// 一種簡(jiǎn)單的樹類



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); // 樹的顏色

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

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

graphics.lineTo(Math.random() * 80 - 40, // 隨機(jī)生成的樹枝

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

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

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

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

?? }

}

}
------------------------------------------------------------------------------
// 利用簡(jiǎn)單樹組成的森林



package {

import flash.display.Sprite;

import flash.events.Event;

import flash.events.KeyboardEvent;

import flash.ui.Keyboard;

[SWF(backgroundColor=0x000000)];?? // 設(shè)置背景為黑色，但不知為什么無效

public class Trees extends Sprite {

??? private var trees:Array; // 存放所有的樹

??? private var numTrees:uint = 100;??? // 定義100顆夠了

??? private var fl:Number = 250; // 屏幕距離眼睛一般設(shè)置為200--300

??? private var vpX:Number = stage.stageWidth / 2; // 物體太小后消失點(diǎn)

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

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

??? private var vz:Number = 0; // Z軸透視深度速度

??? private var friction:Number = 0.98; // 阻尼系數(shù)

??? public function Trees() {

?? init();

??? }

??? private function init():void {

?? trees = new Array();

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

var tree:Tree = new Tree(); // 生成樹

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軸方向的速度

?? sortZ(); // Z軸消隱

??? }

??? private function onKeyDown(event:KeyboardEvent):void {?? // 加減速控制

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

vz -= 1;

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

vz += 1;

?? }

??? }



??? private function move(tree:Tree):void {

?? tree.zpos += vz; // 更新移動(dòng)距離(速度)

?? if (tree.zpos < -fl) { // 如果樹走到眼睛后面，則移動(dòng)到遠(yuǎn)處

tree.zpos += 10000;

?? }

?? if (tree.zpos > 10000 - fl) {?? // 如果樹太遠(yuǎn)，大于屏幕外1000則移回

tree.zpos -= 10000;

?? }

?? var scale:Number = fl / (fl + tree.zpos);?? // 計(jì)算透視深度系數(shù)

?? tree.scaleX = tree.scaleY = scale;

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

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

?? tree.alpha =?? scale * .7 + .3; // 不同距離用不同的alpha混色，顯示大氣透視(朦朧感)

??? }

??? 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);

?? }

??? }

}

}

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