Simulation of Smoke based on Vortex Filament Primitives

Abstract

We describe a method that permits the high performance simulation of fluid phenomena such as smoke, with highlevel control for the artist. Our key primitives are vortex filament and vortex ring: vorticity defines a flow as well as velocity does, and for numerous interesting flows such as smoke or explosions this information is very compact and tightly linked to the visual features of the fluid. We treat these vortices as 1D Lagrangian primitives (i.e. connected particles), which permit unbounded fluids and very accurate positioning of the features. The simulation of passive density particles for rendering is totally independent of the fluid animation itself. Thus, the animation can be efficiently simulated, edited and even stored, while the fluid resolution used for rendering can be arbitrarily high. We aim at plausible fluids rather than physical accuracy. For efficiency and stability, we introduce a new formalization of the Biot-Savart law and a modified Biot-Savart kernel. Our model also introduces a hierarchical filament structure for animation LOD, turbulent noise, and an original scheme for density particles.