gsur

   'gsur' <name(char<9)>|'!' '+|-' 'BLEND|<nurbs>|<shape>' ->
          '+|-' <line|lcmb> '+|-' <line|lcmb> .. (3-5 times)

This keyword is used to define or redefine a surface in the most basic way (see also qsur). Each surface which is intended for a regular mesh must have three to five edges which might consist of a single line or a combined line (see lcmb) to be mesh-able. However, the recommend amount of edges is four. For example,

gsur S004 + BLEND - L002 + L00E + L006 - L00C

will create the surface S004 with a mathematically positive orientation indicated by the ''+'' sign after the surface name. The keyword ''BLEND'' indicates that the interior of the surface will be defined according to Coons [13] or a NURBS surface (nurs) or shape (shpe) is referenced. It should be mentioned that only nurbs or shape related surfaces can be meshed with unstructured triangles. Use a ''+'' or ''-'' in front of the lines or lcmbs to indicate the orientation. These signs will be corrected automatically if necessary. If the surface is intended for an unstructured mesh it is not necessary to care about the correct orientation of the lines and the number of edges is not limmited. If automatic name generation is desired, then use ''!'' instead of a name.