If the projectors are configured for a Fixed Projection Point the CAVELib configuration file needs to change. In this type of setup head tracking can not be done since the projectors themselves are aligned such that the view is correct for a specific viewpoint. This viewpoint is normally the radius distance from the screen and at the center of the vertical height of the screen. In this type of setup the projectors are assuming the video output is a projection plane that sits along the chord in front of the screen. The projectors also overlap so that from a top-down view the virtual projection planes would be sitting in front of the screen like this.
For this type of setup, the projection planes need to be setup in the CAVELib configuration file to have exactly the right corners given the dimension of the screen and the projector configuration. Below is an example configuration file for a 3 pipe setup where the projectors are configured for this Fixed Projetion Point mode also called "Real World" mode. In this setup the screen is a 12' radius, 8' high and 1' off the floor. The HFOV of the projectors is 54 degrees, the offset between projectors is 50 degrees, and the VFOV is 41.05 degrees.
# Configuration file for a 3-pipe IR system driving a 3
# wall curved screen display
#
# Specify here which Display walls you want to run and
# in which graphics pipe
Walls screen0 screen1 screen2
# Display information for walls (pipe # & (optional)
# window geometry)
WallDisplay screen0 :0.0 1280x1024+0+0
WallDisplay screen1 :0.1 1280x1024+0+0
WallDisplay screen2 :0.2 1280x1024+0+0
# data for left screen
ProjectionData screen1 * wall -11.69 1.0 -2.69 -11.68 9.0 -2.69 -4.69 1.0 -11.04 feet
# data for middle wall
ProjectionData screen0 * wall -5.45 1.0 -10.69 -5.45 9.0 -10.69 5.45 1.0 -10.69 feet
# data for right wall,
ProjectionData screen2 * wall 4.69 1.0 -11.04 4.69 9.0 -11.04 11.69 1.0 -2.69 feet
# Leave the wand (sensor #1) as an active sensor, this forces the head position to be fixed
ActiveSensors 1
# Set the head to have a FIXED position of 5.0 feet above the origin
DefaultTrackerPosition 0 5 0 feet