问预渲染as3动画

EN

public class PerlinNoise extends Sprite 
{
    // premenne pre perlin noise
    private var _baseX:Number = 45;
    private var _baseY:Number = 5;
    private var _numOctaves:uint = 3;
    private var _randomSeed:int = 50;
    private var _stitch:Boolean = true;
    private var _fractalNoise:Boolean = false;
    private var _channelOptions:uint = 1;
    private var _grayScale:Boolean = true;
    private var _offsets:Array = [];

    private var _perlinBitmapData : BitmapData;
    private var _debugBmp   : Bitmap;

    public function PerlinNoise() 
    {
        _perlinBitmapData = new BitmapData(275, 50, true);

        // oktavy perlin noisu
        for(var i:int = 0; i < _numOctaves;i++) _offsets[i] = new Point(0,0);

        _debugBmp = new Bitmap(_perlinBitmapData);
        addChild(_debugBmp);

        stage.addEventListener(Event.ENTER_FRAME, onEnterFrame);
    }

    private function onEnterFrame(e:Event):void
    {   
        // animacia perlin noisu
        _offsets[1]['x'] += 1; // 2
        _offsets[1]['y'] += 1/4;//1/4

        // aplikacia perlin noisu
        _perlinBitmapData.perlinNoise(_baseX, _baseY, _numOctaves, _randomSeed, _stitch, _fractalNoise, _channelOptions, _grayScale, _offsets);
    }
}