Entities 

GiD_EntitiesGroups assign|unassign|get|entity_groups
To handle the entities that belong to groups

Note: GiD_WriteCalculationFile could be interesting to tranverse an print data based on groups without the extra cost of GiD_EntitiesGroups serializing potentially big lists of entities.

• GiD_EntitiesGroups assign|unassign|get <group> ?-also_lower_entities? <over> <selection>

To add, remove or know entities of a group

• • GiD_EntitiesGroups assign <group> ?-also_lower_entities? <over> <selection>

To assing the selection of entities of kind over to the group
<group> is the full name of the group
<-also_lower_entities> is an optional flag, to select also all lower entities of the selected ones (e.g. curves and points of the selected surfaces)
<over> could be points, lines, surfaces, volumes, nodes, elements, faces, all_geometry, all_mesh
<selection> is a list of integer entity id's starting from 1.
In case of faces it is a list with 2 items, the first is the list of element id's and the second the list of face id's (the local number of the face on the element: a number from 1 to nfaces of the element)
In case of all_geometry is expected a list with 4 items with the list of ids of points, lines, surfaces and volumes.
In case of all_mesh is expected a list with 3 items with the list of ids of nodes, elements and faces, and for faces there are two subitems {element_ids face_ids}

• • GiD_EntitiesGroups unassign <group> ?-also_lower_entities? ?-element_type <types_allowed>? <over> ?<selection>?

To unassign the selection of entities of kind over of the group.
If -element_type <types_allowed> is specified then only the types of elements listed in <types_allowed> will be taken into account. <types_allowed> must be a list of triangle quadrilateral, etc.
If <selection> is missing, then all entities of kind <over> are unassigned of <group>

• • GiD_EntitiesGroups unassign all_geometry|all_mesh|all

all_geometry:To unassign all groups of all geometric entities
all_mesh: To unassign all groups of all mesh entities
all: To unassign all groups of all entities

• • GiD_EntitiesGroups get <group> <over> ?-count? ?-element_type <types_allowed>? ?-visible?

To get the list of entities of kind <over> that belong to <group>.
If <over> is faces then is obtained a list with 2 sublists: element id's and face id's
If <over> is all_geometry then is obtained a list with 4 sublists: point id's, line id's, surface id's and volume id's
If <over> is all_mesh then is obtained a list with 3 sublists: node id's, element id's, face id's (and face id's is a list with 2 items: element id's and face id's)
if -count is speficified, then only the number of objects is returned instead of its list.
if -element_type <types_allowed> is specified then only the types of elements listed in <types_allowed> will be taken into account. <types_allowed> must be a list of triangle quadrilateral, etc.
if -visible is specified, then only the entities visible must be taken into account

In fact it is returned an 'objarray': a Tcl_Obj object specialized for arrays, implemented as a Tcl package named 'objarray'. (for more information see scripts\objarray\objarray.pdf)

• GiD_EntitiesGroups entity_groups <over> <id>

To get the list of groups to which the entity <id> of type <over> belongs
<over> could be points, lines, surfaces, volumes, nodes, elements, faces
<id> is the entity number, starting from 1. In case of faces it is a list with tho items: {<element_id> <face_id>}, with <face_id> starting from 1