3 \page grouping_elements_page Grouping elements
5 In Mesh module it is possible to create groups of mesh entities:
6 nodes, edges, faces, volumes, 0D elements or balls. One group contains
7 elements of only one type. Groups, unlike sub-meshes, are exported
8 along with mesh entities into the files of following formats: MED, UNV,
9 and CGNS. The group has a color attribute which is used for
10 visualization only and is not exported.
12 There are three types of groups different by their internal
14 <li><b>Standalone group</b> is a static set of mesh entities. Its
15 contents can be explicitly controlled by the user. Upon removal of
16 the entities included into the group, e.g. due to modification of
17 meshing parameter, the group becomes empty and its content can be
18 restored only manually. Hence it is reasonable to create standalone
19 groups when the mesh generation is finished and mesh quality is
21 \warning Creation and edition of large standalone groups in
22 \ref creating_groups_page "Create group" dialog using manual edition
23 is problematic due to poor performance of the dialog.</li>
25 <li><b>Group on geometry</b> is associated to a sub-shape or a group of
26 sub-shapes of the main shape and includes mesh entities generated on
27 these geometrical entities. The association to a geometry is
28 established at group construction and cannot be changed. The group
29 contents are always updated automatically, hence the
30 group can be created even before mesh elements generation.</li>
31 <li><b>Group on filter</b> encapsulates a \ref filters_page "filter",
32 which is used to select mesh entities composing the group from the
33 whole mesh. Criteria of the filter can be changed at any time. The
34 group contents are always updated automatically, hence the group can
35 be created even before mesh elements generation.</li>
37 The group on geometry and group on filter can be converted to
40 \image html groups_in_OB.png "Groups of different types look differently in the Object Browser"
42 The following ways of group creation are possible:
44 - \subpage creating_groups_page "Create group" dialog allows creation of
46 \ref standalone_group "Standalone group",
47 \ref group_on_geom "Group on geometry" and
48 \ref group_on_filter "Group on filter" using dedicated tabs.
49 - \subpage create_groups_from_geometry_page "Create Groups from Geometry"
50 dialog allows creation of several groups on geometry at once.
51 - Standalone groups of all nodes and elements of the chosen sub-mesh
52 (type of elements depends on dimension of sub-mesh geometry) can
53 be created using <b>Mesh -> Construct Group</b> menu item (available
54 from the context menu as well).
55 - Standalone groups of any element type can be created basing on nodes
56 of other groups - using \subpage group_of_underlying_elements_page
57 "Group based on nodes of other groups" dialog.
58 - Standalone groups can be created by applying
59 \subpage using_operations_on_groups_page "Boolean operations" to
61 - Creation of standalone groups is an option of many
62 \ref modifying_meshes_page "mesh modification" operations.
64 The created groups can be later:
66 - \subpage editing_groups_page "Edited"
67 - \subpage deleting_groups_page "Deleted", either as an object or
68 together with contained elements.
69 - The group on geometry and group on filter can be
70 \ref convert_to_standalone "converted into the standalone" group.
71 - \ref importing_exporting_meshes_page "Exported" into a file as a
74 In the Object Browser, if an item contains more than one child group,
75 it is possible to sort the groups by name in ascending order
76 using <b>Sort children</b> context menu item.
78 \image html smesh_sort_groups.png "Sorting groups"
80 An important tool, providing filters for creation of standalone
81 groups and groups on filter is \ref selection_filter_library_page.