171 lines
8.3 KiB
XML
171 lines
8.3 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="glMinmax">
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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>glMinmax</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>glMinmax</refname>
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<refpurpose>define minmax table</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>glMinmax</function></funcdef>
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<paramdef>GLenum <parameter>target</parameter></paramdef>
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<paramdef>GLenum <parameter>internalformat</parameter></paramdef>
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<paramdef>GLboolean <parameter>sink</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>target</parameter></term>
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<listitem>
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<para>
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The minmax table whose parameters are to be set.
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Must be
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<constant>GL_MINMAX</constant>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>internalformat</parameter></term>
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<listitem>
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<para>
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The format of entries in the minmax table.
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Must be one of
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<constant>GL_ALPHA</constant>,
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<constant>GL_ALPHA4</constant>,
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<constant>GL_ALPHA8</constant>,
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<constant>GL_ALPHA12</constant>,
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<constant>GL_ALPHA16</constant>,
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<constant>GL_LUMINANCE</constant>,
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<constant>GL_LUMINANCE4</constant>,
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<constant>GL_LUMINANCE8</constant>,
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<constant>GL_LUMINANCE12</constant>,
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<constant>GL_LUMINANCE16</constant>,
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<constant>GL_LUMINANCE_ALPHA</constant>,
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<constant>GL_LUMINANCE4_ALPHA4</constant>,
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<constant>GL_LUMINANCE6_ALPHA2</constant>,
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<constant>GL_LUMINANCE8_ALPHA8</constant>,
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<constant>GL_LUMINANCE12_ALPHA4</constant>,
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<constant>GL_LUMINANCE12_ALPHA12</constant>,
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<constant>GL_LUMINANCE16_ALPHA16</constant>,
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<constant>GL_R3_G3_B2</constant>,
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<constant>GL_RGB</constant>,
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<constant>GL_RGB4</constant>,
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<constant>GL_RGB5</constant>,
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<constant>GL_RGB8</constant>,
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<constant>GL_RGB10</constant>,
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<constant>GL_RGB12</constant>,
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<constant>GL_RGB16</constant>,
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<constant>GL_RGBA</constant>,
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<constant>GL_RGBA2</constant>,
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<constant>GL_RGBA4</constant>,
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<constant>GL_RGB5_A1</constant>,
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<constant>GL_RGBA8</constant>,
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<constant>GL_RGB10_A2</constant>,
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<constant>GL_RGBA12</constant>, or
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<constant>GL_RGBA16</constant>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>sink</parameter></term>
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<listitem>
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<para>
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If <constant>GL_TRUE</constant>, pixels will be consumed by the minmax
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process and no drawing or texture loading will take place.
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If <constant>GL_FALSE</constant>, pixels will proceed to the final conversion process after
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minmax.
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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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When <constant>GL_MINMAX</constant> is enabled, the RGBA components of incoming pixels are
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compared to the minimum and maximum values for each component, which are
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stored in the two-element minmax table.
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(The first element stores the minima, and the second element stores
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the maxima.)
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If a pixel component is greater than the corresponding component
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in the maximum element, then the maximum element is updated with the
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pixel component value.
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If a pixel component is less than the corresponding component in
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the minimum element, then the minimum element is updated with the
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pixel component value.
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(In both cases, if the internal format of the minmax table includes
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luminance, then the R color component of incoming pixels is used
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for comparison.)
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The contents of the minmax table may be retrieved at a later time
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by calling <citerefentry><refentrytitle>glGetMinmax</refentrytitle></citerefentry>.
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The minmax operation is enabled or disabled by calling <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> or
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<citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry>, respectively, with an argument of <constant>GL_MINMAX</constant>.
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</para>
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<para>
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<function>glMinmax</function> redefines the current minmax table to have entries of the format
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specified by <parameter>internalformat</parameter>.
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The maximum element is initialized with the smallest possible component
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values, and the minimum element is initialized with the largest possible
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component values.
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The values in the previous minmax table, if any, are lost.
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If <parameter>sink</parameter> is <constant>GL_TRUE</constant>, then pixels are discarded after minmax;
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no further processing of the pixels takes place, and no drawing,
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texture loading, or pixel readback will result.
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</para>
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<para>
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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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<function>glMinmax</function> is present only if <code>ARB_imaging</code> is returned when <citerefentry><refentrytitle>glGetString</refentrytitle></citerefentry>
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is called with an argument of <constant>GL_EXTENSIONS</constant>.
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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>target</parameter> is not one of the allowable
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values.
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</para>
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<para>
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<constant>GL_INVALID_ENUM</constant> is generated if <parameter>internalformat</parameter> is not one of the
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allowable values.
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</para>
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<para>
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<constant>GL_INVALID_OPERATION</constant> is generated if <function>glMinmax</function> is executed
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between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> and the corresponding
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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>glGetMinmaxParameter</refentrytitle></citerefentry>
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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>glGetMinmax</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glResetMinmax</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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