🚀 go-pugleaf

Using SunCore to demonstrate a certain convergence in 3D I noted the
zbuffer procedure. It seemed to me the ideal solution to make a nice
picture without having to study the underlying algorithms.  I have
succeeded in plotting a number of 3D polygons, however, after closer
examination, I don't understand how to use the zbuffer procedure (from
C).
Can anybody explain to me (in a clearer way than the manual does) how
the parameters should be used, especially xlist and zlist?  Are xlist
and zlist input or output? Must xlist and zlist be initialized?
I have included a description from the manual below.
Please include some simple sort of example, if available.
Please send responses directly to POMPE@HLERUL5.BITNET.
Thanx.
                                                 Kees Pompe
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Set Z Buffer Cut

set_zbuffer_cut(surface_name, xlist, zlist, n)
struct vwsurf *surface_name;
float xlist [], zlist [];
int n;

set_zbuffer_cut specifies a cutaway view of 3D polygon objects when
hidden surfaces are being removed. set_zbuffer_cut specifies an array
of depths in NDC space. Any parts of objects which are closer to the
viewer than this piecewise-linear function are clipped away.

xlist is assumed to be monotonically increasing. This function
specifies a piecewise-linear cutaway threshold in the z coordinate,
which, given any x coordinate, is constant in y. The default cutaway
depth is 0 for all values of x. Values of x less than xlist [0] or
greater than xlist [n-1] will have the default depth.  The view
surface must have been initialized with the hidden flag on.
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