Not much information is available for this option.  The UNC Tracker
Library is a semi-independent way to interface with the different
types of 3D/6D trackers.  The code is available from ftp.cs.unc.edu in
/pub/project/hmd . You'll need "tracker" and "quat" (and maybe
others?)

  If you are looking to do VR work I strongly suggest you look into
the CAVE library instead as it is portable across more platforms and
probably has better support.  Neither have much support in the current
version of VMD.
