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renderer=
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"text/html; charset=UTF-8" /><title>gluTessBeginPolygon
</title><meta name=
"generator" content=
"DocBook XSL Stylesheets V1.73.2" /></head><body><div class=
"refentry" lang=
"en" xml:
lang=
"en"><a id=
"gluTessBeginPolygon"></a><div class=
"titlepage"></div><div class=
"refnamediv"><h2>Name
</h2><p>gluTessBeginPolygon — delimit a polygon description
</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">gluTessBeginPolygon
</b>(
</code></td><td>GLUtesselator*
</td><td><var class=
"pdparam">tess
</var>,
</td></tr><tr><td> </td><td>GLvoid*
</td><td><var class=
"pdparam">data
</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>data
</code></em></span></dt><dd><p>
6 Specifies a pointer to user polygon data.
7 </p></dd></dl></div></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"description"></a><h2>Description
</h2><p>
8 <code class=
"function">gluTessBeginPolygon
</code> and
<a class=
"citerefentry" href=
"gluTessEndPolygon.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluTessEndPolygon
</span></span></a> delimit the definition of a
9 convex, concave or self-intersecting polygon. Within each
<code class=
"function">gluTessBeginPolygon
</code>/
<a class=
"citerefentry" href=
"gluTessEndPolygon.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluTessEndPolygon
</span></span></a>
10 pair, there must be one or more calls to
<a class=
"citerefentry" href=
"gluTessBeginContour.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluTessBeginContour
</span></span></a>/
<a class=
"citerefentry" href=
"gluTessEndContour.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluTessEndContour
</span></span></a>.
11 Within each contour, there are zero or more calls to
<a class=
"citerefentry" href=
"gluTessVertex.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluTessVertex
</span></span></a>. The vertices
12 specify a closed contour (the last vertex of each contour is automatically linked
13 to the first). See the
<a class=
"citerefentry" href=
"gluTessVertex.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluTessVertex
</span></span></a>,
<a class=
"citerefentry" href=
"gluTessBeginContour.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluTessBeginContour
</span></span></a>, and
14 <a class=
"citerefentry" href=
"gluTessEndContour.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluTessEndContour
</span></span></a> reference pages for more details.
16 <em class=
"parameter"><code>data
</code></em> is a pointer to a user-defined data structure. If the appropriate callback(s)
17 are specified (see
<a class=
"citerefentry" href=
"gluTessCallback.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluTessCallback
</span></span></a>), then this pointer is returned to the
18 callback function(s). Thus, it is a convenient way to store per-polygon information.
20 Once
<a class=
"citerefentry" href=
"gluTessEndPolygon.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluTessEndPolygon
</span></span></a> is called, the polygon is tessellated, and the
21 resulting triangles are described through callbacks.
22 See
<a class=
"citerefentry" href=
"gluTessCallback.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluTessCallback
</span></span></a> for descriptions of the callback functions.
23 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"example"></a><h2>Example
</h2><p>
24 A quadrilateral with a triangular hole in it can be described as follows:
25 </p><pre class=
"programlisting">
26 gluTessBeginPolygon(tobj, NULL);
27 gluTessBeginContour(tobj);
28 gluTessVertex(tobj, v1, v1);
29 gluTessVertex(tobj, v2, v2);
30 gluTessVertex(tobj, v3, v3);
31 gluTessVertex(tobj, v4, v4);
32 gluTessEndContour(tobj);
33 gluTessBeginContour(tobj);
34 gluTessVertex(tobj, v5, v5);
35 gluTessVertex(tobj, v6, v6);
36 gluTessVertex(tobj, v7, v7);
37 gluTessEndContour(tobj);
38 gluTessEndPolygon(tobj);
41 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"seealso"></a><h2>See Also
</h2><p>
42 <a class=
"citerefentry" href=
"gluNewTess.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluNewTess
</span></span></a>,
43 <a class=
"citerefentry" href=
"gluTessBeginContour.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluTessBeginContour
</span></span></a>,
44 <a class=
"citerefentry" href=
"gluTessCallback.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluTessCallback
</span></span></a>,
45 <a class=
"citerefentry" href=
"gluTessEndPolygon.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluTessEndPolygon
</span></span></a>,
46 <a class=
"citerefentry" href=
"gluTessNormal.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluTessNormal
</span></span></a>,
47 <a class=
"citerefentry" href=
"gluTessProperty.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluTessProperty
</span></span></a>,
48 <a class=
"citerefentry" href=
"gluTessVertex.xml"><span class=
"citerefentry"><span class=
"refentrytitle">gluTessVertex
</span></span></a>
49 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"Copyright"></a><h2>Copyright
</h2><p>
50 Copyright
<span class=
"trademark"></span>©
1991-
2006
51 Silicon Graphics, Inc. This document is licensed under the SGI
52 Free Software B License. For details, see
53 <a class=
"ulink" href=
"http://oss.sgi.com/projects/FreeB/" target=
"_top">http://oss.sgi.com/projects/FreeB/
</a>.
54 </p></div></div></body></html>