Optimizing Particle Tracing in Unsteady Vector Fields,
Al Globus, Computer Sciences Corporation, Report RNR-94-001
RNR-94-001
10 January 1994
Abstract
Unsteady 3-D computational fluid dynamics (CFD) results can be
very large. Some recent solutions exceed 100 gigabytes. Visualization
techniques that access the entire data set will, therefor, be
excruciatingly slow. We show that particle tracing in vector fields
calculated from disk resident solutions can be accomplished in
O(number-of-particles) time, i.e., visualization time is independent
of solution size. This is accomplished using memory mapped files
to avoid unnecessary disk IO, and lazy evaluation of calculated vector
fields to avoid unnecessary CPU operations. A C++ class hierarchy
implements lazy evaluation such that visualization algorithms
are unaware that the vector field is not stored in memory. A numerical
experiment conducted on two solutions differing in size by a
factor of 100 showed that particle tracing times varied by only
10-30%. Other visualization techniques that do not access the entire
solution should also benefit from memory mapping and lazy evaluation.
Postscript version