FG Saving. How often?

Peter M. Gruhn · July 5th, 2008

Today I figured out that the FG map is view dependant. It seems to me that it isn't THAT view dependant. Can I make it gather every, say, three frames like reflection maps? Other than by hand?

SandmanNinja · July 5th, 2008

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).

Justin Hunt · July 5th, 2008

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

SandmanNinja · July 5th, 2008

OOhh...

That really makes sense. The lighting would have to change as the viewer's angle changed.

Thanks for clarifying this, Justin.

Justin Hunt · July 6th, 2008

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

Adrian Bold · July 6th, 2008

Quote:

Originally Posted by Justin Hunt

other things to consider,
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...

jhv

Good call.

Peter M. Gruhn · July 6th, 2008

> 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.

Justin Hunt · July 6th, 2008

Photon are very powerful and quite easy to use, one you understand the logic of cause

jhv

July 5th, 2008	#1 (permalink)
Peter M. Gruhn Senior Member Join Date: Oct 2003 Location: medfield, ma Posts: 130 Name: Peter Gruhn	FG Saving. How often? Today I figured out that the FG map is view dependant. It seems to me that it isn't THAT view dependant. Can I make it gather every, say, three frames like reflection maps? Other than by hand?

July 5th, 2008	#2 (permalink)
SandmanNinja Moderator Join Date: Mar 2007 Location: Ballarat, Victoria, Australia Posts: 1,373 Name: Joel Callahan	Re: FG Saving. How often? 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). __________________ -SandmanNinja website

July 5th, 2008	#3 (permalink)
Justin Hunt Veteran Member Join Date: Jan 2005 Location: Brisbane Age: 33 Posts: 1,361 Name: Justin Hunt	Re: FG Saving. How often? 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

July 5th, 2008	#4 (permalink)
SandmanNinja Moderator Join Date: Mar 2007 Location: Ballarat, Victoria, Australia Posts: 1,373 Name: Joel Callahan	Re: FG Saving. How often? OOhh... That really makes sense. The lighting would have to change as the viewer's angle changed. Thanks for clarifying this, Justin. __________________ -SandmanNinja website

July 6th, 2008	#5 (permalink)
Justin Hunt Veteran Member Join Date: Jan 2005 Location: Brisbane Age: 33 Posts: 1,361 Name: Justin Hunt	Re: FG Saving. How often? 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

July 6th, 2008	#7 (permalink)
Peter M. Gruhn Senior Member Join Date: Oct 2003 Location: medfield, ma Posts: 130 Name: Peter Gruhn	Re: FG Saving. How often? > 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.

July 6th, 2008	#8 (permalink)
Justin Hunt Veteran Member Join Date: Jan 2005 Location: Brisbane Age: 33 Posts: 1,361 Name: Justin Hunt	Re: FG Saving. How often? Photon are very powerful and quite easy to use, one you understand the logic of cause jhv

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