<!DOCTYPE refentry [ <!ENTITY % mathent SYSTEM "math.ent"> %mathent; ]>

<!-- Converted by db4-upgrade version 1.1 -->

<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="glBlendFunc">
    <info>
        <copyright>
            <year>1991-2006</year>
            <holder>Silicon Graphics, Inc.</holder>
        </copyright>
        <copyright>
            <year>2010-2014</year>
            <holder>Khronos Group</holder>
        </copyright>
    </info>
    <refmeta>
        <refentrytitle>glBlendFunc</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glBlendFunc</refname>
        <refpurpose>specify pixel arithmetic</refpurpose>
    </refnamediv>
    <refsynopsisdiv>
        <title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glBlendFunc</function></funcdef>
                <paramdef>GLenum <parameter>sfactor</parameter></paramdef>
                <paramdef>GLenum <parameter>dfactor</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 xml:id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>sfactor</parameter></term>
            <listitem>
                <para>
                    Specifies how the red, green, blue,
                    and alpha source blending factors are computed.
                    The initial value is <constant>GL_ONE</constant>.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>dfactor</parameter></term>
            <listitem>
                <para>
                    Specifies how the red, green, blue,
                    and alpha destination blending factors are computed.
                    The following symbolic constants are accepted:
                    <constant>GL_ZERO</constant>,
                    <constant>GL_ONE</constant>,
                    <constant>GL_SRC_COLOR</constant>,
                    <constant>GL_ONE_MINUS_SRC_COLOR</constant>,
                    <constant>GL_DST_COLOR</constant>,
                    <constant>GL_ONE_MINUS_DST_COLOR</constant>,
                    <constant>GL_SRC_ALPHA</constant>,
                    <constant>GL_ONE_MINUS_SRC_ALPHA</constant>,
                    <constant>GL_DST_ALPHA</constant>,
                    <constant>GL_ONE_MINUS_DST_ALPHA</constant>.
                    <constant>GL_CONSTANT_COLOR</constant>,
                    <constant>GL_ONE_MINUS_CONSTANT_COLOR</constant>,
                    <constant>GL_CONSTANT_ALPHA</constant>, and
                    <constant>GL_ONE_MINUS_CONSTANT_ALPHA</constant>.
                    The initial value is <constant>GL_ZERO</constant>.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 xml:id="description"><title>Description</title>
        <para>
            Pixels can be drawn using a function that blends
            the incoming (source) RGBA values with the RGBA values
            that are already in the frame buffer (the destination values).
            Blending is initially disabled.
            Use <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry> with argument <constant>GL_BLEND</constant>
            to enable and disable blending.
        </para>
        <para>
            <function>glBlendFunc</function> defines the operation of blending when it is enabled.
            <parameter>sfactor</parameter> specifies which method is used to scale the
            source color components.
            <parameter>dfactor</parameter> specifies which method is used to scale the
            destination color components.
            Both parameters must be one of the following symbolic constants:
                    <constant>GL_ZERO</constant>,
                    <constant>GL_ONE</constant>,
                    <constant>GL_SRC_COLOR</constant>,
                    <constant>GL_ONE_MINUS_SRC_COLOR</constant>,
                    <constant>GL_DST_COLOR</constant>,
                    <constant>GL_ONE_MINUS_DST_COLOR</constant>,
                    <constant>GL_SRC_ALPHA</constant>,
                    <constant>GL_ONE_MINUS_SRC_ALPHA</constant>,
                    <constant>GL_DST_ALPHA</constant>,
                    <constant>GL_ONE_MINUS_DST_ALPHA</constant>,
                    <constant>GL_CONSTANT_COLOR</constant>,
                    <constant>GL_ONE_MINUS_CONSTANT_COLOR</constant>,
                    <constant>GL_CONSTANT_ALPHA</constant>,
                    <constant>GL_ONE_MINUS_CONSTANT_ALPHA</constant>,
                    <constant>GL_SRC_ALPHA_SATURATE</constant>,
            The possible methods are described in the following table.
            Each method defines four scale factors,
            one each for red, green, blue, and alpha.
            In the table and in subsequent equations, source
            and destination color components are referred to as
            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- 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 xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- 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 color specified by <citerefentry><refentrytitle>glBlendColor</refentrytitle></citerefentry> is referred to as
            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- eqn: ( R sub c , G sub c , B sub c , A sub c ): -->
                <mml:mfenced open="(" close=")">
                    <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
                    <mml:mi mathvariant="italic">c</mml:mi>
                    </mml:msub>
                    <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
                    <mml:mi mathvariant="italic">c</mml:mi>
                    </mml:msub>
                    <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
                    <mml:mi mathvariant="italic">c</mml:mi>
                    </mml:msub>
                    <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                    <mml:mi mathvariant="italic">c</mml:mi>
                    </mml:msub>
                </mml:mfenced>
            </mml:math></inlineequation>.
                </para>
        <para>
            Source and destination scale factors are referred to as
            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- 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 xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- 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>.
            The scale factors described in the table,
            denoted
            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- eqn: ( f sub R , f sub G , f sub B , f sub A ): -->
                <mml:mfenced open="(" close=")">
                    <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
                    <mml:mi mathvariant="italic">R</mml:mi>
                    </mml:msub>
                    <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
                    <mml:mi mathvariant="italic">G</mml:mi>
                    </mml:msub>
                    <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
                    <mml:mi mathvariant="italic">B</mml:mi>
                    </mml:msub>
                    <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
                    <mml:mi mathvariant="italic">A</mml:mi>
                    </mml:msub>
                </mml:mfenced>
            </mml:math></inlineequation>,
            represent either source or destination factors.
            All scale factors have range
            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- eqn: [0,1]: -->
                <mml:mfenced open="[" close="]">
                    <mml:mn>0</mml:mn>
                    <mml:mn>1</mml:mn>
                </mml:mfenced>
            </mml:math></inlineequation>.
        </para>
                <para>
                Prior to blending, unsigned normalized fixed-point color components undergo
                an implied conversion to floating-point using equation 2.1. This conversion must
                leave the values 0 and 1 invariant. Blending computations are treated as if carried
                out in floating-point and will be performed with a precision and dynamic range no
                lower than that used to represent destination components.
                If the value of <constant>GL_FRAMEBUFFER_ATTACHMENT_COLOR_ENCODING</constant> for the
                framebuffer attachment corresponding to the destination buffer is <constant>GL_SRGB</constant>,
                the R, G, and B destination color values (after conversion from fixed-point
                to floating-point) are considered to be encoded for the sRGB color space and
                hence must be linearized prior to their use in blending. Each R, G, and B component
                is converted in the same fashion described for sRGB texture components.
        </para>
        <para>
        </para>
        <informaltable>
            <tgroup cols="2" align="left">
                <colspec/>
                <colspec/>
                <thead>
                    <row>
                        <entry>
                            <emphasis role="bold"> Parameter </emphasis>
                        </entry>
                        <entry>
                            <emphasis role="bold">
                            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                                <!-- eqn: ( f sub R ,    f sub G ,    f sub B ,    f sub A ): -->
                                <mml:mfenced open="(" close=")">
                                    <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
                                    <mml:mi mathvariant="italic">R</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
                                    <mml:mi mathvariant="italic">G</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
                                    <mml:mi mathvariant="italic">B</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
                                    <mml:mi mathvariant="italic">A</mml:mi>
                                    </mml:msub>
                                </mml:mfenced>
                            </mml:math></inlineequation>
                            </emphasis>
                        </entry>
                    </row>
                </thead>
                <tbody>
                    <row>
                        <entry>
                        <constant>GL_ZERO</constant>
                        </entry>
                        <entry>
                        <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            <!-- eqn: ( 0,  0,  0,  0 ): -->
                            <mml:mfenced open="(" close=")">
                                <mml:mn>0</mml:mn>
                                <mml:mn>0</mml:mn>
                                <mml:mn>0</mml:mn>
                                <mml:mn>0</mml:mn>
                            </mml:mfenced>
                        </mml:math></inlineequation>
                        </entry>
                    </row>
                    <row>
                        <entry>
                        <constant>GL_ONE</constant>
                        </entry>
                        <entry>
                        <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            <!-- eqn: ( 1,  1,  1,  1 ): -->
                            <mml:mfenced open="(" close=")">
                                <mml:mn>1</mml:mn>
                                <mml:mn>1</mml:mn>
                                <mml:mn>1</mml:mn>
                                <mml:mn>1</mml:mn>
                            </mml:mfenced>
                        </mml:math></inlineequation>
                        </entry>
                    </row>
                    <row>
                        <entry>
                        <constant>GL_SRC_COLOR</constant>
                        </entry>
                        <entry>
                        <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            <!-- eqn: ( R sub s / k sub R ,  G sub s / k sub G ,  B sub s / k sub B ,  A sub s / k sub A ): -->
                            <mml:mfenced open="(" close=")">
                                <mml:mfrac>
                                    <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
                                    <mml:mi mathvariant="italic">s</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                    <mml:mi mathvariant="italic">R</mml:mi>
                                    </mml:msub>
                                </mml:mfrac>
                                <mml:mfrac>
                                    <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
                                    <mml:mi mathvariant="italic">s</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                    <mml:mi mathvariant="italic">G</mml:mi>
                                    </mml:msub>
                                </mml:mfrac>
                                <mml:mfrac>
                                    <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
                                    <mml:mi mathvariant="italic">s</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                    <mml:mi mathvariant="italic">B</mml:mi>
                                    </mml:msub>
                                </mml:mfrac>
                                <mml:mfrac>
                                    <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                    <mml:mi mathvariant="italic">s</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                    <mml:mi mathvariant="italic">A</mml:mi>
                                    </mml:msub>
                                </mml:mfrac>
                            </mml:mfenced>
                        </mml:math></inlineequation>
                        </entry>
                    </row>
                    <row>
                        <entry>
                        <constant>GL_ONE_MINUS_SRC_COLOR</constant>
                        </entry>
                        <entry>
                        <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            <!-- eqn: ( 1,  1,  1,  1 )  -  (R sub s / k sub R ,  G sub s / k sub G ,  B sub s / k sub B ,  A sub s / k sub A ): -->
                            <mml:mrow>
                                <mml:mfenced open="(" close=")">
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                </mml:mfenced>
                                <mml:mo>-</mml:mo>
                                <mml:mfenced open="(" close=")">
                                    <mml:mfrac>
                                        <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
                                        <mml:mi mathvariant="italic">s</mml:mi>
                                        </mml:msub>
                                        <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                        <mml:mi mathvariant="italic">R</mml:mi>
                                        </mml:msub>
                                    </mml:mfrac>
                                    <mml:mfrac>
                                        <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
                                        <mml:mi mathvariant="italic">s</mml:mi>
                                        </mml:msub>
                                        <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                        <mml:mi mathvariant="italic">G</mml:mi>
                                        </mml:msub>
                                    </mml:mfrac>
                                    <mml:mfrac>
                                        <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
                                        <mml:mi mathvariant="italic">s</mml:mi>
                                        </mml:msub>
                                        <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                        <mml:mi mathvariant="italic">B</mml:mi>
                                        </mml:msub>
                                    </mml:mfrac>
                                    <mml:mfrac>
                                        <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                        <mml:mi mathvariant="italic">s</mml:mi>
                                        </mml:msub>
                                        <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                        <mml:mi mathvariant="italic">A</mml:mi>
                                        </mml:msub>
                                    </mml:mfrac>
                                </mml:mfenced>
                            </mml:mrow>
                        </mml:math></inlineequation>
                        </entry>
                    </row>
                    <row>
                        <entry>
                        <constant>GL_DST_COLOR</constant>
                        </entry>
                        <entry>
                        <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            <!-- eqn: ( R sub d / k sub R ,  G sub d / k sub G ,  B sub d / k sub B ,  A sub d / k sub A ): -->
                            <mml:mfenced open="(" close=")">
                                <mml:mfrac>
                                    <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
                                    <mml:mi mathvariant="italic">d</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                    <mml:mi mathvariant="italic">R</mml:mi>
                                    </mml:msub>
                                </mml:mfrac>
                                <mml:mfrac>
                                    <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
                                    <mml:mi mathvariant="italic">d</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                    <mml:mi mathvariant="italic">G</mml:mi>
                                    </mml:msub>
                                </mml:mfrac>
                                <mml:mfrac>
                                    <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
                                    <mml:mi mathvariant="italic">d</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                    <mml:mi mathvariant="italic">B</mml:mi>
                                    </mml:msub>
                                </mml:mfrac>
                                <mml:mfrac>
                                    <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                    <mml:mi mathvariant="italic">d</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                    <mml:mi mathvariant="italic">A</mml:mi>
                                    </mml:msub>
                                </mml:mfrac>
                            </mml:mfenced>
                        </mml:math></inlineequation>
                        </entry>
                    </row>
                    <row>
                        <entry>
                        <constant>GL_ONE_MINUS_DST_COLOR</constant>
                        </entry>
                        <entry>
                        <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            <!-- eqn: ( 1,  1,  1,  1 )  -  (R sub d / k sub R ,  G sub d / k sub G ,  B sub d / k sub B ,  A sub d / k sub A ): -->
                            <mml:mrow>
                                <mml:mfenced open="(" close=")">
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                </mml:mfenced>
                                <mml:mo>-</mml:mo>
                                <mml:mfenced open="(" close=")">
                                    <mml:mfrac>
                                        <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
                                        <mml:mi mathvariant="italic">d</mml:mi>
                                        </mml:msub>
                                        <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                        <mml:mi mathvariant="italic">R</mml:mi>
                                        </mml:msub>
                                    </mml:mfrac>
                                    <mml:mfrac>
                                        <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
                                        <mml:mi mathvariant="italic">d</mml:mi>
                                        </mml:msub>
                                        <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                        <mml:mi mathvariant="italic">G</mml:mi>
                                        </mml:msub>
                                    </mml:mfrac>
                                    <mml:mfrac>
                                        <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
                                        <mml:mi mathvariant="italic">d</mml:mi>
                                        </mml:msub>
                                        <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                        <mml:mi mathvariant="italic">B</mml:mi>
                                        </mml:msub>
                                    </mml:mfrac>
                                    <mml:mfrac>
                                        <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                        <mml:mi mathvariant="italic">d</mml:mi>
                                        </mml:msub>
                                        <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                        <mml:mi mathvariant="italic">A</mml:mi>
                                        </mml:msub>
                                    </mml:mfrac>
                                </mml:mfenced>
                            </mml:mrow>
                        </mml:math></inlineequation>
                        </entry>
                    </row>
                    <row>
                        <entry>
                        <constant>GL_SRC_ALPHA</constant>
                        </entry>
                        <entry>
                        <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            <!-- eqn: ( A sub s / k sub A ,  A sub s / k sub A ,  A sub s / k sub A ,  A sub s / k sub A ): -->
                            <mml:mfenced open="(" close=")">
                                <mml:mfrac>
                                    <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                    <mml:mi mathvariant="italic">s</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                    <mml:mi mathvariant="italic">A</mml:mi>
                                    </mml:msub>
                                </mml:mfrac>
                                <mml:mfrac>
                                    <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                    <mml:mi mathvariant="italic">s</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                    <mml:mi mathvariant="italic">A</mml:mi>
                                    </mml:msub>
                                </mml:mfrac>
                                <mml:mfrac>
                                    <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                    <mml:mi mathvariant="italic">s</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                    <mml:mi mathvariant="italic">A</mml:mi>
                                    </mml:msub>
                                </mml:mfrac>
                                <mml:mfrac>
                                    <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                    <mml:mi mathvariant="italic">s</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                    <mml:mi mathvariant="italic">A</mml:mi>
                                    </mml:msub>
                                </mml:mfrac>
                            </mml:mfenced>
                        </mml:math></inlineequation>
                        </entry>
                    </row>
                    <row>
                        <entry>
                        <constant>GL_ONE_MINUS_SRC_ALPHA</constant>
                        </entry>
                        <entry>
                        <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            <!-- eqn: ( 1,  1,  1,  1 )  -  (A sub s / k sub A ,  A sub s / k sub A ,  A sub s / k sub A ,  A sub s / k sub A ): -->
                            <mml:mrow>
                                <mml:mfenced open="(" close=")">
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                </mml:mfenced>
                                <mml:mo>-</mml:mo>
                                <mml:mfenced open="(" close=")">
                                    <mml:mfrac>
                                        <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                        <mml:mi mathvariant="italic">s</mml:mi>
                                        </mml:msub>
                                        <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                        <mml:mi mathvariant="italic">A</mml:mi>
                                        </mml:msub>
                                    </mml:mfrac>
                                    <mml:mfrac>
                                        <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                        <mml:mi mathvariant="italic">s</mml:mi>
                                        </mml:msub>
                                        <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                        <mml:mi mathvariant="italic">A</mml:mi>
                                        </mml:msub>
                                    </mml:mfrac>
                                    <mml:mfrac>
                                        <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                        <mml:mi mathvariant="italic">s</mml:mi>
                                        </mml:msub>
                                        <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                        <mml:mi mathvariant="italic">A</mml:mi>
                                        </mml:msub>
                                    </mml:mfrac>
                                    <mml:mfrac>
                                        <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                        <mml:mi mathvariant="italic">s</mml:mi>
                                        </mml:msub>
                                        <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                        <mml:mi mathvariant="italic">A</mml:mi>
                                        </mml:msub>
                                    </mml:mfrac>
                                </mml:mfenced>
                            </mml:mrow>
                        </mml:math></inlineequation>
                        </entry>
                    </row>
                    <row>
                        <entry>
                        <constant>GL_DST_ALPHA</constant>
                        </entry>
                        <entry>
                        <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            <!-- eqn: ( A sub d / k sub A ,  A sub d / k sub A ,  A sub d / k sub A ,  A sub d / k sub A ): -->
                            <mml:mfenced open="(" close=")">
                                <mml:mfrac>
                                    <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                    <mml:mi mathvariant="italic">d</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                    <mml:mi mathvariant="italic">A</mml:mi>
                                    </mml:msub>
                                </mml:mfrac>
                                <mml:mfrac>
                                    <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                    <mml:mi mathvariant="italic">d</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                    <mml:mi mathvariant="italic">A</mml:mi>
                                    </mml:msub>
                                </mml:mfrac>
                                <mml:mfrac>
                                    <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                    <mml:mi mathvariant="italic">d</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                    <mml:mi mathvariant="italic">A</mml:mi>
                                    </mml:msub>
                                </mml:mfrac>
                                <mml:mfrac>
                                    <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                    <mml:mi mathvariant="italic">d</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                    <mml:mi mathvariant="italic">A</mml:mi>
                                    </mml:msub>
                                </mml:mfrac>
                            </mml:mfenced>
                        </mml:math></inlineequation>
                        </entry>
                    </row>
                    <row>
                        <entry>
                        <constant>GL_ONE_MINUS_DST_ALPHA</constant>
                        </entry>
                        <entry>
                        <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            <!-- eqn: ( 1,  1,  1,  1 )  -  ( A sub d / k sub A ,  A sub d / k sub A ,  A sub d / k sub A ,  A sub d / k sub A ): -->
                            <mml:mrow>
                                <mml:mfenced open="(" close=")">
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                </mml:mfenced>
                                <mml:mo>-</mml:mo>
                                <mml:mfenced open="(" close=")">
                                    <mml:mfrac>
                                        <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                        <mml:mi mathvariant="italic">d</mml:mi>
                                        </mml:msub>
                                        <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                        <mml:mi mathvariant="italic">A</mml:mi>
                                        </mml:msub>
                                    </mml:mfrac>
                                    <mml:mfrac>
                                        <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                        <mml:mi mathvariant="italic">d</mml:mi>
                                        </mml:msub>
                                        <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                        <mml:mi mathvariant="italic">A</mml:mi>
                                        </mml:msub>
                                    </mml:mfrac>
                                    <mml:mfrac>
                                        <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                        <mml:mi mathvariant="italic">d</mml:mi>
                                        </mml:msub>
                                        <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                        <mml:mi mathvariant="italic">A</mml:mi>
                                        </mml:msub>
                                    </mml:mfrac>
                                    <mml:mfrac>
                                        <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                        <mml:mi mathvariant="italic">d</mml:mi>
                                        </mml:msub>
                                        <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                                        <mml:mi mathvariant="italic">A</mml:mi>
                                        </mml:msub>
                                    </mml:mfrac>
                                </mml:mfenced>
                            </mml:mrow>
                        </mml:math></inlineequation>
                        </entry>
                    </row>
                    <row>
                        <entry>
                        <constant>GL_CONSTANT_COLOR</constant>
                        </entry>
                        <entry>
                        <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            <!-- eqn: ( R sub c, G sub c, B sub c, A sub c ): -->
                            <mml:mfenced open="(" close=")">
                                <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
                                <mml:mi mathvariant="italic">c</mml:mi>
                                </mml:msub>
                                <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
                                <mml:mi mathvariant="italic">c</mml:mi>
                                </mml:msub>
                                <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
                                <mml:mi mathvariant="italic">c</mml:mi>
                                </mml:msub>
                                <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                <mml:mi mathvariant="italic">c</mml:mi>
                                </mml:msub>
                            </mml:mfenced>
                        </mml:math></inlineequation>
                        </entry>
                    </row>
                    <row>
                        <entry>
                        <constant>GL_ONE_MINUS_CONSTANT_COLOR</constant>
                        </entry>
                        <entry>
                        <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            <!-- eqn: ( 1,  1,  1,  1 )  -  ( R sub c, G sub c, B sub c, A sub c ): -->
                            <mml:mrow>
                                <mml:mfenced open="(" close=")">
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                </mml:mfenced>
                                <mml:mo>-</mml:mo>
                                <mml:mfenced open="(" close=")">
                                    <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
                                    <mml:mi mathvariant="italic">c</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
                                    <mml:mi mathvariant="italic">c</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
                                    <mml:mi mathvariant="italic">c</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                    <mml:mi mathvariant="italic">c</mml:mi>
                                    </mml:msub>
                                </mml:mfenced>
                            </mml:mrow>
                        </mml:math></inlineequation>
                        </entry>
                    </row>
                    <row>
                        <entry>
                        <constant>GL_CONSTANT_ALPHA</constant>
                        </entry>
                        <entry>
                        <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            <!-- eqn: ( A sub c, A sub c, A sub c, A sub c ): -->
                            <mml:mfenced open="(" close=")">
                                <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                <mml:mi mathvariant="italic">c</mml:mi>
                                </mml:msub>
                                <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                <mml:mi mathvariant="italic">c</mml:mi>
                                </mml:msub>
                                <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                <mml:mi mathvariant="italic">c</mml:mi>
                                </mml:msub>
                                <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                <mml:mi mathvariant="italic">c</mml:mi>
                                </mml:msub>
                            </mml:mfenced>
                        </mml:math></inlineequation>
                        </entry>
                    </row>
                    <row>
                        <entry>
                        <constant>GL_ONE_MINUS_CONSTANT_ALPHA</constant>
                        </entry>
                        <entry>
                        <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            <!-- eqn: ( 1,  1,  1,  1 )  -  ( A sub c, A sub c, A sub c, A sub c ): -->
                            <mml:mrow>
                                <mml:mfenced open="(" close=")">
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                    <mml:mn>1</mml:mn>
                                </mml:mfenced>
                                <mml:mo>-</mml:mo>
                                <mml:mfenced open="(" close=")">
                                    <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                    <mml:mi mathvariant="italic">c</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                    <mml:mi mathvariant="italic">c</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                    <mml:mi mathvariant="italic">c</mml:mi>
                                    </mml:msub>
                                    <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                    <mml:mi mathvariant="italic">c</mml:mi>
                                    </mml:msub>
                                </mml:mfenced>
                            </mml:mrow>
                        </mml:math></inlineequation>
                        </entry>
                    </row>
                    <row>
                        <entry>
                        <constant>GL_SRC_ALPHA_SATURATE</constant>
                        </entry>
                        <entry>
                        <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            <!-- eqn: ( i,  i,  i,  1 ): -->
                            <mml:mfenced open="(" close=")">
                                <mml:mi mathvariant="italic">i</mml:mi>
                                <mml:mi mathvariant="italic">i</mml:mi>
                                <mml:mi mathvariant="italic">i</mml:mi>
                                <mml:mn>1</mml:mn>
                            </mml:mfenced>
                        </mml:math></inlineequation>
                        </entry>
                    </row>
                </tbody>
            </tgroup>
        </informaltable>
        <para>
            In the table,
        </para>
        <para>
            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- eqn: i  =   min (A sub s ,  k sub A  -  A sub d )  /  k sub A: -->
                <mml:mrow>
                    <mml:mi mathvariant="italic">i</mml:mi>
                    <mml:mo>=</mml:mo>
                    <mml:mfrac>
                        <mml:mrow>
                            <mml:mi mathvariant="italic">min</mml:mi>
                            <mml:mo>&af;</mml:mo>
                            <mml:mfenced open="(" close=")">
                                <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                <mml:mi mathvariant="italic">s</mml:mi>
                                </mml:msub>
                                <mml:mrow>
                                    <mml:msub><mml:mi mathvariant="italic">k</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:mrow>
                            </mml:mfenced>
                        </mml:mrow>
                        <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                        <mml:mi mathvariant="italic">A</mml:mi>
                        </mml:msub>
                    </mml:mfrac>
                </mml:mrow>
            </mml:math></inlineequation>
        </para>
        <para>
            To determine the blended RGBA values of a pixel,
            the system uses the following equations:
        </para>
        <para>
            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- eqn: R sub d  =      min ( k sub R,  R sub s s sub R + R sub d d sub R ): -->
                <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:mrow>
                        <mml:mi mathvariant="italic">min</mml:mi>
                        <mml:mo>&af;</mml:mo>
                        <mml:mfenced open="(" close=")">
                            <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                            <mml:mi mathvariant="italic">R</mml:mi>
                            </mml:msub>
                            <mml:mrow>
                                <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
                                <mml:mi mathvariant="italic">s</mml:mi>
                                </mml:msub>
                                <mml:mo>&it;</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>&it;</mml:mo>
                                <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
                                <mml:mi mathvariant="italic">R</mml:mi>
                                </mml:msub>
                            </mml:mrow>
                        </mml:mfenced>
                    </mml:mrow>
                </mml:mrow>
            </mml:math></inlineequation>
            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- eqn: G sub d  =    min ( k sub G,  G sub s s sub G + G sub d d sub G ): -->
                <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:mrow>
                        <mml:mi mathvariant="italic">min</mml:mi>
                        <mml:mo>&af;</mml:mo>
                        <mml:mfenced open="(" close=")">
                            <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                            <mml:mi mathvariant="italic">G</mml:mi>
                            </mml:msub>
                            <mml:mrow>
                                <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
                                <mml:mi mathvariant="italic">s</mml:mi>
                                </mml:msub>
                                <mml:mo>&it;</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>&it;</mml:mo>
                                <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
                                <mml:mi mathvariant="italic">G</mml:mi>
                                </mml:msub>
                            </mml:mrow>
                        </mml:mfenced>
                    </mml:mrow>
                </mml:mrow>
            </mml:math></inlineequation>
            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- eqn: B sub d  =    min ( k sub B,  B sub s s sub B + B sub d d sub B ): -->
                <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:mrow>
                        <mml:mi mathvariant="italic">min</mml:mi>
                        <mml:mo>&af;</mml:mo>
                        <mml:mfenced open="(" close=")">
                            <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                            <mml:mi mathvariant="italic">B</mml:mi>
                            </mml:msub>
                            <mml:mrow>
                                <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
                                <mml:mi mathvariant="italic">s</mml:mi>
                                </mml:msub>
                                <mml:mo>&it;</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>&it;</mml:mo>
                                <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
                                <mml:mi mathvariant="italic">B</mml:mi>
                                </mml:msub>
                            </mml:mrow>
                        </mml:mfenced>
                    </mml:mrow>
                </mml:mrow>
            </mml:math></inlineequation>
            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- eqn: A sub d  =    min ( k sub A,  A sub s s sub A + A sub d d sub A ): -->
                <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:mrow>
                        <mml:mi mathvariant="italic">min</mml:mi>
                        <mml:mo>&af;</mml:mo>
                        <mml:mfenced open="(" close=")">
                            <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
                            <mml:mi mathvariant="italic">A</mml:mi>
                            </mml:msub>
                            <mml:mrow>
                                <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
                                <mml:mi mathvariant="italic">s</mml:mi>
                                </mml:msub>
                                <mml:mo>&it;</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>&it;</mml:mo>
                                <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
                                <mml:mi mathvariant="italic">A</mml:mi>
                                </mml:msub>
                            </mml:mrow>
                        </mml:mfenced>
                    </mml:mrow>
                </mml:mrow>
            </mml:math></inlineequation>
        </para>
        <para>
            If the value of <constant>GL_FRAMEBUFFER_ATTACHMENT_COLOR_ENCODING</constant> for the framebuffer
            attachment corresponding to the destination buffer is <constant>GL_SRGB</constant>, the R, G, and B
            values after blending are converted into the non-linear sRGB color space by computing
                <!-- Missing equation! -->
            where cl is the R, G, or B element and cs is the result (effectively converted into an
            sRGB color space).
            If <constant>GL_FRAMEBUFFER_ATTACHMENT_COLOR_ENCODING</constant> is not <constant>GL_SRGB</constant>, then
            cs = cl:
            The resulting cs values for R, G, and B, and the unmodified A form a new
            RGBA color value. If the color buffer is fixed-point, each component is clamped
            to the range [0; 1] and then converted to a fixed-point value using equation
        </para>
    </refsect1>
    <refsect1 xml:id="examples"><title>Examples</title>
        <para>
        </para>
        <para>
            Transparency is best implemented using blend function
            (<constant>GL_SRC_ALPHA</constant>, <constant>GL_ONE_MINUS_SRC_ALPHA</constant>)
            with primitives sorted from farthest to nearest.
            Note that this transparency calculation does not require
            the presence of alpha bitplanes in the frame buffer.
        </para>
        <para>
            Blend function
            (<constant>GL_SRC_ALPHA</constant>, <constant>GL_ONE_MINUS_SRC_ALPHA</constant>)
            is also useful for rendering antialiased points and lines
            in arbitrary order.
        </para>
    </refsect1>
    <refsect1 xml:id="notes"><title>Notes</title>
        <para>
            Incoming (source) alpha is correctly thought of as a material opacity,
            ranging from 1.0
            (<inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- eqn: K sub A: -->
                <mml:msub><mml:mi mathvariant="italic">K</mml:mi>
                <mml:mi mathvariant="italic">A</mml:mi>
                </mml:msub>
            </mml:math></inlineequation>),
            representing complete opacity,
            to 0.0 (0), representing complete
            transparency.
        </para>
        <para>
            When more than one color buffer is enabled for drawing,
            the GL performs blending separately for each enabled buffer,
            using the contents of that buffer for destination color.
            (See <citerefentry><refentrytitle>glDrawBuffers</refentrytitle></citerefentry>.)
        </para>
    </refsect1>
    <refsect1 xml:id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if either <parameter>sfactor</parameter>
            or <parameter>dfactor</parameter> is not an accepted value.
        </para>
    </refsect1>
    <refsect1 xml:id="associatedgets"><title>Associated Gets</title>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_BLEND_SRC</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_BLEND_DST</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_BLEND</constant>
        </para>
        <para>
        </para>
    </refsect1>
    <refsect1 xml:id="versions">
        <title>API Version Support</title>
        <informaltable>
            <tgroup cols="4" align="left">
                <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apifunchead.xml" xpointer="xpointer(/*/*)"/>
                <tbody>
                    <row>
                        <entry>glBlendFunc</entry>
                        <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='es20']/*)"/>
                    </row>
                </tbody>
            </tgroup>
        </informaltable>
    </refsect1>
    <refsect1 xml:id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glBlendColor</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glBlendEquation</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glBlendFuncSeparate</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glClear</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glDrawBuffers</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glEnable</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"/> 2010-2014 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>
