title: How to switch between rendering and presenting framebuffers in iPhone OpenGL ES 2.0?
body: <p>iPhone OpenGL ES 2.0..</p>
  
  <ul>
  <li>First frame, render to my framebuffer then present it (as it works by default in the template OpenGL ES application).  </li>
  <li>On the next frame, I want to use that rendered framebuffer as an input in to my shaders, while rendering to another framebuffer and presenting that 2nd framebuffer.  </li>
  <li>The next frame, I want to use framebuffer2 as input in to my shaders, while rendering to the first framebuffer again.</li>
  <li>Repeat</li>
  </ul>
  
  <p>How do I do this?</p>