SideFX - Houdini 21 Flow Solver Experiments

Year: 2025
Client: SideFX
Discipline: Procedural Simulation / R&D
Role: Marketing FX Artist (Intern)

Painted Dunes: a current sketched as a curve in SOPs becomes the input for the Flow Solver

The velocity field beside the flow it drives

The animated texture applied to the grains

Coral Synapse: reaction–diffusion carried and stretched by the Flow Solver

Mycelial Trace, regular 2D simulation: the pattern breaks at every UV seam

With UV island hopping, pixels jump across seams and the growth stays continuous

Seam-aware growth across the bark, before modelling

I joined SideFX as a Marketing FX Artist intern, with a simple brief: learn the new features of Houdini 21, break them, find the bugs, and see how far they could be pushed creatively. Most of that time went into the Flow Solver, a new GPU solver in Copernicus that moves pixels like a fluid, so motion can be sculpted in image space and iterated almost in real time.

To learn its limits, I gave myself two weeks, a few simulations a day and no polishing, to see how many different looks it could produce. The more interesting results came from leaving pure 2D: geometry driving the flow, and flow data driving geometry back in SOPs.

Three pieces grew out of that. In Painted Dunes, a wind current drawn as a curve becomes the flow that carries Vellum grains across the dunes, and an up-res pass turns ten million grains into a hundred and twenty million. Coral Synapse runs three solvers in step: the flow carries a reaction–diffusion pattern while Vellum flexes the membrane to the same motion. Mycelial Trace runs a 2D simulation over a 3D branch; building on Yancy Lindquist’s UV Island Hopping technique, pixels jump across UV seams so the pattern grows without breaking. I presented the work at OFFF, and the setups are available in the SideFX Content Library.