PK_ERROR_code_t                  PK_FACE_replace_surfs_2
(
--- received arguments ---
int                              n_faces,        --- number of faces
const PK_FACE_t                  faces[],        --- faces
const PK_SURF_t                  surfs[],        --- replacement surfaces
const PK_LOGICAL_t               senses[],       --- surface orientation
double                           tolerance,      --- tolerance for operation
const PK_FACE_replace_surfs_o_t *options,        --- options

--- returned arguments ---
PK_TOPOL_track_r_t        *const tracking,       --- tracking information
PK_FACE_replace_surfs_r_t *const results         --- status information
)


This function replaces the geometry of the given faces with the
supplied surfaces.

NOTE: This function supersedes PK_FACE_replace_surfs, which is now obsolete.


Specific Errors:
    PK_ERROR_tool_faces_many_bodies   faces do not belong to a single body
    PK_ERROR_not_implemented          user options not implemented



Introduction
All geometry of the given faces is replaced by the given geometry
in surfs. The surface orientation with respect to the face is
specified by the logical value in senses.

The number of surfaces and sense flags passed to the function, via the
surfs and senses arguments, must be identical to the number faces
in the faces array.

The geometry of the edges and vertices connected to the modified faces
will be deleted and recalculated. Where edges are adjacent to faces whose
geometry is being replaced, the edge curves are re-computed as the
intersection of the face surfaces.

Where edges or faces (sharing a vertex or edge at the boundary of the
faces to be modified) have geometry which is inextendable, it may not
be possible to recalculate vertices or edges. This is because the curve
or surface do not intersect the new surface. If such edges have a user
defined tolerance, this is likely to occur since SP-curves are
inextendable.

If the given faces are on a sheet body, they must not share an edge with
any rubber faces.

Surface Sense Parameter

The sense flag for a particular face/surface combination is interpreted as
follows :

 o PK_LOGICAL_true
   When the new surface is attached to the face, the face normal must be
   in the same direction as the natural surface normal (as calculated by
   the function PK_SURF_eval_with_normal).

 o PK_LOGICAL_false
   When the new surface is attached to the face, the face normal must be
   in the opposite direction to the natural surface normal (as calculated by
   the function PK_SURF_eval_with_normal).


Checking options
The extent to which checking is applied to the body is specified by
the check_fa_fa field of the option structure. At present
check_fa_fa field can only be used to turn on or off face-face
checking, by setting it to PK_check_fa_fa_yes_c or PK_check_fa_fa_no_c
respectively.  If face-face checking is turned on, then face-face
checks are done on the body in addition to default checks.  For most
applications face-face checking will be tuned off, which will give an
adequate level of checking.

Tracking Information
The function returns tracking information relating to which topology
was split, deleted and created. For more information regarding
these structures, please refer to the PK documentation for the
PK_TOPOL_track_r_t structure.

Returned Status and Error Information
If this function returns a value of PK_ERROR_no_errors, the result of
the "replace surface" operation will be indicated by the value of the
status field within the results structure.

There are two values for the status field which can indicate a
successful operation :

 o PK_local_status_ok_c      : Indicates that the operation was successful
                               and the modified body is valid.

 o PK_local_status_nocheck_c : Indicates that the operation was successful,
                               but the check_fa_fa field in the option
                               structure was set to PK_check_fa_fa_no_c.

The remaining `PK_local_status_...' codes indicate some failure. The failure
code is normally accompanied by an array of entities which indicate where
the failure or problem occurs. For more information regarding these failure
codes and the returned error entities, please refer to the PK documentation
for the PK_FACE_replace_surfs_r_t structure.