FumeFX: Billowing Smoke that doesn't rise much, if at all?

#1

Hey all Fumers, I need to create the effect of smoke billowing up from a source in a floor, but the smoke needs to be heavy so that it “spills” out along the floor radially, yet it needs to have a billowy look to it, like one might find in a massive explosion or a cloud.

My problem is not the animation of the smoke, but getting it to look billowy and maintain said billowiness. In an explosive plume, the smoke billows and then dissipates, and continues to do so over time repeatedly. But in an explosion, the smoke is rising. In my case, I just want the smoke to rise up about a foot off the ground, then fall down around itself and “pour” out toward the edges of the sim box, all the while maintain a “puffy cloud” billowy look.

Basically, instead of creating a plume of billowy smoke that is rising, how can I make it go out radially without rising much at all, and still be billowy? Everything I do has it thinning out.

#2

That’s Solitudes Department :slight_smile:

#3

That’s cool. I’ll try not to make a lame joke about loneliness.

#4

:surprised My department? Surely you can provide some insight :slight_smile:

Crank the smoke density on the source to like a bajiliion (not really that high)… you crank it high enough and the smoke will become heavy, causing it to fall (also increasing gravity helps). This will also help the dissipation, which even when set to 0, smoke will start to dissipate. OR you can use negative temperature, which will basically just make it really cold, also causing it to fall instead of rise. You can use both too, of course… that’s really about all you should need to get started.

#5

Fantastic. Thanks, man!

#6

Naw just my bad trying to continue a lame ass joke from another thread :slight_smile:

I could… but well you just had those nice explosive huge billowing smoke shots! :wink:

My insight, play with your gravity/buoyancy too.

#7

I had not thought to increase the smoke this much, but I ramped my object source’s smoke to like 150. With some speed, that created a nice jet of liquid smoke (actually it looked like a super clean Krakatoa render). The problem I’m having is that as Solitude said, even with dissipation set to 0, it still dissipates and settles into a fog on the ground. Perhaps my temperature dissipation needs to be worked on as well?

But the cool thing that I wasn’t expecting is the interesting look you can get with crazy high smoke amounts in the object source.

#8

Sorry for the double post, but here’s a quick render I did last night. This is not the effect I want, but I found it interesting anyway.

The “expulsion” in this render reminds me of the Krakatoa look, but once the smoke starts thinning out and settling, it loses it.

http://www.youtube.com/watch?v=3x8A8rwNRm0

#9

Do you have a lot of turbulence? Turbulence and swirly settings (low time scale also kills detail) tend to spread the smoke out between the voxels, so it inherently becomes (but mostly looks) less dense. It’s a tough one to get right… looks cool so far though! If you can, lower grid spacing a bit too to help add in some of the detail that you are losing…

#10

Yeah I didn’t sim it too high for this. Just messing around.

I had very low turbulence, if any. I wanted to reduce that as much as possible. However, I think my object source had its default turbulence values. I’ve not yet grasped the relationship between the object source’s turbulence and the simulation’s turbulence.

#11

The source turbulence afaik is just little variations in the source values… not the same as the grid turbulence, which adds a noise field to the simulation.

#12

Yeah, Think of it like a noise map for your source values. It doesn’t add any turbulence to the grid.

#13

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