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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
<refentry id="gluBeginCurve">
<refmeta>
<refmetainfo>
<copyright>
<year>1991-2006</year>
<holder>Silicon Graphics, Inc.</holder>
</copyright>
</refmetainfo>
<refentrytitle>gluBeginCurve</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>gluBeginCurve</refname>
<refpurpose>delimit a NURBS curve definition</refpurpose>
</refnamediv>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>gluBeginCurve</function></funcdef>
<paramdef>GLUnurbs* <parameter>nurb</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>gluEndCurve</function></funcdef>
<paramdef>GLUnurbs* <parameter>nurb</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<!-- eqn: ignoring delim $$ -->
<refsect1 id="parameters"><title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>nurb</parameter></term>
<listitem>
<para>
Specifies the NURBS object (created with <citerefentry><refentrytitle>gluNewNurbsRenderer</refentrytitle></citerefentry>).
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="description"><title>Description</title>
<para>
Use <function>gluBeginCurve</function> to mark the beginning of a NURBS
curve definition.
After
calling <function>gluBeginCurve</function>, make one or more calls to
<citerefentry><refentrytitle>gluNurbsCurve</refentrytitle></citerefentry> to define the attributes of the curve.
Exactly one of the calls to <citerefentry><refentrytitle>gluNurbsCurve</refentrytitle></citerefentry> must have
a curve type of <constant>GLU_MAP1_VERTEX_3</constant> or <constant>GLU_MAP1_VERTEX_4</constant>.
To mark the end of the NURBS curve definition, call <citerefentry><refentrytitle>gluEndCurve</refentrytitle></citerefentry>.
</para>
<para>
GL evaluators are used to render the NURBS curve as a series of line
segments.
Evaluator state is preserved during rendering
with <citerefentry><refentrytitle>glPushAttrib</refentrytitle></citerefentry>(<constant>GLU_EVAL_BIT</constant>) and
<citerefentry><refentrytitle>glPopAttrib</refentrytitle></citerefentry>().
See the <citerefentry><refentrytitle>glPushAttrib</refentrytitle></citerefentry> reference page for details on exactly what state
these calls preserve.
</para>
</refsect1>
<refsect1 id="example"><title>Example</title>
<para>
The following commands render a textured NURBS curve with normals;
texture coordinates and normals are also specified as NURBS curves:
<programlisting>
gluBeginCurve(nobj);
gluNurbsCurve(nobj, ..., GL_MAP1_TEXTURE_COORD_2);
gluNurbsCurve(nobj, ..., GL_MAP1_NORMAL);
gluNurbsCurve(nobj, ..., GL_MAP1_VERTEX_4);
gluEndCurve(nobj);
</programlisting>
</para>
</refsect1>
<refsect1 id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>gluBeginSurface</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>gluBeginTrim</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>gluNewNurbsRenderer</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>gluNurbsCurve</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glPopAttrib</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glPushAttrib</refentrytitle></citerefentry>
</para>
</refsect1>
<refsect1 id="Copyright"><title>Copyright</title>
<para>
Copyright <trademark class="copyright"></trademark> 1991-2006
Silicon Graphics, Inc. This document is licensed under the SGI
Free Software B License. For details, see
<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
</para>
</refsect1>
</refentry>