粒子爆炸效果

数学公式：

var angle:Number = Math.atan2(y,x);
ball.x += Math.cos(angle) * vx;
ball.y += Math.sin(angle) * vy;

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首先自己在flash里面画个Ball

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以下是源码：

package  
{
	import flash.display.MovieClip;
	import flash.display.DisplayObject;
	import flash.events.*;
	import flash.system.System;
	import net.hires.debug.Stats;
	[SWF(width = "700",height = "480",frameRate = "25",backgroundColor = "0x000000")]
	/**
	 * ...
	 * @author Li灬Star
     * @contact QQ:168527720
     */
	
	public class LiZi extends MovieClip
	{
		private var container:MovieClip = new MovieClip();
		private static const NUM:int = 400;
		public function LiZi() 
		{
			init();
		}
		
		private function init():void {
		    addChild(new Stats());
			this.addChild(container);
			stage.addEventListener(MouseEvent.MOUSE_DOWN,downHandler);
		}
		
		private function downHandler(e:MouseEvent):void {
		    for (var i:int = 0; i < NUM; i++ ) {
			    var ball:Ball = new Ball();
				container.addChild(ball);
				ball.x = mouseX;
				ball.y = mouseY;
				//--------------------->定义每个ball的x,y速度
				ball.vx = Math.random() * 4 + 2;
				ball.vy = Math.random() * 5 + 2;
				//---------------------->定义每个ball运动的方向角度
				var angle:Number = Math.atan2(Math.random() * 480 - ball.y,Math.random() * 700 - ball.x);//随机一个角度,返回的值为弧度
				ball.angle = angle;
				ball.addEventListener(Event.ENTER_FRAME,enterFrameHandler);
			}	
		}
		
		private function enterFrameHandler(e:Event):void {
		    e.currentTarget.x += Math.cos(e.currentTarget.angle) * e.currentTarget.vx;
			e.currentTarget.y += Math.sin(e.currentTarget.angle) * e.currentTarget.vy;
			
			if (e.currentTarget.x<0||e.currentTarget.x>stage.stageWidth||
			    e.currentTarget.y<0||e.currentTarget.y>stage.stageHeight
			) {
			    e.currentTarget.removeEventListener(Event.ENTER_FRAME,enterFrameHandler);
				var obj:DisplayObject = e.currentTarget as DisplayObject;
				container.removeChild(obj);
				obj = null;
				System.gc();
				
			}
		}
	}

}

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