--- /dev/null
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
+ "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
+<refentry id="gluTessVertex">
+ <refmeta>
+ <refmetainfo>
+ <copyright>
+ <year>1991-2006</year>
+ <holder>Silicon Graphics, Inc.</holder>
+ </copyright>
+ </refmetainfo>
+ <refentrytitle>gluTessVertex</refentrytitle>
+ <manvolnum>3G</manvolnum>
+ </refmeta>
+ <refnamediv>
+ <refname>gluTessVertex</refname>
+ <refpurpose>specify a vertex on a polygon</refpurpose>
+ </refnamediv>
+ <refsynopsisdiv><title>C Specification</title>
+ <funcsynopsis>
+ <funcprototype>
+ <funcdef>void <function>gluTessVertex</function></funcdef>
+ <paramdef>GLUtesselator* <parameter>tess</parameter></paramdef>
+ <paramdef>GLdouble * <parameter>location</parameter></paramdef>
+ <paramdef>GLvoid* <parameter>data</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ </refsynopsisdiv>
+ <!-- eqn: ignoring delim $$ -->
+ <refsect1 id="parameters"><title>Parameters</title>
+ <variablelist>
+ <varlistentry>
+ <term><parameter>tess</parameter></term>
+ <listitem>
+ <para>
+ Specifies the tessellation object (created with <citerefentry><refentrytitle>gluNewTess</refentrytitle></citerefentry>).
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>location</parameter></term>
+ <listitem>
+ <para>
+ Specifies the location of the vertex.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>data</parameter></term>
+ <listitem>
+ <para>
+ Specifies an opaque pointer passed back to the program with the vertex callback
+ (as specified by <citerefentry><refentrytitle>gluTessCallback</refentrytitle></citerefentry>).
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+ <refsect1 id="description"><title>Description</title>
+ <para>
+ <function>gluTessVertex</function> describes a vertex on a polygon that the program defines. Successive
+ <function>gluTessVertex</function> calls describe a closed contour. For example,
+ to describe a quadrilateral, <function>gluTessVertex</function> should be called four times.
+ <function>gluTessVertex</function> can only be called between <citerefentry><refentrytitle>gluTessBeginContour</refentrytitle></citerefentry> and
+ <citerefentry><refentrytitle>gluTessEndContour</refentrytitle></citerefentry>.
+ </para>
+ <para>
+ <parameter>data</parameter> normally points to a structure containing the vertex
+ location, as well as other per-vertex attributes such as color and normal.
+ This pointer is passed back to the user through the <constant>GLU_TESS_VERTEX</constant>
+ or <constant>GLU_TESS_VERTEX_DATA</constant> callback after tessellation
+ (see the <citerefentry><refentrytitle>gluTessCallback</refentrytitle></citerefentry> reference page).
+ </para>
+ </refsect1>
+ <refsect1 id="example"><title>Example</title>
+ <para>
+ A quadrilateral with a triangular hole in it can be described as follows:
+ <programlisting>
+gluTessBeginPolygon(tobj, NULL);
+ gluTessBeginContour(tobj);
+ gluTessVertex(tobj, v1, v1);
+ gluTessVertex(tobj, v2, v2);
+ gluTessVertex(tobj, v3, v3);
+ gluTessVertex(tobj, v4, v4);
+ gluTessEndContour(tobj);
+ gluTessBeginContour(tobj);
+ gluTessVertex(tobj, v5, v5);
+ gluTessVertex(tobj, v6, v6);
+ gluTessVertex(tobj, v7, v7);
+ gluTessEndContour(tobj);
+gluTessEndPolygon(tobj);
+ </programlisting>
+ </para>
+ </refsect1>
+ <refsect1 id="notes"><title>Notes</title>
+ <para>
+ It is a common error to use a local variable for <parameter>location</parameter> or <parameter>data</parameter> and store
+ values into it as part of a loop.
+ For example:
+ <programlisting>
+for (i = 0; i < NVERTICES; ++i) {
+ GLdouble data[3];
+ data[0] = vertex[i][0];
+ data[1] = vertex[i][1];
+ data[2] = vertex[i][2];
+ gluTessVertex(tobj, data, data);
+}
+ </programlisting>
+ </para>
+ <para>
+ This doesn't work.
+ Because the pointers specified by <parameter>location</parameter> and <parameter>data</parameter> might not be
+ dereferenced until <citerefentry><refentrytitle>gluTessEndPolygon</refentrytitle></citerefentry> is executed,
+ all the vertex coordinates but the very last set could be overwritten
+ before tessellation begins.
+ </para>
+ <para>
+ Two common symptoms of this problem are when the data consists of a single
+ point (when a local variable is used for <parameter>data</parameter>) and a
+ <constant>GLU_TESS_NEED_COMBINE_CALLBACK</constant> error (when a local variable is
+ used for <parameter>location</parameter>).
+ </para>
+ </refsect1>
+ <refsect1 id="seealso"><title>See Also</title>
+ <para>
+ <citerefentry><refentrytitle>gluNewTess</refentrytitle></citerefentry>,
+ <citerefentry><refentrytitle>gluTessBeginContour</refentrytitle></citerefentry>,
+ <citerefentry><refentrytitle>gluTessBeginPolygon</refentrytitle></citerefentry>,
+ <citerefentry><refentrytitle>gluTessCallback</refentrytitle></citerefentry>,
+ <citerefentry><refentrytitle>gluTessEndPolygon</refentrytitle></citerefentry>,
+ <citerefentry><refentrytitle>gluTessNormal</refentrytitle></citerefentry>,
+ <citerefentry><refentrytitle>gluTessProperty</refentrytitle></citerefentry>
+ </para>
+ </refsect1>
+ <refsect1 id="Copyright"><title>Copyright</title>
+ <para>
+ Copyright <trademark class="copyright"></trademark> 1991-2006
+ Silicon Graphics, Inc. This document is licensed under the SGI
+ Free Software B License. For details, see
+ <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
+ </para>
+ </refsect1>
+</refentry>
HCoop / clinton / guile-figl.git / blobdiff