3D doesn't mean 3 eyes. We see in 3D partly because each eye sees things from a slightly different angle. And you can tell distance from triangulation. Something farther away will appear the same to both eyes, but as something gets closer the differences in perspective will increase (your left eye will see part of the left side, your right eye will see part of the right side) and that lets us perceive three dimensions. This is why losing an eye often causes a loss in depth perception. There are a number of other different ways to judge depth (http://en.wikipedia.org/wiki/Depth_perception) but this is how they make 3-D movies or 3-D photography, they use two lenses a short distance apart.

Umm ok well when I pan my hand back and forth from my face it seems to appear bigger and smaller depending on how far it is. so thats 3D?

No, that still happens when you close one eye, or move your hand on television. But if you had a hand that could get larger and smaller rapidly compared to one that moved closer and farther, you wouldn't be able to tell the difference without some other factor such as shadow or triangulation.

well when i pan my hand with one eye shut it still looks the same when i have both eyes free

No, it doesn't, not if both of your eyes are working properly. It doesn't seem like much of a difference, but try an experiment: hold a pencil or pen in each hand by the end, close one eye, and try to touch the other ends of the pencil together in front of you (without your arms fully extended, because they are probably the same length.) This should prove difficult with one eye closed and easy with two eyes open.

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ur r not so important and handsome

since depth IS the third dimension and two eyes lets us see depth, we do see in 3d.

3D is judged by how fast an object appears to get bigger as it comes toward you.

uh, no, 3d is judged as something that has length width and depth. objects getting larger as you walk towards them has nothing to do with 3d, that's called perspective.

Ummmm WTF

I am so confused this is alien to me

If you stand on railroad tracks and look down them they will appear to meet at a distant point. This is perspective. If you have a clay sculpture that is 3d because it's not flat. A Painting is 2d, but with the aid of perspective it can have the appearance of 3d, even though it isn't.

perspective is 3D

No. We have perspective BECAUSE of 3d.

Umm ok well when I pan my hand back and forth from my face it seems to appear bigger and smaller depending on how far it is. so thats 3D?

No. That's perspective.....Seriously, what aren't you getting about this concept?

I am so confused right now.

I know 3D can also mean like 3D models etc.

god damn it now we're back to square one....*sigh* Let's try this ONE MORE TIME. IF something is 3D that means it has length, width, and depth. A drawing of a square is two dimensional however a drawing of a cube is 2d BUT representing a three dimensional object. You need two eyes to perceive the third dimension, because without two eyes there is no perception of depth. 3d models are called three dimensional models because they exist as 3d objects and can be turned, rotated, or flipped. unlike a picture of a house a 3d model of a house can be turned to see other angles because it exists in three dimensions. If this doesn't make sense I can't explain it to you any better.