Hello,

I am trying to figure out how to pull smoke towards a point.
The setup involves a fire consuming a source, and then that smoke is supposed to get pulled towards a point to form something like a sphere.

I tried sourcing velocities and divergence. Obviously velocities won't work because the pressurefield just cancels them out to avoid compression. But I want the compression! mh.
Negative divergence just makes the smoke and flames disappear.

Any idea how I can maybe scale down the effect of the pressure field, or some other ideas how to solve this isse?


All the best and thanks,
Oliver

edit: added some text

Negative divergence should work, just make sure it's only in the tight region around the point you want your sink to be and not everywhere

Thank you for the quick reply.
Indeed my negative divergence field encompasses the whole scene. Once I'm back at the desk tomorrow I will try tweaking the size.
Do I understand right that negative divergence reverses the effect of the pressure projection?

Thanks a lot!

Anak_Sulap
Do I understand right that negative divergence reverses the effect of the pressure projection?

It doesn't reverse it
The pressure projection but default tries to achieve 0 divergence in the final velocity field

By altering divergence field you are simply setting target divergence for the pressure projection, so that the final velocity field will preserve negative or positive divergence in specified areas according to target divergence field hence allowing expansion or contraction in those areas

Thanks a lot Tomas, it's working now!

As usual, the next problem showed up. Now the smoke dissipates once it's pulled to the area of negative divergence. Do you or anyone else know why this would happen?
I tested with and without the divergence and it's a clear difference how long the smoke stays around. I also tested with super low dissipation values.

I am using the sparse pyrosolver by the way.
Maybe there's some cutoff happening?

I want the smoke ultimately to build something like a ball of smoke that is still affected by turbulence.

Once again, thanks!

edit: again added some text