One of the glitches that I had hit while developing iBeams was an odd visual humming when turning motion blur all away up. I’ve attempted to fix this by rendering into an off-screen frame buffer and discovered some nice side benefits:
I’ve seen a couple of discussions on the web suggesting that the iPhone didn’t support Frame buffer objects, they definitely work although I didn’t have much luck getting them to render into a buffer that was bigger then the screen resolution (320 x 480).
By ping-ponging between two FBO’s I was able to create a feedback loop much like you’d get by pointing a video camera at a monitor showing the video camera’s view, or a hall of mirrors. With a couple of parameter tweaks, iBeams now emulates a dynamic Spirograph stretching off into infinity. I’m hoping to get the changes submitted to the store in the next couple of days.