visualizing magnet force and sample it onto a field?

[Chaoren]

I'm trying to use Houdini to generate vector fields for my own volume renderer. Like I said, how can I visualize a magnet force which is defined simply by two metaballs, and sample it to a vector field/volume?

Please give a detailed explanation if possible, I'm new to Houdini, only know building stuff from simple scratch, appreciate

[tjeeds]

There's no super-simple way to do this as far as I know, you've got to roll your own metaball sampling in a Volume vop, like in the attached example. If you need to get axial forces off the metaballs then it becomes a bit more complicated, radial/magnet forces are much simpler.

metaballsdeep.hip

[eetu]

Here's a setup of how you can get any DOP force out as a vector field.

It integrates the forces to a velocity field using Gas External Forces DOP, so technically it's the velocity imparted by the forces, but for the end result it shouldn't really matter. I think

tjeeds_metaballsdeep_eetu.hip