### http://itp.nyu.edu/~cvm232/blog/?p=149

Classes
Introduction to Physical Computing

The goal of this project is to create a linked identity between a real object and it's digital self, which we project on top of it. When you sit in the chair, a pressure sensor embedded in the seat controls the playback speed of an animation in Processing. The animation shows the chair emerging from its physical self and turning into a tree. When you place your hands on the capacitive sensors on the arms of the chair, the volume of a soundscape gradually increases. Both of these processes take time - you must sit calmly and wait as the sound envelopes you. When you stand, the video plays backwards slowly, and the sound returns to silence. It is just a chair again.

Background
Much of our time was spent familiarizing ourselves with various libraries in Processing. We wanted to have a movie and sound controlled independently, as well as a live video capture. The most difficult thing was figuring out how to use the data we were getting from the capacitive sensors. We had to average the instantaneous value with the previous ten, so that an individual fluctuation would not mess up the sound. We also had to simulate a gradual fade in the minim sound library, accounting for the fact that the decibel scale is logarithmic.

Audience
This is an art installation. It could be appreciated by anyone with a 30 second attention span.

User Scenario
A couple of people walk into the chair's space and are enticed by its beautiful purple appearance. There are no buttons or apparent tricks so they sit and activate the video and sound. Perhaps they sit for a while and enjoy the soundscape. Perhaps they sit and stand, touch the arms individually, then at the same time to figure out how they're affecting what's happening.

Implementation
A pressure sensor embedded in the seat of the chair controls the playback speed of an animation in Processing. When you sit, it plays forward – the chair grows into a tree. When you stand, it plays backwards, returning to it’s original appearance. Becky made this animation in Flash.

We made capacitive touch sensors from aluminum foil and attached them to the arms of the chair. The sensors use the capacitance of the human body in a circuit. When you place your hands on the arms of the chair, the value returned by the capacitive sensors is higher than when untouched. While skin is in contact with the sensors, a counter variable increments in Processing. This counter controls the volume of an audio file – the longer you sit in the chair, the louder the audio environment becomes. When you remove your hands, the sound slowly fades. I made this soundscape in Protools and used Soundhack for some signal processing. I used field recordings, some convolved with chords from the Ravel Piano Trio to make the tonal elements, and mixed these with a recording of a Pine Forest filled with birds.

Roy made a housing that attaches to the bottom of the chair where the Arduino lives, with wires neatly packaged.

Conclusion
The end result is much more beautiful that we anticipated.