多物体碰撞模拟

1.构建小球精灵

package 
{
    import flash.display.Sprite;

    public class Ball extends Sprite
    {
        public var radius:Number;
        public var color:uint;
        public var vx:Number=0;
        public var vy:Number=0;

        public function Ball (radius:Number,color:uint)
        {
            this.radius=radius;
            this.color=color;
            Init ();
        }
        public function Init ():void
        {
            graphics.beginFill (color);
            graphics.drawCircle (0,0,radius);
            graphics.endFill ();
        }
    }
}

2.模拟碰撞动画

package 
{
    import flash.events.Event;
    import flash.display.Sprite;

    public class Bubbles2 extends Sprite
    {
        private var balls:Array;
        private var bounce:Number=-0.1;
        private var spring:Number=0.1;
        private var gravity:Number=0.2;
        private var numBalls:Number=30;

        public function Bubbles2 ()
        {
            Init ();
        }
        private function Init ():void
        {
            balls=new Array();
            for (var i:int=0; i<numBalls; i++)
            {
                var ball:Ball=new Ball(Math.random()*50+5,Math.random()*0xFFFFFF);
                addChild (ball);
                ball.x=Math.random()*stage.stageWidth;
                ball.y=Math.random()*stage.stageHeight;
                ball.vx=Math.random()*6-3;
                ball.vy=Math.random()*6-3;
                balls.push (ball);
            }
            addEventListener (Event.ENTER_FRAME,EnterFrame);
        }
        private function EnterFrame (e:Event):void
        {
            for (var i:int=0; i<numBalls-1; i++)
            {
                var ball0:Ball=balls[i];
                for (var j:int=i+1; j<numBalls; j++)
                {
                    var ball1:Ball=balls[j];
                    var dx:Number=ball1.x-ball0.x;
                    var dy:Number=ball1.y-ball0.y;
                    var dist:Number=Math.sqrt(dx*dx+dy*dy);
                    var minDist:Number=ball0.radius+ball1.radius;
                    if (dist<minDist)
                    {
                        var tx:Number=ball0.x+dx/dist*minDist;
                        var ty:Number=ball0.y+dy/dist*minDist;
                        var ax:Number=(tx-ball1.x)*spring;
                        var ay:Number=(ty-ball1.y)*spring;
                        ball0.vx-=ax;
                        ball0.vy-=ay;
                        ball1.vx+=ax;
                        ball1.vy+=ay;
                    }
                }
            }
            for (var i:int=0; i<numBalls; i++)
            {
                var ball:Ball=balls[i];
                Move (ball);
            }
        }
        private function Move (ball:Ball):void
        {
            ball.vy+=gravity;
            ball.x+=ball.vx;
            ball.y+=ball.vy;
            if (ball.x+ball.radius>stage.stageWidth)
            {
                ball.x=stage.stageWidth-ball.radius;
                ball.vx*=bounce;
            }
            else if (ball.x-ball.radius<0)
            {
                ball.x=ball.radius;
                ball.vx*=bounce;
            }
            if (ball.y+ball.radius>stage.stageHeight)
            {
                ball.y=stage.stageHeight-ball.radius;
                ball.vy*=bounce;
            }
            else if (ball.y-ball.radius<0)
            {
                ball.y=ball.radius;
                ball.vy*=bounce;
            }
        }
    }
}

 

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碰撞算法优化

多个精灵进行碰撞的一般算法：

sprite1	with	sprite2	sprite3	sprite4	sprite5	sprite6	sprite7	sprite8
sprite2	with	sprite1	sprite3	sprite4	sprite5	sprite6	sprite7	sprite8
sprite3	with	sprite2	sprite1	sprite4	sprite5	sprite6	sprite7	sprite8
sprite4	with	sprite2	sprite3	sprite1	sprite5	sprite6	sprite7	sprite8
sprite5	with	sprite2	sprite3	sprite4	sprite1	sprite6	sprite7	sprite8
sprite6	with	sprite2	sprite3	sprite4	sprite5	sprite1	sprite7	sprite8
sprite7	with	sprite2	sprite3	sprite4	sprite5	sprite6	sprite1	sprite8
sprite8	with	sprite2	sprite3	sprite4	sprite5	sprite6	sprite7	sprite1

精简算法：

sprite1	with	sprite2	sprite3	sprite4	sprite5	sprite6	sprite7	sprite8
sprite2	with	sprite3	sprite4	sprite5	sprite6	sprite7	sprite8
sprite3	with	sprite4	sprite5	sprite6	sprite7	sprite8
sprite4	with	sprite5	sprite6	sprite7	sprite8
sprite5	with	sprite6	sprite7	sprite8
sprite6	with	sprite7	sprite8
sprite7	with	sprite8
sprite8	with	nothing