—There-reality environments are those virtual environments which evoke the same perceptual response from a viewer as if they were actually present, or there, in the real scene being depicted. While it is possible to compute highly accurate representations of real scenes, the computational requirements of such a full physically-based global illumination solution are significant, currently precluding its computation on even a powerful modern PC in reasonable let alone real time. However, to provide a useful tool, there-reality environments need to be interactive. A key factor to consider if we are ever to achieve such “Realism in Real-Time” is that we are computing images for humans to look at. Although the human visual system is very good, it is by no means perfect. By understanding what the human does, or perhaps more importantly, does not see, enables us to save substantial computation effort without any loss of perceptual quality of the resultant image. This paper describes the...