View Full Version : Why So Long For FPrime ?

05-04-2004, 06:38 PM
I render this in LW radiosity takes 35 minutes, while render
in Fprime take around 30 minutes( same setting). The scene is pretty complex with huge polygons and 6 area light. This is my 1st time to render something with Fprime, am I doing something wrong with the setting? Why Fprime also take so long to render
something like this? and the result is so grainy... I still very confuse right now, can anyone giV me some guide, thanks!:bowdown:


LW radiosity - Backdrop only, Intensity-100%, Ray Per Evaluation-4 x 12
FPrime - Background Radiosity, Intensity - 135%, Stop at level - 6

05-04-2004, 06:42 PM
Area lights and FPrime don't mix very well. Unless you wait longer for it to finish, after which the grainyness is gone also.

I think.

FPrime isn't faster in every scenario. I depends. You have to run a few tests to find out if F9 or Fprime is the way to go.

05-04-2004, 06:51 PM
Yeah you got to check deformation setting and render order..once you set those fprime gets faster as those things get checked every refresh which takes fprime longer to relaod into its que.

05-04-2004, 07:06 PM
erm, sorry Julez.. is it we need to set all object to FPrime in the deformation setting?

05-04-2004, 07:12 PM
Wasn't there also a way to get a speed boost from FPrime by putting things on different layers or was that just a bug that was fixed in 1.01/1.02?

05-04-2004, 09:24 PM
well the one trick i know is that all polys must be quads or tris. so check the model and anything that is 4+ polys just tripple. that speeds it up a bit.

it works better with area lights from what has been said by other users but that is as much as i know.

do a search.

policarpo and others have been experimenting with it last month when it came out and have more info on getting good speed.

that said it is not always the fastest in all cases. so keep that in mind.

05-04-2004, 10:04 PM
Under Render Options in Layout set the number of bounces for radiosity to 2 (default is 16). That should really speed it up.

Oh just noticed your using Background Radiosity so not sure if this applies.

Brett H.
05-04-2004, 10:55 PM
There seems to be a lot of misinformation regarding Fprime going around. I'm thinking about setting up a site with some Fprime information that I keep seeing repeated incorrectly (with my extremely limited spare time, that's still a maybe):) .

First, are you using the Fprime renderer, or the preview window? You should be using the renderer. It gives different results, and seems to do GI alot quicker than the preview window. And don't use the quality numbers you may have gotten from the preview window as a measure of the quality numbers in the renderer, they just don't relate to each other. Keep checking the render in 5 minute increments to see how much it has refined.

Area lights work great with Fprime, but with Monte Carlo radiosity. Not sure why you'd want background radiosity in this scene (other than for speed), as the background isn't really a factor in this scene. Try Monte Carlo with one bounce to begin with, then up it to 2 if it seems the scene needs it.

The render panel in LW Layout has nothing to do with Fprime. It has its' own interface for radiosity, and the default is not 16 bounces. I think you're thinking of Ray Recursion Limit in the render options panel. It can be turned way down in this scene, try 2 as a start. The only time you need to fire extra rays is with transparency/refraction, in which case you would turn it back up (try 4 or 6, 16 is a bit overkill).

All polys do not have to be quads or tris (Fprime renders ngons just fine in non-subpatch objects), but I've seen tests in which tripling geometry has sped up Fprime renders. Give it a shot, it can't hurt, especially since you say the scene has "huge polys." Subdividing those might help. Same goes for major objects on different layers, give that a shot as well, it may speed things up.

The deformation plug for Fprime only gets applied to objects that are deforming, and in this scene it doesn't appear that there would be any deformation. I could be wrong, but I don't think that's the problem here (all due respect Julez).

That's all I have time for now (dinner's ready) but hopefully that'll get your render times down a bit.


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