title: ipad 3 - openGL bug with kEAGLDrawablePropertyRetainedBacking and retina?
body: <p>i have an iOS openGL app which uses the kEAGLDrawablePropertyRetainedBacking property to draw the current frame on top of the previous frame. it's a cheap way of getting effects like motion trails.</p>
  
  <p>it works great on all devices (including iPhone w/ retina) and all device simulators, but on the actual iPad 3 device, the previous frame is vertically squished to 75% of its previous size.</p>
  
  <p>for example, if i were to draw a 100 x 100 square at the bottom of the screen each frame,
  then in frame 0 i have one square, in frame 2 there's an echo that's 100 x 75 and offset towards the top of the screen, in frame three there's an additional echo that's 100 x 56 (56 ~= 75 * 0.75) and is more offset towards the top, and so-on. what <em>should</em> happen is that all the echoes remain in place.</p>
  
  <p>i've verified the behavior on two devices, so i don't think it's a just a broken iPad.</p>
  
  <p>any ideas ?</p>
  
  <p>tia,
  orion</p>