Green Goop and Polygon Soup

Wednesday, October 13, 2004 - 17:30
TH 331
James O'Brien, UC Berkeley

Applications ranging from commercial entertainment to surgical training demand efficient methods for realistically modeling the appearance of physical phenomena in synthetic environments. In this talk I will describe methods we have developed for simulating the behavior of a wide class of materials known as viscoelastic fluids. These materials, such as mucus, liquid soap, pudding, toothpaste, or clay, exhibit a combination of both fluid and solid characteristics. Like a solid they can resist strain elastically, but under large or sustained strains they flow like a fluid. Our methods builds upon prior Eulerian techniques for animating incompressible fluids with free surfaces by including additional elasto-plastic terms in the basic Navier-Stokes equations. These terms are computed by advecting integrated strain-rate throughout the fluid. Transition from elastic resistance to viscous flow is controlled by von Mises's yield condition, and subsequent behavior governed by a time-dependent quasi-linear plasticity model.

I will also briefly describe other simulation techniques for modeling phenomena such as explosions, fracture, real-time deformation, and even sound. One issue that arises recurrently is that all of these simulation techniques require clear geometric descriptions of the objects and environments they model. To address this need I will show how highly detailed implicit surfaces can be built from defective input models using moving-least-squares interpolation techniques.


James O'Brien is an Assistant Professor of Computer Science at the University of California, Berkeley. His primary area of interest is Computer Animation, with an emphasis on generating realistic motion using physically based simulation and motion capture techniques. He has authored several papers on these topics, including ten presented at the ACM SIGGRAPH conference and his work has been featured multiple times in the SIGGRAPH Electronic Theater. He received his doctorate from the Georgia Institute of Technology in 2000, the same year he joined the Faculty at U.C. Berkeley. Professor O'Brien is a Sloan Fellow, Technology Review selected him as one of their TR-100 for 2004, and he was recently awarded research grants from the Okawa and Hellman Foundations.