title: glReadPixels returns empty buffer on the device for iOS6
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/12528365/why-is-glreadpixels-failing-in-this-code-in-ios-6-0">Why is glReadPixels() failing in this code in iOS 6.0?</a>  </p>
  </blockquote>
  
  
  
  <p>The following line works great on the iOS 6 simulator but doesn't work on iOS 6 device. What could be wrong ? How to fix this ? Thanks a lot.</p>
  
  <pre><code>glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
  </code></pre>