How to stop the forces acting on a body in box2d

问题:

I am using box2d on the iphone to create a game. I have a body that is effected by gravity to move down and not right or left. It will get hit by another body and will then be moving right or left. I then have a reset button which moves the body back to its starting point. The only problem is that it is still moving right or left. How can I counteract the forces that a ball is already traveling? How can I get rid of this right and left movement when I reset my game?

回答1:

box2d automatically clears forces each simulation step. I think you are just changing you body's position when reseting, but not it's velocity. Add this code to your reset method:

body->SetLinearVelocity(b2Vec2(0,0));
body->SetAngularVelocity(0);