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phix314
08-23-2008, 10:06 PM
Making a flame for a torch on a title sequence, and it looks alright, have to do some more tweaks on the shading and whatnot, but as you can see, it goes good, explodes, gives up, then regroups. Any idea why this would happen?

http://www.youtube.com/watch?v=t8RZd5cv0Yo

It's batch rendered without a cache (huge cache, errors out on creation), and the fluid container is inside a group which rotates. It's affected by an external turbulence field, other than that nothing too fancy. Few expressions on the emitter to control scale and emission, velocity swirl, etc, high detail solver on.

I did some tests a while ago with heat explosions and whatnot, and when the high-detail rendering was on, it had a similar effect. Any ideas why the high-detail solver would cause it to explode (in a bad way... ;) ) ?

phix314
08-24-2008, 12:06 AM
It seems its the high-detail velocity part... when I turn it to "All Grids except Velocity" it behaves. Anyone know why? Maybe when the swirl too much the solver goes nuts...?

Aikiman
08-24-2008, 01:00 AM
Maybe your field force is too high or turbulence too high. I find if those things are out it breaks up the fluid just like you have there and burns all the temperature and density too quickly. Also uncached fluids can be the cause during the batch render, for some reason during rendering the simulation will stop or not turn out the way you expected.

phix314
08-24-2008, 09:27 PM
Yea that sounds about right.

Reading around it seems there's a little problem with caches over 2gb. These are pushing 4 and higher, especially with high resolutions and 500 frames. :-/

Duncan
08-25-2008, 10:48 PM
If you use the high detail solve then it can become unstable when the velocity per step is high relative to the voxel size. Possible solutions are to use substeps( although this can be problematic when cache per frame is needed ), a little damp. As well it might help to enable bounds on the sides and bottom of the container. If you have swirl then lower its value.

It is also possible to do substeps with cache per frame by changing the frame rate to double, caching then setting the frame rate back to what it was.

Duncan

phix314
08-26-2008, 01:41 AM
Nice, thank you for the under-the-hood explanation. I kinda narrowed it down to the swirl, but that confirms :)

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08-26-2008, 01:41 AM
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