Gridless Advection methods

Here's an implementation of Gridless Advection methods described in the Volumetric methods siggraph course by Jerry Tessendorf.

The implementation is done in houdini.

Course has some great insights on volumetric methods followed by various vfx facilities on production.

Though its a process which happens at rendertime, I implemented it in SOPs to get interactive feedback (Though same/similar setup could also be used with volume procedurals).

Following are the two screen shots of a simple sphere with and without GA applied to it (Just one iteration. My laptop starts to freak out after that   :D). The resolution of volumes is 200 (uniform divisions).

The setup could also be used within a SOP solver to get all sorts of interesting results 

with finer details.

The velocity field (the advecting field used here) is created by using very low res particle sim.

Will be posting some other tests soon.