Event Location: 1305 Newell Simon Hall
Bio: James F. O’Brien is an Associate 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
numerous papers on these topics. In addition to his research pursuits,
Prof. O’Brien has worked with several game companies on integrating advanced
simulation physics into game engines, and his methods for destruction
modeling were recently used in the film Avatar. 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 and ACM
Distinguished Scientist, Technology Review selected him as one of their
TR-100, and he has been awarded research grants from the Okawa and Hellman
Foundations. He is currently serving as ACM SIGGRAPH Director at Large.

Abstract: This talk will discuss the use of dynamic remeshing and sparse
matrix factorization in the context of real-time dynamics simulations. The
first part of the talk will focus on two systems that have been developed
for specific applications: destructible environments in “Star Wars: The
Force Unleashed” and interactive modeling of prostate brachytherapy.
Although dynamic remeshing is often dismissed as impractically slow, in both
cases it plays a key part to making the simulations work effectively in a
real-time setting. The second part of the talk will focus on an incremental
update method for the Cholesky factors of sparse matrices that out-performs
standard iterative methods for solving elastodynamic problems. The factors
are not recomputed at each time step, but the nonlinearities that normally
compel refactoring are not ignored either. Instead, the algorithm makes
local incremental updates to the Cholesky factors to maintain error limits
on the solution. The results presented will include captured footage from
the live game, comparisons of simulated needle insertion to footage with gel
tissue phantoms, and demonstrations of the sparse direct solver on large
meshes.