[ODE] de-activated bodies

[Benny Kramek]

You should understand that the dynamics calculations and the collision 
detection are two totally seperate things.

> - in a turn-based game, only the current player should be able to move.  all other players should collide but be frozen in place and act like a piece of furniture.

If you want to freeze an object in place you should either joint it to 
the world with a fixed joint or don't simulate it as a rigid body. Just 
have a geometry that resembles the object collide with the rest of the scene

> - floating powerups (gravity mode = 0) should collide with the player *BUT* when the player is far enough away, the powerup bodies are de-activated so they don't take up CPU cycles.

Also here, since the powerups don't have to move around, you don't have 
to simulate them as a rigid body.