CRBSPS ( dim, uorder, vorder, ncol, nrow, ctrl, uknots, vknots, nprops, props, 
===============================================================================
         bs, ifail )
         ===========

  Create B-surface from B-spline data

Receives:
  KI_int_dimension         *dim            --- dimension of control points
  KI_int_order             *uorder         --- order of surface in u
  KI_int_order             *vorder         --- order of surface in v
  KI_int_nitems            *ncol           --- number of cols of control points
  KI_int_nitems            *nrow           --- number of rows of control points
  KI_dbl_coefficients       ctrl[dim * ncol * nrow] --- control points
  KI_dbl_knots              uknots[]       --- knot vector for the rows
  KI_dbl_knots              vknots[]       --- knot vector for the columns
 <KI_int_nitems>           *nprops         --- number of surface properties
  KI_cod_papr               props[nprops]  --- array of surface properties

Returns:
  KI_tag_b_surface         *bs             --- B-surface
  KI_cod_error             *ifail          --- failure indicator

Specific errors:
  KI_bad_knots              Invalid knot vector
  KI_weight_le_0            weights are non positive
  KI_insufficient_points    insufficient control points
  KI_bad_parametric_prop    property not applicable

Description:
  This function creates a B-surface from B-spline data - i.e. a set
  of B-spline vertices (control points), and knot vectors for both the u and v
  directions. The surface may be either periodic or non-periodic, in either u
  or v, and the 'props' array supplies this information.

  Dimension of control points 'dim':
  . For rational surfaces 'dim'=4.
  . For non-rational surfaces 'dim'=3.

  Order of the surface in u and v respectively, 'uorder' and 'vorder':
  . The order is the degree + 1.
  . The minimum order is 2.

  Number of columns of control points 'ncol':
  . For surfaces with non-periodic rows 'ncol' >= 'uorder'.
  . For surfaces with periodic rows     'ncol' >=  3.
  . The number of control points in each row is 'ncol'.

  Number of rows of control points 'nrow':
  . For surfaces with non-periodic columns 'nrow' >= 'vorder'.
  . For surfaces with periodic columns     'nrow' >= 3.
  . The number of control points in each column is 'nrow'.

  Control points 'ctrl':
  . The control points are supplied row by row, each row containing 'ncol'
    vectors.
  . For non-rational surfaces, the vectors are points in 3-space and
    must be supplied [x0,y0,z0,x1,y1,z1,...]
  . For rational surfaces each vector contains a point in 3-space followed by a
    weight for the point. The points are supplied [x0,y0,z0,w0,x1,y1,z1,w1,...]
    The weight must be positive. Increasing the weight of a control point will
    pull the surface closer to that point.

  Knot vector for the rows 'uknots':
  . The knot values must form a non-decreasing sequence.
  . For non-periodic rows there must be ('ncol' + 'uorder') knot values,
    the maximum multiplicity of an internal knot value is ('uorder' - 1), and
    the maximum multiplicity of an end knot value is 'uorder'.
  . For periodic rows there must be ('ncol' + 1) knot values, and the
    maximum multiplicity of any knot value is ('uorder' - 1).  If the periodic
    knot has multiplicity greater than 1, repetitions must be given at the end
    of the knot vector.

  Knot vector for the columns 'vknots':
  . The knot values must form a non-decreasing sequence.
  . For non-periodic columns there must be ('nrow' + 'vorder') knot values,
    the maximum multiplicity of an internal knot value is ('vorder' - 1), and
    the maximum multiplicity of an end knot value is 'vorder'.
  . For periodic columns there must be ('nrow' + 1) knot values, and the
    maximum multiplicity of any knot value is ('vorder' - 1).  If the periodic
    knot has multiplicity greater than 1, repetitions must be given at the end
    of the knot vector.

  Number of properties 'nprops':
  . Gives the number of properties in the 'props' array.
  . There are only two properties (periodicity of rows and columns) and so
    'nprops' must be either 0, 1 or 2.

  Properties array 'props':
  . PAPRPU - the surface is periodic in u (i.e. the rows are periodic).
  . PAPRPV - the surface is periodic in v (i.e. the columns are periodic).

  In both cases, the default is non-periodic.