DATE     94/01/10

    Opérateur ARETE                            See also :TRAC 
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                                                         CONT 

    ARET1 = ARETE VOLU1 ( TETA ) ;


    Description :
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    The ARETE operator constructs a mesh composed of SEG2 elements
    which represent the sharp edges of a three-dimensional mesh.
    In this operator, an edge is considered to be sharp whenever
    the difference of angle between the normals of the adjacent 
    facets is greater than a boundary TETA equalling 20 degrees by
    default.

    Contents :
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    ARET1 : MAILLAGE type object containing only SEG2 elements
            representing the sharp edges

    VOLU1 : three-dimensional MAILLAGE type object

    TETA  : angle criterion in degrees (FLOTTANT type)