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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="gluTessNormal"> | |
5 | <refmeta> | |
6 | <refmetainfo> | |
7 | <copyright> | |
8 | <year>1991-2006</year> | |
9 | <holder>Silicon Graphics, Inc.</holder> | |
10 | </copyright> | |
11 | </refmetainfo> | |
12 | <refentrytitle>gluTessNormal</refentrytitle> | |
13 | <manvolnum>3G</manvolnum> | |
14 | </refmeta> | |
15 | <refnamediv> | |
16 | <refname>gluTessNormal</refname> | |
17 | <refpurpose>specify a normal for a polygon</refpurpose> | |
18 | </refnamediv> | |
19 | <refsynopsisdiv><title>C Specification</title> | |
20 | <funcsynopsis> | |
21 | <funcprototype> | |
22 | <funcdef>void <function>gluTessNormal</function></funcdef> | |
23 | <paramdef>GLUtesselator* <parameter>tess</parameter></paramdef> | |
24 | <paramdef>GLdouble <parameter>valueX</parameter></paramdef> | |
25 | <paramdef>GLdouble <parameter>valueY</parameter></paramdef> | |
26 | <paramdef>GLdouble <parameter>valueZ</parameter></paramdef> | |
27 | </funcprototype> | |
28 | </funcsynopsis> | |
29 | </refsynopsisdiv> | |
30 | <!-- eqn: ignoring delim $$ --> | |
31 | <refsect1 id="parameters"><title>Parameters</title> | |
32 | <variablelist> | |
33 | <varlistentry> | |
34 | <term><parameter>tess</parameter></term> | |
35 | <listitem> | |
36 | <para> | |
37 | Specifies the tessellation object (created with <citerefentry><refentrytitle>gluNewTess</refentrytitle></citerefentry>). | |
38 | </para> | |
39 | </listitem> | |
40 | </varlistentry> | |
41 | <varlistentry> | |
42 | <term><parameter>valueX</parameter></term> | |
43 | <listitem> | |
44 | <para> | |
45 | Specifies the first component of the normal. | |
46 | </para> | |
47 | </listitem> | |
48 | </varlistentry> | |
49 | <varlistentry> | |
50 | <term><parameter>valueY</parameter></term> | |
51 | <listitem> | |
52 | <para> | |
53 | Specifies the second component of the normal. | |
54 | </para> | |
55 | </listitem> | |
56 | </varlistentry> | |
57 | <varlistentry> | |
58 | <term><parameter>valueZ</parameter></term> | |
59 | <listitem> | |
60 | <para> | |
61 | Specifies the third component of the normal. | |
62 | </para> | |
63 | </listitem> | |
64 | </varlistentry> | |
65 | </variablelist> | |
66 | </refsect1> | |
67 | <refsect1 id="description"><title>Description</title> | |
68 | <para> | |
69 | <function>gluTessNormal</function> describes a normal for a polygon that the program is defining. | |
70 | All input data will be projected onto a plane perpendicular to one of | |
71 | the three coordinate axes before tessellation and all output triangles | |
72 | will be oriented CCW with | |
73 | respect to the normal (CW orientation can be obtained by reversing the | |
74 | sign of the supplied normal). For example, if you know that all polygons | |
75 | lie in the x-y plane, call <function>gluTessNormal</function>(tess, 0.0, 0.0, 1.0) | |
76 | before rendering any polygons. | |
77 | </para> | |
78 | <para> | |
79 | If the supplied normal is (0.0, 0.0, 0.0) (the initial value), the normal is | |
80 | determined as follows. The direction of the normal, up to its sign, is | |
81 | found by fitting a plane to the vertices, without regard to how the | |
82 | vertices are connected. It is expected that the input data lies approximately | |
83 | in the plane; otherwise, projection perpendicular to one of the three | |
84 | coordinate axes may substantially change the geometry. The sign of the | |
85 | normal is chosen so that the sum of the signed areas of all input | |
86 | contours is nonnegative (where a CCW contour has positive area). | |
87 | </para> | |
88 | <para> | |
89 | The supplied normal persists until it is changed by another call to | |
90 | <function>gluTessNormal</function>. | |
91 | </para> | |
92 | </refsect1> | |
93 | <refsect1 id="seealso"><title>See Also</title> | |
94 | <para> | |
95 | <citerefentry><refentrytitle>gluTessBeginPolygon</refentrytitle></citerefentry>, | |
96 | <citerefentry><refentrytitle>gluTessEndPolygon</refentrytitle></citerefentry> | |
97 | </para> | |
98 | </refsect1> | |
99 | <refsect1 id="Copyright"><title>Copyright</title> | |
100 | <para> | |
101 | Copyright <trademark class="copyright"></trademark> 1991-2006 | |
102 | Silicon Graphics, Inc. This document is licensed under the SGI | |
103 | Free Software B License. For details, see | |
104 | <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>. | |
105 | </para> | |
106 | </refsect1> | |
107 | </refentry> |