To compensate for the variability in the orientation of that receiver a calibration mechanism was build into the program. Before starting an experiment subject was asked to look straight ahead while the initial orientation of the receiver was measured to be later used as zero reference angles. Another calibration feature allowed experimenter to reposition the Polhemus transmitter. Receiver number 1 is positioned at the specified coordinated in the room while it's position is measured by the tracker. Using the coordinates returned by the tracker and the known actual coordinates of the point where the receiver was placed program can compute the new position of the transmitter.
Program saves all calibration values in files.
Virtual environment was generated by the SGI ONYX computer. R4400 processors was dedicated to running the graphics code, while the other was restricted to serial line communication with the Polhemus tracker. The two processors communicated through shared memory. This arrangement allowed the program to maintain a frame rate of 30 updates per second with the minimal obtainable tracking delay. Graphics program generates a different image for each of the two LCDs creating a stereoscopic view of the environment.