Wow, thanks for the immediate reply, and sorry about not posting the bug report right away. Here it goes...
With regards to the application exhibiting the problem, it's rather large. However, it is officially released under the GPL, and you can download a slightly older version from http://www.keckcaves.org/software/VISUALIZERCG
if you really want. I can dig up a link to the particular data file I was using and post it in a follow-up. Steps to recreate problem:
- Run Visualizer on large 3D input file.
- Extract large isosurface using a seeded isosurface tool.
- Observe displayed fps value and compare / contrast.
In case it helps, here is the gist of the actual rendering code:
glDrawElements(GL_TRIANGLES,numRenderTriangles*3,G L_UNSIGNED_INT,static_cast<const Index*>(0)); // numRenderTriangles is about 2M