Fusion has created a number of fx involving fumefx + krakatoa elements, but typically the production schedule on commercial projects doesn't allow the time to push the elements to reach their full potential, in terms of detail level and particle count. For this project, we had a fumefx sim created as a sort of dense ink-in-water effect emitting off geo, and thought this would make a nice little r&d project. We wanted to experiment with the particle counts needed to get the sim looking like a hero element in HD. So we did a few adjusts to the fumefx sim, increasing the res and having the fluid first fall down and then curl back up from below, to make it a bit more interesting. We had already worked out the physical parameters for the ink-in-water type behavior.
Next up we did a series of tests to define the density slice for having pflow trigger krakatoa particles, that would give us really nice internal structure definition on the fluid. Then we started cranking out krakatoa particle partitions. We rendered different numbers of partitions to see where we started getting nice results, where the fluid at HD started feeling believably volumetric, rather than grainy, including in the more dilute and thin parts of the cloud like against the geometry and at the outer edges of the cloud. In the end it took 20 partitions, amounting to a little over 86 million particles, to get the right sort of quality.
The final fumefx sim took about 3hrs (of course, it took a few days of tweaking sims before getting to this point), the partitioning took an overnight, and the render took a few hours. Hope you like it!