\page grouping_elements_page Grouping elements
-In Mesh module it is possible to create groups of mesh elements:
+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. The following ways of creation are
-possible:
-
-- by selecting the elements using filters and/or directly on the
- presentation in the VTK viewer, and/or by using elements of other
- mesh objects - \ref standalone_group "Standalone group"
- tab of \ref creating_groups_page "Create group" dialog.
-- by creating a group of elements generated on the chosen geometrical
- object - \ref group_on_geom "Group on geometry" tab of
- \subpage creating_groups_page "Create group" dialog and
- \subpage create_groups_from_geometry_page "Create Groups from Geometry"
- dialog.
-- by creating a group of elements satisfying to certain criteria -
- \ref group_on_filter "Group on filter" tab of
- \subpage creating_groups_page "Create group" dialog.
-- by creating groups of nodes and elements from the chosen submesh
- (type of elements depends on dimension of submesh geometry) -
- using <b>Mesh -> Construct Group</b> menu item (available in context
- menu as well).
-- by creating groups of entities from existing groups of superior
- dimensions - using \subpage group_of_underlying_elements_page
- "Create Group of Underlying Elements" dialog.
+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 explicitely controlled by the user. Upon removal of
+ the entities included into the group, the group becomes empty and
+ the user is to pay efforts to restore its contents. Hence it is
+ resonable 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 geomerty</b> is associated to one or a group of
+ sub-shapes of the main shape and includes mesh entities generated on
+ this geometrical entities. The association to geometry is
+ established at group construction and can't be changed. The group
+ contents is always up-to-date without user's efforts, hence the
+ group can be created even before mesh elements generation.</li>
+<li><b>Group on filter</b> encapsulates a 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 is always up-to-date without user's efforts, 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
+the 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 of all the three types:
+ \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
+ in 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:
- \subpage editing_groups_page "Edited"
-- \subpage using_operations_on_groups_page "Subjected to Boolean operations"
-- \subpage deleting_groups_page "Deleted"
+- \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 groups or sub-meshes container item has more
-than one child sub-object, it is possible to sort the children in
-ascending order. For this, select the parent object in the Object
+In the Object Browser, if groups container item includes more
+than one group, it is possible to sort the groups by name in
+ascending order. For this, select the groups container in the Object
Browser and choose <b>Sort children</b> context menu item.
-\image html smesh_sort.png "Sorting of sub-objects"
+\image html smesh_sort_groups.png "Sorting groups"
-An important tool, providing filters for creation of \b Standalone
-groups and groups <b>On Filter</b> is \ref selection_filter_library_page.
+An important tool, providing filters for creation of standalone
+groups and groups on filter is \ref selection_filter_library_page.
*/
