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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="glShadeModel"> | |
5 | <refmeta> | |
6 | <refmetainfo> | |
7 | <copyright> | |
8 | <year>1991-2006</year> | |
9 | <holder>Silicon Graphics, Inc.</holder> | |
10 | </copyright> | |
11 | </refmetainfo> | |
12 | <refentrytitle>glShadeModel</refentrytitle> | |
13 | <manvolnum>3G</manvolnum> | |
14 | </refmeta> | |
15 | <refnamediv> | |
16 | <refname>glShadeModel</refname> | |
17 | <refpurpose>select flat or smooth shading</refpurpose> | |
18 | </refnamediv> | |
19 | <refsynopsisdiv><title>C Specification</title> | |
20 | <funcsynopsis> | |
21 | <funcprototype> | |
22 | <funcdef>void <function>glShadeModel</function></funcdef> | |
23 | <paramdef>GLenum <parameter>mode</parameter></paramdef> | |
24 | </funcprototype> | |
25 | </funcsynopsis> | |
26 | </refsynopsisdiv> | |
27 | <!-- eqn: ignoring delim $$ --> | |
28 | <refsect1 id="parameters"><title>Parameters</title> | |
29 | <variablelist> | |
30 | <varlistentry> | |
31 | <term><parameter>mode</parameter></term> | |
32 | <listitem> | |
33 | <para> | |
34 | Specifies a symbolic value representing a shading technique. | |
35 | Accepted values are <constant>GL_FLAT</constant> and <constant>GL_SMOOTH</constant>. | |
36 | The initial value is <constant>GL_SMOOTH</constant>. | |
37 | </para> | |
38 | </listitem> | |
39 | </varlistentry> | |
40 | </variablelist> | |
41 | </refsect1> | |
42 | <refsect1 id="description"><title>Description</title> | |
43 | <para> | |
44 | GL primitives can have either flat or smooth shading. | |
45 | Smooth shading, | |
46 | the default, | |
47 | causes the computed colors of vertices to be interpolated as the | |
48 | primitive is rasterized, | |
49 | typically assigning different colors to each resulting pixel fragment. | |
50 | Flat shading selects the computed color of just one vertex | |
51 | and assigns it to all the pixel fragments | |
52 | generated by rasterizing a single primitive. | |
53 | In either case, the computed color of a vertex is the result of | |
54 | lighting if lighting is enabled, | |
55 | or it is the current color at the time the vertex was specified if | |
56 | lighting is disabled. | |
57 | </para> | |
58 | <para> | |
59 | Flat and smooth shading are indistinguishable for points. | |
60 | Starting when <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> is issued and counting vertices and | |
61 | primitives from 1, the GL gives each flat-shaded line segment | |
62 | <inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation> | |
63 | the | |
64 | computed color of vertex | |
65 | <inlineequation><mml:math> | |
66 | <!-- eqn: i + 1:--> | |
67 | <mml:mrow> | |
68 | <mml:mi mathvariant="italic">i</mml:mi> | |
69 | <mml:mo>+</mml:mo> | |
70 | <mml:mn>1</mml:mn> | |
71 | </mml:mrow> | |
72 | </mml:math></inlineequation>, | |
73 | its second vertex. | |
74 | Counting similarly from 1, | |
75 | the GL gives each flat-shaded polygon the computed color of the vertex listed | |
76 | in the following table. | |
77 | This is the last vertex to specify the polygon in all cases except single | |
78 | polygons, | |
79 | where the first vertex specifies the flat-shaded color. | |
80 | </para> | |
81 | <para> | |
82 | </para> | |
83 | <informaltable frame="topbot"> | |
84 | <tgroup cols="2" align="left"> | |
85 | <colspec/> | |
86 | <colspec align="center"/> | |
87 | <thead> | |
88 | <row> | |
89 | <entry rowsep="1" align="left"><emphasis role="bold"> | |
90 | Primitive Type of Polygon | |
91 | <inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation> | |
92 | </emphasis></entry> | |
93 | <entry rowsep="1" align="center"><emphasis role="bold"> | |
94 | Vertex | |
95 | </emphasis></entry> | |
96 | </row> | |
97 | </thead> | |
98 | <tbody> | |
99 | <row> | |
100 | <entry align="left"> | |
101 | Single polygon | |
102 | (<inlineequation><mml:math> | |
103 | <!-- eqn: i == 1:--> | |
104 | <mml:mrow> | |
105 | <mml:mi mathvariant="italic">i</mml:mi> | |
106 | <mml:mo>==</mml:mo> | |
107 | <mml:mn>1</mml:mn> | |
108 | </mml:mrow> | |
109 | </mml:math></inlineequation>) | |
110 | </entry> | |
111 | <entry align="center"> | |
112 | 1 | |
113 | </entry> | |
114 | </row> | |
115 | <row> | |
116 | <entry align="left"> | |
117 | Triangle strip | |
118 | </entry> | |
119 | <entry align="center"> | |
120 | <inlineequation><mml:math> | |
121 | <!-- eqn: i + 2:--> | |
122 | <mml:mrow> | |
123 | <mml:mi mathvariant="italic">i</mml:mi> | |
124 | <mml:mo>+</mml:mo> | |
125 | <mml:mn>2</mml:mn> | |
126 | </mml:mrow> | |
127 | </mml:math></inlineequation> | |
128 | </entry> | |
129 | </row> | |
130 | <row> | |
131 | <entry align="left"> | |
132 | Triangle fan | |
133 | </entry> | |
134 | <entry align="center"> | |
135 | <inlineequation><mml:math> | |
136 | <!-- eqn: i + 2:--> | |
137 | <mml:mrow> | |
138 | <mml:mi mathvariant="italic">i</mml:mi> | |
139 | <mml:mo>+</mml:mo> | |
140 | <mml:mn>2</mml:mn> | |
141 | </mml:mrow> | |
142 | </mml:math></inlineequation> | |
143 | </entry> | |
144 | </row> | |
145 | <row> | |
146 | <entry align="left"> | |
147 | Independent triangle | |
148 | </entry> | |
149 | <entry align="center"> | |
150 | <inlineequation><mml:math> | |
151 | <!-- eqn: 3 i:--> | |
152 | <mml:mrow> | |
153 | <mml:mn>3</mml:mn> | |
154 | <mml:mo>⁢</mml:mo> | |
155 | <mml:mi mathvariant="italic">i</mml:mi> | |
156 | </mml:mrow> | |
157 | </mml:math></inlineequation> | |
158 | </entry> | |
159 | </row> | |
160 | <row> | |
161 | <entry align="left"> | |
162 | Quad strip | |
163 | </entry> | |
164 | <entry align="center"> | |
165 | <inlineequation><mml:math> | |
166 | <!-- eqn: 2 i + 2:--> | |
167 | <mml:mrow> | |
168 | <mml:mn>2</mml:mn> | |
169 | <mml:mo>⁢</mml:mo> | |
170 | <mml:mi mathvariant="italic">i</mml:mi> | |
171 | <mml:mo>+</mml:mo> | |
172 | <mml:mn>2</mml:mn> | |
173 | </mml:mrow> | |
174 | </mml:math></inlineequation> | |
175 | </entry> | |
176 | </row> | |
177 | <row> | |
178 | <entry align="left"> | |
179 | Independent quad | |
180 | </entry> | |
181 | <entry align="center"> | |
182 | <inlineequation><mml:math> | |
183 | <!-- eqn: 4 i:--> | |
184 | <mml:mrow> | |
185 | <mml:mn>4</mml:mn> | |
186 | <mml:mo>⁢</mml:mo> | |
187 | <mml:mi mathvariant="italic">i</mml:mi> | |
188 | </mml:mrow> | |
189 | </mml:math></inlineequation> | |
190 | </entry> | |
191 | </row> | |
192 | </tbody> | |
193 | </tgroup> | |
194 | </informaltable> | |
195 | <para> | |
196 | Flat and smooth shading are specified by <function>glShadeModel</function> with <parameter>mode</parameter> set to | |
197 | <constant>GL_FLAT</constant> and <constant>GL_SMOOTH</constant>, respectively. | |
198 | </para> | |
199 | </refsect1> | |
200 | <refsect1 id="errors"><title>Errors</title> | |
201 | <para> | |
202 | <constant>GL_INVALID_ENUM</constant> is generated if <parameter>mode</parameter> is any value other than | |
203 | <constant>GL_FLAT</constant> or <constant>GL_SMOOTH</constant>. | |
204 | </para> | |
205 | <para> | |
206 | <constant>GL_INVALID_OPERATION</constant> is generated if <function>glShadeModel</function> | |
207 | is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> | |
208 | and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>. | |
209 | </para> | |
210 | </refsect1> | |
211 | <refsect1 id="associatedgets"><title>Associated Gets</title> | |
212 | <para> | |
213 | <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_SHADE_MODEL</constant> | |
214 | </para> | |
215 | </refsect1> | |
216 | <refsect1 id="seealso"><title>See Also</title> | |
217 | <para> | |
218 | <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>, | |
219 | <citerefentry><refentrytitle>glColor</refentrytitle></citerefentry>, | |
220 | <citerefentry><refentrytitle>glLight</refentrytitle></citerefentry>, | |
221 | <citerefentry><refentrytitle>glLightModel</refentrytitle></citerefentry> | |
222 | </para> | |
223 | </refsect1> | |
224 | <refsect1 id="Copyright"><title>Copyright</title> | |
225 | <para> | |
226 | Copyright <trademark class="copyright"></trademark> 1991-2006 | |
227 | Silicon Graphics, Inc. This document is licensed under the SGI | |
228 | Free Software B License. For details, see | |
229 | <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>. | |
230 | </para> | |
231 | </refsect1> | |
232 | </refentry> |