PK_ERROR_code_t PK_SURF_eval_grid
(
--- received arguments ---
PK_SURF_t       surf,        --- surface
int             n_u,         --- number of u parameters
const double    u[],         --- u paramters
int             n_v,         --- number of v parameters
const double    v[],         --- v parameters
int             n_u_derivs,  --- number of u derivatives
int             n_v_derivs,  --- number of v derivatives
PK_LOGICAL_t    triangular,  --- triangular derivative array required

--- returned arguments ---
PK_VECTOR_t     p[]          --- points
)


This function evaluates points on a rectangular grid of parameters on the given
surface.


Specific Errors:
    PK_ERROR_bad_parameter            cannot evaluate parameters that are out
                                      of range on non_periodic and
                                      non_extendable surfaces.
    PK_ERROR_too_many_derivatives     too many derivatives requested
    PK_ERROR_eval_failure             internal evaluator failure


n_u_derivs and n_v_derivs must be zero.

It is not necessarily required that the supplied parameters lie inside the
ranges as given by PK_SURF_ask_params.  If the surface is
PK_PARAM_periodic_yes_c or PK_PARAM_periodic_seamed_c in a parametric direction
then any value is acceptable for that parameter.  If a parameter is outside
the range but the surface is PK_PARAM_bound_extendable_c in that parametric
direction, then the evaluation will be performed on the surface extension.

The return argument p is a vector array returning the points, the
array being filled as follows:

    p[0]       is the point evaluated at     u[0],      v[0]
    p[1]       is the point evaluated at     u[1],      v[0]
     .                                         .          .
     .                                         .          .
     .                                         .          .
    p[n_u]     is the point evaluated at     u[0],      v[1]
    p[n_u+1]   is the point evaluated at     u[1],      v[1]
     .                                         .          .
     .                                         .          .
     .                                         .          .
    p[(n_u*n_v)-1] is the point evaluated at u[n_u-1],   v[n_v-1]