### `plsurf3d`: Plot shaded 3-d surface plot

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

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 Section called Three Dimensional Surface Plots in Chapter 3.

 `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.

Redacted form: `plsurf3d(x, y, z, opt, clevel)`

This function is used in example 8.