Wearable, camera based, head-tracking systems use spatial image registration algorithms to align images taken as the wearer gazes around their environment. This allows for computer-generated information to appear to the user as though it was anchored in the real world. Often, these algorithms require creation of a multiscale Gaussian pyramid or repetitive re-projection of the images. Such operations, however, can be computationally expensive, and such head-tracking algorithms are desired to run in real-time on a body borne computer. In this paper, we present a method of using the 3D computer graphics hardware that is available in a typical wearable computer to accelerate the repetitive image projections required in many computer vision algorithms. We apply this "graphics for vision" technique to a wearable camera based head-tracking algorithm, implemented on a wearable computer with 3D graphics hardware. We perform an analysis of the acceleration achieved by applying graphics hardware to computer vision to create a Mediated Reality.