Controlling Fluid Flow Simulation

Simulating fluid dynamics can be a powerful approach to animating liquids and gases, but it is often difficult to ``direct'''' the simulation to ``perform'''' as desired. We introduce a simple yet powerful technique of controlling incompressible flow simulation for computer animation purposes that works for any simulation method using a projection scheme for numerically solving the Navier-Stokes equations. In our technique, an abstract vector field representing the desired influence over the simulated flow is modelled using simple primitives. This technique allows an arbitrarily degree of control over the simulated flow at every point while still conserving mass, momentum, and energy.