I have a sphere and used the wispy smoke shelf tool on it.
The sphere source is very dense with smoke. Is there a way to ramp in the opacity of the density so it only becomes visible as it ages?

T

Increase dissipation in the simulation by adjusting it on the pyro solver.

There is no ‘age’ in pyro simulations, therefore you cannot fade out by age post simulation.

That would make the smoke fade out faster, not fade in… right?

T

oh, I read that wrong. You want it to become more dense over time? You can use gas linear combination to add density to itself, scaled by some timestep and scale value.

You could use temperature to remap the density. It is like age.

jsmack
You can use gas linear combination to add density to itself, scaled by some timestep and scale value.

kelvincai
You could use temperature to remap the density. It is like age.

I poked around for awhile, but never really got anywhere. Perhaps using the “Wispy Smoke” pre-set doesn't activate all of the properties? Gas is pretty far outside my understanding right now. Is there a resource that breaks down some of the settings and how they affect the sim?
I'm pretty new to houdini. I have some experience with Maya fluids. I can usually get what I'm after with Maya's fluids, but it's mostly trial and error.

I was able to make a Volume VOP (after the import_pyro_visualiztion inside the pyro_import node,) which multiplies the density by it's position in world Z. Seems to be absolute world position. Not sure how to use the position of an animated null as a local coord system instead.
I tried Object merging in my volume source geo and putting that in Input #2 and then using P from there instead… but I didn't get what I thought I should.
Also, bind export of a parameter doesn't seem to ‘work’ in a volume VOP. At least it doesn't show up in the Geo Spreadsheet or the “info” on the node up a level.

Thx for helping :-)

T