FUNCTION VOID DiffShad (nShades, nPoints,
                        Slope,
                        Window,
                        Coords, Trans,
                        DifShadSky, DifShadGrd, THREE, FOUR)

/* Calculate reduction factors DifShadSky, DifShadGrd
   due to shading, separate for radiation from sky and from ground. */

  LANGUAGE F77

  INPUT 
     INT   nShades, nPoints, THREE, FOUR;
     FLOAT Slope,
           Window[Three,Four],
           Coords[THREE,nPoints], Trans[nShades];

  OUTPUT
     FLOAT DifShadSky, DifShadGrd;

  EXTERNAL DiffShad (nShades, nPoints,
                     Slope,
                     Window,
                     Coords, Trans,
                     DifShadSky, DifShadGrd, THREE, FOUR)
END_FUNCTION