PDA

View Full Version : Particles render differently when F10 render is resumed some other time



motörmonk
04-01-2010, 10:18 AM
Hello all,

I need some serious troubleshooting help.

I am using LW 9.6 on an Intel Mac. I am rendering a scene with particle dynamics using HyperVoxels in sprite mode to achieve smoke effects.

The scene uses radiosity (interpolated, not cached) and naturally the render time per frame is significant. I am rendering some frames and resuming the rest of the render on relatively free times. I also want to distribute rendering over other machines.

So the smoke I render looks different than the smoke rendered another time or rendering another segment of frames on a different machine with the same files. Even when I close the scene and reopen it another time, the smoke renders differently/jumps around.

I have a couple of theories:

1. I thought I could get away with rendering with interpolated GI with no cache (animation) since not much moves, the scene is mostly white and it seemed to work for with sprite smoke. Still, it may be rendering the same HV sprite smoke with different seeds each time I reopen the file. Thus a rendering difference.

2. Particles may be recalculated from scratch at each frame when I do a F10 render then when I render a single frame with F9. Thus a dynamics calculation difference.

3. Particles' HV Sprite has billowing effect turned on and it has some kind of random seed (which it shouldn't for consistency by the way) that I don't know of. Thus a rendering difference.

What do you think? It is too annoying to loose hours of computation time when you discover the smoke breaks in continuity over different batches of files.

Help please!

Naz

dballesg
04-01-2010, 01:39 PM
Did you calculated your particles and saved them as a PFX file?

David

motörmonk
04-01-2010, 02:21 PM
They were calculated before but I was assuming the previous calculation was kept in the scene file because it didn't need any extra processing to neither display in the viewport nor render (not that it notified me).

Do you think it recalculates the particles each time I do an F10 render?

By the way, I baked radiosity cache and was just trying to get a pair of small segments rendered after reopening the file to compare them, to pin down the possible effect of interpolation.

So, I should bake the particles too?

motörmonk
04-01-2010, 06:02 PM
Yup, it worked. It was F10 render recalculating particles.

Saved the motion on an external file like you suggested and it seems to have solved the problem.

Thank you very much!

Naz

dballesg
04-01-2010, 10:29 PM
Yup, it worked. It was F10 render recalculating particles.

Saved the motion on an external file like you suggested and it seems to have solved the problem.

Thank you very much!

Naz

Your welcome. I'm glad it solved your problem.

If you are going to sent that scene to a render farm, Particles always need to be saved as PFX files.

David