Viewfactor uses rules to determine which Patran Thermal radiation resistors to make. Which resistors are made depends on the data in the VFAC Templates and VFRAWDAT file. This chapter describes these rules. Restrictions on the valid ranges of data in the VFAC Templates is described in the previous chapter in the section on the VFAC Template data specification, VFRAWDAT (Raw Viewfactor Data), 140. These will not be repeated here.