I used processing as the core of this setup. It also uses arduino based spray can and radio receiver. Plus makes use of Classiclll's wiimote library.

http://www.instructables.com/id/virtual-graffiti

* The spray can has an infra red LED that shines through the projector screen and is seen by the wiimote's camera.
* The wiimote sends the X and Y co-ordinates of the can to the computer via a bluetooth radio link.
* The computer is running a simple painting program that uses a projector to "paint" the lines as you draw with the can. It also takes care of mapping the wiimote camera to the screen using a 4 point calibration system.
* The spray can also detect its distance from the screen and the nozzle pressure: the further you are away the bigger the dot drawn, the harder you press the nozzle, the more opaque the paint dot becomes.

blindfish wrote on Dec 21^st, 2009, 1:08pm:


Based on this info on the site: "The spray can has an infra red LED that shines through the projector screen and is seen by the wiimote's camera."  I'm guessing 'no', since the infrared dot would be visible on the backside of the canvas regardless of the angle. In that case, this concept is brilliant, if not, it is still very cool!