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The Collision detection example has a scene node picker, which uses bounding boxes, how would you implement a scene node picker which is more accurate. It would be very poor if I used a bounding box to test what a bullet hit.
Handle your models as the map mesh in the collision demo (IIRC you can shoot bullets at the map, which appear just in front of the mesh then?) ? But for more advanced collision detection I would advice you to use a real physics engine like ODE, Newton, Novodex, ...