207 lines
10 KiB
XML
207 lines
10 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="gluNurbsSurface">
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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>gluNurbsSurface</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>gluNurbsSurface</refname>
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<refpurpose>define the shape of a NURBS surface</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>gluNurbsSurface</function></funcdef>
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<paramdef>GLUnurbs* <parameter>nurb</parameter></paramdef>
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<paramdef>GLint <parameter>sKnotCount</parameter></paramdef>
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<paramdef>GLfloat* <parameter>sKnots</parameter></paramdef>
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<paramdef>GLint <parameter>tKnotCount</parameter></paramdef>
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<paramdef>GLfloat* <parameter>tKnots</parameter></paramdef>
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<paramdef>GLint <parameter>sStride</parameter></paramdef>
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<paramdef>GLint <parameter>tStride</parameter></paramdef>
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<paramdef>GLfloat* <parameter>control</parameter></paramdef>
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<paramdef>GLint <parameter>sOrder</parameter></paramdef>
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<paramdef>GLint <parameter>tOrder</parameter></paramdef>
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<paramdef>GLenum <parameter>type</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>nurb</parameter></term>
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<listitem>
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<para>
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Specifies the NURBS object (created with <citerefentry><refentrytitle>gluNewNurbsRenderer</refentrytitle></citerefentry>).
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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>sKnotCount</parameter></term>
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<listitem>
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<para>
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Specifies the number of knots in the parametric <emphasis>u</emphasis> direction.
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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>sKnots</parameter></term>
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<listitem>
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<para>
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Specifies an array of <parameter>sKnotCount</parameter> nondecreasing knot values in the parametric
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<emphasis>u</emphasis> direction.
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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>tKnotCount</parameter></term>
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<listitem>
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<para>
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Specifies the number of knots in the parametric <emphasis>v</emphasis> direction.
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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>tKnots</parameter></term>
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<listitem>
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<para>
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Specifies an array of <parameter>tKnotCount</parameter> nondecreasing knot values in the parametric
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<emphasis>v</emphasis> direction.
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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>sStride</parameter></term>
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<listitem>
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<para>
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Specifies the offset (as a number of single-precision floating-point values)
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between successive control points in the parametric <emphasis>u</emphasis> direction
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in <parameter>control</parameter>.
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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>tStride</parameter></term>
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<listitem>
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<para>
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Specifies the offset (in single-precision floating-point values)
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between successive control points in the parametric <emphasis>v</emphasis> direction
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in <parameter>control</parameter>.
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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>control</parameter></term>
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<listitem>
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<para>
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Specifies an array containing control points for the NURBS surface.
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The offsets between successive control points in the parametric <emphasis>u</emphasis>
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and <emphasis>v</emphasis> directions are given by <parameter>sStride</parameter> and <parameter>tStride</parameter>.
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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>sOrder</parameter></term>
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<listitem>
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<para>
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Specifies the order of the NURBS surface in the parametric <emphasis>u</emphasis>
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direction. The order is one more than the degree, hence
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a surface that is cubic in <emphasis>u</emphasis> has a <emphasis>u</emphasis> order of 4.
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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>tOrder</parameter></term>
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<listitem>
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<para>
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Specifies the order of the NURBS surface in the parametric <emphasis>v</emphasis>
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direction. The order is one more than the degree, hence
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a surface that is cubic in <emphasis>v</emphasis> has a <emphasis>v</emphasis> order of 4.
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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>type</parameter></term>
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<listitem>
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<para>
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Specifies type of the surface. <parameter>type</parameter> can be any of the valid
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two-dimensional evaluator types (such as <constant>GLU_MAP2_VERTEX_3</constant> or
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<constant>GLU_MAP2_COLOR_4</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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Use <function>gluNurbsSurface</function> within a NURBS (Non-Uniform Rational B-Spline) surface
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definition to describe the shape of a NURBS surface (before
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any trimming). To mark the beginning of
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a NURBS surface definition, use the <citerefentry><refentrytitle>gluBeginSurface</refentrytitle></citerefentry> command.
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To mark the end of a NURBS surface definition, use the
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<citerefentry><refentrytitle>gluEndSurface</refentrytitle></citerefentry> command. Call <function>gluNurbsSurface</function> within a NURBS
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surface definition only.
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</para>
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<para>
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Positional, texture, and color coordinates are associated
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with a surface by presenting each as a separate <function>gluNurbsSurface</function> between a
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<citerefentry><refentrytitle>gluBeginSurface</refentrytitle></citerefentry>/<citerefentry><refentrytitle>gluEndSurface</refentrytitle></citerefentry> pair. No more than
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one call to <function>gluNurbsSurface</function> for each of color, position, and texture
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data can be made within a single <citerefentry><refentrytitle>gluBeginSurface</refentrytitle></citerefentry>/<citerefentry><refentrytitle>gluEndSurface</refentrytitle></citerefentry>
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pair. Exactly one call must be made to describe the position of the
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surface (a <parameter>type</parameter> of <constant>GLU_MAP2_VERTEX_3</constant> or <constant>GLU_MAP2_VERTEX_4</constant>).
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</para>
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<para>
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A NURBS surface can be trimmed by using the commands
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<citerefentry><refentrytitle>gluNurbsCurve</refentrytitle></citerefentry> and <citerefentry><refentrytitle>gluPwlCurve</refentrytitle></citerefentry> between calls to
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<citerefentry><refentrytitle>gluBeginTrim</refentrytitle></citerefentry> and <citerefentry><refentrytitle>gluEndTrim</refentrytitle></citerefentry>.
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</para>
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<para>
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Note that a <function>gluNurbsSurface</function> with <parameter>sKnotCount</parameter> knots in the <emphasis>u</emphasis> direction
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and <parameter>tKnotCount</parameter> knots in the <emphasis>v</emphasis> direction with orders
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<parameter>sOrder</parameter> and <parameter>tOrder</parameter> must have
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(<parameter>sKnotCount</parameter> - <parameter>sOrder</parameter>)
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<inlineequation><mml:math><mml:mi mathvariant="italic">times</mml:mi></mml:math></inlineequation>
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(<parameter>tKnotCount</parameter> - <parameter>tOrder</parameter>) control points.
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</para>
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</refsect1>
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<refsect1 id="example"><title>Example</title>
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<para>
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The following commands render a textured NURBS surface with normals;
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the texture coordinates and normals are also NURBS surfaces:
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<programlisting>
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gluBeginSurface(nobj);
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gluNurbsSurface(nobj, ..., GL_MAP2_TEXTURE_COORD_2);
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gluNurbsSurface(nobj, ..., GL_MAP2_NORMAL);
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gluNurbsSurface(nobj, ..., GL_MAP2_VERTEX_4);
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gluEndSurface(nobj);
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</programlisting>
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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>gluBeginSurface</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>gluBeginTrim</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>gluNewNurbsRenderer</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>gluNurbsCurve</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>gluPwlCurve</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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