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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="glBlendEquation">
<refmeta>
<refmetainfo>
<copyright>
<year>1991-2006</year>
<holder>Silicon Graphics, Inc.</holder>
</copyright>
</refmetainfo>
<refentrytitle>glBlendEquation</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>glBlendEquation</refname>
<refpurpose>specify the equation used for both the RGB blend equation and the Alpha blend equation</refpurpose>
</refnamediv>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glBlendEquation</function></funcdef>
<paramdef>GLenum <parameter>mode</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<!-- eqn: ignoring delim $$ -->
<refsect1 id="parameters"><title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>mode</parameter></term>
<listitem>
<para>
specifies how source and destination colors are combined.
It must be <constant>GL_FUNC_ADD</constant>, <constant>GL_FUNC_SUBTRACT</constant>,
<constant>GL_FUNC_REVERSE_SUBTRACT</constant>, <constant>GL_MIN</constant>, <constant>GL_MAX</constant>.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="description"><title>Description</title>
<para>
The blend equations determine how a new pixel (the ''source'' color)
is combined with a pixel already in the framebuffer (the ''destination''
color). This function sets both the RGB blend equation and the alpha
blend equation to a single equation.
</para>
<para>
These equations use the source and destination blend factors
specified by either <citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry> or
<citerefentry><refentrytitle>glBlendFuncSeparate</refentrytitle></citerefentry>.
See <citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry> or <citerefentry><refentrytitle>glBlendFuncSeparate</refentrytitle></citerefentry>
for a description of the various blend factors.
</para>
<para>
In the equations that follow, source and destination
color components are referred to as
<inlineequation><mml:math>
<!-- eqn: ( R sub s, G sub s, B sub s, A sub s ):-->
<mml:mfenced open="(" close=")">
<mml:msub><mml:mi mathvariant="italic">R</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
<mml:msub><mml:mi mathvariant="italic">G</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
<mml:msub><mml:mi mathvariant="italic">B</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
<mml:msub><mml:mi mathvariant="italic">A</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
</mml:mfenced>
</mml:math></inlineequation>
and
<inlineequation><mml:math>
<!-- eqn: ( R sub d, G sub d, B sub d, A sub d ):-->
<mml:mfenced open="(" close=")">
<mml:msub><mml:mi mathvariant="italic">R</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
<mml:msub><mml:mi mathvariant="italic">G</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
<mml:msub><mml:mi mathvariant="italic">B</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
<mml:msub><mml:mi mathvariant="italic">A</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
</mml:mfenced>
</mml:math></inlineequation>,
respectively.
The result color is referred to as
<inlineequation><mml:math>
<!-- eqn: ( R sub r, G sub r, B sub r, A sub r ):-->
<mml:mfenced open="(" close=")">
<mml:msub><mml:mi mathvariant="italic">R</mml:mi>
<mml:mi mathvariant="italic">r</mml:mi>
</mml:msub>
<mml:msub><mml:mi mathvariant="italic">G</mml:mi>
<mml:mi mathvariant="italic">r</mml:mi>
</mml:msub>
<mml:msub><mml:mi mathvariant="italic">B</mml:mi>
<mml:mi mathvariant="italic">r</mml:mi>
</mml:msub>
<mml:msub><mml:mi mathvariant="italic">A</mml:mi>
<mml:mi mathvariant="italic">r</mml:mi>
</mml:msub>
</mml:mfenced>
</mml:math></inlineequation>.
The source and destination blend factors are denoted
<inlineequation><mml:math>
<!-- eqn: ( s sub R, s sub G, s sub B, s sub A ):-->
<mml:mfenced open="(" close=")">
<mml:msub><mml:mi mathvariant="italic">s</mml:mi>
<mml:mi mathvariant="italic">R</mml:mi>
</mml:msub>
<mml:msub><mml:mi mathvariant="italic">s</mml:mi>
<mml:mi mathvariant="italic">G</mml:mi>
</mml:msub>
<mml:msub><mml:mi mathvariant="italic">s</mml:mi>
<mml:mi mathvariant="italic">B</mml:mi>
</mml:msub>
<mml:msub><mml:mi mathvariant="italic">s</mml:mi>
<mml:mi mathvariant="italic">A</mml:mi>
</mml:msub>
</mml:mfenced>
</mml:math></inlineequation>
and
<inlineequation><mml:math>
<!-- eqn: ( d sub R, d sub G, d sub B, d sub A ):-->
<mml:mfenced open="(" close=")">
<mml:msub><mml:mi mathvariant="italic">d</mml:mi>
<mml:mi mathvariant="italic">R</mml:mi>
</mml:msub>
<mml:msub><mml:mi mathvariant="italic">d</mml:mi>
<mml:mi mathvariant="italic">G</mml:mi>
</mml:msub>
<mml:msub><mml:mi mathvariant="italic">d</mml:mi>
<mml:mi mathvariant="italic">B</mml:mi>
</mml:msub>
<mml:msub><mml:mi mathvariant="italic">d</mml:mi>
<mml:mi mathvariant="italic">A</mml:mi>
</mml:msub>
</mml:mfenced>
</mml:math></inlineequation>,
respectively.
For these equations all color components are understood to have values
in 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>.
<informaltable frame="topbot">
<tgroup cols="3" align="left">
<colspec colwidth="1.1*" />
<colspec colwidth="1*" />
<colspec colwidth="1*" />
<thead>
<row>
<entry rowsep="1" align="left"><emphasis role="bold">
Mode
</emphasis></entry>
<entry rowsep="1" align="left"><emphasis role="bold">
RGB Components
</emphasis></entry>
<entry rowsep="1" align="left"><emphasis role="bold">
Alpha Component
</emphasis></entry>
</row>
</thead>
<tbody>
<row>
<entry align="left">
<constant>GL_FUNC_ADD</constant>
</entry>
<entry align="left">
<informalequation><mml:math>
<!-- eqn: Rr = R sub s s sub R + R sub d d sub R :-->
<mml:mrow>
<mml:mi mathvariant="italic">Rr</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">R</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">s</mml:mi>
<mml:mi mathvariant="italic">R</mml:mi>
</mml:msub>
<mml:mo>+</mml:mo>
<mml:msub><mml:mi mathvariant="italic">R</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">d</mml:mi>
<mml:mi mathvariant="italic">R</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
<informalequation><mml:math>
<!-- eqn: Gr = G sub s s sub G + G sub d d sub G :-->
<mml:mrow>
<mml:mi mathvariant="italic">Gr</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">G</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">s</mml:mi>
<mml:mi mathvariant="italic">G</mml:mi>
</mml:msub>
<mml:mo>+</mml:mo>
<mml:msub><mml:mi mathvariant="italic">G</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">d</mml:mi>
<mml:mi mathvariant="italic">G</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
<informalequation><mml:math>
<!-- eqn: Br = B sub s s sub B + B sub d d sub B :-->
<mml:mrow>
<mml:mi mathvariant="italic">Br</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">B</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">s</mml:mi>
<mml:mi mathvariant="italic">B</mml:mi>
</mml:msub>
<mml:mo>+</mml:mo>
<mml:msub><mml:mi mathvariant="italic">B</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">d</mml:mi>
<mml:mi mathvariant="italic">B</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
</entry>
<entry align="left">
<informalequation><mml:math>
<!-- eqn: Ar = A sub s s sub A + A sub d d sub A :-->
<mml:mrow>
<mml:mi mathvariant="italic">Ar</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">A</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">s</mml:mi>
<mml:mi mathvariant="italic">A</mml:mi>
</mml:msub>
<mml:mo>+</mml:mo>
<mml:msub><mml:mi mathvariant="italic">A</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">d</mml:mi>
<mml:mi mathvariant="italic">A</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
</entry>
</row>
<row>
<entry align="left">
<constant>GL_FUNC_SUBTRACT</constant>
</entry>
<entry align="left">
<informalequation><mml:math>
<!-- eqn: Rr = R sub s s sub R - R sub d d sub R :-->
<mml:mrow>
<mml:mi mathvariant="italic">Rr</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">R</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">s</mml:mi>
<mml:mi mathvariant="italic">R</mml:mi>
</mml:msub>
<mml:mo>-</mml:mo>
<mml:msub><mml:mi mathvariant="italic">R</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">d</mml:mi>
<mml:mi mathvariant="italic">R</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
<informalequation><mml:math>
<!-- eqn: Gr = G sub s s sub G - G sub d d sub G :-->
<mml:mrow>
<mml:mi mathvariant="italic">Gr</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">G</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">s</mml:mi>
<mml:mi mathvariant="italic">G</mml:mi>
</mml:msub>
<mml:mo>-</mml:mo>
<mml:msub><mml:mi mathvariant="italic">G</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">d</mml:mi>
<mml:mi mathvariant="italic">G</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
<informalequation><mml:math>
<!-- eqn: Br = B sub s s sub B - B sub d d sub B :-->
<mml:mrow>
<mml:mi mathvariant="italic">Br</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">B</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">s</mml:mi>
<mml:mi mathvariant="italic">B</mml:mi>
</mml:msub>
<mml:mo>-</mml:mo>
<mml:msub><mml:mi mathvariant="italic">B</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">d</mml:mi>
<mml:mi mathvariant="italic">B</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
</entry>
<entry align="left">
<informalequation><mml:math>
<!-- eqn: Ar = A sub s s sub A - A sub d d sub A :-->
<mml:mrow>
<mml:mi mathvariant="italic">Ar</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">A</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">s</mml:mi>
<mml:mi mathvariant="italic">A</mml:mi>
</mml:msub>
<mml:mo>-</mml:mo>
<mml:msub><mml:mi mathvariant="italic">A</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">d</mml:mi>
<mml:mi mathvariant="italic">A</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
</entry>
</row>
<row>
<entry align="left">
<constant>GL_FUNC_REVERSE_SUBTRACT</constant>
</entry>
<entry align="left">
<informalequation><mml:math>
<!-- eqn: Rr = R sub d d sub R - R sub s s sub R :-->
<mml:mrow>
<mml:mi mathvariant="italic">Rr</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">R</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">d</mml:mi>
<mml:mi mathvariant="italic">R</mml:mi>
</mml:msub>
<mml:mo>-</mml:mo>
<mml:msub><mml:mi mathvariant="italic">R</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">s</mml:mi>
<mml:mi mathvariant="italic">R</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
<informalequation><mml:math>
<!-- eqn: Gr = G sub d d sub G - G sub s s sub G :-->
<mml:mrow>
<mml:mi mathvariant="italic">Gr</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">G</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">d</mml:mi>
<mml:mi mathvariant="italic">G</mml:mi>
</mml:msub>
<mml:mo>-</mml:mo>
<mml:msub><mml:mi mathvariant="italic">G</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">s</mml:mi>
<mml:mi mathvariant="italic">G</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
<informalequation><mml:math>
<!-- eqn: Br = B sub d d sub B - B sub s s sub B :-->
<mml:mrow>
<mml:mi mathvariant="italic">Br</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">B</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">d</mml:mi>
<mml:mi mathvariant="italic">B</mml:mi>
</mml:msub>
<mml:mo>-</mml:mo>
<mml:msub><mml:mi mathvariant="italic">B</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">s</mml:mi>
<mml:mi mathvariant="italic">B</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
</entry>
<entry align="left">
<informalequation><mml:math>
<!-- eqn: Ar = A sub d d sub A - A sub s s sub A :-->
<mml:mrow>
<mml:mi mathvariant="italic">Ar</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">A</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">d</mml:mi>
<mml:mi mathvariant="italic">A</mml:mi>
</mml:msub>
<mml:mo>-</mml:mo>
<mml:msub><mml:mi mathvariant="italic">A</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
<mml:mo>⁢</mml:mo>
<mml:msub><mml:mi mathvariant="italic">s</mml:mi>
<mml:mi mathvariant="italic">A</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
</entry>
</row>
<row>
<entry align="left">
<constant>GL_MIN</constant>
</entry>
<entry align="left">
<informalequation><mml:math>
<!-- eqn: Rr = min ( R sub s, R sub d):-->
<mml:mrow>
<mml:mi mathvariant="italic">Rr</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:mi mathvariant="italic">min</mml:mi>
<mml:mo>⁡</mml:mo>
<mml:mfenced open="(" close=")">
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">R</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
</mml:mrow>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">R</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
<informalequation><mml:math>
<!-- eqn: Gr = min ( G sub s, G sub d):-->
<mml:mrow>
<mml:mi mathvariant="italic">Gr</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:mi mathvariant="italic">min</mml:mi>
<mml:mo>⁡</mml:mo>
<mml:mfenced open="(" close=")">
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">G</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
</mml:mrow>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">G</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
<informalequation><mml:math>
<!-- eqn: Br = min ( B sub s, B sub d):-->
<mml:mrow>
<mml:mi mathvariant="italic">Br</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:mi mathvariant="italic">min</mml:mi>
<mml:mo>⁡</mml:mo>
<mml:mfenced open="(" close=")">
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">B</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
</mml:mrow>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">B</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
</entry>
<entry align="left">
<informalequation><mml:math>
<!-- eqn: Ar = min ( A sub s, A sub d):-->
<mml:mrow>
<mml:mi mathvariant="italic">Ar</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:mi mathvariant="italic">min</mml:mi>
<mml:mo>⁡</mml:mo>
<mml:mfenced open="(" close=")">
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">A</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
</mml:mrow>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">A</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
</entry>
</row>
<row>
<entry align="left">
<constant>GL_MAX</constant>
</entry>
<entry align="left">
<informalequation><mml:math>
<!-- eqn: Rr = max ( R sub s, R sub d):-->
<mml:mrow>
<mml:mi mathvariant="italic">Rr</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:mi mathvariant="italic">max</mml:mi>
<mml:mo>⁡</mml:mo>
<mml:mfenced open="(" close=")">
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">R</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
</mml:mrow>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">R</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
<informalequation><mml:math>
<!-- eqn: Gr = max ( G sub s, G sub d):-->
<mml:mrow>
<mml:mi mathvariant="italic">Gr</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:mi mathvariant="italic">max</mml:mi>
<mml:mo>⁡</mml:mo>
<mml:mfenced open="(" close=")">
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">G</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
</mml:mrow>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">G</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
<informalequation><mml:math>
<!-- eqn: Br = max ( B sub s, B sub d):-->
<mml:mrow>
<mml:mi mathvariant="italic">Br</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:mi mathvariant="italic">max</mml:mi>
<mml:mo>⁡</mml:mo>
<mml:mfenced open="(" close=")">
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">B</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
</mml:mrow>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">B</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
</entry>
<entry align="left">
<informalequation><mml:math>
<!-- eqn: Ar = max ( A sub s, A sub d):-->
<mml:mrow>
<mml:mi mathvariant="italic">Ar</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:mi mathvariant="italic">max</mml:mi>
<mml:mo>⁡</mml:mo>
<mml:mfenced open="(" close=")">
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">A</mml:mi>
<mml:mi mathvariant="italic">s</mml:mi>
</mml:msub>
</mml:mrow>
<mml:mrow>
<mml:msub><mml:mi mathvariant="italic">A</mml:mi>
<mml:mi mathvariant="italic">d</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
<para>
The results of these equations 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>.
</para>
<para>
The <constant>GL_MIN</constant> and <constant>GL_MAX</constant> equations are useful for applications
that analyze image data (image thresholding against a constant color,
for example).
The <constant>GL_FUNC_ADD</constant> equation is useful
for antialiasing and transparency, among other things.
</para>
<para>
Initially, both the RGB blend equation and the alpha blend equation are set to <constant>GL_FUNC_ADD</constant>.
</para>
<para>
</para>
</refsect1>
<refsect1 id="notes"><title>Notes</title>
<para>
The <constant>GL_MIN</constant>, and <constant>GL_MAX</constant> equations do not use
the source or destination factors, only the source and destination colors.
</para>
</refsect1>
<refsect1 id="errors"><title>Errors</title>
<para>
<constant>GL_INVALID_ENUM</constant> is generated if <parameter>mode</parameter> is not one of
<constant>GL_FUNC_ADD</constant>, <constant>GL_FUNC_SUBTRACT</constant>, <constant>GL_FUNC_REVERSE_SUBTRACT</constant>,
<constant>GL_MAX</constant>, or <constant>GL_MIN</constant>.
</para>
<para>
<constant>GL_INVALID_OPERATION</constant> is generated if <function>glBlendEquation</function> is executed
between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> and the corresponding
execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
</para>
</refsect1>
<refsect1 id="associatedgets"><title>Associated Gets</title>
<para>
<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with an argument of <constant>GL_BLEND_EQUATION_RGB</constant>
</para>
<para>
<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with an argument of <constant>GL_BLEND_EQUATION_ALPHA</constant>
</para>
</refsect1>
<refsect1 id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>glGetString</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glBlendColor</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry>
<citerefentry><refentrytitle>glBlendFuncSeparate</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>