upstream-doc/man2/xhtml/gluNextContour.xml

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   3 <?xml-stylesheet type="text/xsl" href="mathml.xsl"?><html xmlns="http://www.w3.org/1999/xhtml" xmlns:pref="http://www.w3.org/2002/Math/preference" pref:renderer="mathplayer-dl"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>gluNextContour</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="gluNextContour"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>gluNextContour — mark the beginning of another contour</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">gluNextContour</b>(</code></td><td>GLUtesselator*  </td><td><var class="pdparam">tess</var>, </td></tr><tr><td> </td><td>GLenum  </td><td><var class="pdparam">type</var><code>)</code>;</td></tr></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>tess</code></em></span></dt><dd><p>
   4                     Specifies the tessellation object (created with <a class="citerefentry" href="gluNewTess.xml"><span class="citerefentry"><span class="refentrytitle">gluNewTess</span></span></a>).
   5                 </p></dd><dt><span class="term"><em class="parameter"><code>type</code></em></span></dt><dd><p>
   6                     Specifies the type of the contour being defined. Valid values are
   7                     <code class="constant">GLU_EXTERIOR</code>,
   8                     <code class="constant">GLU_INTERIOR</code>,
   9                     <code class="constant">GLU_UNKNOWN</code>,
  10                     <code class="constant">GLU_CCW</code>, and
  11                     <code class="constant">GLU_CW</code>.
  12                 </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
  13             <code class="function">gluNextContour</code> is used in describing polygons with multiple contours. After the first
  14             contour has been described through a series of <a class="citerefentry" href="gluTessVertex.xml"><span class="citerefentry"><span class="refentrytitle">gluTessVertex</span></span></a> calls,
  15             a <code class="function">gluNextContour</code> call indicates that the previous contour is complete and that the
  16             next contour is about to begin.
  17             Another series of <a class="citerefentry" href="gluTessVertex.xml"><span class="citerefentry"><span class="refentrytitle">gluTessVertex</span></span></a> calls is then used to describe the new
  18             contour. This process can be repeated until all contours have been described.
  19         </p><p>
  20             <em class="parameter"><code>type</code></em> defines what type of contour follows.
  21             The legal contour types are as follows:
  22         </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GLU_EXTERIOR</code></span></dt><dd><p>
  23                         An exterior contour defines an exterior boundary of the polygon.
  24                     </p></dd><dt><span class="term"><code class="constant">GLU_INTERIOR</code></span></dt><dd><p>
  25                         An interior contour defines an interior boundary of the polygon (such as
  26                         a hole).
  27                     </p></dd><dt><span class="term"><code class="constant">GLU_UNKNOWN</code></span></dt><dd><p>
  28                         An unknown contour is analyzed by the library to determine if it is interior
  29                         or exterior.
  30                     </p></dd><dt><span class="term"><code class="constant">GLU_CCW</code>, </span></dt><dd></dd><dt><span class="term"><code class="constant">GLU_CW</code></span></dt><dd><p>
  31                         The first <code class="constant">GLU_CCW</code> or <code class="constant">GLU_CW</code> contour defined is considered to
  32                         be exterior. All other contours are considered to be exterior if they
  33                         are oriented in the same direction (clockwise or counterclockwise) as
  34                         the first contour, and interior if they are not.
  35                     </p></dd></dl></div><p>
  36             If one contour is of type <code class="constant">GLU_CCW</code> or <code class="constant">GLU_CW</code>, then all
  37             contours must be of the same type (if they are not, then all <code class="constant">GLU_CCW</code>
  38             and <code class="constant">GLU_CW</code> contours will be changed to <code class="constant">GLU_UNKNOWN</code>).
  39         </p><p>
  40             Note that there is no real difference between the <code class="constant">GLU_CCW</code> and
  41             <code class="constant">GLU_CW</code> contour types.
  42         </p><p>
  43             Before the first contour is described, <code class="function">gluNextContour</code> can be called to
  44             define the type of the first contour.
  45             If <code class="function">gluNextContour</code> is not called before the first contour, then the first contour is
  46             marked <code class="constant">GLU_EXTERIOR</code>.
  47         </p><p>
  48             This command is obsolete and is provided for backward compatibility
  49             only. Calls to <code class="function">gluNextContour</code> are mapped to <a class="citerefentry" href="gluTessEndContour.xml"><span class="citerefentry"><span class="refentrytitle">gluTessEndContour</span></span></a>
  50             followed by
  51             <a class="citerefentry" href="gluTessBeginContour.xml"><span class="citerefentry"><span class="refentrytitle">gluTessBeginContour</span></span></a>.
  52         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="example"></a><h2>Example</h2><p>
  53             A quadrilateral with a triangular hole in it can be described as follows:
  54             </p><pre class="programlisting">
  55 gluBeginPolygon(tobj);
  56    gluTessVertex(tobj, v1, v1);
  57    gluTessVertex(tobj, v2, v2);
  58    gluTessVertex(tobj, v3, v3);
  59    gluTessVertex(tobj, v4, v4);
  60 gluNextContour(tobj, GLU_INTERIOR);
  61    gluTessVertex(tobj, v5, v5);
  62    gluTessVertex(tobj, v6, v6);
  63    gluTessVertex(tobj, v7, v7);
  64 gluEndPolygon(tobj);
  65             </pre><p>
  66         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
  67             <a class="citerefentry" href="gluBeginPolygon.xml"><span class="citerefentry"><span class="refentrytitle">gluBeginPolygon</span></span></a>,
  68             <a class="citerefentry" href="gluNewTess.xml"><span class="citerefentry"><span class="refentrytitle">gluNewTess</span></span></a>,
  69             <a class="citerefentry" href="gluTessBeginContour.xml"><span class="citerefentry"><span class="refentrytitle">gluTessBeginContour</span></span></a>,
  70             <a class="citerefentry" href="gluTessCallback.xml"><span class="citerefentry"><span class="refentrytitle">gluTessCallback</span></span></a>,
  71             <a class="citerefentry" href="gluTessVertex.xml"><span class="citerefentry"><span class="refentrytitle">gluTessVertex</span></span></a>
  72         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
  73             Copyright <span class="trademark"></span>© 1991-2006
  74             Silicon Graphics, Inc. This document is licensed under the SGI
  75             Free Software B License. For details, see
  76             <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
  77         </p></div></div></body></html>