PK_FACE_set_pair_t

struct PK_FACE_set_pair_s
    {
    int          n_faces1;   --- Number of faces in first set
    PK_FACE_t   *faces1;     --- First set of faces
    int          n_faces2;   --- Number of faces in second set
    PK_FACE_t   *faces2;     --- Second set of faces
    PK_BODY_t    sheet;      --- Sheet to be trimmed
    PK_LOGICAL_t sheet_pretrimmed;
                             --- Whether 'sheet' is already trimmed
    };
typedef struct PK_FACE_set_pair_s PK_FACE_set_pair_t;



This data structure contains a pair of sets of faces and its
corresponding neutral sheet.

Used in:

PK_BODY_trim_neutral_sheets
PK_BODY_trim_neutral_sheets_2

The faces in 'faces1' and 'faces2' will specify the way the neutral sheet body
given in the field 'sheet' should be trimmed.  Each face set must
contain at least one face and all the faces must belong to the same
solid body. 'sheet' may not be PK_ENTITY_null.

The value of the logical field 'sheet_pretrimmed' indicates whether
the neutral sheet is to be trimmed.  If it is PK_LOGICAL_true, then
trimming of the neutral sheet is not required but the definition of
the face set pair is required to specify how adjacent neutral sheets
are to be trimmed.  If the value of 'sheet_pretrimmed' is
PK_LOGICAL_false, then the neutral sheet is required to be trimmed.

The neutral sheet should be aligned so that its face normals broadly agree
with those of the first set and are opposed to those of the second set.
Expressing this in another way: the first face set lies in front of ( or on )
the neutral sheet and the second set lies behind ( or on ) the neutral sheet.
If the neutral sheet has been made from sets of faces on a solid body using
either PK_FACE_make_neutral_sheet_2 or PK_FACE_offset_2 then this will be the
case.