The installation 'The Virtual Cage' is situated m an auditorium (a 'Theater am Turm' production, Frankfurt) approximately 10 m by 20 m. In the middle of the room there is a hydraulically damped glass platform where the viewer can walk around. Two surface mirrors fastened to the platform and tilted at a 45 degree angle reflect a laser beam across the darkened room as a reference plane. Sensors convey the instantaneous inclination of the platform to an Iris-Indigo workstation in the next room. A second Indigo in the theater foyer is connected via a network.

A five channel audio system controlled by the Indigo computer system fills the room with sound. In the connecting space between the two rooms there is a 3 m by 4 m rear-projection screen. A video beamer located close to the ceiling of the next room projects real-time computer graphics onto the screen from behind. The same program runs on both computer systems. The databases contain a 'wire-frame' model of the room, in which a swarm of dots chase each other around (the creature). The swarm is moved around the room in accordance with the angle at which the platform is tilting under the weight of the viewer. The swarm is allocated two different sounds which are moved around the room by the audience as a perceptible utterance.
The connection between the two computer systems allows two simultaneous ways of seeing:
- the viewer finds himself in the 'computer model' of the room and sees the creature as a fleeting shadow on the screen.
- the viewer sees the whole installation room (virtually) through another camera position (from outside) on the monitor set up in the foyer. The swarm-like creature inside can be seen being chased around the room - interactively -by the viewers.
(Christian Möller)