Overview

The main idea behind the technological setup for this piece was to create a seamless interactive link between dancers, music, and video.

The space is broken up into three spaces or stations, one for each dancer. Across each station, a laser beam-breaker is setup. By moving around within the space, a dancer will cross the beam, which will trigger both musical and video based events.

In the center of the three stations, a small camera attached to a rotating motorized platform is mounted on the ceiling. Using the information from the beam breakers, the camera will automatically rotate to focus on the station in which the most “action” is occurring.

Here is an overhead view of the layout:

Laser Beam-Breakers

The laser beam-breakers are very simple homemade devices that detect whether a beam of laser light is being blocked or not on its way to a photocell positioned across a space.

These are created using cheap store-bought laser pointers mounted on a poll, which point to a photocell, which is encased in a small housing on top of a poll of equal height.

Here is a design model:

The data from the photocell goes out through wires to a box that converts the electrical signals into midi data that a computer can understand. From this box it goes to a computer which uses the information to control the music as well as the motion of the camera.

The Rotating Camera

The camera used for this was the PC-100XS Microvideo Camera. It is only 1.25 square inches large and weighs only a few ounces. This compactness allowed it to easily be mounted onto a small stepper motor, the kind often used for powering clocks.

Here are some of the initial design models for the camera and mounting unit:

The motor attached to the camera is then connected through some driver circuitry to a programmable integrated circuit called a BASIC Stamp II. This chip contains a small program which takes can turn the motor to any direction desired.

To determine where the most “action” on the stage is occurring, the computer controlling the camera looks at the frequency of broken beams for each station. It then figures out where the laser beam is being broken the most often and sends a signal through a serial cable to the BASIC Stamp telling it what station has the most going on within it. The Stamp then takes this information and rotates the camera accordingly.

It should also be noted that the camera does not turn all the way around in one direction. In order to avoid tangling the cord that comes out of the camera, the driver software must turn 359° and then go back all the way in the other direction if it wishes to continue tracking in a given direction.

Here is a picture of the actual unit:

The camera along with its driving circuitry and power supply:

Overall Data Flow

Here is a diagram of the data flow for this setup:

The three laser beam-breaker systems send information (via the midi converter box) to the computer that is controlling the music. This computer then sends information via a serial cable to the tracker, which is the Basic Stamp II circuit. This will turn the camera, which will give video output to the computer that will control the video. The video will be displayed on a screen via a digital projector.