Santa Clara Falls is a still from 'Flow', an animation from the 1993 SIGGRAPH Electronic Theatre, which depicts fluid flow in various forms - donas, a geyser, a stream ,anda waterfall. The title jokingly refers to the Santa Clara Valley, also known as Silicon Valley, where Apple Computer is based. We wrote our own simulation and rendering software, building on a program that was originally written for the 1990 animation 'Splashdance', done with Michael Kass. Water was simulated by combining mesh-based fluid dynamics with an interacting particle system. At the beginning of the simulation, water represented as a mesh fills a basin at the top of the falls. At the lip of the cliff, the water reaches a slope threshold and is converted to particles which descend over the falls. At the base of the falls, particles are converted back to mesh representation.

The animation took about twenty minutes a frame on an SGI Crimson workstation. With 60 MB of main memory, we were able to simulate 700,000particles. The particles are self-shadowing and were rendered with a form of volume rendering called 'splatting'. The terrain height field was painted with an interactive paint program. Terrain colors were taken from a photograph of Bryce Canyon in Utah. (Gavin Miller/Ned Greene)