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<!DOCTYPE refentry [ <!ENTITY % mathent SYSTEM "math.ent"> %mathent; ]>
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<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="glReadBuffer">
<info>
<copyright>
<year>1991-2006</year>
<holder>Silicon Graphics, Inc.</holder>
</copyright>
<copyright>
<year>2011-2014</year>
<holder>Khronos Group</holder>
</copyright>
</info>
<refmeta>
<refentrytitle>glReadBuffer</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>glReadBuffer</refname>
<refname>glNamedFramebufferReadBuffer</refname>
<refpurpose>select a color buffer source for pixels</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glReadBuffer</function></funcdef>
<paramdef>GLenum <parameter>mode</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>void <function>glNamedFramebufferReadBuffer</function></funcdef>
<paramdef>GLuint <parameter>framebuffer</parameter></paramdef>
<paramdef>GLenum <parameter>mode</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 xml:id="parameters">
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>framebuffer</parameter></term>
<listitem>
<para>Specifies the name of the framebuffer object for
<function>glNamedFramebufferReadBuffer</function> function.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>mode</parameter></term>
<listitem>
<para>Specifies a color buffer. Accepted values are
<constant>GL_FRONT_LEFT</constant>,
<constant>GL_FRONT_RIGHT</constant>,
<constant>GL_BACK_LEFT</constant>,
<constant>GL_BACK_RIGHT</constant>, <constant>GL_FRONT</constant>,
<constant>GL_BACK</constant>, <constant>GL_LEFT</constant>,
<constant>GL_RIGHT</constant>, and the constants
<constant>GL_COLOR_ATTACHMENT</constant><emphasis>i</emphasis>.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 xml:id="description">
<title>Description</title>
<para><function>glReadBuffer</function> specifies a color buffer as the
source for subsequent <citerefentry>
<refentrytitle>glReadPixels</refentrytitle>
</citerefentry>, <citerefentry>
<refentrytitle>glCopyTexImage1D</refentrytitle>
</citerefentry>, <citerefentry>
<refentrytitle>glCopyTexImage2D</refentrytitle>
</citerefentry>, <citerefentry>
<refentrytitle>glCopyTexSubImage1D</refentrytitle>
</citerefentry>, <citerefentry>
<refentrytitle>glCopyTexSubImage2D</refentrytitle>
</citerefentry>, and <citerefentry>
<refentrytitle>glCopyTexSubImage3D</refentrytitle>
</citerefentry> commands. <parameter>mode</parameter> accepts one of
twelve or more predefined values. In a fully configured system,
<constant>GL_FRONT</constant>, <constant>GL_LEFT</constant>, and
<constant>GL_FRONT_LEFT</constant> all name the front left buffer,
<constant>GL_FRONT_RIGHT</constant> and <constant>GL_RIGHT</constant> name
the front right buffer, and <constant>GL_BACK_LEFT</constant> and
<constant>GL_BACK</constant> name the back left buffer. Further more, the
constants <constant>GL_COLOR_ATTACHMENT</constant><emphasis>i</emphasis>
may be used to indicate the
<emphasis>i</emphasis><superscript>th</superscript> color attachment where
<emphasis>i</emphasis> ranges from zero to the value of
<constant>GL_MAX_COLOR_ATTACHMENTS</constant> minus one.</para>
<para>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
<function>glReadBuffer</function>.</para>
<para><parameter>mode</parameter> is initially
<constant>GL_FRONT</constant> in single-buffered configurations and
<constant>GL_BACK</constant> in double-buffered configurations.</para>
<para>For <function>glReadBuffer</function>, the target framebuffer object
is that bound to <constant>GL_READ_FRAMEBUFFER</constant>. For
<function>glNamedFramebufferReadBuffer</function>,
<parameter>framebuffer</parameter> must either be zero or the name of the
target framebuffer object. If <parameter>framebuffer</parameter> is zero,
then the default read framebuffer is affected.</para>
</refsect1>
<refsect1 xml:id="errors">
<title>Errors</title>
<para><constant>GL_INVALID_ENUM</constant> is generated if
<parameter>mode</parameter> is not one of the twelve (or more) accepted
values.</para>
<para><constant>GL_INVALID_OPERATION</constant> is generated if
<parameter>mode</parameter> specifies a buffer that does not exist.</para>
<para><constant>GL_INVALID_OPERATION</constant> is generated by
<function>glNamedFramebufferReadBuffer</function> if
<parameter>framebuffer</parameter> is not zero or the name of an existing
framebuffer object.</para>
</refsect1>
<refsect1 xml:id="associatedgets">
<title>Associated Gets</title>
<para><citerefentry>
<refentrytitle>glGet</refentrytitle>
</citerefentry> with argument <constant>GL_READ_BUFFER</constant></para>
</refsect1>
<refsect1 xml:id="versions"><title>Version Support</title>
<informaltable>
<tgroup cols="13" align="left">
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apifunchead.xml" xpointer="xpointer(/*/*)"/>
<tbody>
<row>
<entry><function>glNamedFramebufferReadBuffer</function></entry>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='45']/*)"/>
</row>
<row>
<entry><function>glReadBuffer</function></entry>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='20']/*)"/>
</row>
</tbody>
</tgroup>
</informaltable>
</refsect1>
<refsect1 xml:id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>glCopyTexImage1D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexImage2D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexSubImage1D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexSubImage2D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexSubImage3D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glDrawBuffer</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glReadPixels</refentrytitle></citerefentry>
</para>
</refsect1>
<refsect1 xml:id="Copyright"><title>Copyright</title>
<para>
Copyright <trademark class="copyright"/> 1991-2006 Silicon Graphics, Inc.
Copyright <trademark class="copyright"/> 2011-2014 Khronos Group.
This document is licensed under the SGI
Free Software B License. For details, see
<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</link>.
</para>
</refsect1>
</refentry>
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