<div class="refentry"><a id="glBlendEquationSeparate"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glBlendEquationSeparate — set the RGB blend equation and the alpha blend equation separately</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table class="funcprototype-table" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <strong class="fsfunc">glBlendEquationSeparate</strong>(</code></td><td>GLenum <var class="pdparam">modeRGB</var>, </td></tr><tr><td> </td><td>GLenum <var class="pdparam">modeAlpha</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>modeRGB</code></em></span></dt><dd><p>

specifies the RGB blend equation, how the red, green, and blue components of the source and destination colors are combined.

It must be <code class="constant">GL_FUNC_ADD</code>, <code class="constant">GL_FUNC_SUBTRACT</code>, or

<code class="constant">GL_FUNC_REVERSE_SUBTRACT</code>.

</p></dd><dt><span class="term"><em class="parameter"><code>modeAlpha</code></em></span></dt><dd><p>

specifies the alpha blend equation, how the alpha component of the source and destination colors are combined.

It must be <code class="constant">GL_FUNC_ADD</code>, <code class="constant">GL_FUNC_SUBTRACT</code>, or

<code class="constant">GL_FUNC_REVERSE_SUBTRACT</code>.

</p></dd></dl></div></div><div class="refsect1"><a id="description"></a><h2>Description</h2><p>

The blend equations determines how a new pixel (the ''source'' color)

is combined with a pixel already in the framebuffer (the ''destination''

color). This function specifies one blend equation for the RGB-color

components and one blend equation for the alpha component.

</p><p>

The blend equations use the source and destination blend factors

specified by either <a class="citerefentry" href="glBlendFunc"><span class="citerefentry"><span class="refentrytitle">glBlendFunc</span></span></a> or

<a class="citerefentry" href="glBlendFuncSeparate"><span class="citerefentry"><span class="refentrytitle">glBlendFuncSeparate</span></span></a>.

See <a class="citerefentry" href="glBlendFunc"><span class="citerefentry"><span class="refentrytitle">glBlendFunc</span></span></a> or <a class="citerefentry" href="glBlendFuncSeparate"><span class="citerefentry"><span class="refentrytitle">glBlendFuncSeparate</span></span></a>

for a description of the various blend factors.

</p><p>

In the equations that follow, source and destination

color components are referred to as

<math overflow="scroll">

<mfenced open="(" close=")">

<msub><mi mathvariant="italic">R</mi>

<mi mathvariant="italic">s</mi>

</msub>

<msub><mi mathvariant="italic">G</mi>

<mi mathvariant="italic">s</mi>

</msub>

<msub><mi mathvariant="italic">B</mi>

<mi mathvariant="italic">s</mi>

</msub>

<msub><mi mathvariant="italic">A</mi>

<mi mathvariant="italic">s</mi>

</msub>

</mfenced>

</math>

and

<math overflow="scroll">

<mfenced open="(" close=")">

<msub><mi mathvariant="italic">R</mi>

<mi mathvariant="italic">d</mi>

</msub>

<msub><mi mathvariant="italic">G</mi>

<mi mathvariant="italic">d</mi>

</msub>

<msub><mi mathvariant="italic">B</mi>

<mi mathvariant="italic">d</mi>

</msub>

<msub><mi mathvariant="italic">A</mi>

<mi mathvariant="italic">d</mi>

</msub>

</mfenced>

</math>,

respectively.

The result color is referred to as

<math overflow="scroll">

<mfenced open="(" close=")">

<msub><mi mathvariant="italic">R</mi>

<mi mathvariant="italic">r</mi>

</msub>

<msub><mi mathvariant="italic">G</mi>

<mi mathvariant="italic">r</mi>

</msub>

<msub><mi mathvariant="italic">B</mi>

<mi mathvariant="italic">r</mi>

</msub>

<msub><mi mathvariant="italic">A</mi>

<mi mathvariant="italic">r</mi>

</msub>

</mfenced>

</math>.

The source and destination blend factors are denoted

<math overflow="scroll">

<mfenced open="(" close=")">

<msub><mi mathvariant="italic">s</mi>

<mi mathvariant="italic">R</mi>

</msub>

<msub><mi mathvariant="italic">s</mi>

<mi mathvariant="italic">G</mi>

</msub>

<msub><mi mathvariant="italic">s</mi>

<mi mathvariant="italic">B</mi>

</msub>

<msub><mi mathvariant="italic">s</mi>

<mi mathvariant="italic">A</mi>

</msub>

</mfenced>

</math>

and

<math overflow="scroll">

<mfenced open="(" close=")">

<msub><mi mathvariant="italic">d</mi>

<mi mathvariant="italic">R</mi>

</msub>

<msub><mi mathvariant="italic">d</mi>

<mi mathvariant="italic">G</mi>

</msub>

<msub><mi mathvariant="italic">d</mi>

<mi mathvariant="italic">B</mi>

</msub>

<msub><mi mathvariant="italic">d</mi>

<mi mathvariant="italic">A</mi>

</msub>

</mfenced>

</math>,

respectively.

For these equations all color components are understood to have values

in the range

<math overflow="scroll">

<mfenced open="[" close="]">

<mn>0</mn>

<mn>1</mn>

</mfenced>

</math>.

</p><div class="informaltable"><table><colgroup><col /><col /><col /></colgroup><thead><tr><th><span class="bold"><strong>

Mode

</strong></span></th><th><span class="bold"><strong>

RGB Components

</strong></span></th><th><span class="bold"><strong>

Alpha Component

</strong></span></th></tr></thead><tbody><tr><td>

<code class="constant">GL_FUNC_ADD</code>

</td><td>

<div class="informalequation"><math overflow="scroll">

<mrow>

<mi mathvariant="italic">Rr</mi>

<mo>=</mo>

<mrow>

<msub><mi mathvariant="italic">R</mi>

<mi mathvariant="italic">s</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">s</mi>

<mi mathvariant="italic">R</mi>

</msub>

<mo>+</mo>

<msub><mi mathvariant="italic">R</mi>

<mi mathvariant="italic">d</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">d</mi>

<mi mathvariant="italic">R</mi>

</msub>

</mrow>

</mrow>

</math></div>

<div class="informalequation"><math overflow="scroll">

<mrow>

<mi mathvariant="italic">Gr</mi>

<mo>=</mo>

<mrow>

<msub><mi mathvariant="italic">G</mi>

<mi mathvariant="italic">s</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">s</mi>

<mi mathvariant="italic">G</mi>

</msub>

<mo>+</mo>

<msub><mi mathvariant="italic">G</mi>

<mi mathvariant="italic">d</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">d</mi>

<mi mathvariant="italic">G</mi>

</msub>

</mrow>

</mrow>

</math></div>

<div class="informalequation"><math overflow="scroll">

<mrow>

<mi mathvariant="italic">Br</mi>

<mo>=</mo>

<mrow>

<msub><mi mathvariant="italic">B</mi>

<mi mathvariant="italic">s</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">s</mi>

<mi mathvariant="italic">B</mi>

</msub>

<mo>+</mo>

<msub><mi mathvariant="italic">B</mi>

<mi mathvariant="italic">d</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">d</mi>

<mi mathvariant="italic">B</mi>

</msub>

</mrow>

</mrow>

</math></div>

</td><td>

<div class="informalequation"><math overflow="scroll">

<mrow>

<mi mathvariant="italic">Ar</mi>

<mo>=</mo>

<mrow>

<msub><mi mathvariant="italic">A</mi>

<mi mathvariant="italic">s</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">s</mi>

<mi mathvariant="italic">A</mi>

</msub>

<mo>+</mo>

<msub><mi mathvariant="italic">A</mi>

<mi mathvariant="italic">d</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">d</mi>

<mi mathvariant="italic">A</mi>

</msub>

</mrow>

</mrow>

</math></div>

</td></tr><tr><td>

<code class="constant">GL_FUNC_SUBTRACT</code>

</td><td>

<div class="informalequation"><math overflow="scroll">

<mrow>

<mi mathvariant="italic">Rr</mi>

<mo>=</mo>

<mrow>

<msub><mi mathvariant="italic">R</mi>

<mi mathvariant="italic">s</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">s</mi>

<mi mathvariant="italic">R</mi>

</msub>

<mo>-</mo>

<msub><mi mathvariant="italic">R</mi>

<mi mathvariant="italic">d</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">d</mi>

<mi mathvariant="italic">R</mi>

</msub>

</mrow>

</mrow>

</math></div>

<div class="informalequation"><math overflow="scroll">

<mrow>

<mi mathvariant="italic">Gr</mi>

<mo>=</mo>

<mrow>

<msub><mi mathvariant="italic">G</mi>

<mi mathvariant="italic">s</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">s</mi>

<mi mathvariant="italic">G</mi>

</msub>

<mo>-</mo>

<msub><mi mathvariant="italic">G</mi>

<mi mathvariant="italic">d</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">d</mi>

<mi mathvariant="italic">G</mi>

</msub>

</mrow>

</mrow>

</math></div>

<div class="informalequation"><math overflow="scroll">

<mrow>

<mi mathvariant="italic">Br</mi>

<mo>=</mo>

<mrow>

<msub><mi mathvariant="italic">B</mi>

<mi mathvariant="italic">s</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">s</mi>

<mi mathvariant="italic">B</mi>

</msub>

<mo>-</mo>

<msub><mi mathvariant="italic">B</mi>

<mi mathvariant="italic">d</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">d</mi>

<mi mathvariant="italic">B</mi>

</msub>

</mrow>

</mrow>

</math></div>

</td><td>

<div class="informalequation"><math overflow="scroll">

<mrow>

<mi mathvariant="italic">Ar</mi>

<mo>=</mo>

<mrow>

<msub><mi mathvariant="italic">A</mi>

<mi mathvariant="italic">s</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">s</mi>

<mi mathvariant="italic">A</mi>

</msub>

<mo>-</mo>

<msub><mi mathvariant="italic">A</mi>

<mi mathvariant="italic">d</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">d</mi>

<mi mathvariant="italic">A</mi>

</msub>

</mrow>

</mrow>

</math></div>

</td></tr><tr><td>

<code class="constant">GL_FUNC_REVERSE_SUBTRACT</code>

</td><td>

<div class="informalequation"><math overflow="scroll">

<mrow>

<mi mathvariant="italic">Rr</mi>

<mo>=</mo>

<mrow>

<msub><mi mathvariant="italic">R</mi>

<mi mathvariant="italic">d</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">d</mi>

<mi mathvariant="italic">R</mi>

</msub>

<mo>-</mo>

<msub><mi mathvariant="italic">R</mi>

<mi mathvariant="italic">s</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">s</mi>

<mi mathvariant="italic">R</mi>

</msub>

</mrow>

</mrow>

</math></div>

<div class="informalequation"><math overflow="scroll">

<mrow>

<mi mathvariant="italic">Gr</mi>

<mo>=</mo>

<mrow>

<msub><mi mathvariant="italic">G</mi>

<mi mathvariant="italic">d</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">d</mi>

<mi mathvariant="italic">G</mi>

</msub>

<mo>-</mo>

<msub><mi mathvariant="italic">G</mi>

<mi mathvariant="italic">s</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">s</mi>

<mi mathvariant="italic">G</mi>

</msub>

</mrow>

</mrow>

</math></div>

<div class="informalequation"><math overflow="scroll">

<mrow>

<mi mathvariant="italic">Br</mi>

<mo>=</mo>

<mrow>

<msub><mi mathvariant="italic">B</mi>

<mi mathvariant="italic">d</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">d</mi>

<mi mathvariant="italic">B</mi>

</msub>

<mo>-</mo>

<msub><mi mathvariant="italic">B</mi>

<mi mathvariant="italic">s</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">s</mi>

<mi mathvariant="italic">B</mi>

</msub>

</mrow>

</mrow>

</math></div>

</td><td>

<div class="informalequation"><math overflow="scroll">

<mrow>

<mi mathvariant="italic">Ar</mi>

<mo>=</mo>

<mrow>

<msub><mi mathvariant="italic">A</mi>

<mi mathvariant="italic">d</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">d</mi>

<mi mathvariant="italic">A</mi>

</msub>

<mo>-</mo>

<msub><mi mathvariant="italic">A</mi>

<mi mathvariant="italic">s</mi>

</msub>

<mo>⁢</mo>

<msub><mi mathvariant="italic">s</mi>

<mi mathvariant="italic">A</mi>

</msub>

</mrow>

</mrow>

</math></div>

</td></tr></tbody></table></div><p>

</p><p>

The results of these equations are clamped to the range

<math overflow="scroll">

<mfenced open="[" close="]">

<mn>0</mn>

<mn>1</mn>

</mfenced>

</math>.

</p><p>

The <code class="constant">GL_FUNC_ADD</code> equation is useful

for antialiasing and transparency, among other things.

</p><p>

Initially, both the RGB blend equation and the alpha blend equation are set to <code class="constant">GL_FUNC_ADD</code>.

</p><p>

</p></div><div class="refsect1"><a id="errors"></a><h2>Errors</h2><p>

<code class="constant">GL_INVALID_ENUM</code> is generated if either <em class="parameter"><code>modeRGB</code></em> or <em class="parameter"><code>modeAlpha</code></em> is not one of

<code class="constant">GL_FUNC_ADD</code>, <code class="constant">GL_FUNC_SUBTRACT</code>, or <code class="constant">GL_FUNC_REVERSE_SUBTRACT</code>.

</p></div><div class="refsect1"><a id="associatedgets"></a><h2>Associated Gets</h2><p>

<a class="citerefentry" href="glGet"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with an argument of <code class="constant">GL_BLEND_EQUATION_RGB</code>

</p><p>

<a class="citerefentry" href="glGet"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with an argument of <code class="constant">GL_BLEND_EQUATION_ALPHA</code>

</p></div>

{$pipelinestall}{$examples}

<div class="refsect1"><a id="seealso"></a><h2>See Also</h2><p>

<a class="citerefentry" href="glGetString"><span class="citerefentry"><span class="refentrytitle">glGetString</span></span></a>,

<a class="citerefentry" href="glBlendColor"><span class="citerefentry"><span class="refentrytitle">glBlendColor</span></span></a>,

<a class="citerefentry" href="glBlendEquation"><span class="citerefentry"><span class="refentrytitle">glBlendEquation</span></span></a>,

<a class="citerefentry" href="glBlendFunc"><span class="citerefentry"><span class="refentrytitle">glBlendFunc</span></span></a>,

<a class="citerefentry" href="glBlendFuncSeparate"><span class="citerefentry"><span class="refentrytitle">glBlendFuncSeparate</span></span></a>

</p></div><div class="refsect1"><div id="Copyright"><h2>Copyright</h2><p>

Copyright © 2006 Khronos Group.

This material may be distributed subject to the terms and conditions set forth in

the Open Publication License, v 1.0, 8 June 1999.

<a class="ulink" href="https://opencontent.org/openpub/" target="_top">https://opencontent.org/openpub/</a>.

</p></div></div></div>