package { 

import flash.display.Sprite; 

public class Tree extends Sprite { 

   public var xpos:Number = 0; 

public var ypos:Number = 0; 

   public var zpos:Number = 0; 

   public function Tree() { 

init(); 

   } 

   public function init():void { 

graphics.lineStyle(0, 0x00ff00); // 树的颜色

graphics.lineTo(0, -140 - Math.random() * 20);   // 树干

graphics.moveTo(0, -30 - Math.random() * 30); 

graphics.lineTo(Math.random() * 80 - 40, // 随机生成的树枝

-100 - Math.random() * 40); 

graphics.moveTo(0, -60 - Math.random() * 40); 

graphics.lineTo(Math.random() * 60 - 30, 

-110 - Math.random() * 20); 

   } 

} 

}

------------------------------------------------------------------------------

// 利用简单树组成的森林

package { 

import flash.display.Sprite; 

import flash.events.Event; 

import flash.events.KeyboardEvent; 

import flash.ui.Keyboard; 

[SWF(backgroundColor=0x000000)];   // 设置背景为黑色，但不知为什么无效

public class Trees extends Sprite { 

    private var trees:Array; // 存放所有的树

    private var numTrees:uint = 100;    // 定义100颗够了

    private var fl:Number = 250; // 屏幕距离眼睛一般设置为200--300

    private var vpX:Number = stage.stageWidth / 2; // 物体太小后消失点

    private var vpY:Number = stage.stageHeight / 2; 

    private var floor:Number = 50; // 水平面高度

    private var vz:Number = 0; // Z轴透视深度速度

    private var friction:Number = 0.98; // 阻尼系数

    public function Trees() { 

   init(); 

    } 

    private function init():void { 

   trees = new Array(); 

   for (var i:uint = 0; i < numTrees; i++) { 

var tree:Tree = new Tree(); // 生成树

trees.push(tree); 

tree.xpos = Math.random() * 2000 - 1000; 

tree.ypos = floor; 

tree.zpos = Math.random() * 10000; 

addChild(tree); // 

   } 

   addEventListener(Event.ENTER_FRAME, onEnterFrame); 

   stage.addEventListener(KeyboardEvent.KEY_DOWN, onKeyDown); 

    } 

    private function onEnterFrame(event:Event):void { 

   for (var i:uint = 0; i < numTrees; i++) { 

var tree:Tree = trees; 

move(tree); 

   } 

   vz *= friction; // 阻尼后的Z轴方向的速度

   sortZ(); // Z轴消隐

    } 

    private function onKeyDown(event:KeyboardEvent):void {   // 加减速控制

   if (event.keyCode == Keyboard.UP) { 

vz -= 1; 

   } else if (event.keyCode == Keyboard.DOWN) { 

vz += 1; 

   } 

    } 

    private function move(tree:Tree):void { 

   tree.zpos += vz; // 更新移动距离(速度)

   if (tree.zpos < -fl) { // 如果树走到眼睛后面，则移动到远处

tree.zpos += 10000; 

   } 

   if (tree.zpos > 10000 - fl) {   // 如果树太远，大于屏幕外1000则移回

tree.zpos -= 10000; 

   } 

   var scale:Number = fl / (fl + tree.zpos);   // 计算透视深度系数

   tree.scaleX = tree.scaleY = scale; 

   tree.x = vpX + tree.xpos * scale; 

   tree.y = vpY + tree.ypos * scale; 

   tree.alpha =   scale * .7 + .3; // 不同距离用不同的alpha混色，显示大气透视(朦胧感)

    } 

    private function sortZ():void { 

   trees.sortOn("zpos", Array.DESCENDING | Array.NUMERIC); 

   for (var i:uint = 0; i < numTrees; i++) { 

var tree:Tree = trees; 

setChildIndex(tree, i); 

   } 

    } 

} 

}