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"opengl-man.css" /><title>glBlendEquation - OpenGL
4 Reference Pages
</title><meta name=
"generator" content=
"DocBook XSL Stylesheets V1.69.1" /></head><body><div class=
"refentry" lang=
"en" xml:
lang=
"en"><a id=
"glBlendEquation"></a><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"><p><code class=
"funcdef">void
<b class=
"fsfunc">glBlendEquation
</b>(
</code>GLenum
<var class=
"pdparam">mode
</var><code>)
</code>;
</p><table border=
"0" summary=
"Function synopsis" cellspacing=
"0" cellpadding=
"0"><tr><td><code class=
"funcdef">void
<b class=
"fsfunc">glBlendEquationi
</b>(
</code></td><td>GLuint
</td><td><var class=
"pdparam">buf
</var>,
</td></tr><tr><td> </td><td>GLenum
</td><td><var class=
"pdparam">mode
</var><code>)
</code>;
</td></tr></table></div></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"parameters"></a><h2>Parameters
</h2><div class=
"variablelist"><dl><dt><span class=
"term"><em class=
"parameter"><code>buf
</code></em></span></dt><dd><p>
5 for
<code class=
"function">glBlendEquationi
</code>, specifies the index of the draw buffer
6 for which to set the blend equation.
7 </p></dd><dt><span class=
"term"><em class=
"parameter"><code>mode
</code></em></span></dt><dd><p>
8 specifies how source and destination colors are combined.
9 It must be
<code class=
"constant">GL_FUNC_ADD
</code>,
<code class=
"constant">GL_FUNC_SUBTRACT
</code>,
10 <code class=
"constant">GL_FUNC_REVERSE_SUBTRACT
</code>,
<code class=
"constant">GL_MIN
</code>,
<code class=
"constant">GL_MAX
</code>.
11 </p></dd></dl></div></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"description"></a><h2>Description
</h2><p>
12 The blend equations determine how a new pixel (the ''source'' color)
13 is combined with a pixel already in the framebuffer (the ''destination''
14 color). This function sets both the RGB blend equation and the alpha
15 blend equation to a single equation.
<code class=
"function">glBlendEquationi
</code>
16 specifies the blend equation for a single draw buffer whereas
<code class=
"function">glBlendEquation
</code>
17 sets the blend equation for all draw buffers.
19 These equations use the source and destination blend factors
20 specified by either
<a href=
"glBlendFunc.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glBlendFunc
</span></span></a> or
21 <a href=
"glBlendFuncSeparate.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glBlendFuncSeparate
</span></span></a>.
22 See
<a href=
"glBlendFunc.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glBlendFunc
</span></span></a> or
<a href=
"glBlendFuncSeparate.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glBlendFuncSeparate
</span></span></a>
23 for a description of the various blend factors.
25 In the equations that follow, source and destination
26 color components are referred to as
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63 The result color is referred to as
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</mml:mi>
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"italic">B
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</mml:mi>
76 <mml:msub><mml:mi mathvariant=
"italic">A
</mml:mi>
77 <mml:mi mathvariant=
"italic">r
</mml:mi>
81 The source and destination blend factors are denoted
82 <mml:math xmlns:
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"scroll">
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"(" close=
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</mml:mi>
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"(" close=
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118 For these equations all color components are understood to have values
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"scroll">
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"[" close=
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128 </p><div class=
"informaltable"><table border=
"1"><colgroup><col align=
"left" /><col align=
"left" /><col align=
"left" /></colgroup><thead><tr><th align=
"left"><span class=
"bold"><strong>
130 </strong></span></th><th align=
"left"><span class=
"bold"><strong>
132 </strong></span></th><th align=
"left"><span class=
"bold"><strong>
134 </strong></span></th></tr></thead><tbody><tr><td align=
"left">
135 <code class=
"constant">GL_FUNC_ADD
</code>
136 </td><td align=
"left">
137 <div class=
"informalequation"><mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
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"italic">Rr
</mml:mi>
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"italic">R
</mml:mi>
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"italic">s
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"italic">s
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</mml:mi>
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"scroll">
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"scroll">
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209 </td><td align=
"left">
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"informalequation"><mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
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234 </td></tr><tr><td align=
"left">
235 <code class=
"constant">GL_FUNC_SUBTRACT
</code>
236 </td><td align=
"left">
237 <div class=
"informalequation"><mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
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"italic">Rr
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"informalequation"><mml:math xmlns:
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"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
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</mml:mi>
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"informalequation"><mml:math xmlns:
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"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
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"italic">Br
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"italic">s
</mml:mi>
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"italic">B
</mml:mi>
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"italic">B
</mml:mi>
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"italic">d
</mml:mi>
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"italic">d
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"italic">B
</mml:mi>
309 </td><td align=
"left">
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"informalequation"><mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
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"italic">Ar
</mml:mi>
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"italic">A
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</mml:mi>
334 </td></tr><tr><td align=
"left">
335 <code class=
"constant">GL_FUNC_REVERSE_SUBTRACT
</code>
336 </td><td align=
"left">
337 <div class=
"informalequation"><mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
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"italic">Rr
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"italic">s
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"italic">R
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"informalequation"><mml:math xmlns:
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"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
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</mml:mi>
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"italic">B
</mml:mi>
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"italic">B
</mml:mi>
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"italic">s
</mml:mi>
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"italic">s
</mml:mi>
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"italic">B
</mml:mi>
409 </td><td align=
"left">
410 <div class=
"informalequation"><mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
413 <mml:mi mathvariant=
"italic">Ar
</mml:mi>
416 <mml:msub><mml:mi mathvariant=
"italic">A
</mml:mi>
417 <mml:mi mathvariant=
"italic">d
</mml:mi>
420 <mml:msub><mml:mi mathvariant=
"italic">d
</mml:mi>
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"italic">A
</mml:mi>
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"italic">A
</mml:mi>
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"italic">s
</mml:mi>
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"italic">s
</mml:mi>
429 <mml:mi mathvariant=
"italic">A
</mml:mi>
434 </td></tr><tr><td align=
"left">
435 <code class=
"constant">GL_MIN
</code>
436 </td><td align=
"left">
437 <div class=
"informalequation"><mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
440 <mml:mi mathvariant=
"italic">Rr
</mml:mi>
443 <mml:mi mathvariant=
"italic">min
</mml:mi>
445 <mml:mfenced open=
"(" close=
")">
447 <mml:msub><mml:mi mathvariant=
"italic">R
</mml:mi>
448 <mml:mi mathvariant=
"italic">s
</mml:mi>
452 <mml:msub><mml:mi mathvariant=
"italic">R
</mml:mi>
453 <mml:mi mathvariant=
"italic">d
</mml:mi>
460 <div class=
"informalequation"><mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
463 <mml:mi mathvariant=
"italic">Gr
</mml:mi>
466 <mml:mi mathvariant=
"italic">min
</mml:mi>
468 <mml:mfenced open=
"(" close=
")">
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"italic">G
</mml:mi>
471 <mml:mi mathvariant=
"italic">s
</mml:mi>
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"italic">G
</mml:mi>
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"italic">d
</mml:mi>
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"informalequation"><mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
486 <mml:mi mathvariant=
"italic">Br
</mml:mi>
489 <mml:mi mathvariant=
"italic">min
</mml:mi>
491 <mml:mfenced open=
"(" close=
")">
493 <mml:msub><mml:mi mathvariant=
"italic">B
</mml:mi>
494 <mml:mi mathvariant=
"italic">s
</mml:mi>
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"italic">B
</mml:mi>
499 <mml:mi mathvariant=
"italic">d
</mml:mi>
506 </td><td align=
"left">
507 <div class=
"informalequation"><mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
510 <mml:mi mathvariant=
"italic">Ar
</mml:mi>
513 <mml:mi mathvariant=
"italic">min
</mml:mi>
515 <mml:mfenced open=
"(" close=
")">
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"italic">A
</mml:mi>
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"italic">s
</mml:mi>
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"italic">A
</mml:mi>
523 <mml:mi mathvariant=
"italic">d
</mml:mi>
530 </td></tr><tr><td align=
"left">
531 <code class=
"constant">GL_MAX
</code>
532 </td><td align=
"left">
533 <div class=
"informalequation"><mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
536 <mml:mi mathvariant=
"italic">Rr
</mml:mi>
539 <mml:mi mathvariant=
"italic">max
</mml:mi>
541 <mml:mfenced open=
"(" close=
")">
543 <mml:msub><mml:mi mathvariant=
"italic">R
</mml:mi>
544 <mml:mi mathvariant=
"italic">s
</mml:mi>
548 <mml:msub><mml:mi mathvariant=
"italic">R
</mml:mi>
549 <mml:mi mathvariant=
"italic">d
</mml:mi>
556 <div class=
"informalequation"><mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
559 <mml:mi mathvariant=
"italic">Gr
</mml:mi>
562 <mml:mi mathvariant=
"italic">max
</mml:mi>
564 <mml:mfenced open=
"(" close=
")">
566 <mml:msub><mml:mi mathvariant=
"italic">G
</mml:mi>
567 <mml:mi mathvariant=
"italic">s
</mml:mi>
571 <mml:msub><mml:mi mathvariant=
"italic">G
</mml:mi>
572 <mml:mi mathvariant=
"italic">d
</mml:mi>
579 <div class=
"informalequation"><mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
582 <mml:mi mathvariant=
"italic">Br
</mml:mi>
585 <mml:mi mathvariant=
"italic">max
</mml:mi>
587 <mml:mfenced open=
"(" close=
")">
589 <mml:msub><mml:mi mathvariant=
"italic">B
</mml:mi>
590 <mml:mi mathvariant=
"italic">s
</mml:mi>
594 <mml:msub><mml:mi mathvariant=
"italic">B
</mml:mi>
595 <mml:mi mathvariant=
"italic">d
</mml:mi>
602 </td><td align=
"left">
603 <div class=
"informalequation"><mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
606 <mml:mi mathvariant=
"italic">Ar
</mml:mi>
609 <mml:mi mathvariant=
"italic">max
</mml:mi>
611 <mml:mfenced open=
"(" close=
")">
613 <mml:msub><mml:mi mathvariant=
"italic">A
</mml:mi>
614 <mml:mi mathvariant=
"italic">s
</mml:mi>
618 <mml:msub><mml:mi mathvariant=
"italic">A
</mml:mi>
619 <mml:mi mathvariant=
"italic">d
</mml:mi>
626 </td></tr></tbody></table></div><p>
628 The results of these equations are clamped to the range
629 <mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
631 <mml:mfenced open=
"[" close=
"]">
637 The
<code class=
"constant">GL_MIN
</code> and
<code class=
"constant">GL_MAX
</code> equations are useful for applications
638 that analyze image data (image thresholding against a constant color,
640 The
<code class=
"constant">GL_FUNC_ADD
</code> equation is useful
641 for antialiasing and transparency, among other things.
643 Initially, both the RGB blend equation and the alpha blend equation are set to
<code class=
"constant">GL_FUNC_ADD
</code>.
645 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"notes"></a><h2>Notes
</h2><p>
646 The
<code class=
"constant">GL_MIN
</code>, and
<code class=
"constant">GL_MAX
</code> equations do not use
647 the source or destination factors, only the source and destination colors.
648 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"errors"></a><h2>Errors
</h2><p>
649 <code class=
"constant">GL_INVALID_ENUM
</code> is generated if
<em class=
"parameter"><code>mode
</code></em> is not one of
650 <code class=
"constant">GL_FUNC_ADD
</code>,
<code class=
"constant">GL_FUNC_SUBTRACT
</code>,
<code class=
"constant">GL_FUNC_REVERSE_SUBTRACT
</code>,
651 <code class=
"constant">GL_MAX
</code>, or
<code class=
"constant">GL_MIN
</code>.
653 <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
654 than or equal to the value of
<code class=
"constant">GL_MAX_DRAW_BUFFERS
</code>.
655 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"associatedgets"></a><h2>Associated Gets
</h2><p>
656 <a href=
"glGet.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glGet
</span></span></a> with an argument of
<code class=
"constant">GL_BLEND_EQUATION_RGB
</code>
658 <a href=
"glGet.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glGet
</span></span></a> with an argument of
<code class=
"constant">GL_BLEND_EQUATION_ALPHA
</code>
659 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"seealso"></a><h2>See Also
</h2><p>
660 <a href=
"glBlendColor.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glBlendColor
</span></span></a>,
661 <a href=
"glBlendFunc.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glBlendFunc
</span></span></a>
662 <a href=
"glBlendFuncSeparate.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glBlendFuncSeparate
</span></span></a>
663 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"Copyright"></a><h2>Copyright
</h2><p>
664 Copyright
<span class=
"trademark"></span>©
1991-
2006
665 Silicon Graphics, Inc. This document is licensed under the SGI
666 Free Software B License. For details, see
667 <a href=
"http://oss.sgi.com/projects/FreeB/" target=
"_top">http://oss.sgi.com/projects/FreeB/
</a>.
668 </p></div></div></body></html>