upstream-doc/man2/gluNextContour.xml

   1 <?xml version="1.0" encoding="UTF-8"?>
   2 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
   3               "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
   4 <refentry id="gluNextContour">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>1991-2006</year>
   9                 <holder>Silicon Graphics, Inc.</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>gluNextContour</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>gluNextContour</refname>
  17         <refpurpose>mark the beginning of another contour</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>C Specification</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>void <function>gluNextContour</function></funcdef>
  23                 <paramdef>GLUtesselator* <parameter>tess</parameter></paramdef>
  24                 <paramdef>GLenum <parameter>type</parameter></paramdef>
  25             </funcprototype>
  26         </funcsynopsis>
  27     </refsynopsisdiv>
  28     <!-- eqn: ignoring delim $$ -->
  29     <refsect1 id="parameters"><title>Parameters</title>
  30         <variablelist>
  31         <varlistentry>
  32             <term><parameter>tess</parameter></term>
  33             <listitem>
  34                 <para>
  35                     Specifies the tessellation object (created with <citerefentry><refentrytitle>gluNewTess</refentrytitle></citerefentry>).
  36                 </para>
  37             </listitem>
  38         </varlistentry>
  39         <varlistentry>
  40             <term><parameter>type</parameter></term>
  41             <listitem>
  42                 <para>
  43                     Specifies the type of the contour being defined. Valid values are
  44                     <constant>GLU_EXTERIOR</constant>,
  45                     <constant>GLU_INTERIOR</constant>,
  46                     <constant>GLU_UNKNOWN</constant>,
  47                     <constant>GLU_CCW</constant>, and
  48                     <constant>GLU_CW</constant>.
  49                 </para>
  50             </listitem>
  51         </varlistentry>
  52         </variablelist>
  53     </refsect1>
  54     <refsect1 id="description"><title>Description</title>
  55         <para>
  56             <function>gluNextContour</function> is used in describing polygons with multiple contours. After the first
  57             contour has been described through a series of <citerefentry><refentrytitle>gluTessVertex</refentrytitle></citerefentry> calls,
  58             a <function>gluNextContour</function> call indicates that the previous contour is complete and that the
  59             next contour is about to begin.
  60             Another series of <citerefentry><refentrytitle>gluTessVertex</refentrytitle></citerefentry> calls is then used to describe the new
  61             contour. This process can be repeated until all contours have been described.
  62         </para>
  63         <para>
  64             <parameter>type</parameter> defines what type of contour follows.
  65             The legal contour types are as follows:
  66         </para>
  67         <variablelist>
  68             <varlistentry>
  69                 <term><constant>GLU_EXTERIOR</constant></term>
  70                 <listitem>
  71                     <para>
  72                         An exterior contour defines an exterior boundary of the polygon.
  73                     </para>
  74                 </listitem>
  75             </varlistentry>
  76             <varlistentry>
  77                 <term><constant>GLU_INTERIOR</constant></term>
  78                 <listitem>
  79                     <para>
  80                         An interior contour defines an interior boundary of the polygon (such as
  81                         a hole).
  82                     </para>
  83                 </listitem>
  84             </varlistentry>
  85             <varlistentry>
  86                 <term><constant>GLU_UNKNOWN</constant></term>
  87                 <listitem>
  88                     <para>
  89                         An unknown contour is analyzed by the library to determine if it is interior
  90                         or exterior.
  91                     </para>
  92                 </listitem>
  93             </varlistentry>
  94             <varlistentry>
  95                 <term><constant>GLU_CCW</constant>, </term>
  96                 <listitem>
  97                 </listitem>
  98             </varlistentry>
  99             <varlistentry>
 100                 <term><constant>GLU_CW</constant></term>
 101                 <listitem>
 102                     <para>
 103                         The first <constant>GLU_CCW</constant> or <constant>GLU_CW</constant> contour defined is considered to
 104                         be exterior. All other contours are considered to be exterior if they
 105                         are oriented in the same direction (clockwise or counterclockwise) as
 106                         the first contour, and interior if they are not.
 107                     </para>
 108                 </listitem>
 109             </varlistentry>
 110         </variablelist>
 111         <para>
 112             If one contour is of type <constant>GLU_CCW</constant> or <constant>GLU_CW</constant>, then all
 113             contours must be of the same type (if they are not, then all <constant>GLU_CCW</constant>
 114             and <constant>GLU_CW</constant> contours will be changed to <constant>GLU_UNKNOWN</constant>).
 115         </para>
 116         <para>
 117             Note that there is no real difference between the <constant>GLU_CCW</constant> and
 118             <constant>GLU_CW</constant> contour types.
 119         </para>
 120         <para>
 121             Before the first contour is described, <function>gluNextContour</function> can be called to
 122             define the type of the first contour.
 123             If <function>gluNextContour</function> is not called before the first contour, then the first contour is
 124             marked <constant>GLU_EXTERIOR</constant>.
 125         </para>
 126         <para>
 127             This command is obsolete and is provided for backward compatibility
 128             only. Calls to <function>gluNextContour</function> are mapped to <citerefentry><refentrytitle>gluTessEndContour</refentrytitle></citerefentry>
 129             followed by
 130             <citerefentry><refentrytitle>gluTessBeginContour</refentrytitle></citerefentry>.
 131         </para>
 132     </refsect1>
 133     <refsect1 id="example"><title>Example</title>
 134         <para>
 135             A quadrilateral with a triangular hole in it can be described as follows:
 136             <programlisting>
 137 gluBeginPolygon(tobj);
 138    gluTessVertex(tobj, v1, v1);
 139    gluTessVertex(tobj, v2, v2);
 140    gluTessVertex(tobj, v3, v3);
 141    gluTessVertex(tobj, v4, v4);
 142 gluNextContour(tobj, GLU_INTERIOR);
 143    gluTessVertex(tobj, v5, v5);
 144    gluTessVertex(tobj, v6, v6);
 145    gluTessVertex(tobj, v7, v7);
 146 gluEndPolygon(tobj);
 147             </programlisting>
 148         </para>
 149     </refsect1>
 150     <refsect1 id="seealso"><title>See Also</title>
 151         <para>
 152             <citerefentry><refentrytitle>gluBeginPolygon</refentrytitle></citerefentry>,
 153             <citerefentry><refentrytitle>gluNewTess</refentrytitle></citerefentry>,
 154             <citerefentry><refentrytitle>gluTessBeginContour</refentrytitle></citerefentry>,
 155             <citerefentry><refentrytitle>gluTessCallback</refentrytitle></citerefentry>,
 156             <citerefentry><refentrytitle>gluTessVertex</refentrytitle></citerefentry>
 157         </para>
 158     </refsect1>
 159     <refsect1 id="Copyright"><title>Copyright</title>
 160         <para>
 161             Copyright <trademark class="copyright"></trademark> 1991-2006
 162             Silicon Graphics, Inc. This document is licensed under the SGI
 163             Free Software B License. For details, see
 164             <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
 165         </para>
 166     </refsect1>
 167 </refentry>