<?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="gluNurbsCurve"> <refmeta> <refmetainfo> <copyright> <year>1991-2006</year> <holder>Silicon Graphics, Inc.</holder> </copyright> </refmetainfo> <refentrytitle>gluNurbsCurve</refentrytitle> <manvolnum>3G</manvolnum> </refmeta> <refnamediv> <refname>gluNurbsCurve</refname> <refpurpose>define the shape of a NURBS curve</refpurpose> </refnamediv> <refsynopsisdiv><title>C Specification</title> <funcsynopsis> <funcprototype> <funcdef>void <function>gluNurbsCurve</function></funcdef> <paramdef>GLUnurbs* <parameter>nurb</parameter></paramdef> <paramdef>GLint <parameter>knotCount</parameter></paramdef> <paramdef>GLfloat * <parameter>knots</parameter></paramdef> <paramdef>GLint <parameter>stride</parameter></paramdef> <paramdef>GLfloat * <parameter>control</parameter></paramdef> <paramdef>GLint <parameter>order</parameter></paramdef> <paramdef>GLenum <parameter>type</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> <varlistentry> <term><parameter>knotCount</parameter></term> <listitem> <para> Specifies the number of knots in <parameter>knots</parameter>. <parameter>knotCount</parameter> equals the number of control points plus the order. </para> </listitem> </varlistentry> <varlistentry> <term><parameter>knots</parameter></term> <listitem> <para> Specifies an array of <parameter>knotCount</parameter> nondecreasing knot values. </para> </listitem> </varlistentry> <varlistentry> <term><parameter>stride</parameter></term> <listitem> <para> Specifies the offset (as a number of single-precision floating-point values) between successive curve control points. </para> </listitem> </varlistentry> <varlistentry> <term><parameter>control</parameter></term> <listitem> <para> Specifies a pointer to an array of control points. The coordinates must agree with <parameter>type</parameter>, specified below. </para> </listitem> </varlistentry> <varlistentry> <term><parameter>order</parameter></term> <listitem> <para> Specifies the order of the NURBS curve. <parameter>order</parameter> equals degree + 1, hence a cubic curve has an order of 4. </para> </listitem> </varlistentry> <varlistentry> <term><parameter>type</parameter></term> <listitem> <para> Specifies the type of the curve. If this curve is defined within a <citerefentry><refentrytitle>gluBeginCurve</refentrytitle></citerefentry>/<citerefentry><refentrytitle>gluEndCurve</refentrytitle></citerefentry> pair, then the type can be any of the valid one-dimensional evaluator types (such as <constant>GLU_MAP1_VERTEX_3</constant> or <constant>GLU_MAP1_COLOR_4</constant>). Between a <citerefentry><refentrytitle>gluBeginTrim</refentrytitle></citerefentry>/<citerefentry><refentrytitle>gluEndTrim</refentrytitle></citerefentry> pair, the only valid types are <constant>GLU_MAP1_TRIM_2</constant> and <constant>GLU_MAP1_TRIM_3</constant>. </para> </listitem> </varlistentry> </variablelist> </refsect1> <refsect1 id="description"><title>Description</title> <para> Use <function>gluNurbsCurve</function> to describe a NURBS curve. </para> <para> When <function>gluNurbsCurve</function> appears between a <citerefentry><refentrytitle>gluBeginCurve</refentrytitle></citerefentry>/<citerefentry><refentrytitle>gluEndCurve</refentrytitle></citerefentry> pair, it is used to describe a curve to be rendered. Positional, texture, and color coordinates are associated by presenting each as a separate <function>gluNurbsCurve</function> between a <citerefentry><refentrytitle>gluBeginCurve</refentrytitle></citerefentry>/<citerefentry><refentrytitle>gluEndCurve</refentrytitle></citerefentry> pair. No more than one call to <function>gluNurbsCurve</function> for each of color, position, and texture data can be made within a single <citerefentry><refentrytitle>gluBeginCurve</refentrytitle></citerefentry>/<citerefentry><refentrytitle>gluEndCurve</refentrytitle></citerefentry> pair. Exactly one call must be made to describe the position of the curve (a <parameter>type</parameter> of <constant>GLU_MAP1_VERTEX_3</constant> or <constant>GLU_MAP1_VERTEX_4</constant>). </para> <para> When <function>gluNurbsCurve</function> appears between a <citerefentry><refentrytitle>gluBeginTrim</refentrytitle></citerefentry>/<citerefentry><refentrytitle>gluEndTrim</refentrytitle></citerefentry> pair, it is used to describe a trimming curve on a NURBS surface. If <parameter>type</parameter> is <constant>GLU_MAP1_TRIM_2</constant>, then it describes a curve in two-dimensional (<emphasis>u</emphasis> and <emphasis>v</emphasis>) parameter space. If it is <constant>GLU_MAP1_TRIM_3</constant>, then it describes a curve in two-dimensional homogeneous (<emphasis>u</emphasis>, <emphasis>v</emphasis>, and <emphasis>w</emphasis>) parameter space. See the <citerefentry><refentrytitle>gluBeginTrim</refentrytitle></citerefentry> reference page for more discussion about trimming curves. </para> </refsect1> <refsect1 id="example"><title>Example</title> <para> The following commands render a textured NURBS curve with normals: <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="notes"><title>Notes</title> <para> To define trim curves that stitch well, use <citerefentry><refentrytitle>gluPwlCurve</refentrytitle></citerefentry>. </para> </refsect1> <refsect1 id="seealso"><title>See Also</title> <para> <citerefentry><refentrytitle>gluBeginCurve</refentrytitle></citerefentry>, <citerefentry><refentrytitle>gluBeginTrim</refentrytitle></citerefentry>, <citerefentry><refentrytitle>gluNewNurbsRenderer</refentrytitle></citerefentry>, <citerefentry><refentrytitle>gluPwlCurve</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>