title: AS3 get Bitmap from Movieclip with Mask
body: <p>This works:</p>
  
  <pre><code>var a:BitmapData = new BitmapData(640,480);
  var b:Bitmap = new Bitmap(a);
  a.draw(movieClip);
  </code></pre>
  
  <p>This doesn't work:</p>
  
  <pre><code>movieClip.mask = movieClipMask;
  var a:BitmapData = new BitmapData(640,480);
  var b:Bitmap = new Bitmap(a);
  a.draw(movieClip);
  </code></pre>
  
  <p>How can I draw just the visible part of a MovieClip (that uses a mask) into my Bitmap?</p>