--- /dev/null
+.. _tui_generate_flat_elements_page:
+
+**********************
+Generate flat elements
+**********************
+
+
+.. _tui_double_nodes_on_group_boundaries:
+
+Double nodes on groups boundaries
+#################################
+
+Double nodes on shared faces between groups of volumes and create flat elements on demand.
+
+The list of groups must contain at least two groups. The groups have to be disjoint: no common element into two different groups.
+
+The nodes of the internal faces at the boundaries of the groups are doubled. Optionally, the internal faces are replaced by flat elements.
+
+Triangles are transformed into prisms, and quadrangles into hexahedrons.
+
+The flat elements are stored in groups of volumes.
+
+These groups are named according to the position of the group in the list:
+the group j_n_p is the group of the flat elements that are built between the group \#n and the group \#p in the list.
+If there is no shared faces between the group \#n and the group \#p in the list, the group j_n_p is not created.
+All the flat elements are gathered into the group named "joints3D" (or "joints2D" in 2D situation).
+The flat element of the multiple junctions between the simple junction are stored in a group named "jointsMultiples".
+
+This example represents an iron cable (a thin cylinder) in a concrete bloc (a big cylinder).
+The big cylinder is defined by two geometric volumes.
+
+.. _generate_flat_elements.py:
+
+``generate_flat_elements.py``
+
+.. literalinclude:: ../../../examples/generate_flat_elements.py
+ :linenos:
+ :language: python
+
+:download:`../../../examples/generate_flat_elements.py`
+
+Here, the 4 groups of volumes [Solid_1_1, Solid_2_1, Solid_3_1, Solid_4_1] constitute a partition of the mesh.
+The flat elements on group boundaries and on faces are built with the
+2 last lines of the code above.
+
+If the last argument (Boolean) in DoubleNodesOnGroupBoundaries is set to 1,
+the flat elements are built, otherwise, there is only a duplication of the nodes.
+
+To observe flat element groups, save the resulting mesh on a MED file and reload it.
+
+
