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nurs

       'nurs' [<name(char9)>|'!' ['DEFINE' ['COMPACT'] <u.deg> <v.deg> ->
                               <u.npnt> <v.npnt> <u.nknt> <v.nknt>]|
                              ['CONTROL' <u.index> <v.index> [<pnt>|<x y z>] ->
                              <weight>]|
                              ['KNOT' <U>|<V> <index> <value>]|
                              ['END']] |
              [ <!> <setname(containing surfaces)>]

This keyword is used to define a nurbs shape. Surfaces might use nurbs to define the interior geometry. There are two possible ways of definition. Either by using predefined point-names or by specifying the coordinates explicitly. When the coordinates are defined then the parameter ``COMPACT'' must be used as shown above but when the point names are used then this parameter must be omitted. CAD-interfaces might use this functionality.
There is also a small nurbs-building capability in cgx. It is possible to use surfaces which do not reference to a given nurbs to build one. This nurbs will follow the Coons-algorithm but can be modified by moving the interiour points. The surfaces must be stored in a set. For example
nurs ! surfaceSet
will define nurbs for all surfaces stored in the set surfaceSet.