While this is pretty cool, not sure this concept has much use for haunters. To get a large hologram you would need a very large glass or plexiglass pyramid along with 4 projectors in a very complicated set up. I think the standard projection techniques that most of use do a very good job of creating the illusions most of us are after.
Project onto a screen placed above the glass pyramid, and it would work. It would have to be a material that would be suitable for rear projection.I wonder if it would be possible to set up a video with 4 identical sides like the sample shown earlier, then use one projector either above or below to project on to a Plexiglas pyramid. Would the image be to distorted?