Sunday Morning Evening Illusion

As per a request from last week, we are going to talk about how wiggle stereoscopy works.

For those that don't remember and are too lazy to read older posts, wiggle stereoscopy is this:

Most 3d images take advantage of the fact that we have two eyes and that we process distance mostly by using the comparisson between the images each eye is receiving. Two, slightly different images are sent to each eye and the brain interprets the difference as depth. This is how 3d glasses work, each lens blocks out half of the image and lets the other half through either through polarization, in the case of movie theaters, or colour filtering lenses, as in the case of cereal boxes or viewing void stuff.

Wiggle stereoscopy takes advangage of a very different processing method in the brain. It uses the interpretation of paralax, which is the apparent relative motion of motionless objects cause by moving past them, to create the illusion of depth. There are a lot of limitations to this method, though. It only works well on still images. When things are in motion, their movements override the more subtle effects of paralax. It also seems necessary to have the images alternate at a clearly perceptible frame rate. This makes it pretty choppy to look at. Also, there needs to be a focal point about which the image is rotating somewhere in the image. Note that the baby barely moves in the picture above and the scenery seems to move around her.

It is possible to get a less pronounced version of this effect in a video. Some people will remember having their brain break when they saw Trinity freeze for the first time in The Matrix

There are cameras that you can get that will make making these sort of things easier, but they're not necessary. As long as your subject is perfectly still, you can make them yourself with any digital camera and an animated gif maker.