package {
    import flash.display.Sprite;
    import flash.events.Event;
    import flash.events.KeyboardEvent;
    import flash.ui.Keyboard;
    import flash.display.StageAlign;
    import flash.display.StageScaleMode;
     
    public class Velocity3D extends Sprite {
        private var ball:Ball;
         
        //相当于消失点的坐标
        private var xpos:Number=0;
        private var ypos:Number=0;
        private var zpos:Number=0;
         
        //x,y,z三轴上的速度分量
        private var vx:Number=0;
        private var vy:Number=0;
        private var vz:Number=0;
         
        private var friction:Number=0.98;
        private var fl:Number=250;
         
        //消失点
        private var vpX:Number=stage.stageWidth/2;
        private var vpY:Number=stage.stageHeight/2;
         
        public function Velocity3D() {
            init();
        }
        private function init():void {
            stage.align = StageAlign.TOP_LEFT;  
            stage.scaleMode = StageScaleMode.NO_SCALE;
            ball = new Ball(20);
            addChild(ball);
            addEventListener(Event.ENTER_FRAME, EnterFrameHandler);
            stage.addEventListener(KeyboardEvent.KEY_DOWN, KeyDownHandler);
        }
        private function EnterFrameHandler(event:Event):void {
            vpX =stage.stageWidth/2;
            vpY =stage.stageHeight/2;
             
            xpos+=vx;
            ypos+=vy;
            zpos+=vz;
            vx*=friction;
            vy*=friction;
            vz*=friction;
             
            if (zpos>-fl) {
                var scale:Number = fl / (fl + zpos);
                ball.scaleX=ball.scaleY=scale;
                ball.x=vpX+xpos*scale;
                ball.y=vpY+ypos*scale;
                ball.visible=true;
            } else {
                ball.visible=false;
            }
             
            //辅助线
            graphics.clear();
            graphics.lineStyle(1,0xefefef);
            graphics.moveTo(0,stage.stageHeight/2);
            graphics.lineTo(stage.stageWidth,stage.stageHeight/2);
            graphics.lineTo(stage.stageWidth-15,stage.stageHeight/2-8);
            graphics.moveTo(stage.stageWidth,stage.stageHeight/2);
            graphics.lineTo(stage.stageWidth-15,stage.stageHeight/2+8);
             
            graphics.moveTo(stage.stageWidth/2,0);
            graphics.lineTo(stage.stageWidth/2,stage.stageHeight);
            graphics.lineTo(stage.stageWidth/2-8,stage.stageHeight-15);
            graphics.moveTo(stage.stageWidth/2,stage.stageHeight);
            graphics.lineTo(stage.stageWidth/2+8,stage.stageHeight-15);
            graphics.lineStyle(1,0xdadada);
            graphics.moveTo(vpX,vpY);
            graphics.lineTo(ball.x,ball.y);
             
             
        }
        private function KeyDownHandler(e:KeyboardEvent):void {
            switch (e.keyCode) {
                case Keyboard.UP :
                    vy-=1;
                    break;
                case Keyboard.DOWN :
                    vy+=1;
                    break;
                case Keyboard.LEFT :
                    vx-=1;
                    break;
                case Keyboard.RIGHT :
                    vx+=1;
                    break;
                case Keyboard.SHIFT :
                    vz+=0.5;
                    break;
                case Keyboard.CONTROL :
                    vz-=0.5;
                    break;
                default :
                    break;
            }
        }
    }
}