title: Explain how premultiplied alpha works
body: <p>Can somebody please explain why rendering with premultiplied alpha (and corrected blending function) looks differently than "normal" alpha when, mathematically speaking, those are the same?</p>
  
  <p>I've looked into this post for understanding of premultiplied alpha:</p>
  
  <p><a href="http://blogs.msdn.com/b/shawnhar/archive/2009/11/06/premultiplied-alpha.aspx" rel="nofollow">http://blogs.msdn.com/b/shawnhar/archive/2009/11/06/premultiplied-alpha.aspx</a></p>
  
  <p>The author also said that the end computation is the same:</p>
  
  <p>"Look at the blend equations for conventional vs. premultiplied alpha. If you substitute this color format conversion into the premultiplied blend function, you get the conventional blend function, so either way produces the same end result. The difference is that premultiplied alpha applies the (source.rgb * source.a) computation as a preprocess rather than inside the blending hardware."</p>
  
  <p>Am I missing something? Why is the result different then?</p>
  
  <p>neshone</p>