240 lines
10 KiB
XML
240 lines
10 KiB
XML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
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"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
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<refentry id="glDrawBuffer">
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<refmeta>
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<refmetainfo>
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<copyright>
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<year>1991-2006</year>
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<holder>Silicon Graphics, Inc.</holder>
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</copyright>
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</refmetainfo>
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<refentrytitle>glDrawBuffer</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>glDrawBuffer</refname>
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<refpurpose>specify which color buffers are to be drawn into</refpurpose>
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</refnamediv>
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<refsynopsisdiv><title>C Specification</title>
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<funcsynopsis>
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<funcprototype>
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<funcdef>void <function>glDrawBuffer</function></funcdef>
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<paramdef>GLenum <parameter>mode</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<!-- eqn: ignoring delim $$ -->
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<refsect1 id="parameters"><title>Parameters</title>
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<variablelist>
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<varlistentry>
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<term><parameter>mode</parameter></term>
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<listitem>
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<para>
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Specifies up to four color buffers to be drawn into.
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Symbolic constants
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<constant>GL_NONE</constant>,
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<constant>GL_FRONT_LEFT</constant>,
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<constant>GL_FRONT_RIGHT</constant>,
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<constant>GL_BACK_LEFT</constant>,
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<constant>GL_BACK_RIGHT</constant>,
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<constant>GL_FRONT</constant>,
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<constant>GL_BACK</constant>,
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<constant>GL_LEFT</constant>,
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<constant>GL_RIGHT</constant>,
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<constant>GL_FRONT_AND_BACK</constant>, and
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<constant>GL_AUX</constant><emphasis>i</emphasis>,
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where <emphasis>i</emphasis> is between 0 and the value of <constant>GL_AUX_BUFFERS</constant> minus 1,
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are accepted. (<constant>GL_AUX_BUFFERS</constant> is not the upper limit; use <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry>
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to query the number of available aux buffers.)
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The initial value is <constant>GL_FRONT</constant> for single-buffered contexts,
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and <constant>GL_BACK</constant> for double-buffered contexts.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1 id="description"><title>Description</title>
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<para>
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When colors are written to the frame buffer,
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they are written into the color buffers specified by <function>glDrawBuffer</function>.
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The specifications are as follows:
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</para>
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<variablelist>
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<varlistentry>
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<term><constant>GL_NONE</constant></term>
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<listitem>
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<para>
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No color buffers are written.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>GL_FRONT_LEFT</constant></term>
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<listitem>
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<para>
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Only the front left color buffer is written.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>GL_FRONT_RIGHT</constant></term>
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<listitem>
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<para>
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Only the front right color buffer is written.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>GL_BACK_LEFT</constant></term>
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<listitem>
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<para>
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Only the back left color buffer is written.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>GL_BACK_RIGHT</constant></term>
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<listitem>
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<para>
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Only the back right color buffer is written.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>GL_FRONT</constant></term>
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<listitem>
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<para>
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Only the front left and front right color buffers are written.
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If there is no front right color buffer,
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only the front left color buffer is written.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>GL_BACK</constant></term>
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<listitem>
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<para>
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Only the back left and back right color buffers are written.
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If there is no back right color buffer,
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only the back left color buffer is written.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>GL_LEFT</constant></term>
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<listitem>
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<para>
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Only the front left and back left color buffers are written.
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If there is no back left color buffer,
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only the front left color buffer is written.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>GL_RIGHT</constant></term>
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<listitem>
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<para>
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Only the front right and back right color buffers are written.
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If there is no back right color buffer,
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only the front right color buffer is written.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>GL_FRONT_AND_BACK</constant></term>
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<listitem>
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<para>
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All the front and back color buffers
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(front left, front right, back left, back right)
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are written.
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If there are no back color buffers,
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only the front left and front right color buffers are written.
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If there are no right color buffers,
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only the front left and back left color buffers are written.
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If there are no right or back color buffers,
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only the front left color buffer is written.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>GL_AUX</constant><emphasis>i</emphasis></term>
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<listitem>
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<para>
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Only auxiliary color buffer <emphasis>i</emphasis> is written.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>
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If more than one color buffer is selected for drawing,
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then blending or logical operations are computed and applied independently
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for each color buffer and can produce different results in each buffer.
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</para>
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<para>
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Monoscopic contexts include only
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<emphasis>left</emphasis>
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buffers, and stereoscopic contexts include both
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<emphasis>left</emphasis>
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and
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<emphasis>right</emphasis>
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buffers.
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Likewise, single-buffered contexts include only
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<emphasis>front</emphasis>
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buffers, and double-buffered contexts include both
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<emphasis>front</emphasis>
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and
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<emphasis>back</emphasis>
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buffers.
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The context is selected at GL initialization.
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</para>
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</refsect1>
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<refsect1 id="notes"><title>Notes</title>
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<para>
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It is always the case that <constant>GL_AUX</constant>
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<inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>
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= <constant>GL_AUX0</constant> +
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<inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>.
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</para>
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</refsect1>
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<refsect1 id="errors"><title>Errors</title>
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<para>
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<constant>GL_INVALID_ENUM</constant> is generated if <parameter>mode</parameter> is not an accepted value.
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</para>
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<para>
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<constant>GL_INVALID_OPERATION</constant> is generated if none of the buffers indicated
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by <parameter>mode</parameter> exists.
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</para>
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<para>
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<constant>GL_INVALID_OPERATION</constant> is generated if <function>glDrawBuffer</function>
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is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
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and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
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</para>
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</refsect1>
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<refsect1 id="associatedgets"><title>Associated Gets</title>
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<para>
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<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_DRAW_BUFFER</constant>
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</para>
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<para>
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<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_AUX_BUFFERS</constant>
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</para>
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</refsect1>
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<refsect1 id="seealso"><title>See Also</title>
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<para>
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<citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glColorMask</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glIndexMask</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glLogicOp</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glReadBuffer</refentrytitle></citerefentry>
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</para>
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</refsect1>
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<refsect1 id="Copyright"><title>Copyright</title>
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<para>
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Copyright <trademark class="copyright"></trademark> 1991-2006
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Silicon Graphics, Inc. This document is licensed under the SGI
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Free Software B License. For details, see
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<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
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</para>
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</refsect1>
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</refentry>
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