This is an inexpensive way to turn any surface into an input device that senses the x & y position of multiple simultaneous touch points. The hardware necessary is easy to find online by following the links below, or at a well stocked electronics store: a webcam, two mountable lasers, a power source for the lasers, and something to prop up the camera with. This is not a true multitouch surface, but it is an inexpensive and useful alternative.

There are innumerable uses for a multitouch surface; the software includes one simple audio application. Each finger controls an oscillator with the y-position mapped to volume and the x-position mapped to frequency. The software can also pick up the lean of the fingers using the aspect ratio of the laser beam across the finger. When a finger is perpendicular to the surface, the height of the laser beam across that finger is smaller than when a finger is pitched back. This adds another parameter of control, which, in the included software, is mapped to a timbral change using FM synthesis.

<IMG SRC="" WIDTH=320 HEIGHT=240 ALIGN = "LEFT"> 1. Cut an acrylic rod to about an inch long. Using double sided tape, attach the acrylic rod vertically in front of the laser so that the rod refracts the light into a horizontal plane. Repeat on the other laser.