\page grouping_elements_page Grouping elements
-In Mesh module it is possible to \subpage creating_groups_page "create groups of mesh elements":
-nodes, edges, faces or volumes:
-<ul>
-<li> by selecting the elements of the specified kind by their IDs or
-directly on the presentation in the VTK viewer - <b>Standalone group</b> tab of <b>Create group</b>
-dialog.</li>
-<li> by creating a group of elements of the selected type from all
-such elements of the chosen geometrical object - <b>Group on
-geometry</b> tab of <b>Create group</b> dialog.</li>
-<li> by creating several groups of elements (nodes,
-edges, faces and volumes) from the chosen submesh - using <b>Mesh -> Construct
-Group</b> Menu item. In this case groups of elements are created automatically.</li>
-</ul>
+In Mesh module it is possible to create groups of mesh entities:
+nodes, edges, faces, volumes, 0D elements or balls. One group contains
+elements of only one type. Groups, unlike sub-meshes, are exported
+along with mesh entities into the files of following formats: MED, UNV,
+and CGNS. The group has a color attribute which is used for
+visualization only and is not exported.
+
+There are three types of groups different by their internal
+organization:<ol>
+<li><b>Standalone group</b> is a static set of mesh entities. Its
+ contents can be explicitly controlled by the user. Upon removal of
+ the entities included into the group, e.g. due to modification of
+ meshing parameter, the group becomes empty and its content can be
+ restored only manually. Hence it is reasonable to create standalone
+ groups when the mesh generation is finished and mesh quality is
+ verified.
+ \warning Creation and edition of large standalone groups in
+ \ref creating_groups_page "Create group" dialog using manual edition
+ is problematic due to poor performance of the dialog.</li>
+
+<li><b>Group on geometry</b> is associated to a sub-shape or a group of
+ sub-shapes of the main shape and includes mesh entities generated on
+ these geometrical entities. The association to a geometry is
+ established at group construction and cannot be changed. The group
+ contents are always updated automatically, hence the
+ group can be created even before mesh elements generation.</li>
+<li><b>Group on filter</b> encapsulates a \ref filters_page "filter",
+ which is used to select mesh entities composing the group from the
+ whole mesh. Criteria of the filter can be changed at any time. The
+ group contents are always updated automatically, hence the group can
+ be created even before mesh elements generation.</li>
+</ol>
+The group on geometry and group on filter can be converted to
+a standalone group.
+
+\image html groups_in_OB.png "Groups of different types look differently in the Object Browser"
+
+The following ways of group creation are possible:
+
+- \subpage creating_groups_page "Create group" dialog allows creation of
+ a group of any type:
+ \ref standalone_group "Standalone group",
+ \ref group_on_geom "Group on geometry" and
+ \ref group_on_filter "Group on filter" using dedicated tabs.
+- \subpage create_groups_from_geometry_page "Create Groups from Geometry"
+ dialog allows creation of several groups on geometry at once.
+- Standalone groups of all nodes and elements of the chosen sub-mesh
+ (type of elements depends on dimension of sub-mesh geometry) can
+ be created using <b>Mesh -> Construct Group</b> menu item (available
+ from the context menu as well).
+- Standalone groups of any element type can be created basing on nodes
+ of other groups - using \subpage group_of_underlying_elements_page
+ "Group based on nodes of other groups" dialog.
+- Standalone groups can be created by applying
+ \subpage using_operations_on_groups_page "Boolean operations" to
+ other groups.
+- Creation of standalone groups is an option of many
+ \ref modifying_meshes_page "mesh modification" operations.
The created groups can be later:
-<ul>
-<li>\subpage editing_groups_page "Edited"</li>
-<li>\subpage using_operations_on_groups_page "Subjected to Boolean operations", or</li>
-<li>\subpage deleting_groups_page "Deleted"</li>
-</ul>
+- \subpage editing_groups_page "Edited"
+- \subpage deleting_groups_page "Deleted", either as an object or
+ together with contained elements.
+- The group on geometry and group on filter can be
+ \ref convert_to_standalone "converted into the standalone" group.
+- \ref importing_exporting_meshes_page "Exported" into a file as a
+ whole mesh.
+
+In the Object Browser, if an item contains more than one child group,
+it is possible to sort the groups by name in ascending order
+using <b>Sort children</b> context menu item.
-An important tool, providing filters for creation of \b Standalone
-groups is \subpage selection_filter_library_page</li>.
+\image html smesh_sort_groups.png "Sorting groups"
+An important tool, providing filters for creation of standalone
+groups and groups on filter is \ref selection_filter_library_page.
*/
