   [XNA] performance drop when camera inside a model
  In a XNA game, I have a chase camera behind the player. If you turn the camera in a certain way you can get it to go slightly inside certain large models (.x + .fbx models loaded in the standard Content pipeline). I notice that on some lower end test systems, if the camera happens to move slightly inside a model, frame rate gets cut in half. It is weird that the game gets flawless 60FPS+ with hundreds of particles and dozens of enemies on screen, even on low end systems. But if a part of a model happens to intersect somewhere between the camera and the near clip plane, the frame rate is suddenly halved (even with the same exact number of objects on screen)? Turn the camera back outside the model and frame rate goes back to 60+.Any ideas on why?   