Nape实现坐标旋转角度回弹

乒乓球以一个向量运动，碰到障碍后反弹以一个新的向量运动，如下图：

要实现回弹只需要求出向量v1,把向量v0取反，再旋转(a+b)度就可以得到向量v1.

向量取反:

var v:vec2 = new Vec2(10,10);
v.x = -v.x;
v.y = -v.y;
//或者
v=v.mul(-1);

坐标旋转:

var v:Vec2 = new Vec2(10,10);
v.rotate(Math.PI);//以弧度为单位
//rotate方法的实现
public function rotate(angle:Number):void{  
    var cos:Number = Math.cos (angle);
    var sin:Number = Math.sin (angle);    
    x = x * cos - y * sin;;
    y = x * sin + y * cos;
}

例子代码：

package  {
    import flash.display.MovieClip;
    import nape.callbacks.CbType;
    import nape.callbacks.InteractionType;
    import nape.callbacks.PreCallback;
    import nape.callbacks.PreFlag;
    import nape.callbacks.PreListener;
    import nape.dynamics.CollisionArbiter;
    import nape.geom.Vec2;
    import nape.phys.Body;
    import nape.shape.Circle;

    /**
     * ...
     * @author kingBook
     * 2015-02-01 21:18
     */
    public class Main extends BaseMain {
        
        public function Main() {
            super({gravity:{x:0,y:0}});
        }
        
        private var _circle:Body;
        private var _circleCbType:CbType=new CbType();
        private var _view:MovieClip;
        override protected function createBodies():void {
            _circle = new Body();
            _circle.shapes.add(new Circle(25));
            _circle.position.setxy(100,100);
            _circle.space=_space;
            _circle.velocity.setxy(500,700);//随意设置一个运动向量
            _circle.cbTypes.add(_circleCbType);
            
            _view = new Circle_view();//库中的 Circle_view
            this.addChild(_view);
            
            //侦听与边缘碰撞
            _space.listeners.add(new PreListener(InteractionType.COLLISION,_circleCbType,CbType.ANY_BODY,hitHandler));
        }
        
        
        private function hitHandler(cb:PreCallback):PreFlag{
            var colArb:CollisionArbiter=cb.arbiter.collisionArbiter;
            var normal:Vec2 = colArb.normal;
            var vel:Vec2 = _circle.velocity.copy();
            vel = vel.mul(-1);//取反
            vel.rotate(2*(normal.angle-vel.angle));//旋转2倍法线度与反向运动向量角的差
            _circle.velocity.set(vel);//重新设置向量
            return PreFlag.ACCEPT;
        }
        
        override protected function stepAfter():void{
            //同步外观
            _view.x = _circle.position.x;
            _view.y = _circle.position.y;
            _view.rotation = _circle.rotation*57.3;
        }
        
    }
    
}

效果：

源码下载：

http://yunpan.cn/cVU69GkaYFyKH  访问密码 8515