Ah, well, that would explain why I get 15 FPS when I have a dozen or so bullets flying along parallel with my terrain collision mesh.
I ran a prelimary Pstats and saw a lot of time spent in the traverser. (Around 20ms in the first pass.)
I might investigate the optimized collision solid segment for GMT, but I think for the short term I will see about converting the GeomNodes generated by GMT into CollisionPolys.
I find that using a GMT for visual and another for collision mesh works pretty well as long as they share the same subdivision level. I end up with a quadtree structure that plays nicely with Panda3d’s collision system, and I get a 1-to-1 correspondence with my visual GMT. (Obviously, distant collision polys don’t match the visual mesh so well due to the visual mesh mipping, but it works well enough for the scenario in my game.)
Thanks for the advice, it’s given me some areas to investigate.