Nape 获取碰撞点加特效

package  {
    import nape.phys.Body;
    import nape.shape.Shape;
    import nape.shape.Circle;
    import flash.display.MovieClip;
    import flash.utils.getDefinitionByName;
    import nape.callbacks.CbType;
    import nape.callbacks.PreListener;
    import nape.callbacks.InteractionType;
    import nape.callbacks.PreCallback;
    import nape.dynamics.CollisionArbiter;
    import nape.geom.Vec2;
    import nape.callbacks.InteractionListener;
    import nape.callbacks.CbEvent;
    import nape.callbacks.InteractionCallback;
    import nape.phys.BodyType;
    import nape.shape.Polygon;
    import nape.dynamics.Contact;
    import nape.dynamics.ContactList;

    public class Main extends BaseMain {

        public function Main() {
            super({gravity:{x:0,y:0}});
        }

        private var _cCbType:CbType=new CbType();
        private var _rCbType:CbType=new CbType();
        override protected function createBodies():void {
            //一些用于碰撞的刚体
            for(var i:int=0;i<20;i++){
                var b:Body;
                if(Math.random()>0.5)b=createBox(50,2,stage.stageWidth*Math.random(),stage.stageHeight*Math.random());
                else b=createCircle(25,stage.stageWidth*Math.random(),stage.stageHeight*Math.random());
                b.rotation = 2*Math.PI*Math.random();
                b.type = BodyType.STATIC;
                b.space = _space;
            }

            //圆形
            var c:Body = createCircle(20,stage.stageWidth>>1,stage.stageHeight>>1);
            c.cbTypes.add(_cCbType);
            c.space = _space;
            c.velocity.setxy(500,500);
            _space.listeners.add(new InteractionListener(CbEvent.BEGIN,InteractionType.COLLISION,_cCbType,CbType.ANY_BODY,circleHitBeginHandler));

            //矩形
            var r:Body = createBox(40,40,stage.stageWidth>>1-100,stage.stageHeight>>1);
            r.cbTypes.add(_rCbType);
            r.space = _space;
            r.velocity.setxy(-500,-500);
            _space.listeners.add(new InteractionListener(CbEvent.BEGIN,InteractionType.COLLISION,_rCbType,CbType.ANY_BODY,boxHitBeginHandler));
        }

        private function circleHitBeginHandler(cb:InteractionCallback):void{
            var colArb:CollisionArbiter = cb.arbiters.length>0?cb.arbiters.at(0) as CollisionArbiter:null;
            if(!colArb)return;
            //trace("圆形碰撞点数:"+colArb.contacts.length);//始终只有一个碰撞点
            var hitPos:Vec2 = colArb.contacts.at(0).position;
            addEffect(hitPos.x,hitPos.y);
            //反弹
            var normal:Vec2 = colArb.normal;
            cb.int1.castBody.velocity.set(normal.mul(500));
        }

        private function boxHitBeginHandler(cb:InteractionCallback):void{
            var colArb:CollisionArbiter = cb.arbiters.length>0?cb.arbiters.at(0) as CollisionArbiter:null;
            if(!colArb)return;
            //trace("矩形碰撞点数:"+colArb.contacts.length);//会出现多个碰撞点
            var shape2:nape.shape.Shape = colArb.shape2.body == cb.int2.castBody?colArb.shape2:colArb.shape1;
            //查找出真正碰撞的点
            var contact:Contact = getHitShapeContact(colArb.contacts,shape2);
            if(contact){
                var hitPos:Vec2 = contact.position;
                if(hitPos) addEffect(hitPos.x,hitPos.y);
            }
            //反弹
            var normal:Vec2 = colArb.normal;
            cb.int1.castBody.velocity.set(normal.mul(500));
        }

        private function getHitShapeContact(contacts:ContactList,shape:nape.shape.Shape):Contact{
            var i:int = contacts.length;
            while(--i>=0){
                if(shape.contains(contacts.at(i).position))return contacts.at(i);
            }
            return null;
        }

        private function addEffect(x:Number,y:Number):void{
            var _Class:Class = flash.utils.getDefinitionByName("Effect") as Class;
            var eff:MovieClip = (new _Class()) as MovieClip;
            eff.x = x;
            eff.y = y;
            this.addChild(eff);
        }
    }

}

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