5. The Physiology of Human Vision

What you perceive about the world around you is ``all in your head''. After reading Chapter 4, especially Section 4.4, you should understand that the light around us forms images on our retinas that capture colors, motions, and spatial relationships in the physical world. For someone with normal vision, these captured images may appear to have perfect clarity, speed, accuracy, and resolution, while being distributed over a large field of view. However, we are being fooled. We will see in this chapter that this apparent perfection of our vision is mostly an illusion because neural structures are filling in plausible details to generate a coherent picture in our heads that is consistent with our life experiences. When building VR technology that co-opts these processes, it important to understand how they work. They were designed to do more with less, and fooling these processes with VR produces many unexpected side effects because the display technology is not a perfect replica of the surrounding world.

Section 5.1 continues where Section 4.4 left off by adding some anatomy of the human eye to the optical system. Most of the section is on photoreceptors, which are the ``input pixels'' that get paired with the ``output pixels'' of a digital display for VR. Section 5.2 offers a taste of neuroscience by explaining what is known about the visual information that hierarchically propagates from the photoreceptors up to the visual cortex. Section 5.3 explains how our eyes move, which serves a good purpose, but incessantly interferes with the images in our retinas. Section 5.4 concludes the chapter by applying the knowledge gained about visual physiology to determine VR display requirements, such as the screen resolution.