In addition to such forms of data (also referred to as ???S-CAD data???), the external data 12 may take the form of Volume data that also has internal information such as (1) data directly input by a person using a V-CAD-specific interface (also referred to as a ???V-interface???), (2) digitized surface data such as that obtained by measuring instruments, sensors, and digitizers, (3) voxel data us