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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>glLogicOp - OpenGL 4 Reference Pages</title>
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<header/>
<div class="refentry" id="glLogicOp">
<div class="titlepage"/>
<div class="refnamediv">
<h2>Name</h2>
<p>glLogicOp — specify a logical pixel operation for rendering</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">glLogicOp</strong>(</code>
</td>
<td>GLenum <var class="pdparam">opcode</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>opcode</code>
</em>
</span>
</dt>
<dd>
<p>
Specifies a symbolic constant that selects a logical operation.
The following symbols are accepted:
<code class="constant">GL_CLEAR</code>,
<code class="constant">GL_SET</code>,
<code class="constant">GL_COPY</code>,
<code class="constant">GL_COPY_INVERTED</code>,
<code class="constant">GL_NOOP</code>,
<code class="constant">GL_INVERT</code>,
<code class="constant">GL_AND</code>,
<code class="constant">GL_NAND</code>,
<code class="constant">GL_OR</code>,
<code class="constant">GL_NOR</code>,
<code class="constant">GL_XOR</code>,
<code class="constant">GL_EQUIV</code>,
<code class="constant">GL_AND_REVERSE</code>,
<code class="constant">GL_AND_INVERTED</code>,
<code class="constant">GL_OR_REVERSE</code>, and
<code class="constant">GL_OR_INVERTED</code>. The initial value is <code class="constant">GL_COPY</code>.
</p>
</dd>
</dl>
</div>
</div>
<div class="refsect1" id="description">
<h2>Description</h2>
<p>
<code class="function">glLogicOp</code> specifies a logical operation that,
when enabled,
is applied between the incoming RGBA color
and the RGBA color at the corresponding location in the
frame buffer.
To enable or disable the logical operation, call
<a class="citerefentry" href="glEnable.xhtml"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a> and <a class="citerefentry" href="glDisable.xhtml"><span class="citerefentry"><span class="refentrytitle">glDisable</span></span></a>
using the symbolic constant <code class="constant">GL_COLOR_LOGIC_OP</code>. The initial value is
disabled.
</p>
<p>
</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: center; "/>
</colgroup>
<thead>
<tr>
<th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong> Opcode </strong></span>
</th>
<th style="text-align: center; border-bottom: 2px solid ; ">
<span class="bold"><strong> Resulting Operation </strong></span>
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<code class="constant">GL_CLEAR</code>
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
0
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<code class="constant">GL_SET</code>
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
1
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<code class="constant">GL_COPY</code>
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
s
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<code class="constant">GL_COPY_INVERTED</code>
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
~s
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<code class="constant">GL_NOOP</code>
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
d
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<code class="constant">GL_INVERT</code>
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
~d
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<code class="constant">GL_AND</code>
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
s & d
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<code class="constant">GL_NAND</code>
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
~(s & d)
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<code class="constant">GL_OR</code>
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
s | d
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<code class="constant">GL_NOR</code>
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
~(s | d)
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<code class="constant">GL_XOR</code>
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
s ^ d
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<code class="constant">GL_EQUIV</code>
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
~(s ^ d)
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<code class="constant">GL_AND_REVERSE</code>
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
s & ~d
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<code class="constant">GL_AND_INVERTED</code>
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
~s & d
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<code class="constant">GL_OR_REVERSE</code>
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
s | ~d
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; ">
<code class="constant">GL_OR_INVERTED</code>
</td>
<td style="text-align: center; ">
~s | d
</td>
</tr>
</tbody>
</table>
</div>
<p>
<em class="parameter"><code>opcode</code></em> is a symbolic constant chosen from the list above.
In the explanation of the logical operations,
<span class="emphasis"><em>s</em></span> represents the incoming color and
<span class="emphasis"><em>d</em></span> represents the color in the frame buffer.
Standard C-language operators are used.
As these bitwise operators suggest,
the logical operation is applied independently to each bit pair of the
source and destination colors.
</p>
</div>
<div class="refsect1" id="notes">
<h2>Notes</h2>
<p>
When more than one RGBA color buffer is enabled for drawing,
logical operations are performed separately for each enabled buffer,
using for the destination value the contents of that buffer
(see <a class="citerefentry" href="glDrawBuffer.xhtml"><span class="citerefentry"><span class="refentrytitle">glDrawBuffer</span></span></a>).
</p>
<p>
Logic operations have no effect on floating point draw buffers. However, if
<code class="constant">GL_COLOR_LOGIC_OP</code> is enabled, blending is still disabled
in this case.
</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>opcode</code></em> is not an accepted value.
</p>
</div>
<div class="refsect1" id="associatedgets">
<h2>Associated Gets</h2>
<p>
<a class="citerefentry" href="glGet.xhtml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_LOGIC_OP_MODE</code>.
</p>
<p>
<a class="citerefentry" href="glIsEnabled.xhtml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_COLOR_LOGIC_OP</code>.
</p>
</div>
<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; "/>
<col style="text-align: center; "/>
<col style="text-align: center; " class="lastvers"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left; border-right: 2px solid ; ">
</th>
<th style="text-align: center; border-bottom: 2px solid ; " colspan="12">
<span class="bold"><strong>OpenGL Version</strong></span>
</th>
</tr>
<tr>
<th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>Function / Feature Name</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>2.0</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>2.1</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.0</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.1</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.2</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.3</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.0</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.1</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.2</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.3</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.4</strong></span>
</th>
<th style="text-align: center; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.5</strong></span>
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left; border-right: 2px solid ; ">
<code class="function">glLogicOp</code>
</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; ">✔</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="refsect1" id="seealso">
<h2>See Also</h2>
<p>
<a class="citerefentry" href="glBlendFunc.xhtml"><span class="citerefentry"><span class="refentrytitle">glBlendFunc</span></span></a>,
<a class="citerefentry" href="glDrawBuffer.xhtml"><span class="citerefentry"><span class="refentrytitle">glDrawBuffer</span></span></a>,
<a class="citerefentry" href="glEnable.xhtml"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a>,
<a class="citerefentry" href="glStencilOp.xhtml"><span class="citerefentry"><span class="refentrytitle">glStencilOp</span></span></a>
</p>
</div>
<div class="refsect1" id="Copyright">
<h2>Copyright</h2>
<p>
Copyright <span class="trademark"/>© 1991-2006 Silicon Graphics, Inc.
Copyright <span class="trademark"/>© 2010-2014 Khronos Group.
This document is licensed under the SGI Free Software B License.
For details, see
<a class="link" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
</p>
</div>
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