Examples
========

**Example 1 (topological and logical criteria) :**

Let ma be a mesh that already contains the mesh groups:


.. code-block:: text

    M1 M2 M3

and node groups:


.. code-block:: text

    N1 N2 N3


.. code-block:: text

    ma = DEFI_GROUP (reuse = ma, MAILLAGE = ma,
CREA_GROUP_MA = (_F (NOM = NM1, GROUP_MA = (GMA7, GMA9,...)),
_F (NOM = NM2, UNION = (M1, NM1)),
_F (NOM = NM3, DIFFE = (NM2, M2)),),
CREA_GROUP_NO = _F (TOUT_GROUP_MA = 'OUI'),


.. code-block:: text

    ma = DEFI_GROUP (reuse = ma, MAILLAGE = ma,
CREA_GROUP_MA = _F (NOM = NM4, GROUP_MA = (GMA7, GMA11, GMA13))
CREA_GROUP_NO = (_F (NOM = NN1, INTERSEC = (NM1, N1)),
_F (GROUP_MA = NM4)))

After these two calls to command DEFI_GROUP, the mesh then contains:


* mesh groups:


* M1, M2, M3 (initial)


* NM1 = (stitches: MA7, MA9,...)


* NM2 = M1 "union" NM1


* NM3 = NM2 "minus" M2


* NM4 = (MAILLES: MA7, MA11, MA13)


* node groups:


* N1, N2, N3 (initial)


*M1, M2, M3, NM1, NM2, NM3: group_no containing group_ma nodes with**same names**. These group_nos are created by the 1st command DEFI_GROUP.


* NN1 = NM1 "intersection" N1


* NM4 = (nodes in group_ma NM4)

**Example 2 (geometric criteria) :**


.. code-block:: text

    ma = DEFI_GROUP (reuse = ma, MAILLAGE = ma,
CREA_GROUP_MA = (_F (NOM = facesup, OPTION = 'FACE_NORMALE',
VECT_NORMALE = (0., 0., 1. )),
_F (NOM = S01, OPTION = 'SPHERE',
POINT = (0., 0., 0.), RAYON = 1.),),
CREA_GROUP_NO =( _F (NOM = BO_S01, OPTION = 'ENV_SPHERE',
POINT =( 0.,0.,0.) , RAYON =1. , PRECISION =0.01),
_F (NOM = S01_1, GROUP_MA = S01),
_F (NOM = S01_2, OPTION = 'ENV_SPHERE',
POINT =( 0.,0.,0.) , RAYON =0.5, PRECISION =0.5),),
)

After DEFI_GROUP the ma mesh will contain 2 new GROUP_MA and 3 new GROUP_NO:


* facesup contains facets whose normal is oriented according to :math:`\mathrm{OZ}` (towards :math:`Z>0`),


*S01 contains**all**the cells where**one of the nodes** belongs to the sphere with radius 1. and centered in :math:`O` (origin of the axes),


* B0_S01 is the group of nodes that are in the vicinity of the envelope of the previous sphere (S01),


* S01_1 is the group of all the nodes in the cells in the S01 group of elements; be careful: some nodes in this group may be outside the sphere!


* S01_2 is the group of nodes included in the S01 sphere: :math:`∣d(M,O)-0.5∣\le 0.5`