planar if the last coefficient of its normal is
nearly zero (see <a href="http://www.qhull.org/src/libqhull_r/user_r.h#ZEROdelaunay">qh_ZEROdelaunay</a>).

<p>See <a href=qh-impre.html#delaunay>Imprecision issues :: Delaunay triangulations</a>
for a discussion of precision issues.  Deleted vertices indicate
highly degenerate input.  They are listed in the summary output and
option '<a href="qh-optf.html#Fs">Fs</a>'.</p>

<p>To compute the Delaunay triangulation of points on a sphere,
compute their convex hu