Re:Handicap distress... (Score 1)

I often find people who ask, "Is viewing the actual world through one eye only really in 2D?" I ask in return: When you close or cover one eye, does the image in the other eye suddenly become flattened? Doesn't everything shift to the same apparent depth? Not in my experience.

If it is accepted that two eyes are required for 3D vision, then it logically follows that anything less is not really 3D. But the very premise is wrong. It is incorrect to assume that binocular vision (using two eyes) is a necessary requirement for depth perception.

What does 3D vision or depth perception mean? It is the ability of the mind to associate an item being viewed with a position in 3D space, to a desired degree of accuracy. And there are several aspects involved, absolute distance estimation (how far away?), relative placement, (which objects are further away than others?), and velocity estimation (how fast is an object approaching or receding?)

The (human) brain uses many cues to determine depth. The most important of these factors is focusing power, which only requires one eye. In a way this makes sense, as one can also use the focus on a camera or telescope to measure the distances to objects.

Note that a simple experiment may seem to invalidate this claim. Wearing or removing corrective lenses does not cause a shift in the apparent depth of objects. The lack of this expected effect, is usually explained by brain's consideration of the many other clues used to determine depth. But when the number and quality of those other clues is reduced, this affect can be made to occur. There is another simple experiment you can try. View a computer screen with text of three very different sizes, but the same font and color. Look through a tube so that the other portions of the screen are not visible. Many people report that after intentionally blurring their focus for a few seconds, the smaller text appears to drift further away. Restoring sharp visual focus brings all the text back to the same depth. Basically, this makes the brain disregard focus as a criteria for evaluating depth, and the brain is left with only the knowledge that objects further away appear smaller, and assumes the smaller text is further away based on this rule.

Other factors known to influence depth perception include: binocular vision, small movements of the head (which provide separate vantage points just as binocular vision does), perception of textures (the better a texture can be seen, such as the fur on an animal, the closer it must be), lighting and shadows, assumptions about the shapes of objects, and comparison to other objects with known positions. The more of these factors the brain can take into account, the more accurate depth perception becomes. (Depth perception is a matter of degree, not a binary on/off switching.) Consider that most optical illusions have two requirements, the first is the provision of ambiguous or contradictory information; the second is the elimination of most other inputs that would otherwise help the brain to resolve the problem.

The goal of 3D displays is to trick the brain into seeing objects on the display at different depths, even when they truly are not. The goal is deception, not truth; and considering just these techniques will not give a complete or truthful idea of how visual perception works. We've had tremendous success using binocular vision as part of this "tricking the brain" process. This has been done in many ways. Side by side images for each eye, dot stereogrammes, and red/green glasses or shutter glasses are the most widely known. But this should be not taken to imply that the brain requires binocular vision for depth perception (it doesn't), nor that binocular vision is the only method that will work for tricking the brain into perceiving depth from a flat screen or page.