One hitch in bringing 3-D motion pictures to home theaters has been the glasses—people hate them. Yet viewers have been enjoying motionless 3-D images unassisted since at least the 1960s. At that time, VariVue was printing postcards covered with a lenticular array that sent each eye a slightly different view. This year Toshiba demonstrated a similar kind of glasses-free 3-D display, and Nintendo released its 3DS. Instead of a lens, the 3DS uses a barrier to produce the stereoscopic effect.

Click the image above for an animation detailing how a parallax barrier glasses-free display works. If you are on a device without Flash capabilities, click here for a static version.