DATE     97/04/15
     Operateur TRIANGULATION
     -----------------------
     
     SURF1 = TRIA LIG1 (N1) ;


    Description :
    ____________

    The  TRIANGULATION  operator  constructs  a mesh  of a planar 
 domain which is defined by its  boundary (LIG1 object).  No node 
 is added on the boundary, nodes  are  added in  the interior  to 
 improve the shape of the triangles. The number of added nodes is 
 kept minimal and can be limited by N1 value.
 
    Contents :
    __________

    LIG1 : object of MAILLAGE type. It is composed of one or more 
 closed lines. Their orientation and  order  can  vary. LIG1  may 
 contain isolated edges and open lines. The edges are imposed and 
 the resulting mesh (SURF1) will contain them.Of course they must 
 be situated within the given boundary.
 
   N1   : object of ENTIER type.It is the maximum number of nodes 
 the resulting mesh can have. It must be greater  or equal to the 
 number of nodes of the existing mesh (LIG1).
 
    Note :
    ______

    The   TRIANGULATION   operator  generates  a  low  number  of 
 triangles;  it is not recommended to use the result directly for 
 finite element computation.  It  is  recommended  to compute the 
 size function  first  and  then adapt the element size with RAFT 
 operator.
 
    The density computed at each node of the mesh is the  current 
 density (see DENS). It can be positive or nul (unknown).

    TRIANGULATION works only on linear elements :  LIG1  must  be 
 composed of SEG2 type and SURF1 will be composed of  TRI3  type.