绳关节(b2RopeJoint)

package{
    import Box2D.Collision.b2AABB;
    import Box2D.Collision.b2RayCastInput;
    import Box2D.Collision.b2RayCastOutput;
    import Box2D.Collision.Shapes.b2CircleShape;
    import Box2D.Collision.Shapes.b2PolygonShape;
    import Box2D.Collision.Shapes.b2Shape;
    import Box2D.Common.Math.b2Vec2;
    import Box2D.Dynamics.b2Body;
    import Box2D.Dynamics.b2BodyDef;
    import Box2D.Dynamics.b2Fixture;
    import Box2D.Dynamics.b2FixtureDef;
    import Box2D.Dynamics.b2World;
    import flash.display.Sprite;
    import flash.utils.getTimer;
    import Box2D.Dynamics.Joints.b2PulleyJoint;
    import Box2D.Dynamics.Joints.b2PulleyJointDef;
    import Box2D.Dynamics.Joints.b2RopeJointDef;
    import Box2D.Dynamics.Joints.b2RopeJoint;

    //出现脱节时，调velocityIterations, positionIterations
    //_world.Step(1/30,128,128);
    public class Main extends BaseMain{

        public function Main(){
            super(new b2Vec2(0,10));
        }

        private const ropeW:Number=20;
        private const ropeH:Number=20;

        override protected function init():void{
            var bodies:Vector.<b2Body>=new Vector.<b2Body>();
            var i:int;
            for(i=0;i<10;i++){
                var body:b2Body=createBox(ropeW,ropeH,400+i*ropeW,100);
                bodies[i]=body;
                if(i>0){
                    var bodyA:b2Body=bodies[i-1];
                    var bodyB:b2Body=bodies[i];
                    var halfW:Number=ropeW*0.5/_ptm_ratio;
                    var anchorA:b2Vec2=new b2Vec2(bodyA.GetPosition().x+halfW,bodyA.GetPosition().y);
                    var anchorB:b2Vec2=new b2Vec2(bodyB.GetPosition().x-halfW,bodyB.GetPosition().y);
                    var maxLength:Number=0.1;
                    createRopeJoint(bodyA,bodyB,anchorA,anchorB,maxLength);
                }
            }
            bodies[0].SetType(b2Body.b2_staticBody);

            var bigBox:b2Body=createBox(400,400,400+i*ropeW,100);
            bigBox.SetSensor(true);
            createRopeJoint(bodies[bodies.length-1],bigBox,
                            new b2Vec2(bodies[bodies.length-1].GetPosition().x+halfW,bodies[bodies.length-1].GetPosition().y),//anchorA
                            new b2Vec2(bigBox.GetPosition().x-200/_ptm_ratio,bigBox.GetPosition().y),//anchorB
                            0.1);//maxLength
        }

        private function createRopeJoint(bodyA:b2Body,bodyB:b2Body,anchorA:b2Vec2,anchorB:b2Vec2,maxLength:Number):void{
            var jointDef:b2RopeJointDef=new b2RopeJointDef();
            jointDef.Initialize(bodyA,bodyB,anchorA,anchorB,maxLength);
            jointDef.length=5;
            b2RopeJoint(_world.CreateJoint(jointDef));
        }

        override protected function stepBefore():void{ 

        }

    };
}

源码下载：http://pan.baidu.com/s/1jIjpjIu