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Type of Talk: ICES Seminar

Speaker/Af

filiation: James F. O''Brien/EECS, Computer Science Division, U.C. Berkel

ey

Date/Time: Tuesday, November 22, 2011, 3:30 p.m.

Location:

ACES 6.304

Host: Tom Hughes and Chandrajit Bajaj

Talk Title: Dest

ruction Effects and Sparse Matrix Factorization

Talk Abstract: In this
talk I will briefly discuss the use of finite element simulations for gene

rating destruction effects in games and film. With this context as motivati

on I will then present a nonlinear finite element formulation for elastodyn

amic simulation that achieves fast performance by making only partial or de

layed changes to the simulation''s linearized system matrices.

Coupled
with an algorithm for incremental updates to a sparse Cholesky factorizati

on, the method realizes the stability and scalability of a sparse direct m

ethod while avoiding the need for expensive refactorization each time step

, and allowing a controlled trade-off between accuracy and speed. This fin

ite element formulation combines the widely used corotational method with s

tiffness warping so that changes in the per-element rotations are initially
approximated by inexpensive per-node rotations. When the errors of this a

pproximation grow too large, the per-element rotations are selectively cor

rected by updating parts of the matrix chosen according to locally measured
errors. These changes to the system matrix are propagated to its Cholesky
factor by incremental updates that are much faster than refactoring the ma

trix from scratch. A nested-dissection ordering of the system matrix gives
rise to a hierarchical factorization in which changes to the system matrix
cause limited, well-structured changes to the Cholesky factor.

Spe

aker Bio: James F. O''Brien is a Professor of Computer Science at the Unive

rsity of California, Berkeley. His primary area of interest is Computer A

nimation, 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''Br

ien has worked with several game companies on integrating advanced simulati

on physics into game engines, and his methods for destruction modeling wer

e recently used in the films Avatar, Sucker Punch, and X-Men: First Class

. He received his doctorate from the Georgia Institute of Technology in 20

00, the same year he joined the Faculty at U.C. Berkeley. Professor O''Br

ien is a Sloan Fellow and ACM Distinguished Scientist, Technology Review s

elected him as one of their TR-100, and he has been awarded research grant

s from the Okawa and Hellman Foundations. He is currently serving as ACM S

IGGRAPH Director at Large. http://obrien.berkeley.edu/