Have fun with strabismus!

Experience 3D by 2D methods (Part 1)

It is often said that if you have a squint, you can't perceive depth. It's not true. Depth perception is a complex process involving much more information than just the slightly disparate images of two eyes pointing in the same direction. Here are the other clues on which depth perception is based:

Motion parallax

If you look at two things, one being closer to you than the other, and you move your head, you'll see the thing closest to you, move the most.

Linear perspective

For example railroad tracks that run parallel, seem to come closer and closer together the farther they are away from you.

Overlay of contours

If an object is in front of another object (but not completely obscuring it), it will interrupt the contours of the object farthest away from you. The object closest to you will be perceived as being in front of the other object. It is quite obvious that this driver is standing in front of a train.

Distribution of light and shadows

Sunlight most usually comes from up above, so we tend to infer a lot of depth information based on highlights and shadows. This image is lighted from above.	The same image, put upside-down. Depth appears reversed.

Size of known objects

Relative distance can be estimated based on the apparent size of the objects. If you know something is smaller or the same size, but it appears larger than another, it is perceived as being nearer.The biggest helicopter the nearest.

The car that appears the largest is the nearest. Two important other clues are present in this image as well: linear perspective and aerial perspective.