point on the paraboloid. It
        corresponds to a unique input site. </li>
    <li><em>point-at-infinity</em> - a point added above the
        paraboloid by option '<a href="qh-optq.html#Qz">Qz</a>'</li>
    <li><em>lower facet</em> - a facet corresponding to a
        Delaunay region. The last coefficient of its normal is
        clearly negative.</li>
    <li><em>upper facet</em> - a facet corresponding to a
        furthest-site Delaunay region. The last coefficient of
        its normal is clearly p