Check out this large-scale tagging projector created by an artist using a standard notebook computer, 5000 ANSI DLP projector, a 60mw green laser (apparently super illegal in a lot of places and very dangerous), an astronomer’s camera, and some other random crap.
The L.A.S.E.R.TAG tracks the motion of the hand held green laser through the camera and then projects the ‘ink’ onto any large flat surface. Anyone with a high-powered, strong green laser from any direction can write what ever they want on the screen. Check out the video and see for yourself.
The lab has instructions on how to get started with creating your own tagging projector with the source code.
[found at Pop Sci]
L.A.S.E.R.TAG video demo
High-powered green lasers demo
Warning: Powerful lasers could damage your eyesight (probably permanently.)