[away3d] Mystery wys of away3D !!

[ben]

I didn't notice it at first sight, but what about those line in away3D
light :

//hack to get framerate up in cs4
        var background:Sprite = new Sprite();
        background.graphics.lineStyle(1, 0);
        background.graphics.drawRect(-stage.stageWidth/2, -stage.stageHeight/
2, stage.stageWidth, stage.stageHeight);
        view.addChild(background);

Could I know more about it ???