></em>. The initial value
                    is <code class="constant">GL_KEEP</code>.
                </p></dd></dl></div></div><div class="refsect1"><a id="description"></a><h2>Description</h2><p>
            Stenciling,
            like depth-buffering,
            enables and disables drawing on a per-pixel basis.
            You draw into the stencil planes using GL drawing primitives,
            then render geometry and images,
            using the stencil planes to mask out portions of the screen.