You're right, their doing head tracking. But again, the head tracking thread is just setting the variables for the matrix transformation. That's it. There's no extra or special code. And if you'll notice, there's no complex lighting whatsoever; the pixel shader code is basically byte copies. You should not be flabbergasted; this is why GPUs were developed in the first place. Think of the pad movement as a joystick movement for a stationary camera. head tracking thread: CPU and DSP most everything else: GPU A dual-core CPU and that monster GPU makes this a simple task for an iPad 2. EDIT: And actually, this would be simple for an n900, or any similarly configured device.