This post continues from my recent blog entry, Particle Advection by Reaction Diffusion in SideFX Houdini. In this project, I've done away with the VEX in the DOP network, and replaced it with a VDB Analysis node to create a vector field that represents the gradient in the reaction diffusion volume. This allows me to use a POP Advect by Volumes node in the DOP network rather than hand coding by own force wrangle.
The network that creates the advecting force is:
This solver isn't super fast, so rather than recalculating it every time I run the simulation, it's saved to a file using a File Cache node.
The Gradient Field network box creates a vector field from the cached geometry. Here, the geometry is converted to a fog VDB and that, in turn, is converted to a vector field using a VDB Analysis gradient operator. I played around by adding intermediate nodes to resample and convert the VDB topology to SDF to get an effective field.
I used the POP shelf tool to create a particle system and simply added a POP Advect by Volumes to advect the particles.
Easy 🙂
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