Slow Smoke Plumes in FumeFX

[Jordan]

Im trying to animate the time scale/burn rate/turbulence size to quickly fill the frame with smoke plumes then have it slow down (and going to 1/3 the time scale) but have noticed that I begin to lose a lot of detail in the smoke and flames. Its is getting much softer and the edges of the smoke are softening and the scale of the "lumps" in the smoke is getting larger and smoother. The Flames are also smoothing out and loosing the small scale detail.
I would have thought the result of changing the timescale wouldnt do that type of thing.
Any suggestions to get the detail back in the slow part of the sim, or just getting detailed slow looking smoke.
Cheers,
Jordan

[bdemetz]

Higher timescale = faster speed, but also due to how fume propagates, more detail. SitniSati could propably explain technically why this is. I usually try to keep the timescale as high as I can and use other settings to slow it down.

[Jordan]

Cheers, I'll give it a go!
Have you been able to achieve slow burning smoke plumes (Large looking) smoke with this method?

Jordan

[bdemetz]

Yes. You will also need to cheat the scale on your scene - sometimes up to 5-10x larger or higher. Keep in mind, alot of parameters may have to change.

[Jordan]

Cheers. I have something working now!
Set the time scale to 3 for the 400 frame pre roll and then dropped it to 1.5 after that and had to scale the fumeFX grid 20x, but am getting ok results now.

[bdemetz]

Awesome - glad to hear it. One caveat to keep in mind. If you set your timescale high to throw some perturbing detail into a sim and then animate it lower to slow everything down, you will not be able to completely hold the detail that the initial timescale gave you, though it does help a little. It is better to try to keep the timescale up if possible and adjust other parameters accordingly. But, if you've got something that's working well, then gruvee.

Best,

[Jordan]

Just out of interest, what settings would you normally use to slow a high timescale sim down? Just burn rates, fuel adjustments and smoke amounts?

[bdemetz]

Well it really depends on the look you want, and many parameters play off each other. Bouyancy and temperature should be kept low. Keep extra velocity low if emitting from a mesh object. If from a simple source, keep directional and radial velocity low. But too little of anything and you won't get nice billowing. So its a power struggle. The joy of mastering fluid dynamics.

btw, in my post on 7/3/08 4:48pm, "animate it lower" used to say "animate it higher". I've corrected it in the post.