Water simulation using a responsive surface tracking for flow-type changes

The realistic simulation of fluids largely depends on a temporally coherent surface tracking method that can deal effectively with transitions between different types of flows. We model these transitions by constructing a very smooth fluid surface and a much rougher, splashy surface separately, and then blending them together in proportions that depend on the flow speed. This allows creative control of the behavior of the fluids as well as the visual results of the simulation. We overcome the well-known difficulty of obtaining smooth surfaces from Lagrangian particles by allowing them to carry normal vectors as well as signed distances from the level set surface and by introducing a new surface construction algorithm inspired by the moving least-squares method. We also implemented an adaptive form of the fluid-implicit-particle method that only places particles near visually interesting regions, which improves performance. Additionally, we introduce a novel subgrid solver based on the material point method to increase the amount of detail produced by the FLIP method. We present several examples that show visually convincing water flows.