PK_BSURF_add_u_knot

PK_ERROR_code_t PK_BSURF_add_u_knot
(
--- received arguments ---
PK_BSURF_t      bsurf,      --- bsurf
double          u           --- U split parameter

--- returned arguments ---
)


This modifies the given 'bsurf' by inserting a knot at the given 'u' split
parameter.


Specific Errors:
    PK_ERROR_is_attached            'bsurf' is attached to topology (MILD)
    PK_ERROR_bad_parameter          bad 'u' parameter given (MILD)
    PK_ERROR_bad_knots              invalid knot multiplicity (MILD)


This function modifies a B-surface by inserting a U knot, resulting in
the addition of a row of patches.
The shape of the B-surface is not changed.

The parameter 'u' at which the new knot is to be inserted must be within the
range as given by PK_SURF_ask_params.

The new knot must not increase the multiplicity of any existing knot to more
than the order for an end knot, or order-1 for an internal knot.

If 'u' lies within a patch then a new row of patches will be added to the
surface.

If 'u' lies on a patch boundary then the row of patches added will be null.
Adding a null segment to a surface only affects the B-spline
representation (it duplicates a knot).


A B-surface cannot be modified if it is attached to topology.