cooper@pbsvax.DEC (TOPHER COOPER DTN-225-5819) (11/26/85)
Doug Williams: > Also, try Disney World in Florida's Haunted Castle for *moving* >holograms: ghosts float around and as the ride is about to exit >there is a mirror on the wall so you can see the ghost sitting on your >shoulder! Wow, it's neat stuff. Yeah, it is neat stuff, but I don't think its a hologram. There are, as I remember several real holograms in the show but the effects your describing are not done with them. The effects looked to me to be produced with a much older technology -- beam splitters. Here is what I think is being done: Between you and the mirror (to use that example) is a sheet of glass slanted at 45 degrees. In the direction the glass slants is is a mechanical model in a dark room. It is colored with materials which fluoresce in UV. At first you see only your own reflection in the mirror since the "ghost" is in darkness. Then the UV light is faded in and the ghost starts to glow. It reflects in the glass sheet, and you see that reflection superimposed over your (obviously reflected) image in the mirror. Just as for any plane reflection it appears to be in full depth. glass | | v \ | \ | \ | \ | You \ | <-- Mirror \ | \ | \ | \ | Ghost A similar effect is used, I think, in the "haunted banquet hall." The ghosts are above the hall, the "further" ones higher than the "nearer". The same mechanism is frequently used in museum displays, to "cross-fade" one scene to another (for example a human figure to a human skeleton, or morning to evening scenes). Its really quite nice, even though its low-tech. Topher Cooper USENET: ...{allegra,decvax,ihnp4,ucbvax}!decwrl!dec-rhea!dec-pbsvax!cooper ARPA/CSNET: cooper%pbsvax.DEC@decwrl