title: the paper folding/unfolding effect in twitter for iPad
body: <p>Twitter for iPad implements a fancy "pinch to expand paper fold" effect.  A short video clip here.
  <a href="http://www.youtube.com/watch?v=B0TuPsNJ-XY">http://www.youtube.com/watch?v=B0TuPsNJ-XY</a></p>
  
  <p>Can this be done with <code>CATransform3D</code> without OpenGL? A working example would be thankful.</p>
  
  <p><strong>Update:</strong> I was interested in the approach or implementation to this animation effect. That's why I offered bounty on this question - srikar</p>