3D projection is any method of mapping three-dimensional points to a two-dimensional plane. It was not until 1950 that 3D projection reached mass appeal. During this time, the white cardboard glasses with red and blue lenses – called anaglyph – came into vogue. The blue lens filters out red light and the red lens filters out blue light so each eye sees a slightly different image. When a 3D movie is projected on a screen, two images are displayed, one in red and one in blue. Since each lens of the glasses has a filter, only one of the two images can reach each eye. The brain merges both images together, which results in the illusion of an image popping out of the screen. Despite anaglyph glasses’ universal association with 3D, they are rarely used anymore.