Remember watching movies with those red/blue cellophane glasses? Movies where they would inevitably use cheap gags to make things "poke out of the screen" at you? Well, that was an inexpensive, decidedly low-quality form of stereoscopic 3D. We see the world in 3D because our left and right eyes see slightly different views, and our brain combines them to form a 3D image.

If you can use a TV, movie theater screen, PC monitor, or projector to show a left eye view only to the left eye and a right eye view only to the right eye, you can fool the brain into seeing that 2D flat plane as if it was 3D.

Things have come a long way since those early red/blue glasses. Some theaters project both the left and right eye image onto the screen with polarization rotated 90 degrees. Viewers wear plastic glasses that are polarized such that only the light from the left eye projection goes through the left eyepiece, and only the right eye image goes through the right eyepiece.

You can read the entire article at ExtremeTech.