Swirly, smoky background

[thlypsis]

I'm trying to create a background of swirling, bubbling mist or smoke for a top-down game.  Could anyone recommend a way to do this?  My experiences with 3D particle effects have resulted in major performance issues.

Thanks in advance!

[unikronsoftware]

You should probably look into using a shader for this. Particles will require significant amounts of overdraw.