164 lines
8.3 KiB
XML
164 lines
8.3 KiB
XML
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<?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="gluNurbsCurve">
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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>gluNurbsCurve</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>gluNurbsCurve</refname>
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<refpurpose>define the shape of a NURBS curve</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>gluNurbsCurve</function></funcdef>
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<paramdef>GLUnurbs* <parameter>nurb</parameter></paramdef>
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<paramdef>GLint <parameter>knotCount</parameter></paramdef>
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<paramdef>GLfloat * <parameter>knots</parameter></paramdef>
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<paramdef>GLint <parameter>stride</parameter></paramdef>
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<paramdef>GLfloat * <parameter>control</parameter></paramdef>
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<paramdef>GLint <parameter>order</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>knotCount</parameter></term>
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<listitem>
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<para>
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Specifies the number of knots in <parameter>knots</parameter>.
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<parameter>knotCount</parameter> equals the number of control points plus the order.
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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>knots</parameter></term>
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<listitem>
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<para>
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Specifies an array of <parameter>knotCount</parameter> nondecreasing knot 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><parameter>stride</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 curve control points.
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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 a pointer to an array of control points. The coordinates must
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agree with <parameter>type</parameter>, specified below.
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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>order</parameter></term>
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<listitem>
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<para>
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Specifies the order of the NURBS curve. <parameter>order</parameter> equals degree + 1, hence
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a cubic curve has an 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 the type of the curve. If this curve is defined within a
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<citerefentry><refentrytitle>gluBeginCurve</refentrytitle></citerefentry>/<citerefentry><refentrytitle>gluEndCurve</refentrytitle></citerefentry> pair, then
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the type can be any of the valid
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one-dimensional evaluator types (such as <constant>GLU_MAP1_VERTEX_3</constant> or
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<constant>GLU_MAP1_COLOR_4</constant>). Between a <citerefentry><refentrytitle>gluBeginTrim</refentrytitle></citerefentry>/<citerefentry><refentrytitle>gluEndTrim</refentrytitle></citerefentry> pair,
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the only valid types are <constant>GLU_MAP1_TRIM_2</constant> and <constant>GLU_MAP1_TRIM_3</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>gluNurbsCurve</function> to describe a NURBS curve.
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</para>
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<para>
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When <function>gluNurbsCurve</function> appears between a <citerefentry><refentrytitle>gluBeginCurve</refentrytitle></citerefentry>/<citerefentry><refentrytitle>gluEndCurve</refentrytitle></citerefentry> pair, it is
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used to describe a curve to be rendered.
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Positional, texture, and color coordinates are associated
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by presenting each as a separate <function>gluNurbsCurve</function> between a
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<citerefentry><refentrytitle>gluBeginCurve</refentrytitle></citerefentry>/<citerefentry><refentrytitle>gluEndCurve</refentrytitle></citerefentry> pair. No more than
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one call to <function>gluNurbsCurve</function> for each of color, position, and texture
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data can be made within a single <citerefentry><refentrytitle>gluBeginCurve</refentrytitle></citerefentry>/<citerefentry><refentrytitle>gluEndCurve</refentrytitle></citerefentry>
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pair. Exactly one call must be made to describe the position of the
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curve (a <parameter>type</parameter> of <constant>GLU_MAP1_VERTEX_3</constant> or <constant>GLU_MAP1_VERTEX_4</constant>).
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</para>
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<para>
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When <function>gluNurbsCurve</function> appears between a <citerefentry><refentrytitle>gluBeginTrim</refentrytitle></citerefentry>/<citerefentry><refentrytitle>gluEndTrim</refentrytitle></citerefentry> pair, it is
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used to describe a trimming curve on a NURBS surface. If <parameter>type</parameter> is
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<constant>GLU_MAP1_TRIM_2</constant>, then it describes a curve in two-dimensional (<emphasis>u</emphasis>
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and <emphasis>v</emphasis>)
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parameter space. If it is <constant>GLU_MAP1_TRIM_3</constant>, then it describes a
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curve in two-dimensional homogeneous (<emphasis>u</emphasis>, <emphasis>v</emphasis>, and <emphasis>w</emphasis>)
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parameter space.
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See the <citerefentry><refentrytitle>gluBeginTrim</refentrytitle></citerefentry> reference page for more discussion about trimming
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curves.
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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 curve with normals:
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<programlisting>
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gluBeginCurve(nobj);
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gluNurbsCurve(nobj, ..., GL_MAP1_TEXTURE_COORD_2);
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gluNurbsCurve(nobj, ..., GL_MAP1_NORMAL);
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gluNurbsCurve(nobj, ..., GL_MAP1_VERTEX_4);
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gluEndCurve(nobj);
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</programlisting>
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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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To define trim curves that stitch well, use <citerefentry><refentrytitle>gluPwlCurve</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>gluBeginCurve</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>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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