<div class="refentry"><a id="glBlendFuncSeparate"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glBlendFuncSeparate — specify pixel arithmetic for RGB and alpha components 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">glBlendFuncSeparate</strong>(</code></td><td>GLenum <var class="pdparam">srcRGB</var>, </td></tr><tr><td> </td><td>GLenum <var class="pdparam">dstRGB</var>, </td></tr><tr><td> </td><td>GLenum <var class="pdparam">srcAlpha</var>, </td></tr><tr><td> </td><td>GLenum <var class="pdparam">dstAlpha</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>srcRGB</code></em></span></dt><dd><p>

Specifies how the red, green, and blue blending factors are computed.

The following symbolic constants are accepted:

<code class="constant">GL_ZERO</code>,

<code class="constant">GL_ONE</code>,

<code class="constant">GL_SRC_COLOR</code>,

<code class="constant">GL_ONE_MINUS_SRC_COLOR</code>,

<code class="constant">GL_DST_COLOR</code>,

<code class="constant">GL_ONE_MINUS_DST_COLOR</code>,

<code class="constant">GL_SRC_ALPHA</code>,

<code class="constant">GL_ONE_MINUS_SRC_ALPHA</code>,

<code class="constant">GL_DST_ALPHA</code>,

<code class="constant">GL_ONE_MINUS_DST_ALPHA</code>,

<code class="constant">GL_CONSTANT_COLOR</code>,

<code class="constant">GL_ONE_MINUS_CONSTANT_COLOR</code>,

<code class="constant">GL_CONSTANT_ALPHA</code>,

<code class="constant">GL_ONE_MINUS_CONSTANT_ALPHA</code>, and

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

The initial value is <code class="constant">GL_ONE</code>.

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

Specifies how the red, green, and blue destination blending factors are

computed. The following symbolic constants are accepted:

<code class="constant">GL_ZERO</code>,

<code class="constant">GL_ONE</code>,

<code class="constant">GL_SRC_COLOR</code>,

<code class="constant">GL_ONE_MINUS_SRC_COLOR</code>,

<code class="constant">GL_DST_COLOR</code>,

<code class="constant">GL_ONE_MINUS_DST_COLOR</code>,

<code class="constant">GL_SRC_ALPHA</code>,

<code class="constant">GL_ONE_MINUS_SRC_ALPHA</code>,

<code class="constant">GL_DST_ALPHA</code>,

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

<code class="constant">GL_CONSTANT_COLOR</code>,

<code class="constant">GL_ONE_MINUS_CONSTANT_COLOR</code>,

<code class="constant">GL_CONSTANT_ALPHA</code>, and

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

The initial value is <code class="constant">GL_ZERO</code>.

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

Specified how the alpha source blending factor is computed. The same

symbolic constants are accepted as for <em class="parameter"><code>srcRGB</code></em>.

The initial value is <code class="constant">GL_ONE</code>.

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

Specified how the alpha destination blending factor is computed. The same

symbolic constants are accepted as for <em class="parameter"><code>dstRGB</code></em>.

The initial value is <code class="constant">GL_ZERO</code>.

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

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 <a class="citerefentry" href="glEnable"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a> and <a class="citerefentry" href="glDisable"><span class="citerefentry"><span class="refentrytitle">glDisable</span></span></a> with argument <code class="constant">GL_BLEND</code>

to enable and disable blending.

</p><p>

<code class="function">glBlendFuncSeparate</code> defines the operation of blending when it is enabled.

<em class="parameter"><code>srcRGB</code></em> specifies which method is used to scale the

source RGB-color components.

<em class="parameter"><code>dstRGB</code></em> specifies which method is used to scale the

destination RGB-color components.

Likewise, <em class="parameter"><code>srcAlpha</code></em> specifies which method is used to scale the source alpha

color component, and <em class="parameter"><code>dstAlpha</code></em> specifies which method is used to scale the

destination alpha component.

The possible methods are described in the following table.

Each method defines four scale factors,

one each for red, green, blue, and alpha.

</p><p>

In the table and in subsequent equations, source and destination

color components are referred to as

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and

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The color specified by <a class="citerefentry" href="glBlendColor"><span class="citerefentry"><span class="refentrytitle">glBlendColor</span></span></a> is referred to as

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where

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and

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is the number of red,

green,

blue,

and alpha bitplanes.

</p><p>

Source and destination scale factors are referred to as

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All scale factors have range

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</p><p>

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

Parameter

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

RGB Factor

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

Alpha Factor

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

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

</td><td>

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<mn>0</mn>

<mn>0</mn>

<mn>0</mn>

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</td><td>

<math overflow="scroll">

<mn>0</mn>

</math>

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

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

</td><td>

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

<mn>1</mn>

<mn>1</mn>

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</td><td>

<math overflow="scroll">

<mn>1</mn>

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

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

</td><td>

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<mfrac>

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

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

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

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</mfrac>

<mfrac>

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

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

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</td><td>

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

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

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

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

</td><td>

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

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

</td><td>

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<mfrac>

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

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</td><td>

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

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

</td><td>

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

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

</td><td>

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

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

</td><td>

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

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

</td><td>

<math overflow="scroll">

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

<mfrac>

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

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

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

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

</td><td>

<math overflow="scroll">

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<mn>1</mn>

<mn>1</mn>

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<mfrac>

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

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

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

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</td><td>

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<mfrac>

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

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

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

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

</msub>

</mfrac>

</mrow>

</math>

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

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

</td><td>

<math overflow="scroll">

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

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

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

</msub>

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

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

</msub>

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

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

</msub>

</mfenced>

</math>

</td><td>

<math overflow="scroll">

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

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

</msub>

</math>

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

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

</td><td>

<math overflow="scroll">

<mrow>

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

<mn>1</mn>

<mn>1</mn>

<mn>1</mn>

</mfenced>

<mo>-</mo>

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

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

</msub>

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

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

</msub>

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

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

</msub>

</mfenced>

</mrow>

</math>

</td><td>

<math overflow="scroll">

<mrow>

<mn>1</mn>

<mo>-</mo>

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