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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> |