title: about fast swapping texture on IOS opengl ES
body: <p>i'm work on a buffer for load very large pictures ( screen size)  to single surface.
  The idea is to animate a lot of pictures ( more than the video memory can store ) frame by frame.</p>
  
  <p>I have create a code for make a buffer but i have a big problem with the loading time of bitmap.</p>
  
  <p>My code work a this : </p>
  
  <ol>
  <li><p>I load an array of local bitmap files path.</p></li>
  <li><p>I (think ) i preload my bitmap datas in memory. I'm using a thread for store a CGImageRef in an NSArray for all my picture ( 40 for moment )</p></li>
  <li><p>In a second thread, the code look another NSArray for determine if is empty of not, if is empty, i bind my cgimageRef to the video memory by creating textures. ( use sharedgroup for this)
  This array store the adress of 20 textures names, and it's use directly by openGL for draw the surface. this array is my (buffer)</p></li>
  </ol>
  
  <p>When i play my animation, i delete old textures from my "buffer" and my thread ( at point 3) load a new texture.</p>
  
  <p>It's work great, but is really slow, and after few second, the animation lack.</p>
  
  <p>Can you help me for optimise my code ?</p>