 the stored stencil value while stenciling is enabled.
            If the stencil test fails,
            no change is made to the pixel's color or depth buffers,
            and <em class="parameter"><code>sfail</code></em> specifies what happens to the stencil buffer contents.
            The following eight actions are possible.
        </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="constant">GL_KEEP</code></span></dt><dd><p>
                        Keeps the c