Graphics, Imaging, and Games Lab

User control over fluid simulations is a long-standing research problem
in computer graphics. Applications in games and films often require
recognizable creatures or objects formed from smoke, water,
or flame. This paper describes a two-layer approach to the problem,
in which a bulk velocity drives a particle system towards a target
distribution, while simultaneously a vortex particle simulation adds
recognizable fluid motion.

A bulk velocity field is obtained by distributing target particles
within a mesh, then matching control particles with target particles;
control particles are given a trajectory bringing them to their
targets, and a field is obtained by interpolating values from the control
particles. A detail velocity field is obtained by traditional vortex
particle simulation. We render the final particle system using
stochastic shadow mapping. We spend some effort optimizing our
processes for speed, obtaining simulations at interactive or nearinteractive
rates: from 70 to 500 milliseconds per frame depending
on the configuration.