Box2d FilterData

Box2D.Dynamics.b2ContactFilter类,碰撞源码：

public virtual function ShouldCollide(fixtureA:b2Fixture, fixtureB:b2Fixture) : Boolean{
    var filter1:b2FilterData = fixtureA.GetFilterData();
    var filter2:b2FilterData = fixtureB.GetFilterData();
    
    if (filter1.groupIndex == filter2.groupIndex && filter1.groupIndex != 0)
    {
        return filter1.groupIndex > 0;
    }
    
    var collide:Boolean = (filter1.maskBits & filter2.categoryBits) != 0 && (filter1.categoryBits & filter2.maskBits) != 0;
    return collide;
}