We constructed a prototype of a Force Sensitive Resistor (FSR) out of wire, plastic grocery bags and Scotch tape.
These will be placed within each pixel to give the software readouts on roughly where people are standing. This can be used for a large-scale version of "DDR," Human pong, control of games like Tetris, and ambient effects like having a cluster of lit pixels follow people as they walk across the floor.
The FSR's work by placing plastic in between two contacts to act as a dielectric (does not conduct electricity). When compressed, the thin film begins to conduct enough that resistance changes from around a MegaOhm to as little as 1 Ohm (it varies, of course).
These are still in the prototype stage as other materials are considered. Once the mechanical design of the floor is finished we will have a better idea of what sort of "sensitivity" these will need. The layers and materials used for the dielectric can then be tested to conform to specifications. If they are too easy to trigger (cause resistance to --> 0) then pixels may be stuck "on"; too hard to trigger means none of the intended effects will work.