Of course it’s not really a hologram, it’s an illusion.
It’s good to understand some background to this project, the prior work by others etc.
To start with, let’s talk about Pepper’s Ghost !.
Pepper’s Ghost is an visual trick first used in the theatre in the eighteen hundreds. The trick was to create an illusion of a ghost appearing on stage next to the other actors. A sheet of glass is hung across the front of the stage so that the image of an actor standing in the orchestra pit appears to float on stage. It was first shown at the Royal Polytechnic Institution in London by ‘Professor’ John Henry Pepper (1821–1900) on Christmas Eve, 1862.
This illusion is still used today and some so-called holograms use this trick. (I’ll explain holograms in a separate blog post).
As an evolution of this concept, Xuan Luo, Jason Lawrence and Steven Seitz of the University of Washington, Seattle produced a concept they called Peppers Cone. (Published in 2017 as “Pepper’s Cone: An Inexpensive Do-It-Yourself 3D Display” in UIST 2017At: Quebec City, Canada).
Here, a 3D display is built from a tablet and a plastic sheet folded into a cone. The display allows viewing a three-dimensional object from any side without the use of special glasses. The image is pre-distorted so that when the reflection is viewed on the cone, the image is of the correct proportions. An App on the tablet changes the image as the tablet is rotated giving the illusion of the image object being rotated. The person moves the tablet around to see around the object, the person themselves don’t walk around the tablet.
First, I took a ‘Lazy Susan’, this is a turntable (rotating tray) placed on a table to aid in distributing food. It has an inner ring (annulus) and an outer ring, with bearing between the two, so one can be still and the other rotating.
On the inner ring I mounted a display, a transparent dome was placed onto the outer ring with which a rear projection film was placed. This meant the display would remain in the same place and the dome could be rotated around. On top of the dome (out of sight) was placed a Smartphone.
I wrote an App using Unity which altered the camera view around a 3D object according to the angular position of the smartphone (i.e., taking data from its accelerometer, gyroscope etc.). The Smartphone display was wirelessly mirrored onto the fixed display. When the dome was rotated (and hence the Smartphone), the camera view (within the App) on the 3D object changed and it therefore gave the illusion that the object was rotating with the dome, when the display inside the dome was static.
