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<?xml-stylesheet type="text/xsl" href="mathml.xsl"?><html xmlns="http://www.w3.org/1999/xhtml" xmlns:pref="http://www.w3.org/2002/Math/preference" pref:renderer="mathplayer-dl"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>glSampleCoverage</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1" /></head><body><div class="refentry"><a id="glSampleCoverage"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glSampleCoverage — specify multisample coverage parameters</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <strong class="fsfunc">glSampleCoverage</strong>(</code></td><td>GLclampf <var class="pdparam">value</var>, </td></tr><tr><td> </td><td>GLboolean <var class="pdparam">invert</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>value</code></em></span></dt><dd><p>
                    Specify a single floating-point sample coverage value.  The value is
                    clamped to the range 
                    <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                        
                        <mml:mfenced open="[" close="]">
                            <mml:mn>0</mml:mn>
                            <mml:mn>1</mml:mn>
                        </mml:mfenced>
                    </mml:math>.
                    The initial value is 1.0.
                </p></dd><dt><span class="term"><em class="parameter"><code>invert</code></em></span></dt><dd><p>
                    Specify a single boolean value representing if the coverage masks should be
                    inverted.  <code class="constant">GL_TRUE</code> and <code class="constant">GL_FALSE</code> are accepted.  The initial value
                    is <code class="constant">GL_FALSE</code>.
                </p></dd></dl></div></div><div class="refsect1"><a id="description"></a><h2>Description</h2><p>
            Multisampling samples a pixel multiple times at various
            implementation-dependent subpixel locations to generate antialiasing
            effects.  Multisampling transparently antialiases points, lines, polygons,
            bitmaps, and images if it is enabled.
        </p><p>
            <em class="parameter"><code>value</code></em> is used in constructing a temporary mask used in determining which
            samples will be used in resolving the final fragment color.  This mask is
            bitwise-anded with the coverage mask generated from the multisampling
            computation.  If the <em class="parameter"><code>invert</code></em> flag is set, the temporary mask is inverted
            (all bits flipped) and then the bitwise-and is computed.
        </p><p>
            If an implementation does not have any multisample buffers available, or
            multisampling is disabled, rasterization occurs with only a single sample
            computing a pixel's final RGB color.
        </p><p>
            Provided an implementation supports multisample buffers, and multisampling
            is enabled, then a pixel's final color is generated by combining several
            samples per pixel.  Each sample contains color, depth, and stencil
            information, allowing those operations to be performed on each sample.
        </p></div><div class="refsect1"><a id="notes"></a><h2>Notes</h2><p>
            <code class="function">glSampleCoverage</code> is available only if the GL version is 1.3 or greater.
        </p></div><div class="refsect1"><a id="errors"></a><h2>Errors</h2><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glSampleCoverage</code> is executed between the
            execution of <a class="citerefentry" href="glBegin.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a> and the corresponding execution of <a class="citerefentry" href="glEnd.xml"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>.
        </p></div><div class="refsect1"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
            <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_SAMPLE_COVERAGE_VALUE</code>
        </p><p>
            <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_SAMPLE_COVERAGE_INVERT</code>
        </p><p>
            <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MULTISAMPLE</code>
        </p><p>
            <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_SAMPLE_ALPHA_TO_COVERAGE</code>
        </p><p>
            <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_SAMPLE_ALPHA_TO_ONE</code>
        </p><p>
            <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_SAMPLE_COVERAGE</code>
        </p></div><div class="refsect1"><a id="seealso"></a><h2>See Also</h2><p>
            <a class="citerefentry" href="glEnable.xml"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a>,
            <a class="citerefentry" href="glPushAttrib.xml"><span class="citerefentry"><span class="refentrytitle">glPushAttrib</span></span></a>
        </p></div><div class="refsect1"><a id="Copyright"></a><h2>Copyright</h2><p>
            Copyright <span class="trademark"></span>© 1991-2006
            Silicon Graphics, Inc. This document is licensed under the SGI
            Free Software B License. For details, see
            <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
        </p></div></div></body></html>