
plfsurf3d: Plot shaded 3-d surface plot 

DESCRIPTION:

    This function is used in example 8. 

SYNOPSIS:

plfsurf3d(x, y, zops, zp, nx, ny, opt, clevel, nlevel)

ARGUMENTS:

    x (const PLFLT *, input) :      Pointer to set of x coordinate values at
    which the function is evaluated. 

    y (const PLFLT *, input) :      Pointer to set of y coordinate values at
    which the function is evaluated. 

    zops (PLF2OPS, input) :    Pointer to a function for processing the
    data contained in zp. 

    zp (PLPointer, input) :    Pointer to the data to be plotted, either
    as a vectored  two-dimensional array with set of function values
    or as a PLfGrid2 structure. 

    nx (PLINT, input) :    Number of x values at which function is
    evaluated. 

    ny (PLINT, input) :    Number of y values at which function is
    evaluated. 

    opt (PLINT, input) :    Determines the way in which the surface is
    represented. To specify more than one option just add the options,
    e.g. FACETED + SURF_CONT opt=FACETED: Network of lines is drawn
    connecting points at which function is defined. 
        opt=BASE_CONT: A contour plot is drawn at the base XY plane
        using parameters 
    nlevel and 
    clevel. 
        opt=SURF_CONT: A contour plot is drawn at the surface plane
        using parameters 
    nlevel and 
    clevel. 
        opt=DRAW_SIDES: draws a curtain between the base XY plane and
        the borders of the plotted function. 
        opt=MAG_COLOR: the surface is colored according to the value
        of Z; if MAG_COLOR is not used, then the default the surface
        is colored according to the intensity of the reflected light
        in the surface from a light source whose position is set using
        pllightsource. 


    clevel (const PLFLT *, input) :    Pointer to the array that defines
    the contour level spacing. 

    nlevel (PLINT, input) :    Number of elements in the clevel array. 
