title: Using GLKView with a UIViewController
body: <p>I wanted to use OpenGL to do some simple Image processing, so I started off with <code>GLKView</code>. Since I don't need to refresh the view every few seconds, I didn't use the <code>GLKViewController</code> and instead used a normal <code>UIViewController</code> subclass.</p>
  
  <p>My question is that do I simply make the viewController's view as a <code>GLKView</code> or do I add the <code>GLKView</code> as a subview of the view controller's view. Since I'm adding a <code>UISlider</code> to the view as  well, I think the latter seems better, but I'm not sure. I also need to call <code>setNeedsDisplay</code> on the GLKView on certain occasions.</p>