OUBLSS ( surfac, bltype, ssurf1, ssurf2, ssurf3, iipa12, iipa23, iipa31, 
=========================================================================
         nipars, irpa12, irpa23, irpa31, nrpars, sense, ifail )
         ======================================================

  Output blending surface.

Receives:
  KI_tag_surface           *surfac         --- blending surface

Returns:
  KI_cod_tybl              *bltype         --- blend type
  KI_tag_surface           *ssurf1         --- first supporting surface
  KI_tag_surface           *ssurf2         --- second supporting surface
 <KI_tag_surface>          *ssurf3         --- third supporting surface
  KI_tag_list_int          *iipa12         --- integer parameters for ssurf1,2
 <KI_tag_list_int>         *iipa23         --- integer parameters for ssurf2,3
 <KI_tag_list_int>         *iipa31         --- integer parameters for ssurf3,1
  KI_int_nitems            *nipars         --- length of int parameter lists
  KI_tag_list_dbl          *irpa12         --- double parameters for ssurf1,2
 <KI_tag_list_dbl>         *irpa23         --- double parameters for ssurf2,3
 <KI_tag_list_dbl>         *irpa31         --- double parameters for ssurf3,1
  KI_int_nitems            *nrpars         --- length of real parameter lists
  KI_cod_logical           *sense          --- surface sense. explained below
  KI_cod_error             *ifail          --- failure code

Specific errors:
  KI_wrong_sub_type         surface is not a blend

Description:

  The blending surface definition is output with a type-code, 'bltype',
  that enables it to be interpreted as follows:

              TYBL1B      blended edge

  The length of the lists 'iipa12', 'iipa23' and 'iipa31' is given by 'nipars'.
  In the current version 'nipars' will always be 3. The length of the lists
  'irpa12', 'irpa23', and 'irpa31' is given by 'nrpars'. In the current version
  'nrpars' will always be 5.

  As from version 3.0, offset blends ( ITYPE = 1 ) have been withdrawn.

  Contents of the lists 'iipaXY'
  ------------------------------
      position      contents and its significance
      in list
         1          ITYPE 3 => rolling ball blend

  Contents of the lists 'irpaXY'
  ------------------------------

  ITYPEs 3  - Rolling ball blends

      position      value and its significance
      in list
         1      radiusX           The radii of the blend surface. RadiusX and
         2      radiusY           radiusY always have the same magnitude but
                                  may differ in sign.

  The surface junction which is blended is indicated by the signs of the
  radii. A positive value signifies that the blend lies on the same side
  of the supporting surface as the supporting surface's normal. (The supporting
  surface's normal direction is affected by the surface's sense).


  Summary of the data returned
  ----------------------------

        Return:             ssurfX              iipXX,irpXX
                       1      2    3         12      23     31
        SSTYPE:      ==========================================
        TYBL1B         S     S     -          L       -      -

              S - Tag of surface
              - - Null tag
              L - List of length 'nipars' or 'nrpars'

  The normal to a blending surface whose sense is KI_true is away from the
  centre of curvature.