<div class="refentry" id="glBlendEquation">

<div class="titlepage"></div>

<div class="refnamediv">

<h2>Name</h2>

<p>glBlendEquation — specify the equation used for both the RGB blend equation and the Alpha blend equation</p>

</div>

<div class="refsynopsisdiv">

<h2>C Specification</h2>

<div class="funcsynopsis">

<table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">

<tr>

<td>

<code class="funcdef">void <strong class="fsfunc">glBlendEquation</strong>(</code>

</td>

<td>GLenum <var class="pdparam">mode</var><code>)</code>;</td>

</tr>

</table>

<div class="funcprototype-spacer"> </div>

<table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">

<tr>

<td>

<code class="funcdef">void <strong class="fsfunc">glBlendEquationi</strong>(</code>

</td>

<td>GLuint <var class="pdparam">buf</var>, </td>

</tr>

<tr>

<td> </td>

<td>GLenum <var class="pdparam">mode</var><code>)</code>;</td>

</tr>

</table>

<div class="funcprototype-spacer"> </div>

</div>

</div>

<div class="refsect1" id="parameters">

<h2>Parameters</h2>

<div class="variablelist">

<dl class="variablelist">

<dt>

<span class="term">

<em class="parameter">

<code>buf</code>

</em>

</span>

</dt>

<dd>

<p>

for <code class="function">glBlendEquationi</code>, specifies the index of the draw buffer

for which to set the blend equation.

</p>

</dd>

<dt>

<span class="term">

<em class="parameter">

<code>mode</code>

</em>

</span>

</dt>

<dd>

<p>

specifies how source and destination colors are combined.

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

<code class="constant">GL_FUNC_REVERSE_SUBTRACT</code>, <code class="constant">GL_MIN</code>, <code class="constant">GL_MAX</code>.

</p>

</dd>

</dl>

</div>

</div>

<div class="refsect1" id="description">

<h2>Description</h2>

<p>

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. <code class="function">glBlendEquationi</code>

specifies the blend equation for a single draw buffer whereas <code class="function">glBlendEquation</code>

sets the blend equation for all draw buffers.

</p>

<p>

These 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 style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">

<colgroup>

<col style="text-align: left; "/>

<col style="text-align: left; "/>

<col style="text-align: left; "/>

</colgroup>

<thead>

<tr>

<th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">

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

</th>

<th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">

<span class="bold"><strong> RGB Components </strong></span>

</th>

<th style="text-align: left; border-bottom: 2px solid ; ">

<span class="bold"><strong> Alpha Component </strong></span>

</th>

</tr>

</thead>

<tbody>

<tr>

<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">

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

</td>

<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">

<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>

<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>

<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>

</td>

<td style="text-align: left; border-bottom: 2px solid ; ">

<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>

</td>

</tr>

<tr>

<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">

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

</td>

<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">

<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>

<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>

<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>

</td>

<td style="text-align: left; border-bottom: 2px solid ; ">

<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>

</td>

</tr>

<tr>

<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">

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

</td>

<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">

<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>

<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>

<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>

</td>

<td style="text-align: left; border-bottom: 2px solid ; ">

<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>

</td>

</tr>

<tr>

<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">

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

</td>

<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">

<math overflow="scroll">

<mrow>

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

<mo>=</mo>

<mrow>

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

<mo>⁡</mo>

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

<mrow>

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

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

</msub>

</mrow>

<mrow>

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

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

</msub>

</mrow>

</mfenced>

</mrow>

</mrow>

</math>

<math overflow="scroll">

<mrow>

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

<mo>=</mo>

<mrow>

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

<mo>⁡</mo>

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

<mrow>

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

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

</msub>

</mrow>

<mrow>

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

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

</msub>

</mrow>

</mfenced>

</mrow>

</mrow>

</math>

<math overflow="scroll">

<mrow>

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

<mo>=</mo>

<mrow>

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

<mo>⁡</mo>

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

<mrow>

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

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

</msub>

</mrow>

<mrow>

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

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

</msub>

</mrow>

</mfenced>

</mrow>

</mrow>

</math>

</td>

<td style="text-align: left; border-bottom: 2px solid ; ">

<math overflow="scroll">

<mrow>

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

<mo>=</mo>

<mrow>

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

<mo>⁡</mo>

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

<mrow>

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

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

</msub>

</mrow>

<mrow>

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

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

</msub>

</mrow>

</mfenced>

</mrow>

</mrow>

</math>

</td>

</tr>

<tr>

<td style="text-align: left; border-right: 2px solid ; ">

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

</td>

<td style="text-align: left; border-right: 2px solid ; ">

<math overflow="scroll">

<mrow>

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

<mo>=</mo>

<mrow>

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

<mo>⁡</mo>

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

<mrow>

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

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

</msub>

</mrow>

<mrow>

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

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

</msub>

</mrow>

</mfenced>

</mrow>

</mrow>

</math>

<math overflow="scroll">

<mrow>

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

<mo>=</mo>

<mrow>

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

<mo>⁡</mo>

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

<mrow>

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

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

</msub>

</mrow>

<mrow>

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

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

</msub>

</mrow>

</mfenced>

</mrow>

</mrow>

</math>

<math overflow="scroll">

<mrow>

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

<mo>=</mo>

<mrow>

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

<mo>⁡</mo>

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

<mrow>

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

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

</msub>

</mrow>

<mrow>

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

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

</msub>

</mrow>

</mfenced>

</mrow>

</mrow>

</math>

</td>

<td style="text-align: left; ">

<math overflow="scroll">

<mrow>

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

<mo>=</mo>

<mrow>

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

<mo>⁡</mo>

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

<mrow>

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

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

</msub>

</mrow>

<mrow>

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

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

</msub>

</mrow>

</mfenced>

</mrow>

</mrow>

</math>

</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_MIN</code> and <code class="constant">GL_MAX</code> equations are useful for applications

that analyze image data (image thresholding against a constant color,

for example).

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" id="notes">

<h2>Notes</h2>

<p>

The <code class="constant">GL_MIN</code>, and <code class="constant">GL_MAX</code> equations do not use

the source or destination factors, only the source and destination colors.

</p>

</div>

<div class="refsect1" id="errors">

<h2>Errors</h2>

<p>

<code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>mode</code></em> is not one of

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

<code class="constant">GL_MAX</code>, or <code class="constant">GL_MIN</code>.

</p>

<p>

<code class="constant">GL_INVALID_VALUE</code> is generated by <code class="function">glBlendEquationi</code> if <em class="parameter"><code>buf</code></em> is greater

than or equal to the value of <code class="constant">GL_MAX_DRAW_BUFFERS</code>.

</p>

</div>

<div class="refsect1" id="associatedgets">

<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" id="versions">

<h2>Version Support</h2>

<div class="informaltable">

<table style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">

<colgroup>

<col style="text-align: left; "/>

<col style="text-align: center; " class="firstvers"/>

<col style="text-align: center; "/>

<col style="text-align: center; "/>

<col style="text-align: center; "/>

<col style="text-align: center; "/>

<col style="text-align: center; "/>

<col style="text-align: center; "/>

<col style="text-align: center; "/>

<col style="text-align: center; "/>

<col style="text-align: center; "/>