Physics Simulation Forum

I am somewhat confused. I would like to use bullet firstly as a collision detector to activate triggers and stuff, but I am also interested in using bullet for wall, grounds, character and stuff.

in the starting guide, it states that btCollisionWorld does the collision detection, while btDynamicsWorld add the other stuff in. am I to assume this means I can use btDynamicsWorld as a collision engine by disabling the physic and stuff for certain object?

I have one other noob question, what is the best way to 'ground' a character to a vehicle, say he is standing on a moving train, how do I keep him from topping...