Beyond staring at a rectangle

Figure 1.29: (a) The first stereoscope, developed by Charles Wheatstone in 1838, used mirrors to present a different image to each eye; the mirrors were replaced by lenses soon afterward. (b) The View-Master is a mass-produced stereoscope that has been available since the 1930s. (c) In 1957, Morton Heilig's Sensorama added motion pictures, sound, vibration, and even smells to the experience. (d) In competition to stereoscopic viewing, Cinerama offered a larger field of view. Larger movie screens caused the popularity of 3D movies to wane in the 1950s.

The concepts so far are still closely centered on staring at a rectangle that is fixed on a wall. Two important steps come next: 1) Presenting a separate picture to each eye to induce a ``3D'' effect. 2) Increasing the field of view so that the user is not distracted by the stimulus boundary. One way our brains infer the distance of objects from our eyes is by stereopsis. Information is gained by observing and matching features in the world that are visible to both the left and right eyes. The differences between their images on the retina yield cues about distances; keep in mind that there are many more such cues, which are explained in Section 6.1. The first experiment that showed the 3D effect of stereopsis was performed in 1838 by Charles Wheatstone in a system called the stereoscope (Figure 1.29(a)). By the 1930s, a portable version became a successful commercial product known to this day as the View-Master (Figure 1.29(b)). Pursuing this idea further led to Sensorama, which added motion pictures, sound, vibration, and even smells to the experience (Figure 1.29(c)). An unfortunate limitation of these designs is requiring that the viewpoint is fixed with respect to the picture. If the device is too large, then the user's head also becomes fixed in the world. An alternative has been available in movie theaters since the 1950s. Stereopsis was achieved when participants wore special glasses that select a different image for each eye using polarized light filters. This popularized 3D movies, which are viewed the same way in the theaters today.

Another way to increase the sense of immersion and depth is to increase the field of view. The Cinerama system from the 1950s offered a curved, wide field of view that is similar to the curved, large LED (Light-Emitting Diode) displays offered today (Figure 1.29(d)). Along these lines, we could place screens all around us. This idea led to one important family of VR systems called the CAVE, which was introduced in 1992 at the University of Illinois [49] (Figure 1.30(a)). The user enters a room in which video is projected onto several walls. The CAVE system also offers stereoscopic viewing by presenting different images to each eye using polarized light and special glasses. Often, head tracking is additionally performed to allow viewpoint-dependent video to appear on the walls.

Figure 1.30: (a) CAVE virtual environment, Illinois Simulator Laboratory, Beckman Institute, University of Illinois at Urbana-Champaign, 1992 (photo by Hank Kaczmarski). (b) Sutherland's Ultimate Display, 1968. (c) VPL Eyephones, 1980s. (d) Virtuality gaming, 1990s. (e) Nintendo Virtual Boy, 1995. (f) Oculus Rift, 2016.