The 3D craze in all forms of entertainment has spread to the extent that the swag bags for journalists at Toronto’s G8/G20 summit include an iPhone cover designed to let you view 3D media. 3D is all the rage for movies and games, as consumers flock to something novel and seemingly high-tech and entertainment companies sense an excuse to boost ticket prices and (for now) offer something that pirated media does not.
I have one big problem with all of this: while it is easy enough to exploit binocular vision to produce the illusion of three dimensions on a flat screen, doing so doesn’t really take into account how people see. The effect works because of how our brain interprets parallax – the situation in which the perspective on a scene differs slightly when the viewpoint used changes. This is a problem for many point-and-shoot cameras, with viewfinders offset from the lens; you can compose a photo nicely as viewed through the former, only to discover that it doesn’t look so great when viewed through the latter. It also applies to the different perspectives offered by your two eyes. Your brain uses the differences between the two views as one source of information about how far away things are, feeding into our overall awareness about the three-dimensionality of the world.
Parallax is one important way in which our brains make sense of a three-dimensional world. Others include geometric cues, like how parallel lines seem to converge as they approach the horizon. Exploiting these sorts of cues allows artists to make works that seem to have depth. It is also one way in which optical illusions can be created. It is one reason why the very cool hollow face illusion works. Indeed, that particular illusion only works when seen without the benefit of binocular vision, which allows our brains to figure out that we are in danger of being tricked by geometry.
The trouble with 3D is what happens when our eyes go beyond perceiving a scene and into responding to it: specifically, by refocusing. When we see a rhino charging at us, the muscles around our eyes change the shape of our lenses so as to keep the beast in focus. Our eyes also turn inward, toward our noses. Unfortunately, when we are just looking at a false 3D image of a rhino, the re-focusing is not necessary. After all, we are still really looking at the same flat screen. This may explain why watching 3D movies is nauseating for some people; more worrisomely, it could cause people to learn to see in unnatural ways, in a manner that extends beyond the movie theatre experience.
This is not a problem that can be overcome, so long as our chosen mode of producing faux-three-dimensional images relies upon information displayed on flat panels. How important it ultimately will be, I can’t really comment on. Still, it is worth knowing that the exciting 3D experience consumers are being promised is premised on a limited understanding of how people really see moving images.