Box2D Forums

Hi! I'm looking for some help in mixing my own movement logic with Box2Ds movement. Specifically, while the majority of my game objects would, say, bounce from a collision, some might move on a predetermined path, or be controlled by the mouse. If I manually set the position and velocity of an object, after doing some math to get its position based on whatever controls it, and then call step(), the object would move again, according to Box2Ds idea of where it should go, right? Will adjusting the position and velocity of an object mess with the underlying space partitioning? Will Box2D undo my work when it step()s?

Alternatively, can I do all my own motion and just use the collision detection that Box2D provides?

bump

Use kinematic bodies. With type = kinematic (as opposed to static or dynamic) you set the velocity manually. So if you want to move your object from x1, y1 to x2, y2 it's pretty easy to figure out the velocity as x2 - x1, y2 - y1 and set that every timestep.

This is how it works in the WCK port. If you look at the demos you'll see a lot of pre-programmed/animated movement combined with Box2D physics:

http://www.sideroller.com/wck/