PK_ERROR_code_t     PK_FACE_is_uvbox
(
--- received arguments ---
PK_FACE_t           face,       --- face for which uvbox required

--- returned arguments ---
PK_LOGICAL_t *const is_uvbox,   --- whether face is parametric rectangle
PK_UVBOX_t   *const uvbox       --- faces uvbox if `is_uvbox is
                                --- PK_LOGICAL_true
)


This function detects whether a face is parametrically rectangular.


Specific Errors:
    PK_ERROR_no_geometry            face has no geometry attached


If is_uvbox is returned as PK_LOGICAL_true then uvbox will
contain the parameter limits of the rectangular area of the surface in
which the face is defined.

If is_uvbox is returned as PK_LOGICAL_false then all the elements of
uvbox will be 0.0.

PK_FACE_is_uvbox does not guarantee to detect that a face is parametrically
rectangular but it will never claim a face is parametrically rectangular
when it is not.