NAME

       tetrahedron - reference element (rheolef-7.2)

DESCRIPTION

       The edge reference_element(6) is

           K = { 0 < x0 < 1 and 0 < x1 < 1-x0 and 0 < x2 < 1-x0-x1 }

                             x2
                           .
                         ,/
                        /
                      3
                    ,/|`\\
                  ,/  |  `\\
                ,/    '.   `\\
              ,/       |     `\\
            ,/         |       `\\
           0-----------'.--------2 --> x1
            `\\.         |      ,/
               `\\.      |    ,/
                  `\\.   '. ,/
                     `\\. |/
                        `1
                           `\\.
                             ` x0

        The orientation is such that the trihedral (01, 02, 03) is direct, and all faces, see
       from exterior, are in the direct sens. See

           P. L. Georges,
           Generation automatique de maillages,
           page 24-, coll RMA, 16, Masson, 1994.

        This three-dimensional reference_element(6) is then transformed, after the Piola
       geometrical application, as a tetrahedron in a physical space, as a geo_element(6).

       Curved high order Pk tetrahedra (k >= 1) in 3D geometries are supported. These tetrahedra
       have additional edge-nodes, face-nodes and internal volume-nodes. These nodes are numbered
       as: first vertex, then edge-node, following the edge numbering order and orientation, then
       face-nodes following the face numbering order and orientation, and finally the face
       internal nodes, following the tetrahedron lattice. See below for edges and faces numbering
       and orientation.

                      3
                    ,/|`\\
                  ,/  |  `\\
                ,7    '.   `9
              ,/       |     `\\
            ,/         8       `\\
           0--------6--'.--------2
            `\\.         |      ,/
               `\\.      |    ,5
                  `4.   '. ,/
                     `\\. |/
                        `1
                     P2

        Notice that the edge-nodes and face-nodes numbering slightly differ from those used in
       the gmsh mesh generator when using high-order elements. This difference is handled by the
       msh2geo_1 mesh file converter.

IMPLEMENTATION

       This documentation has been generated from file fem/geo_element/tetrahedron.icc

       const size_t dimension = 3;
       const Float  measure = Float(1.)/Float(6.);
       const size_t n_vertex = 4;
       const point vertex [n_vertex] = {
               point( 0, 0, 0 ),
               point( 1, 0, 0 ),
               point( 0, 1, 0 ),
               point( 0, 0, 1 ) };
       const size_t  n_face = 4;
       const size_t face [n_face][3] = {
               { 0, 2, 1 },
               { 0, 3, 2 },
               { 0, 1, 3 },
               { 1, 2, 3 } };
       const size_t  n_edge = 6;
       const size_t edge [n_edge][2] = {
               { 0, 1 },
               { 1, 2 },
               { 2, 0 },
               { 0, 3 },
               { 1, 3 },
               { 2, 3 } };

AUTHOR

       Pierre  Saramito  <Pierre.Saramito@imag.fr>

COPYRIGHT

       Copyright   (C)  2000-2018  Pierre  Saramito  <Pierre.Saramito@imag.fr> GPLv3+: GNU GPL
       version 3 or later  <http://gnu.org/licenses/gpl.html>.  This  is  free  software:  you
       are free to change and redistribute it.  There is NO WARRANTY, to the extent permitted by
       law.