设置3d rotationY 旋转之后元件大小改变解决方案

在工作中做类似3D图片切换功能的时候，设置了所有图片元件的rotationY之后，发现图片元件越靠近舞台右边旋转之后大小就越大。

针对此问题特别写了一个demo，代码如下：

请在fla文件中绘制一个元件并导出类TestMC，TestMC不需要做任何改变。

import flash.display.MovieClip;

var a:TestMC = new TestMC();
var b:TestMC = new TestMC();
var c:TestMC = new TestMC();

var aa:MovieClip = new MovieClip();
aa.addChild(a);
var bb:MovieClip = new MovieClip();
bb.addChild(b);
var cc:MovieClip = new MovieClip();
cc.addChild(c);

this.addChild(aa);
this.addChild(bb);
this.addChild(cc);

aa.y = 20;
bb.y = 20;
cc.y = 20;
aa.x = 20;
bb.x = aa.x + aa.width + 20;
cc.x = bb.x + bb.width + 20;

var per:PerspectiveProjection = new PerspectiveProjection();
per.projectionCenter = new Point(0,0);
aa.transform.perspectiveProjection = per;
bb.transform.perspectiveProjection = per;
cc.transform.perspectiveProjection = per;

a.rotationY = 20;
b.rotationY = 20;
c.rotationY = 20;