Box2D Forums

I'm shooting fireballs which have a tail and I want them to rotate when they bounce off objects. I tried to change their rotation on END_CONTACT but it won't let you alter its rotation once it's moving and I read this messes up the events. Now I'm destroying them on collision and recreating new ones that are rotated the correct direction. This mostly works but sometimes crashes my game. I assume there is a much easier way. Anyone have any ideas?

Does it really matter what rotation the physics body itself has?
Could you just draw the fireball in the appropriate angle based on the current direction of movement?

That's what I tried to do. I did fireball.rotation = new trajectory but the engine wouldn't let it work. I can only change the rotation before the object is working in the physics world. Once it's bouncing around, changing the rotation doesn't have any effect. I also read a post by they guy that created Box2d saying that changing the rotation in this way would mess up the events of Box2d. What am I missing?

That wont work because WCK sets the rotation of the movieclip each frame to the rotation of the b2body. You actually have to rotate the b2body:

If this doesn't work inside of your contact event listener, try changing it after the timestep.