
plsurf3d: Plot shaded 3-d surface plot 

DESCRIPTION:

    Plots a three dimensional shaded surface plot within the environment
    set up by plw3d.  The surface is defined by the two-dimensional array
    z[
    nx][
    ny], the point z[i][j] being the value of the function at (
    x[i], 
    y[j]).  Note that the points in arrays x and y do not need to be
    equally spaced, but must be stored in ascending order. For further
    details see the PLplot documentation. 

SYNOPSIS:

plsurf3d(x, y, z, nx, ny, opt, clevel, nlevel)

ARGUMENTS:

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

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

    z (PLFLT **, input) :    Pointer to a vectored two-dimensional array
    with set of function values. 

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

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