pclaes, on 27 February 2011 - 05:35 AM, said:
I asked Julien to have a look at it and he suggested the following:
In order to get your volume to expand more, you can scatter points in it on every frame and have those points add to the divergence field. You could choose to use your vorticles too. You can also scatter vorticles on the edge of the fluid at every frame to break up the edges of your smoke volume. (So you would have two sets of vorticles, 1) which flows and gets advected with the simulation and another set which just advects the edges (and gets regenerated each frame) -- basically you scatter points only on the edges where your "density < 0.3" for example.)
(gas particle to field will help you transfer values). Generally you want a non-divergent simulation, but with explosions you actually want the smoke to diverge hugely, so you want to add to your divegence field.
Also the vorticles that get advected by the sim can inject heat into the sim. You make sure that the default cooling rate is quite high, so the smoke cools down quickly, that way when you keep adding "hot spots" within the volume you get the "bubbling smoke" feeling. The rolling clouds come from the hot core to the outside edge.
Divergence is a float field (like density). And in the fluid sim the gradient of the divergence field will be used to advect your fields. In simple terms: think about density, the difference from a point with high density and low density will give you a vector. This vector is added/blended with the existing velocity. Generally density can be used for divergence, but as I said, you can add to your divergence field manually and make it expand a lot more. The difference between the high and low value is called "the gradient" (not just in fluid sims).
In the files that came with my thesis I use custom fields to manipulate the velocity, temperature and color and I build my own gradient vector based on custom volumes and add it to the velocity directly, so you can have a look at that for an example.
Not sure if I'm convinced by the cmivfx tutorial. It looks ok - haven't seen it yet, so can't really comment. If he's using default pyro it might be a bit slow.
My computer lies in pieces as I'm doing watercooling atm, but Julien might post you a file tomorrow.
If you have questions about the above, please ask as I don't know exactly how detailed I should explain.
Thanks, this is definitely working better already. I had a play around and Ive managed to get particles advecting (divergence?) the pyro system. My main stumbling block has been the vorticle emission along the edge of the fluids.
Gas Vorticle DOP does not seem to import vorticles every frame, only the start frame, any way around that? Am I right in thinking the scattered points need to be connected to the third (not fourth) input of the pyro solver? Ive currently resorted to a sop geometry dop, though that doesn't get evaluated the same way as vorticles does it?
I'll attach a file soon!
Thanks a load:)
p.s. And watercooling, you overclocking
(Was able to get an extra 1.5ghz out of 975 with watercooling, should be fun, now all you need to do is connect it to your graphic cards aswell:p)
Edited by aghourab, 27 February 2011 - 03:07 PM.