further FG samples are calculated, such as if you are doing a solar study and the camera is static, then FG will only be saved for the first frame and skiped for the rest. Solution, move the camera

 

Sometimes if you calculate too many frames you can run into problems running out of memeory when reloading the solution. 64bit doesn't have this issue

 

To save time and memory, us Photons and FG. Photons are not view dependant so only need to be calculated once. You only need the FG to "clean up" the photon solution so only the first bounce of FG is used so leave it a 0 bounce. Also very low FG settings work better.

 

jhv

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> To save time and memory, us Photons and FG.

 

Soon as I get my Photons questions worked out and probably sample images up. So far my experience with the photons has been "would be nice, too bad they suck." That strikes me as "gruhn must be doing something wrong." More later.

 

Thanks for all the insights, y'all.

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