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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
+ "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
+<refentry id="glDrawBuffers">
+ <refmeta>
+ <refentrytitle>glDrawBuffers</refentrytitle>
+ <manvolnum>3G</manvolnum>
+ </refmeta>
+ <refnamediv>
+ <refname>glDrawBuffers</refname>
+ <refpurpose>Specifies a list of color buffers to be drawn into</refpurpose>
+ </refnamediv>
+ <refsynopsisdiv><title>C Specification</title>
+ <funcsynopsis>
+ <funcprototype>
+ <funcdef>void <function>glDrawBuffers</function></funcdef>
+ <paramdef>GLsizei <parameter>n</parameter></paramdef>
+ <paramdef>const GLenum *<parameter>bufs</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ </refsynopsisdiv>
+ <refsect1 id="parameters"><title>Parameters</title>
+ <variablelist>
+ <varlistentry>
+ <term><parameter>n</parameter></term>
+ <listitem>
+ <para>Specifies the number of buffers in
+ <parameter>bufs</parameter>.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>bufs</parameter></term>
+ <listitem>
+ <para>Points to an array of symbolic constants
+ specifying the buffers into which fragment colors or
+ data values will be written.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+ <refsect1 id="description"><title>Description</title>
+ <para><function>glDrawBuffers</function> defines an array of
+ buffers into which outputs from the fragment shader data will
+ be written. If a fragment shader writes a value
+ to one or more user defined output
+ variables, then the value of each variable will be written into the
+ buffer specified at a location within <parameter>bufs</parameter>
+ corresponding to the location assigned to that user defined output.
+ The draw buffer used for user defined outputs assigned to locations
+ greater than or equal to <parameter>n</parameter> is implicitly set
+ to <constant>GL_NONE</constant> and any data written to such an output
+ is discarded.</para>
+
+ <para>The symbolic constants contained in
+ <parameter>bufs</parameter> may be any of the following:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><constant>GL_NONE</constant></term>
+ <listitem>
+ <para>The fragment shader output value is not written into
+ any color buffer.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><constant>GL_FRONT_LEFT</constant></term>
+ <listitem>
+ <para>The fragment shader output value is written into the
+ front left color buffer.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><constant>GL_FRONT_RIGHT</constant></term>
+ <listitem>
+ <para>The fragment shader output value is written into the
+ front right color buffer.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><constant>GL_BACK_LEFT</constant></term>
+ <listitem>
+ <para>The fragment shader output value is written into the
+ back left color buffer.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><constant>GL_BACK_RIGHT</constant></term>
+ <listitem>
+ <para>The fragment shader output value is written into the
+ back right color buffer.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><constant>GL_COLOR_ATTACHMENT<emphasis>n</emphasis></constant></term>
+ <listitem>
+ <para>The fragment shader output value is written into the
+ <emphasis>n</emphasis>th color attachment of the current framebuffer.
+ <emphasis>n</emphasis> may range from 0 to the value of
+ <constant>GL_MAX_COLOR_ATTACHMENTS</constant>.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <para>Except for <constant>GL_NONE</constant>, the preceding
+ symbolic constants may not appear more than once in
+ <parameter>bufs</parameter>. The maximum number of draw buffers
+ supported is implementation dependent and can be queried by
+ calling
+ <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry>
+ with the argument <constant>GL_MAX_DRAW_BUFFERS</constant>.</para>
+ </refsect1>
+ <refsect1 id="notes"><title>Notes</title>
+
+ <para>The symbolic constants <constant>GL_FRONT</constant>,
+ <constant>GL_BACK</constant>, <constant>GL_LEFT</constant>,
+ <constant>GL_RIGHT</constant>, and
+ <constant>GL_FRONT_AND_BACK</constant> are not allowed in the
+ <parameter>bufs</parameter> array since they may refer to
+ multiple buffers.</para>
+
+ <para>If a fragment shader does not write to a user defined output variable,
+ the values of the fragment
+ colors following shader execution are undefined. For each
+ fragment generated in this situation, a different value may be
+ written into each of the buffers specified by
+ <parameter>bufs</parameter>.</para>
+ </refsect1>
+ <refsect1 id="errors"><title>Errors</title>
+ <para><constant>GL_INVALID_ENUM</constant> is generated if one of the
+ values in <parameter>bufs</parameter> is not an accepted
+ value.</para>
+
+ <para><constant>GL_INVALID_ENUM</constant> is generated if the GL is bound
+ to the default framebuffer and one or more of the values in
+ <parameter>bufs</parameter> is one of the <constant>GL_COLOR_ATTACHMENT<emphasis>n</emphasis></constant>
+ tokens.</para>
+
+ <para><constant>GL_INVALID_ENUM</constant> is generated if the GL is bound
+ to a framebuffer object and one or more of the values in <parameter>bufs</parameter>
+ is anything other than <constant>GL_NONE</constant> or one of the
+ <constant>GL_COLOR_ATTACHMENTS<emphasis>n</emphasis></constant> tokens.</para>
+
+ <para><constant>GL_INVALID_ENUM</constant> is generated if
+ <parameter>n</parameter> is less than 0.</para>
+
+ <para><constant>GL_INVALID_OPERATION</constant> is generated if a
+ symbolic constant other than <constant>GL_NONE</constant>
+ appears more than once in <parameter>bufs</parameter>.</para>
+
+ <para><constant>GL_INVALID_OPERATION</constant> is generated if any of
+ the entries in <parameter>bufs</parameter> (other than
+ <constant>GL_NONE</constant> ) indicates a color buffer that
+ does not exist in the current GL context.</para>
+
+ <para><constant>GL_INVALID_VALUE</constant> is generated if
+ <parameter>n</parameter> is greater than
+ <constant>GL_MAX_DRAW_BUFFERS</constant>.</para>
+
+ </refsect1>
+ <refsect1 id="associatedgets"><title>Associated Gets</title>
+ <para><citerefentry><refentrytitle>glGet</refentrytitle></citerefentry>
+ with argument <constant>GL_MAX_DRAW_BUFFERS</constant></para>
+
+ <para><citerefentry><refentrytitle>glGet</refentrytitle></citerefentry>
+ with argument <constant>GL_DRAW_BUFFER<emphasis>i</emphasis></constant> where
+ <code><emphasis>i</emphasis></code> indicates the number of the draw buffer
+ whose value is to be queried</para>
+ </refsect1>
+ <refsect1 id="seealso"><title>See Also</title>
+ <para> <citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry>,
+ <citerefentry><refentrytitle>glColorMask</refentrytitle></citerefentry>,
+ <citerefentry><refentrytitle>glDrawBuffers</refentrytitle></citerefentry>,
+ <citerefentry><refentrytitle>glLogicOp</refentrytitle></citerefentry>,
+ <citerefentry><refentrytitle>glReadBuffer</refentrytitle></citerefentry></para>
+ </refsect1>
+ <refsect1 id="Copyright"><title>Copyright</title>
+ <para>
+ Copyright <trademark class="copyright"></trademark> 2003-2005 3Dlabs Inc. Ltd.
+ This material may be distributed subject to the terms and conditions set forth in
+ the Open Publication License, v 1.0, 8 June 1999.
+ <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
+ </para>
+ </refsect1>
+</refentry>
HCoop / clinton / guile-figl.git / blobdiff