Graduate student Xuan Luo has developed a pretty damn amazing Pepper’s Cone effect using stuff you probably have lying around your house right now: some clear plastic (a cup will do), an iPad, and a nickel. 

If you try to reflect a normal image into a cone or pyramid, as the above video shows, it’ll warp and not work from all viewpoints. Working with Professors Jason Lawrence and Steven Seitz, Luo has put together an algorithm that pre-warps the image being projected, so that it looks perfect in the 3d display regardless of the point from which it’s viewed. From the description:

This display allows viewing a three-dimensional object from any direction over a 360-degree path of travel without the use of special glasses. Inspired by the classic Pepper’s Ghost illusion, our approach uses a curved transparent surface to reflect the image displayed on a 2D display. By properly pre-distorting the displayed image our system can produce a perspective-correct image to the viewer that appears to be suspended inside the reflector. We use the gyroscope integrated into modern tablets to adjust the rendered image based on the relative orientation of the viewer. Our particular reflector geometry was determined by analyzing the optical performance and stereo-compatibility of a space of rotationally-symmetric conic surfaces.

The effect is remarkable, even supporting animation and audio. The code for the algorithm has yet to be released, but will be open sourced when it is. Check out the project page for more detailed information, or to sign up to be informed when the code is available. If you’re more tech-minded, you can read the full details in the project’s PDF.