Alexander Vasilenko’s Guided Bubbles & Wet Foam Solver is an advanced whitewater solver for creating Houdini water simulations. It resolves POP Fluid’s biggest drawback, which is its lack of support for variable particle radii, allowing for more creative freedom in setting up simulations.
The solver is based on Wētā’s research paper, Guided Bubbles and Wet Foam for Realistic Whitewater Simulation, dedicated to studying ways to enhance water simulations by improving the look of bubbles and foam. In the article, researchers suggest treating bubbles as discrete air particles in the water that are converted into foam and simulated separately once they reach the surface.
As the original paper suggests, Vasilenko’s underwater bubble system features a locally resimulated fluid and applies two-way coupling to the bubbles. “The foam is handled via an SPH simulation projected onto a 2D manifold of the water surface. The solver implements standard SPH forces such as viscosity (mu), cohesion (C for strength, beta_c for radius), and surface friction against the water,” the artist explained.