227 lines
12 KiB
XML
227 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="glGetMap">
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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>glGetMap</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>glGetMap</refname>
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<refpurpose>return evaluator parameters</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>glGetMapdv</function></funcdef>
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<paramdef>GLenum <parameter>target</parameter></paramdef>
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<paramdef>GLenum <parameter>query</parameter></paramdef>
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<paramdef>GLdouble * <parameter>v</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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<funcsynopsis>
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<funcprototype>
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<funcdef>void <function>glGetMapfv</function></funcdef>
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<paramdef>GLenum <parameter>target</parameter></paramdef>
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<paramdef>GLenum <parameter>query</parameter></paramdef>
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<paramdef>GLfloat * <parameter>v</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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<funcsynopsis>
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<funcprototype>
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<funcdef>void <function>glGetMapiv</function></funcdef>
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<paramdef>GLenum <parameter>target</parameter></paramdef>
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<paramdef>GLenum <parameter>query</parameter></paramdef>
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<paramdef>GLint * <parameter>v</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<!-- eqn: ignoring delim $$ -->
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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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Specifies the symbolic name of a map.
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Accepted values are
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<constant>GL_MAP1_COLOR_4</constant>,
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<constant>GL_MAP1_INDEX</constant>,
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<constant>GL_MAP1_NORMAL</constant>,
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<constant>GL_MAP1_TEXTURE_COORD_1</constant>,
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<constant>GL_MAP1_TEXTURE_COORD_2</constant>,
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<constant>GL_MAP1_TEXTURE_COORD_3</constant>,
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<constant>GL_MAP1_TEXTURE_COORD_4</constant>,
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<constant>GL_MAP1_VERTEX_3</constant>,
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<constant>GL_MAP1_VERTEX_4</constant>,
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<constant>GL_MAP2_COLOR_4</constant>,
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<constant>GL_MAP2_INDEX</constant>,
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<constant>GL_MAP2_NORMAL</constant>,
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<constant>GL_MAP2_TEXTURE_COORD_1</constant>,
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<constant>GL_MAP2_TEXTURE_COORD_2</constant>,
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<constant>GL_MAP2_TEXTURE_COORD_3</constant>,
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<constant>GL_MAP2_TEXTURE_COORD_4</constant>,
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<constant>GL_MAP2_VERTEX_3</constant>, and
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<constant>GL_MAP2_VERTEX_4</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>query</parameter></term>
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<listitem>
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<para>
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Specifies which parameter to return.
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Symbolic names
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<constant>GL_COEFF</constant>,
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<constant>GL_ORDER</constant>, and
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<constant>GL_DOMAIN</constant> are accepted.
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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>v</parameter></term>
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<listitem>
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<para>
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Returns the requested data.
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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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<citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry> define evaluators.
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<function>glGetMap</function> returns evaluator parameters.
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<parameter>target</parameter> chooses a map,
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<parameter>query</parameter> selects a specific parameter,
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and <parameter>v</parameter> points to storage where the values will be returned.
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</para>
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<para>
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The acceptable values for the <parameter>target</parameter> parameter are described
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in the <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry> reference pages.
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</para>
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<para>
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<parameter>query</parameter> can assume the following values:
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</para>
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<variablelist>
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<varlistentry>
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<term><constant>GL_COEFF</constant></term>
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<listitem>
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<para>
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<parameter>v</parameter> returns the control points for the evaluator function.
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One-dimensional evaluators return
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<inlineequation><mml:math><mml:mi mathvariant="italic">order</mml:mi></mml:math></inlineequation>
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control points,
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and two-dimensional evaluators return
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<inlineequation><mml:math>
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<!-- eqn: uorder times vorder:-->
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<mml:mrow>
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<mml:mi mathvariant="italic">uorder</mml:mi>
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<mml:mo>×</mml:mo>
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<mml:mi mathvariant="italic">vorder</mml:mi>
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</mml:mrow>
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</mml:math></inlineequation>
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control points.
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Each control point consists of one, two, three, or four integer,
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single-precision floating-point,
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or double-precision floating-point values,
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depending on the type of the evaluator.
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The GL returns two-dimensional control points in row-major order,
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incrementing the
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<inlineequation><mml:math><mml:mi mathvariant="italic">uorder</mml:mi></mml:math></inlineequation>
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index quickly
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and the
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<inlineequation><mml:math><mml:mi mathvariant="italic">vorder</mml:mi></mml:math></inlineequation>
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index after each row.
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Integer values,
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when requested,
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are computed by rounding the internal floating-point values to the
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nearest integer values.
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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><constant>GL_ORDER</constant></term>
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<listitem>
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<para>
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<parameter>v</parameter> returns the order of the evaluator function.
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One-dimensional evaluators return a single value,
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<inlineequation><mml:math><mml:mi mathvariant="italic">order</mml:mi></mml:math></inlineequation>.
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The initial value is 1.
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Two-dimensional evaluators return two values,
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<inlineequation><mml:math><mml:mi mathvariant="italic">uorder</mml:mi></mml:math></inlineequation>
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and
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<inlineequation><mml:math><mml:mi mathvariant="italic">vorder</mml:mi></mml:math></inlineequation>.
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The initial value is 1,1.
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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><constant>GL_DOMAIN</constant></term>
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<listitem>
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<para>
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<parameter>v</parameter> returns the linear
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<inlineequation><mml:math><mml:mi mathvariant="italic">u</mml:mi></mml:math></inlineequation>
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and
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<inlineequation><mml:math><mml:mi mathvariant="italic">v</mml:mi></mml:math></inlineequation>
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mapping parameters.
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One-dimensional evaluators return two values,
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<inlineequation><mml:math><mml:mi mathvariant="italic">u1</mml:mi></mml:math></inlineequation>
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and
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<inlineequation><mml:math><mml:mi mathvariant="italic">u2</mml:mi></mml:math></inlineequation>,
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as specified by <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry>.
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Two-dimensional evaluators return four values
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(<inlineequation><mml:math><mml:mi mathvariant="italic">u1</mml:mi></mml:math></inlineequation>,
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<inlineequation><mml:math><mml:mi mathvariant="italic">u2</mml:mi></mml:math></inlineequation>,
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<inlineequation><mml:math><mml:mi mathvariant="italic">v1</mml:mi></mml:math></inlineequation>,
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and
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<inlineequation><mml:math><mml:mi mathvariant="italic">v2</mml:mi></mml:math></inlineequation>)
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as specified by <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>.
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Integer values,
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when requested,
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are computed by rounding the internal floating-point values to the
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nearest integer values.
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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="notes"><title>Notes</title>
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<para>
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If an error is generated,
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no change is made to the contents of <parameter>v</parameter>.
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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 either <parameter>target</parameter> or <parameter>query</parameter> is not
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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>glGetMap</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="seealso"><title>See Also</title>
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<para>
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<citerefentry><refentrytitle>glEvalCoord</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glMap2</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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