My setup is pretty crude, but it worked for a good test run. The acrylic screen is only 15" inches, but I was pretty surprised at how close I could get the projector. My home projector only needed to be about 3 1/2 feet away.
Here's the setup I was working with.
I had the screen setup vertically, but the fingers didn't give it enough pressure for my FTIR setup. I had to press my fingers a little harder than it was comfortable, but I think gravity would make this much easier once the screen is horizontal.
The hardware responded a bit slow once I got it running. You can see a few points were missed in the picture below.
I'm using a camera that advertises 25 fps, so maybe a faster camera will give better results. Maybe if I tried some software that used point interpolation it would react better. As it was though, the recognition was pretty slow. (Btw, the hanging projection paper gives the image the ripple effect, another reason to go to a horizontal setup =D ).Overall though, the project is looking good. The touchlib framework acts as a web server, so the multitouch is compatible with any programming language. You just need to connect to the proper ports (3000/3333), and any C++, Java, or Flash application can work with it. Technically you can interact with other computers across the network, but if the reaction time is less than a fraction of a second it'll feel wrong.
Next steps are to build a cage and look into getting a faster IR camera.
