People think they want holograms, but they (usually) don’t. These are illusions, images trapped on two-dimensional surfaces that give the impression of a three-dimensional object.

What people really want are “volumetric images” — a display of free-floating light that actually takes up 3-D space, visible from all angles. (Bonus points if you can interact with it.) Many of the coolest movies have them, from Tony Stark’s displays in Iron Man, to the projection table in Avatar, and perhaps th