package {
    import flash.display.Sprite;
    import flash.events.Event;
    import flash.geom.ColorTransform;
    public class Collision3D extends Sprite {
        private var balls:Array;
        private var numBalls:uint=8;
        private var fl:Number=250;
        private var vpX:Number=stage.stageWidth/2;
 
        private var vpY:Number=stage.stageHeight/2;
        private var top:Number=-100;
        private var bottom:Number=100;
        private var left:Number=-100;
        private var right:Number=100;
        private var front:Number=100;
        private var back:Number=-100;
        public function Collision3D() {
            init();
        }
        private function init():void {
            balls = new Array();
            for (var i:uint = 0; i < numBalls; i++) {
                var ball:Ball3D=new Ball3D(10);
                balls.push(ball);
                ball.xpos=Math.random()*400-200;
                ball.ypos=Math.random()*400-200;
                ball.zpos=Math.random()*400-200;
                ball.vx=Math.random()*10-5;
                ball.vy=Math.random()*10-5;
                ball.vz=Math.random()*10-5;
                addChild(ball);
            }
            addEventListener(Event.ENTER_FRAME, onEnterFrame);
        }
        private function onEnterFrame(event:Event):void {
            for (var i:uint = 0; i < numBalls; i++) {
                var ball:Ball3D=balls[i];
                move(ball);
            }
            for (i = 0; i < numBalls - 1; i++) {
                var ballA:Ball3D=balls[i];
                for (var j:uint = i + 1; j < numBalls; j++) {
                    var ballB:Ball3D=balls[j];
                    var dx:Number=ballA.xpos-ballB.xpos;
                    var dy:Number=ballA.ypos-ballB.ypos;
                    var dz:Number=ballA.zpos-ballB.zpos;
                    var dist:Number=Math.sqrt(dx*dx+dy*dy+dz*dz);
                    if (dist<ballA.radius+ballB.radius) {
                        var newTransform:ColorTransform =
                        new ColorTransform(0, 1, 1, 1, Math.random()*255, Math.random()*255, Math.random()*255, 0);
                        ballA.transform.colorTransform=newTransform;
                        ballB.transform.colorTransform=newTransform;
                    }
                }
            }
            sortZ();
        }
        private function move(ball:Ball3D):void {
 
            var radius:Number=ball.radius;
            ball.xpos+=ball.vx;
            ball.ypos+=ball.vy;
            ball.zpos+=ball.vz;
            if (ball.xpos+radius>right) {
                ball.xpos=right-radius;
                ball.vx*=-1;
            } else if (ball.xpos - radius < left) {
                ball.xpos=left+radius;
                ball.vx*=-1;
            }
            if (ball.ypos+radius>bottom) {
                ball.ypos=bottom-radius;
                ball.vy*=-1;
            } else if (ball.ypos - radius < top) {
                ball.ypos=top+radius;
                ball.vy*=-1;
            }
            if (ball.zpos+radius>front) {
                ball.zpos=front-radius;
                ball.vz*=-1;
            } else if (ball.zpos - radius < back) {
                ball.zpos=back+radius;
                ball.vz*=-1;
            }
            if (ball.zpos>- fl) {
                var scale:Number = fl / (fl + ball.zpos);
                ball.scaleX=ball.scaleY=scale;
                ball.x=vpX+ball.xpos*scale;
                ball.y=vpY+ball.ypos*scale;
                ball.visible=true;
            } else {
                ball.visible=false;
            }
        }
        private function sortZ():void {
            balls.sortOn("zpos", Array.DESCENDING | Array.NUMERIC);
            for (var i:uint = 0; i < numBalls; i++) {
                var ball:Ball3D=balls[i];
                setChildIndex(ball, i);
            }
        }
    }
}