111 lines
5.5 KiB
XML
111 lines
5.5 KiB
XML
<?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="gluTessBeginPolygon">
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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>gluTessBeginPolygon</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>gluTessBeginPolygon</refname>
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<refpurpose>delimit a polygon description</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>gluTessBeginPolygon</function></funcdef>
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<paramdef>GLUtesselator* <parameter>tess</parameter></paramdef>
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<paramdef>GLvoid* <parameter>data</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>data</parameter></term>
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<listitem>
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<para>
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Specifies a pointer to user polygon data.
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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>gluTessBeginPolygon</function> and <citerefentry><refentrytitle>gluTessEndPolygon</refentrytitle></citerefentry> delimit the definition of a
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convex, concave or self-intersecting polygon. Within each <function>gluTessBeginPolygon</function>/<citerefentry><refentrytitle>gluTessEndPolygon</refentrytitle></citerefentry>
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pair, there must be one or more calls to <citerefentry><refentrytitle>gluTessBeginContour</refentrytitle></citerefentry>/<citerefentry><refentrytitle>gluTessEndContour</refentrytitle></citerefentry>.
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Within each contour, there are zero or more calls to <citerefentry><refentrytitle>gluTessVertex</refentrytitle></citerefentry>. The vertices
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specify a closed contour (the last vertex of each contour is automatically linked
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to the first). See the <citerefentry><refentrytitle>gluTessVertex</refentrytitle></citerefentry>, <citerefentry><refentrytitle>gluTessBeginContour</refentrytitle></citerefentry>, and
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<citerefentry><refentrytitle>gluTessEndContour</refentrytitle></citerefentry> reference pages for more details.
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</para>
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<para>
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<parameter>data</parameter> is a pointer to a user-defined data structure. If the appropriate callback(s)
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are specified (see <citerefentry><refentrytitle>gluTessCallback</refentrytitle></citerefentry>), then this pointer is returned to the
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callback function(s). Thus, it is a convenient way to store per-polygon information.
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</para>
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<para>
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Once <citerefentry><refentrytitle>gluTessEndPolygon</refentrytitle></citerefentry> is called, the polygon is tessellated, and the
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resulting triangles are described through callbacks.
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See <citerefentry><refentrytitle>gluTessCallback</refentrytitle></citerefentry> for descriptions of the callback functions.
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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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gluTessBeginPolygon(tobj, NULL);
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gluTessBeginContour(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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gluTessEndContour(tobj);
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gluTessBeginContour(tobj);
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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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gluTessEndContour(tobj);
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gluTessEndPolygon(tobj);
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</programlisting>
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</para>
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<para>
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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>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>gluTessEndPolygon</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>gluTessNormal</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>gluTessProperty</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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