struct PK_boolean_region_select_o_s
    {
    int                          o_t_version;       --- version number
    PK_boolean_region_t          select_type;       --- (PK_boolean_include_c)
    int                          n_region_selectors;--- (0)
    const PK_TOPOL_t            *selectors;         --- (NULL)
    const PK_boolean_select_t   *selector_types;    --- (NULL)
    int                          n_help_points;     --- (0)
    const PK_VECTOR_t           *help_points;       --- (NULL)
    };
typedef struct PK_boolean_region_select_o_s PK_boolean_region_select_o_t;




This option structure is used to identify regions of the tool body to be
included or excluded from a boolean.


A region is this context is a boundary faceset which lies wholly inside or
outside the target body. (Tool faces which intersect the target body have
been split by the boolean: the resultant faces lie wholly inside or outside
the target body)

Each region is identified by a single face, edge or vertex which is interior
to it; it is not possible to specify some regions for inclusion and some
for exclusion, they will all be either included or excluded.

Description of fields:



select_type        Indicates whether to include or exclude specified regions,
                     permitted values are

                     PK_boolean_include_c
                     PK_boolean_exclude_c


n_region_selectors The number of topological entities supplied.


selectors          Topological entities which each uniquely identify a
                     region. The array may contain a mixture of faces, edges
                     or vertices, but no other types.
                     The first n_help_points elements of this array are
                     associated with the elements of the help_points array.
                     If a help point is not to be associated with any tool
                     face, then the appropriate element of this array must
                     be set to PK_ENTITY_null.



selector_types     Indicates the type of region selection. This array may
                     be null or contain n_region_selectors elements.
                     If a null array is specified, then a default type of
                     PK_boolean_select_specific_c is assumed.
                     Permitted values are,

                     PK_boolean_select_specific_c
                     PK_boolean_select_adjacent_c
                     PK_boolean_select_propagate_c

                     The PK_boolean_select_propagate_c type is only
                     valid for faces and edges specified as regions.


n_help_points      The number of help points (vectors) supplied.


help_points        Help points (vectors) which, when combined with the
                     appropriate topological entity from the selectors
                     array, unambiguously identifies a region.
                     The elements of this array are associated with the
                     first n_help_points of the selectors array.

                     Help points may only be associated with a face. If
                     a help point is associated with PK_ENTITY_null,
                     then the tool face closest to the help point is
                     located and used as the face.