275 lines
12 KiB
XML
275 lines
12 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
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"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
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<refentry id="glLogicOp">
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<refmeta>
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<refmetainfo>
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<copyright>
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<year>1991-2006</year>
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<holder>Silicon Graphics, Inc.</holder>
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</copyright>
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</refmetainfo>
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<refentrytitle>glLogicOp</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>glLogicOp</refname>
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<refpurpose>specify a logical pixel operation for color index rendering</refpurpose>
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</refnamediv>
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<refsynopsisdiv><title>C Specification</title>
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<funcsynopsis>
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<funcprototype>
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<funcdef>void <function>glLogicOp</function></funcdef>
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<paramdef>GLenum <parameter>opcode</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1 id="parameters"><title>Parameters</title>
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<variablelist>
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<varlistentry>
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<term><parameter>opcode</parameter></term>
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<listitem>
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<para>
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Specifies a symbolic constant that selects a logical operation.
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The following symbols are accepted:
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<constant>GL_CLEAR</constant>,
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<constant>GL_SET</constant>,
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<constant>GL_COPY</constant>,
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<constant>GL_COPY_INVERTED</constant>,
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<constant>GL_NOOP</constant>,
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<constant>GL_INVERT</constant>,
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<constant>GL_AND</constant>,
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<constant>GL_NAND</constant>,
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<constant>GL_OR</constant>,
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<constant>GL_NOR</constant>,
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<constant>GL_XOR</constant>,
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<constant>GL_EQUIV</constant>,
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<constant>GL_AND_REVERSE</constant>,
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<constant>GL_AND_INVERTED</constant>,
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<constant>GL_OR_REVERSE</constant>, and
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<constant>GL_OR_INVERTED</constant>. The initial value is <constant>GL_COPY</constant>.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1 id="description"><title>Description</title>
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<para>
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<function>glLogicOp</function> specifies a logical operation that,
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when enabled,
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is applied between the incoming color index or RGBA color
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and the color index or RGBA color at the corresponding location in the
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frame buffer.
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To enable or disable the logical operation, call
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<citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry>
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using the symbolic constant <constant>GL_COLOR_LOGIC_OP</constant> for RGBA mode or
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<constant>GL_INDEX_LOGIC_OP</constant> for color index mode. The initial value is
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disabled for both operations.
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</para>
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<para>
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</para>
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<informaltable frame="topbot">
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<tgroup cols="2" align="left">
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<colspec/>
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<colspec/>
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<thead>
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<row>
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<entry rowsep="1" align="left"><emphasis role="bold">
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Opcode
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</emphasis></entry>
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<entry rowsep="1" align="left"><emphasis role="bold">
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Resulting Operation
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</emphasis></entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry align="left">
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<constant>GL_CLEAR</constant>
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</entry>
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<entry align="center">
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0
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</entry>
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</row>
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<row>
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<entry align="left">
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<constant>GL_SET</constant>
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</entry>
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<entry align="center">
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1
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</entry>
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</row>
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<row>
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<entry align="left">
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<constant>GL_COPY</constant>
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</entry>
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<entry align="center">
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s
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</entry>
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</row>
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<row>
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<entry align="left">
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<constant>GL_COPY_INVERTED</constant>
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</entry>
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<entry align="center">
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~s
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</entry>
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</row>
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<row>
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<entry align="left">
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<constant>GL_NOOP</constant>
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</entry>
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<entry align="center">
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d
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</entry>
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</row>
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<row>
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<entry align="left">
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<constant>GL_INVERT</constant>
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</entry>
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<entry align="center">
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~d
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</entry>
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</row>
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<row>
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<entry align="left">
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<constant>GL_AND</constant>
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</entry>
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<entry align="center">
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s & d
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</entry>
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</row>
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<row>
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<entry align="left">
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<constant>GL_NAND</constant>
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</entry>
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<entry align="center">
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~(s & d)
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</entry>
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</row>
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<row>
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<entry align="left">
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<constant>GL_OR</constant>
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</entry>
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<entry align="center">
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s | d
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</entry>
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</row>
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<row>
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<entry align="left">
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<constant>GL_NOR</constant>
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</entry>
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<entry align="center">
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~(s | d)
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</entry>
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</row>
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<row>
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<entry align="left">
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<constant>GL_XOR</constant>
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</entry>
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<entry align="center">
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s ^ d
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</entry>
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</row>
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<row>
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<entry align="left">
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<constant>GL_EQUIV</constant>
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</entry>
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<entry align="center">
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~(s ^ d)
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</entry>
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</row>
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<row>
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<entry align="left">
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<constant>GL_AND_REVERSE</constant>
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</entry>
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<entry align="center">
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s & ~d
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</entry>
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</row>
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<row>
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<entry align="left">
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<constant>GL_AND_INVERTED</constant>
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</entry>
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<entry align="center">
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~s & d
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</entry>
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</row>
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<row>
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<entry align="left">
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<constant>GL_OR_REVERSE</constant>
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</entry>
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<entry align="center">
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s | ~d
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</entry>
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</row>
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<row>
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<entry align="left">
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<constant>GL_OR_INVERTED</constant>
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</entry>
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<entry align="center">
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~s | d
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</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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<para>
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<parameter>opcode</parameter> is a symbolic constant chosen from the list above.
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In the explanation of the logical operations,
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<emphasis>s</emphasis> represents the incoming color index and
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<emphasis>d</emphasis> represents the index in the frame buffer.
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Standard C-language operators are used.
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As these bitwise operators suggest,
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the logical operation is applied independently to each bit pair of the
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source and destination indices or colors.
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</para>
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</refsect1>
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<refsect1 id="notes"><title>Notes</title>
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<para>
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Color index logical operations are always supported. RGBA logical
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operations are supported only if the GL version is 1.1 or greater.
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</para>
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<para>
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When more than one RGBA color or index buffer is enabled for drawing,
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logical operations are performed separately for each enabled buffer,
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using for the destination value the contents of that buffer
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(see <citerefentry><refentrytitle>glDrawBuffer</refentrytitle></citerefentry>).
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</para>
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</refsect1>
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<refsect1 id="errors"><title>Errors</title>
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<para>
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<constant>GL_INVALID_ENUM</constant> is generated if <parameter>opcode</parameter> is not an accepted value.
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</para>
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<para>
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<constant>GL_INVALID_OPERATION</constant> is generated if <function>glLogicOp</function>
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is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
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and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
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</para>
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</refsect1>
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<refsect1 id="associatedgets"><title>Associated Gets</title>
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<para>
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<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_LOGIC_OP_MODE</constant>.
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</para>
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<para>
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<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_COLOR_LOGIC_OP</constant> or <constant>GL_INDEX_LOGIC_OP</constant>.
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</para>
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</refsect1>
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<refsect1 id="seealso"><title>See Also</title>
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<para>
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<citerefentry><refentrytitle>glAlphaFunc</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glDrawBuffer</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glStencilOp</refentrytitle></citerefentry>
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</para>
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</refsect1>
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<refsect1 id="Copyright"><title>Copyright</title>
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<para>
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Copyright <trademark class="copyright"></trademark> 1991-2006
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Silicon Graphics, Inc. This document is licensed under the SGI
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Free Software B License. For details, see
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<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
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</para>
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</refsect1>
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</refentry>
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