Illusions in three dimensions

Julian Beever makes amazing pastel pavement drawings that, when viewed from the right angle, create stunning 3-d illusions. Unfortunately, a lot of the best ones don't have "wrong angle" shots to show you the trick. Here's one of the decent ones, although the angle of the initial shot is very slightly off.
I think it was LadySusan who first put me on to his great stuff.




Here's a fascinating gallery of 3-d optical illusions created by painting rooms so that a form appears when viewed from precisely the right angle. They're very impressive. I've seen them linked a couple of times, but there doesn't seem to be much background on who created them or where. Neat anyway.
Via Random Good Stuff.