PK_CURVE_is_isoparam

PK_ERROR_code_t                 PK_CURVE_is_isoparam
(
--- received arguments ---
PK_CURVE_t                      curve,          --- curve to test
PK_INTERVAL_t                   bounds,         --- range to bound the curve
PK_SURF_t                       surf,           --- embedding surface
const PK_CURVE_is_isoparam_o_t *options,        --- options structure

--- returned arguments ---
PK_CURVE_is_isoparam_t   *const is_isoparam,    --- whether given curve is an
                                                --- isoparameter
double                   *const iso_value,      --- value of the constant
                                                --- surface parameter
PK_PARAM_direction_t     *const iso_direction,  --- which surface parameter
                                                --- (u or v) is constant
PK_INTERVAL_t            *const param_interval, --- interval in the surface's
                                                --- non-constant parameter
                                                --- covered by bounded curve
PK_isoparam_alignment_t  *const param_alignment --- how the the surface's non-
                                                --- constant parameter varies
                                                --- with respect to the curve
                                                --- parameterisation.
)


Tests whether a bounded curve lying within a surface is a constant-parameter
curve (i.e., an isoparameter) for that surface.

This function does not support facet geometry [NF]


Specific Errors:
    PK_ERROR_not_on_surface     Could not ascertain that 'curve' lies
                                entirely within 'surf' over the given
                                parameter 'bounds'.
                                (MILD)

    PK_ERROR_bad_parameter      Given 'bounds' lie outside 'curve''s domain
                                of definition.
                                (MILD)

    PK_ERROR_interval_le_0      Length of 'bounds' <= 0.
                                (MILD)

    PK_ERROR_curve_too_short    Segment of 'curve' too short for analysis.
                                (MILD)

    PK_ERROR_not_implemented    Unavailable functionality called.
                                (MILD)


This function tests whether a given segment of 'curve' with parameter interval
'bounds' is an isoparameter on a surface 'surf'. If so, it also returns which
surface parameter is constant, and that parameter's value.

In order for a curve to be identified as an isoparameter of a surface, it
must (1) be an exact isoparameter; and (2) cover a single, well-defined range
in the surface's parameter space (so it may not, for example, cross a seam in
a closed but non-periodic surface).

The curve's 'bounds' should be such that the curve segment lies entirely
within the surface. If not, the error code PK_ERROR_not_on_surface will be
returned.

'is_isoparam' is set to PK_CURVE_ask_isoparam_yes_c if the curve is determined
to be an isoparameter of the surface. It is set to PK_CURVE_ask_isoparam_no_c
otherwise.

'iso_value' is the value of the constant parameter, if the curve is an
isoparameter of the surface. Otherwise, it is set to zero.

'iso_direction' indicates which of the surface's parameters is constant, and
is one of either PK_PARAM_direction_u or PK_PARAM_direction_v, if the curve is
an isoparameter. Otherwise, it is set to PK_PARAM_direction_u.

'param_interval' is the interval on the surface's non-constant parameter
occupied by the curve. It is only computed and set if the flag 'want_interval'
in 'options' is set to PK_LOGICAL_true. It returns an interval [0.0, 0.0] if
the curve is not an isoparameter.

'param_alignment' is PK_isoparam_alignment_aligned_c if the surface's
non-constant parameter increases with increasing curve parameter, or
conversely PK_isoparam_alignment_opposed_c. It is set to
PK_isoparam_alignment_unset_c if the curve is not an isoparameter.
'param_alignment' is only computed and set if the flag 'want_alignment' in
'options' is set to PK_LOGICAL_true.

This function does not support foreign geometry. If either 'curve' or 'surf'
is foreign, the error code PK_ERROR_not_implemented will be returned.