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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="glBlendColor">
<refmeta>
<refmetainfo>
<copyright>
<year>1991-2006</year>
<holder>Silicon Graphics, Inc.</holder>
</copyright>
</refmetainfo>
<refentrytitle>glBlendColor</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>glBlendColor</refname>
<refpurpose>set the blend color</refpurpose>
</refnamediv>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glBlendColor</function></funcdef>
<paramdef>GLclampf <parameter>red</parameter></paramdef>
<paramdef>GLclampf <parameter>green</parameter></paramdef>
<paramdef>GLclampf <parameter>blue</parameter></paramdef>
<paramdef>GLclampf <parameter>alpha</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<!-- eqn: ignoring delim $$ -->
<refsect1 id="parameters"><title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>red</parameter></term>
<term><parameter>green</parameter></term>
<term><parameter>blue</parameter></term>
<term><parameter>alpha</parameter></term>
<listitem>
<para>
specify the components of <constant>GL_BLEND_COLOR</constant>
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="description"><title>Description</title>
<para>
The <constant>GL_BLEND_COLOR</constant> may be used to calculate the source and destination
blending factors. The color components are clamped to the range
<inlineequation><mml:math>
<!-- eqn: [0,1]:-->
<mml:mfenced open="[" close="]">
<mml:mn>0</mml:mn>
<mml:mn>1</mml:mn>
</mml:mfenced>
</mml:math></inlineequation>
before being stored. See <citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry> for a complete description of the
blending operations.
Initially the <constant>GL_BLEND_COLOR</constant> is set to (0, 0, 0, 0).
</para>
</refsect1>
<refsect1 id="notes"><title>Notes</title>
<para>
<function>glBlendColor</function> is part of the <code>ARB_imaging</code> subset. <function>glBlendColor</function> is present only
if <code>ARB_imaging</code> is returned when <citerefentry><refentrytitle>glGetString</refentrytitle></citerefentry> is called with
<constant>GL_EXTENSIONS</constant> as its argument.
</para>
</refsect1>
<refsect1 id="errors"><title>Errors</title>
<para>
<constant>GL_INVALID_OPERATION</constant> is generated if <function>glBlendColor</function> is executed
between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> and the corresponding
execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
</para>
<para>
</para>
</refsect1>
<refsect1 id="associatedgets"><title>Associated Gets</title>
<para>
<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with an argument of <constant>GL_BLEND_COLOR</constant>
</para>
</refsect1>
<refsect1 id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>glBlendEquation</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glGetString</refentrytitle></citerefentry>
</para>
</refsect1>
<refsect1 id="Copyright"><title>Copyright</title>
<para>
Copyright <trademark class="copyright"></trademark> 1991-2006
Silicon Graphics, Inc. This document is licensed under the SGI
Free Software B License. For details, see
<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
</para>
</refsect1>
</refentry>