反向运动学: 拖拽与伸展

package cn.d
{
    import flash.display.Sprite;
    import flash.display.StageAlign;
    import flash.display.StageScaleMode;
    import flash.events.Event;
    import flash.geom.Point;

    public class TwoSegmentResh extends Sprite
    {
        private var sg1:Segment;
        private var sg2:Segment;

        private var num:int=20;
        private var sglist:Array=[];

        public function TwoSegmentResh()
        {
            super();
            stage.scaleMode=StageScaleMode.NO_SCALE;
            //stage.align=StageAlign.TOP_LEFT;
            init();
        }

        private function init():void
        {

            for (var i:int=0; i < num; i++)
            {
                sg1=new Segment(100, 20);
                this.addChild(sg1);
                sglist.push(sg1);
                
            }

            sglist[0].x=stage.stageWidth / 2;
            sglist[0].y=stage.stageHeight / 2;


            this.addEventListener(Event.ENTER_FRAME, onEnterFrame)
        }

        private function onEnterFrame(e:Event):void
        {
            var targetP:Point=resh(sglist[0], mouseX, mouseY);

            for (var i:int=1; i < num; i++)
            {
                targetP=resh(sglist[i], targetP.x, targetP.y);
            }
            
            for (var _i:int=num-1; _i>0; _i--)
            {
                postion(sglist[_i-1],sglist[_i]);
            }
        }

        private function resh(sg:Segment, _x:Number, _y:Number):Point
        {
            var dx:Number=_x - sg.x;
            var dy:Number=_y - sg.y;

            sg.rotation=Math.atan2(dy, dx) * 180 / Math.PI;

            var w:Number=sg.getPin().x - sg.x;
            var h:Number=sg.getPin().y - sg.y;

            return new Point(_x - w, _y - h);
        }

        private function postion(sgA:Segment, sgB:Segment):void
        {
            sgA.x=sgB.getPin().x;
            sgA.y=sgB.getPin().y;
        }


    }
}