title: How can you apply distortions to a UIImage using OpenGL ES?
body: <p>Is there any way to create effects like dents, pinching, twisting, squashing, etc. on a UIImage using OpenGL ES as in the iPhone application <a href="http://itunes.apple.com/us/app/phototwist/id288084356?mt=8" rel="noreferrer">PhotoTwist</a>?</p>
  
  <p>Are there any references or guidelines for doing this? I don't want code, just a reference on how to do this.</p>