John, Take a look at vtk.scorec.rpi.edu/pub/contrib/isoViewer.* The first program uses VTK to generate (and save in a file) the polygon lists while the second builds an OpenGL display list from the file for each time step. The first may take hours but the second only seconds. Kent E. Eschenberg, Ph.D. Sci Vis Tech Lead, ERDC MSRC, Vicksburg, MS