PK_ERROR_code_t                 PK_BSURF_ask_splinewise
(
--- received arguments ---
PK_BSURF_t                      bsurf,              --- b-surface

--- returned arguments ---
PK_BSURF_splinewise_sf_t *const bsurf_splinewise_sf --- b-surface standard form
)


This function returns the splinewise standard form of a b-surface.


Specific Errors:
    PK_ERROR_unsuitable_entity      degree of surface is greater than 3
                                    in at least one parametric direction or
                                    degree is less than 3 and surface has more
                                    than one segment in that parametric
                                    direction
    PK_ERROR_bad_knots              surface has unsuitable knot vector


Takes a b-surface and returns its splinewise standard form.
Refer to the documentation of PK_BSURF_splinewise_sf_t.

Not all b-surfaces have a splinewise standard form.  All b-surfaces created by
PK_BSURF_create_splinewise have splinewise standard forms.  The following
conditions are required for a surface to have a splinewise standard form:

  - it must be non-rational.
  - in each parametric direction:
       - it must be of cubic or lower degree.
       - it must have continuous first and second derivatives (note that for a
         surface which is linear or quadratic in this direction it may only
         have one segment)
       - if the surface is periodic it must not have any repeated knots.
       - if the surface is non-periodic it may only have repeated knots at the
         ends.