A very smart friend of mine sent me a passage about the limits of stereoscopic vision from a book he’s reading, Visual Thinking for Design, by Colin Ware (book link).
Some depth cues are not captured in a static image, and are therefore not pictorial. One kind of depth cue comes from the fact that humans, like many other animals, have two front-facing eyes. Visual area 1 contains specialized mechanisms for using the small differences in the images in the two eyes to extract distance information; this ability is called stereoscopic depth perception.
Different depth cues have different uses depending on the tasks we are trying to perform. Stereoscopic vision is optimal for visually guiding our hands as we reach for nearby objects. It works best in making judgments of the relative distances of nearby objects, within a meter or two of our heads. Stereoscopic depth judgments are also most precise for objects that are at nearly the same depth. The brain is not good at using stereo information to judge large relative distances. Because of these properties, people who have little or no stereo depth perception (20 percent of the population) still have no difficulty driving cars or walking around, although they will be clumsy when trying to thread needles.
Stereo technology has, for the most part, been a story of fads that faded, and this is largely because of a failure to understand that the main virtue of stereo vision is the precise guidance of hand movements. The Victorians were fascinated with stereo photos and sold thousands of stereo images. Now they clutter the stands of flea markets. Stereo cameras had a heyday in the 1930s and 1940s but now are almost unobtainable. Many inventors and entrepreneurs have lost their shirts on stereographic movies and television systems. The problem is that none of these technologies allowed for manual interaction with the visual three-dimensional objects that were represented. If we had virtual three-dimensional environments that allowed us to reach in and move things, then we would appreciate stereo technology more. [p. 94, emphasis added]
While I may disagree with some of his particular points (“clutter the stands of flea markets?” Oh, really? Where??!), I think his conclusion is basically correct. We can see stereoscopic depth at a distance, but our brains are really geared to use it best at arm’s length.
That in turn made me remember a delightful (but somewhat jarring) new VR game I saw advertised this week called Beat Saber. Here’s an article about the game, but you can get the idea of the game pretty quickly from this YouTube video.
Here’s a video showing actual game play from the perspective of the player.
This is an outstanding use of 3D in that arm’s length zone, or pretty close. I’d love to try this game, even if I’m terrible at it. It’s like the Dance Dance Revolution of the VR world.