Box2D AS3-刷新形状还是Hitbox？

Question

I'm currently trying to implement a "crouch" function in my game. I'm using WCK with Box2D.

I have something rather basic, I generate my main character as an extension of a shape. This means that collision is automatically generated from the getgo. This is wonderful for a lot of things, but not everything.

I have a crouch/roll function. The problem is that the hitbox for crouching and standing are the same, so if a box drops onto you while crouching it "levitates" ontop of you since the hitbox is still the standing hitbox.

How would I go about "refreshing" the shape collision? Is there a way to delete the collision and make Box2D recalculate?

Answer 1

It's possible to filter contacts and prevent them from happening (using a contact listener or iterating the world's contact list) but I think there are better ways to do what you want.

You could split the body in two parts, and connect them with a prismatic joint (limits and motor enabled, collideConnected disabled). Standing up you'd have the motor push the parts apart to the upper limit and when crouching you'd pull them together to the lower limit thus reducing the height.

If you need really different shapes (eg a rectangle when standing and a circle for rolling around metroid style) this might work: Add both shape's fixtures to the body and use mask filtering to prevent the one you don't need from colliding with anything.