This display does an impossible task ! it keeps the image ALWAYS facing the spectator whatever the angle of observation !
EVERY spectator at the SAME TIME have the impression that the display is following his direction..
That have some applications like in Halloween where frightening figures can be made to appear following everybody. No one can escape his gaze.
The effect is impressive but the principle is very simple : a cylinder with a vertical slot and a printed sheet of paper. The cylinder is rotating at high speed and a source of light is at the top.
Code that can be imported in Processing (processing.org).
Please note that this code works under Processing version 3.
This program will distort an image in order to be correctly displayed by the prototype I used ( Pringles Can).
See video description of the project (4 minutes long) : https://www.youtube.com/watch?v=3ESE02ywSxQ