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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>glReadBuffer - OpenGL 4 Reference Pages</title>
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<div class="refentry" id="glReadBuffer">
<div class="titlepage"/>
<div class="refnamediv">
<h2>Name</h2>
<p>glReadBuffer, glNamedFramebufferReadBuffer — select a color buffer source for pixels</p>
</div>
<div class="refsynopsisdiv">
<h2>C Specification</h2>
<div class="funcsynopsis">
<table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
<tr>
<td>
<code class="funcdef">void <strong class="fsfunc">glReadBuffer</strong>(</code>
</td>
<td>GLenum <var class="pdparam">mode</var><code>)</code>;</td>
</tr>
</table>
<div class="funcprototype-spacer"> </div>
<table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
<tr>
<td>
<code class="funcdef">void <strong class="fsfunc">glNamedFramebufferReadBuffer</strong>(</code>
</td>
<td>GLuint <var class="pdparam">framebuffer</var>, </td>
</tr>
<tr>
<td> </td>
<td>GLenum <var class="pdparam">mode</var><code>)</code>;</td>
</tr>
</table>
<div class="funcprototype-spacer"> </div>
</div>
</div>
<div class="refsect1" id="parameters">
<h2>Parameters</h2>
<div class="variablelist">
<dl class="variablelist">
<dt>
<span class="term">
<em class="parameter">
<code>framebuffer</code>
</em>
</span>
</dt>
<dd>
<p>Specifies the name of the framebuffer object for
<code class="function">glNamedFramebufferReadBuffer</code> function.</p>
</dd>
<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</code><span class="emphasis"><em>i</em></span>.</p>
</dd>
</dl>
</div>
</div>
<div class="refsect1" id="description">
<h2>Description</h2>
<p><code class="function">glReadBuffer</code> specifies a color buffer as the
source for subsequent <a class="citerefentry" href="glReadPixels.xhtml"><span class="citerefentry"><span class="refentrytitle">glReadPixels</span></span></a>, <a class="citerefentry" href="glCopyTexImage1D.xhtml"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage1D</span></span></a>, <a class="citerefentry" href="glCopyTexImage2D.xhtml"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage2D</span></span></a>, <a class="citerefentry" href="glCopyTexSubImage1D.xhtml"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage1D</span></span></a>, <a class="citerefentry" href="glCopyTexSubImage2D.xhtml"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage2D</span></span></a>, and <a class="citerefentry" href="glCopyTexSubImage3D.xhtml"><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</code><span class="emphasis"><em>i</em></span>
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>
<p>For <code class="function">glReadBuffer</code>, the target framebuffer object
is that bound to <code class="constant">GL_READ_FRAMEBUFFER</code>. For
<code class="function">glNamedFramebufferReadBuffer</code>,
<em class="parameter"><code>framebuffer</code></em> must either be zero or the name of the
target framebuffer object. If <em class="parameter"><code>framebuffer</code></em> is zero,
then the default read framebuffer is affected.</p>
</div>
<div class="refsect1" id="errors">
<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>
<p><code class="constant">GL_INVALID_OPERATION</code> is generated by
<code class="function">glNamedFramebufferReadBuffer</code> if
<em class="parameter"><code>framebuffer</code></em> is not zero or the name of an existing
framebuffer object.</p>
</div>
<div class="refsect1" id="associatedgets">
<h2>Associated Gets</h2>
<p><a class="citerefentry" href="glGet.xhtml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_READ_BUFFER</code></p>
</div>
<div class="refsect1" id="versions">
<h2>Version Support</h2>
<div class="informaltable">
<table style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">
<colgroup>
<col style="text-align: left; "/>
<col style="text-align: center; " class="firstvers"/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; " class="lastvers"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left; border-right: 2px solid ; ">
</th>
<th style="text-align: center; border-bottom: 2px solid ; " colspan="12">
<span class="bold"><strong>OpenGL Version</strong></span>
</th>
</tr>
<tr>
<th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>Function / Feature Name</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>2.0</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>2.1</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.0</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.1</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.2</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.3</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.0</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.1</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.2</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.3</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.4</strong></span>
</th>
<th style="text-align: center; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.5</strong></span>
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<code class="function">glNamedFramebufferReadBuffer</code>
</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">-</td>
<td style="text-align: center; border-bottom: 2px solid ; ">✔</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; ">
<code class="function">glReadBuffer</code>
</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; ">✔</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="refsect1" id="seealso">
<h2>See Also</h2>
<p>
<a class="citerefentry" href="glCopyTexImage1D.xhtml"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage1D</span></span></a>,
<a class="citerefentry" href="glCopyTexImage2D.xhtml"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage2D</span></span></a>,
<a class="citerefentry" href="glCopyTexSubImage1D.xhtml"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage1D</span></span></a>,
<a class="citerefentry" href="glCopyTexSubImage2D.xhtml"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage2D</span></span></a>,
<a class="citerefentry" href="glCopyTexSubImage3D.xhtml"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage3D</span></span></a>,
<a class="citerefentry" href="glDrawBuffer.xhtml"><span class="citerefentry"><span class="refentrytitle">glDrawBuffer</span></span></a>,
<a class="citerefentry" href="glReadPixels.xhtml"><span class="citerefentry"><span class="refentrytitle">glReadPixels</span></span></a>
</p>
</div>
<div class="refsect1" id="Copyright">
<h2>Copyright</h2>
<p>
Copyright <span class="trademark"/>© 1991-2006 Silicon Graphics, Inc.
Copyright <span class="trademark"/>© 2011-2014 Khronos Group.
This document is licensed under the SGI
Free Software B License. For details, see
<a class="link" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
</p>
</div>
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