AS3.0 2D游戏人物影子实现思路

package com.game.engine.gameobject.entity.base
{
 import com.game.GlobalConst;
 
 import flash.display.BitmapData;
 import flash.display.DisplayObject;
 import flash.display.Shape;
 import flash.display.Sprite;
 import flash.geom.Matrix;
 import flash.geom.Rectangle;
 
 
 public class EntityShadow extends Sprite{
  public  static const DIRECTION_RIGHT:int =  1;
  public  static const DIRECTION_LEFT :int = -1;

  private var vertices  :Vector.<Number>; 
  private var indices   :Vector.<int>; 
  private var uvtData   :Vector.<Number> ; 
  private var bmpd      :BitmapData;
  private var bodySprite:Shape;
  private var direction :int;
  private var delay     :int;
  private var matrix    :Matrix
  
  public function EntityShadow(direction:int = DIRECTION_LEFT){
   this.direction     = direction;
   this.bodySprite    = new Shape();
   this.vertices      = new Vector.<Number>(); 
   this.indices       = new Vector.<int>();
   this.uvtData       = new Vector.<Number>(); 
   this.matrix        = new Matrix();
   
   this.mouseChildren = false;
   this.mouseEnabled  = false;
   
   this.indices.push(0, 3, 4); 
   this.indices.push(0, 1, 4); 
   this.indices.push(1, 4, 5); 
   this.indices.push(1, 2, 5); 
   
   this.uvtData.push(1, -1); 
   this.uvtData.push(0, -1); 
   this.uvtData.push(0, 1); 
   this.uvtData.push(1, -1); 
   this.uvtData.push(1, -1); 
   this.uvtData.push(1, 1);
  }
  public   function render(oMovieClips:Array):void{
   if(delay <= 0){ //提升效率，两帧渲染一次
        this.delay = 2;
        this.dispose();

        //OMovieClip 是自己封装的一位图序列帧播放器

        //这里的数组包括的是人物、武器、翅膀位图
      for each(var omc:OMovieClip in oMovieClips){
               if(omc.bitmapData != null){
                   matrix.b =  0;
                   matrix.c =  0;
                   matrix.d =  1;
                   matrix.tx=  omc.x;
                   matrix.ty=  omc.y;
                  if(!omc.isMirro){ //位图是使用了镜像
                      matrix.a =  1;
                      bodySprite.graphics.beginBitmapFill(omc.bitmapData,matrix);
                      bodySprite.graphics.drawRect(omc.x,omc.y,omc.bitmapData.width,omc.bitmapData.height);
                      bodySprite.graphics.endFill();
              }else{
                 matrix.a = -1;
                 bodySprite.graphics.beginBitmapFill(omc.bitmapData,matrix);
                 bodySprite.graphics.drawRect(omc.x-omc.bitmapData.width,omc.y,
                                                                omc.bitmapData.width,omc.bitmapData.height);
                 bodySprite.graphics.endFill();
           }
        }
     }

    //上面是把一个人物包含所有位图（人物、武器、翅膀）画成一个Shape,方便下面位图拉伸
     this.update(bodySprite);
    }else{
         this.delay--;
    }
  }

 //进行位图拉伸
  private  function update(display:DisplayObject):void{
   var rect:Rectangle  = display.getRect(display);
   if(rect.width > 0 && rect.height > 0){
           var tempH:Number    = rect.height;

            //把Shape转换成BitmapData
            this.bmpd = new BitmapData(rect.width,rect.height,true,0xFFFFFF);
            this.bmpd.lock();
            this.bmpd.draw(display,new Matrix(1,0,0,.95,-rect.x,-rect.y));

            //将合成的位图添加一个半透明的黑色滤镜，new ColorMatrixFilter([0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,.5,0]);
            this.bmpd.applyFilter(this.bmpd,bmpd.rect,GlobalConst.ZERO_POINT,
                                             GlobalConst.ALPHA_BLACK_COLORMATRIXFILTER);
            this.bmpd.unlock();
      

          //下面就是进行位图拉伸，可以自己查看相对应的api文档

   
          //这里在这120×120的位图上定义了6个点 
            this.vertices.splice(0,vertices.length);
 
            this.vertices.push(0,0);
            this.vertices.push(tempH*this.direction,0); //这里如果是 vertices.push(0, 60);则左边不扭曲 
            this.vertices.push(0, rect.height); 
            this.vertices.push(rect.width, 0); 
            this.vertices.push(rect.width+tempH*this.direction,0); //这里如果是 vertices.push(120, 60);则右边不扭曲 
            this.vertices.push(rect.width,rect.height);
    
            this.graphics.beginBitmapFill(bmpd,null,false); 
            this.graphics.drawTriangles(vertices,indices,uvtData);
            this.graphics.endFill();
            this.x = rect.x;
            this.y = rect.y;
      }
  }

  /**销毁，位图不用时需要从内存销毁**/
  public   function dispose():void{
        this.graphics.clear();
        this.bodySprite.graphics.clear();
        if(this.bmpd != null)  this.bmpd.dispose();
  }
 }
}