Albert Einstein Optical Illusion

Isn't this the illusion painters use so that the eyes in a portrait seem to follow you around the room? It's how they add depth to a 2-D painting using light, shadow and perspective.
http://entertainment.howstuffworks.com/arts/artwork/eyes-in-painting-follow.htm
Something else happens when you have a 3-D image and light can shine through the material. Light seems to fill the space, giving the mask life, making it that much more plausible to our brains. Willa Shalit (daughter of Gene Shalit) did a series of casts of the faces of famous people. They were good casts alone, but when she shone a light from behind them, they came alive like a halogram. The material she used for casting was white, but thin enough that light could penetrate.
http://science.howstuffworks.com/hologram1.htm

this illusion works off the same principle I believe, so I dont think the material or transparency matters.