You can check out the video here before I get to details.
http://www.youtube.com/watch?v=H457HUOZjpg
So... Its really easy to make. You just need
some piece off plexiglass and cover it with tracing paper.
Underneath you put some sort off light and a webcam.
That all the hardware you need.
Software used for blob tracking is called TBeta or
you can use reacTIVision (you know Reactable).
They send TUIO OSC messages which needs to be
translated to MIDI and best software for that is OSCulator.
And thats it. You have yourself a multitouch midi controler
If you wanna know more or have some problems with your setup
you are free to ask and I will try to help.
More information you can find here:
http://nuigroup.com/forums
http://nuigroup.com/forums/viewthread/1731/
http://www.osculator.net/wiki/
Have fun! I know I am having
P.S. It was a good project to forget about my studio
problems
Best regards,
Tomislav