struct PK_FACE_tracking_r_s
    {
    PK_FACE_t   original_face;
    int         n_times_instanced;
    PK_FACE_t  *instanced_faces;
    int        *instance_index;
    };
typedef struct PK_FACE_tracking_r_s PK_FACE_tracking_r_t;



For a tool face which is instanced at least once in the resultant body, this
structure gives those faces which are instanced copies of that face and which
instance they belong to.


Description of fields:



original_face     The original face in the tool body (unmodified).


n_times_instanced Total number of times instanced copies of this face appear
                    in the resultant body, if a face fragments then each
                    fragment has a separate entry.


instanced_faces   The instanced faces of original_face.


instance_index    Indices of instanced_faces, faces appearing in the
                    instanced copy corresponding to the first transform
                    in the given array will have an index value of 0, those
                    corresponding to the second transform will have an index
                    value 1 and so on.