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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" /><link rel="stylesheet" type="text/css" href="opengl-man.css" /><title>glReadBuffer - OpenGL 4 Reference Pages</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glReadBuffer"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glReadBuffer — select a color buffer source for pixels</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><p><code class="funcdef">void <b class="fsfunc">glReadBuffer</b>(</code>GLenum <var class="pdparam">mode</var><code>)</code>;</p></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>mode</code></em></span></dt><dd><p>
                    Specifies a color buffer.
                    Accepted values are
                    <code class="constant">GL_FRONT_LEFT</code>,
                    <code class="constant">GL_FRONT_RIGHT</code>,
                    <code class="constant">GL_BACK_LEFT</code>,
                    <code class="constant">GL_BACK_RIGHT</code>,
                    <code class="constant">GL_FRONT</code>,
                    <code class="constant">GL_BACK</code>,
                    <code class="constant">GL_LEFT</code>,
                    <code class="constant">GL_RIGHT</code>, and the constants
                    <code class="constant">GL_COLOR_ATTACHMENT<span class="emphasis"><em>i</em></span></code>.
                </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
            <code class="function">glReadBuffer</code> specifies a color buffer as the source for subsequent
            <a href="glReadPixels.xml"><span class="citerefentry"><span class="refentrytitle">glReadPixels</span></span></a>, <a href="glCopyTexImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage1D</span></span></a>, <a href="glCopyTexImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage2D</span></span></a>,
            <a href="glCopyTexSubImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage1D</span></span></a>, <a href="glCopyTexSubImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage2D</span></span></a>, and
            <a href="glCopyTexSubImage3D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage3D</span></span></a> commands.
            <em class="parameter"><code>mode</code></em> accepts one of twelve or more predefined values.
            In a fully configured system,
            <code class="constant">GL_FRONT</code>,
            <code class="constant">GL_LEFT</code>, and
            <code class="constant">GL_FRONT_LEFT</code> all name the front left buffer,
            <code class="constant">GL_FRONT_RIGHT</code> and
            <code class="constant">GL_RIGHT</code> name the front right buffer, and
            <code class="constant">GL_BACK_LEFT</code> and
            <code class="constant">GL_BACK</code> name the back left buffer.
            Further more, the constants <code class="constant">GL_COLOR_ATTACHMENT<span class="emphasis"><em>i</em></span></code> may be used to indicate the
            <span class="emphasis"><em>i</em></span><sup>th</sup> color attachment where <span class="emphasis"><em>i</em></span> ranges from zero to the
            value of <code class="constant">GL_MAX_COLOR_ATTACHMENTS</code> minus one.
        </p><p>
            Nonstereo double-buffered configurations have only a front left and a
            back left buffer.
            Single-buffered configurations have a front left and a front right
            buffer if stereo, and only a front left buffer if nonstereo.
            It is an error to specify a nonexistent buffer to <code class="function">glReadBuffer</code>.
        </p><p>
            <em class="parameter"><code>mode</code></em> is initially <code class="constant">GL_FRONT</code> in single-buffered configurations
            and <code class="constant">GL_BACK</code> in double-buffered configurations.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
            <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>mode</code></em> is not one of the twelve
            (or more) accepted values.
        </p><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if <em class="parameter"><code>mode</code></em> specifies a buffer
            that does not exist.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
            <a href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_READ_BUFFER</code>
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
            <a href="glCopyTexImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage1D</span></span></a>,
            <a href="glCopyTexImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage2D</span></span></a>,
            <a href="glCopyTexSubImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage1D</span></span></a>,
            <a href="glCopyTexSubImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage2D</span></span></a>,
            <a href="glCopyTexSubImage3D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage3D</span></span></a>,
            <a href="glDrawBuffer.xml"><span class="citerefentry"><span class="refentrytitle">glDrawBuffer</span></span></a>,
            <a href="glReadPixels.xml"><span class="citerefentry"><span class="refentrytitle">glReadPixels</span></span></a>
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
            Copyright <span class="trademark"></span>© 1991-2006 Silicon Graphics, Inc.
            Copyright <span class="trademark"></span>© 2011 Khronos Group.
            This document is licensed under the SGI
            Free Software B License. For details, see
            <a href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
        </p></div></div></body></html>
