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What Our Brains Really Need From 3D Movies

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I was recently in San Francisco at the SPIE conference on electronic imaging and attended a 2-hour session demonstrating samples of state-of-the-art 3D videos from upcoming movies, video games, advertisements and artistic pieces. The general reaction of the several hundred people there was positive, and I enjoyed it as well.

But that might not be saying much, because most of us even enjoy looking at static stereo images, even ridiculously simple ones like a square floating in front of a background. The success of the "Magic Eye" stereo books, for example, relied upon our easy-to-please appetite for 3D.

The question is not whether 3D films are fun -- of course they are, even the bad ones. The question is whether 3D filmmakers can do better. These movies are still in their infancy, relatively speaking, and there are technical communities (like the conference I attended) scrambling to make the 3D experience better.

I have no doubt they will, but I believe they are destined to achieve only cosmetic changes around the edges rather than revolutionary breakthroughs in the experience. And there is a simple reason for this: 3D movies are not 3D movies. Or, rather, they are much more than that: They are binocular movies.

When we say "3D movies" or "stereo movies," we are referring to the stereo depth perception we get from our two eyes, called stereopsis. Possibly in part due to the intrinsic excitement that the perception of stereoscopic depth engenders, books on binocular vision are essentially books on stereopsis.

But binocular vision has other important functions besides stereopsis. Binocular vision refers merely to the use of two eyes for vision, whereas stereopsis is just one of the functions binocular vision gives us.

The problem with 3D filmmakers is that they don't realize, or at least have not sufficiently taken to heart, that the medium they're working in is "binocular film," not merely "3D film." And once one realizes this, it is possible to see that there are whole domains of potential film experiences that have gone entirely untapped.

For starters, let's ask why we have such a large binocular field in the first place. That is, why do we have eyes that face forward rather than sideways, like rabbits, birds and most fish? If we had the tiny sliver of the binocular field rabbits have, we might not bother with 3D -- ahem -- binocular movies.

As I have argued in my research and book, "The Vision Revolution," we have forward-facing eyes in order to see well in cluttered forested habitats. Our large binocular fields evolved for peering past layers of clutter, and integrating the two eyes' disparate views of the scene beyond into a single unified perception. It is the animals that can benefit from this better-view-in-clutter that have forward-facing eyes, whereas animals in non-forested habitats, for example, all have sideways-facing eyes (and thus only a tiny binocular region). I call this function of binocular vision "X-ray vision" because we have mechanisms that allow us to perceive the clutter, but also to render it as semi-transparent through which we perceive the scene beyond.

If 3D filmmakers are going to throw binocular images at our big binocular fields, then they should be sending us views of the kind our large binocular field evolved to process: views within cluttered environments, whether it is a leafy forest or a creepy spider web-filled chamber.

Even more fundamental than "X-ray vision," binocular vision is not about seeing the world so much as seeing ourselves. One of the principal uses of an eye is to acquire visual feedback about what one's grasper -- usually the mouth, or muzzle -- is doing. The problem, though, is that if one puts the muzzle in one's visual field -- i.e., out in front of the eye -- then although one can see the muzzle, the muzzle now occludes one's view of the world beyond it, and seeing the world out there is the other principal role of the eye.

How can one see one's muzzle so as to be able to get the brilliant motor control that's needed without it blocking the view of the world beyond? Evolution's answer was to have two eyes, and to put the muzzle in the binocular region. That way each eye gets occluded, but what one eye misses the other sees, and the brain can then create a unified perception of what is out there beyond the muzzle, yet nevertheless include the muzzle within the visual field, seen from both sides and rendered as semi-transparent so it doesn't block the view. The binocular region (even for animals with small regions) is most fundamentally about seeing oneself -- in particular, seeing one's own muzzle and other graspers as they interact with the world.

In this light, "3D film" ought to be about putting the viewer into the body and eyes of characters in the story, immersing them in the milieu of the complex interactions between the character's body and the surrounding world. And part of this is the experience of being in the body of the character. It is possible to render what it is truly like to view the world from the perspective of another, but it requires including the character's nose and other visible body parts on screen (including the lips, cheeks, brows and sometimes the hands and legs).

With binocular technology, filmmakers can include these self-visible body parts on screen, and yet not occlude the view of the scene beyond, just like real life. This "3D technology" can be a conduit for allowing viewers to truly see out of the eyes of another, and to experience the character's world-self boundary. (See also earlier pieces here and here.)

I'm no artist, and so I am a poor guide to the best way these binocular functions can be exploited in movies (or video games). But I am confident in anticipating that "3D movies" have only begun to scratch the surface of the screen, because they have only been playing their game on one small, relatively unimportant playing field among binocular vision's many talents.

And a simple first pedagogical step forward is to begin calling them "binocular movies," not "3D movies."

Mark Changizi is Director of Human Cognition at 2AI. He is the author of books such as "The Vision Revolution" (2009) and his new book "Harnessed: How Language and Music Mimicked Nature and Transformed Ape to Man" (2011). This piece first appeared in "Forbes."

Around the Web

Binocular vision - Wikipedia, the free encyclopedia

No 3D in 'U2 3D' without binocular vision | Geek Gestalt - CNET News

Stereo-Blind: People who can't see 3D

Why 3D Movies Could Be So Much More - Forbes