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168 lines
7.5 KiB
XML
168 lines
7.5 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="gluNextContour">
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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>gluNextContour</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>gluNextContour</refname>
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<refpurpose>mark the beginning of another contour</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>gluNextContour</function></funcdef>
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<paramdef>GLUtesselator* <parameter>tess</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>tess</parameter></term>
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<listitem>
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<para>
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Specifies the tessellation object (created with <citerefentry><refentrytitle>gluNewTess</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>type</parameter></term>
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<listitem>
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<para>
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Specifies the type of the contour being defined. Valid values are
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<constant>GLU_EXTERIOR</constant>,
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<constant>GLU_INTERIOR</constant>,
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<constant>GLU_UNKNOWN</constant>,
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<constant>GLU_CCW</constant>, and
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<constant>GLU_CW</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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<function>gluNextContour</function> is used in describing polygons with multiple contours. After the first
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contour has been described through a series of <citerefentry><refentrytitle>gluTessVertex</refentrytitle></citerefentry> calls,
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a <function>gluNextContour</function> call indicates that the previous contour is complete and that the
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next contour is about to begin.
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Another series of <citerefentry><refentrytitle>gluTessVertex</refentrytitle></citerefentry> calls is then used to describe the new
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contour. This process can be repeated until all contours have been described.
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</para>
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<para>
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<parameter>type</parameter> defines what type of contour follows.
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The legal contour types are as follows:
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</para>
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<variablelist>
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<varlistentry>
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<term><constant>GLU_EXTERIOR</constant></term>
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<listitem>
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<para>
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An exterior contour defines an exterior boundary of the polygon.
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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>GLU_INTERIOR</constant></term>
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<listitem>
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<para>
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An interior contour defines an interior boundary of the polygon (such as
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a hole).
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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>GLU_UNKNOWN</constant></term>
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<listitem>
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<para>
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An unknown contour is analyzed by the library to determine if it is interior
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or exterior.
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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>GLU_CCW</constant>, </term>
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<listitem>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>GLU_CW</constant></term>
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<listitem>
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<para>
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The first <constant>GLU_CCW</constant> or <constant>GLU_CW</constant> contour defined is considered to
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be exterior. All other contours are considered to be exterior if they
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are oriented in the same direction (clockwise or counterclockwise) as
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the first contour, and interior if they are not.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>
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If one contour is of type <constant>GLU_CCW</constant> or <constant>GLU_CW</constant>, then all
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contours must be of the same type (if they are not, then all <constant>GLU_CCW</constant>
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and <constant>GLU_CW</constant> contours will be changed to <constant>GLU_UNKNOWN</constant>).
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</para>
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<para>
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Note that there is no real difference between the <constant>GLU_CCW</constant> and
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<constant>GLU_CW</constant> contour types.
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</para>
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<para>
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Before the first contour is described, <function>gluNextContour</function> can be called to
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define the type of the first contour.
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If <function>gluNextContour</function> is not called before the first contour, then the first contour is
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marked <constant>GLU_EXTERIOR</constant>.
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</para>
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<para>
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This command is obsolete and is provided for backward compatibility
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only. Calls to <function>gluNextContour</function> are mapped to <citerefentry><refentrytitle>gluTessEndContour</refentrytitle></citerefentry>
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followed by
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<citerefentry><refentrytitle>gluTessBeginContour</refentrytitle></citerefentry>.
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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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A quadrilateral with a triangular hole in it can be described as follows:
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<programlisting>
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gluBeginPolygon(tobj);
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gluTessVertex(tobj, v1, v1);
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gluTessVertex(tobj, v2, v2);
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gluTessVertex(tobj, v3, v3);
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gluTessVertex(tobj, v4, v4);
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gluNextContour(tobj, GLU_INTERIOR);
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gluTessVertex(tobj, v5, v5);
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gluTessVertex(tobj, v6, v6);
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gluTessVertex(tobj, v7, v7);
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gluEndPolygon(tobj);
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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>gluBeginPolygon</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>gluNewTess</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>gluTessBeginContour</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>gluTessCallback</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>gluTessVertex</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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