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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="glHint"> | |
5 | <refmeta> | |
6 | <refmetainfo> | |
7 | <copyright> | |
8 | <year>1991-2006</year> | |
9 | <holder>Silicon Graphics, Inc.</holder> | |
10 | </copyright> | |
11 | </refmetainfo> | |
12 | <refentrytitle>glHint</refentrytitle> | |
13 | <manvolnum>3G</manvolnum> | |
14 | </refmeta> | |
15 | <refnamediv> | |
16 | <refname>glHint</refname> | |
17 | <refpurpose>specify implementation-specific hints</refpurpose> | |
18 | </refnamediv> | |
19 | <refsynopsisdiv><title>C Specification</title> | |
20 | <funcsynopsis> | |
21 | <funcprototype> | |
22 | <funcdef>void <function>glHint</function></funcdef> | |
23 | <paramdef>GLenum <parameter>target</parameter></paramdef> | |
24 | <paramdef>GLenum <parameter>mode</parameter></paramdef> | |
25 | </funcprototype> | |
26 | </funcsynopsis> | |
27 | </refsynopsisdiv> | |
28 | <refsect1 id="parameters"><title>Parameters</title> | |
29 | <variablelist> | |
30 | <varlistentry> | |
31 | <term><parameter>target</parameter></term> | |
32 | <listitem> | |
33 | <para> | |
34 | Specifies a symbolic constant indicating the behavior to be controlled. | |
35 | <constant>GL_LINE_SMOOTH_HINT</constant>, | |
36 | <constant>GL_POLYGON_SMOOTH_HINT</constant>, | |
37 | <constant>GL_TEXTURE_COMPRESSION_HINT</constant>, and | |
38 | <constant>GL_FRAGMENT_SHADER_DERIVATIVE_HINT</constant> | |
39 | are accepted. | |
40 | </para> | |
41 | </listitem> | |
42 | </varlistentry> | |
43 | <varlistentry> | |
44 | <term><parameter>mode</parameter></term> | |
45 | <listitem> | |
46 | <para> | |
47 | Specifies a symbolic constant indicating the desired behavior. | |
48 | <constant>GL_FASTEST</constant>, | |
49 | <constant>GL_NICEST</constant>, and | |
50 | <constant>GL_DONT_CARE</constant> are accepted. | |
51 | </para> | |
52 | </listitem> | |
53 | </varlistentry> | |
54 | </variablelist> | |
55 | </refsect1> | |
56 | <refsect1 id="description"><title>Description</title> | |
57 | <para> | |
58 | Certain aspects of GL behavior, | |
59 | when there is room for interpretation, | |
60 | can be controlled with hints. | |
61 | A hint is specified with two arguments. | |
62 | <parameter>target</parameter> is a symbolic | |
63 | constant indicating the behavior to be controlled, | |
64 | and <parameter>mode</parameter> is another symbolic constant indicating the desired | |
65 | behavior. The initial value for each <parameter>target</parameter> is <constant>GL_DONT_CARE</constant>. | |
66 | <parameter>mode</parameter> can be one of the following: | |
67 | </para> | |
68 | <variablelist> | |
69 | <varlistentry> | |
70 | <term><constant>GL_FASTEST</constant></term> | |
71 | <listitem> | |
72 | <para> | |
73 | </para> | |
74 | <para> | |
75 | The most efficient option should be chosen. | |
76 | </para> | |
77 | </listitem> | |
78 | </varlistentry> | |
79 | <varlistentry> | |
80 | <term><constant>GL_NICEST</constant></term> | |
81 | <listitem> | |
82 | <para> | |
83 | </para> | |
84 | <para> | |
85 | The most correct, | |
86 | or highest quality, | |
87 | option should be chosen. | |
88 | </para> | |
89 | </listitem> | |
90 | </varlistentry> | |
91 | <varlistentry> | |
92 | <term><constant>GL_DONT_CARE</constant></term> | |
93 | <listitem> | |
94 | <para> | |
95 | </para> | |
96 | <para> | |
97 | No preference. | |
98 | </para> | |
99 | </listitem> | |
100 | </varlistentry> | |
101 | </variablelist> | |
102 | <para> | |
103 | Though the implementation aspects that can be hinted are well defined, | |
104 | the interpretation of the hints depends on the implementation. | |
105 | The hint aspects that can be specified with <parameter>target</parameter>, | |
106 | along with suggested semantics, | |
107 | are as follows: | |
108 | </para> | |
109 | <variablelist> | |
110 | <varlistentry> | |
111 | <term><constant>GL_FRAGMENT_SHADER_DERIVATIVE_HINT</constant></term> | |
112 | <listitem> | |
113 | <para> | |
114 | </para> | |
115 | <para> | |
116 | Indicates the accuracy of the derivative calculation for the GL shading language fragment processing built-in functions: | |
117 | <constant>dFdx</constant>, <constant>dFdy</constant>, and <constant>fwidth</constant>. | |
118 | </para> | |
119 | </listitem> | |
120 | </varlistentry> | |
121 | <varlistentry> | |
122 | <term><constant>GL_LINE_SMOOTH_HINT</constant></term> | |
123 | <listitem> | |
124 | <para> | |
125 | </para> | |
126 | <para> | |
127 | Indicates the sampling quality of antialiased lines. | |
128 | If a larger filter function is applied, hinting <constant>GL_NICEST</constant> can | |
129 | result in more pixel fragments being generated during rasterization. | |
130 | </para> | |
131 | </listitem> | |
132 | </varlistentry> | |
133 | <varlistentry> | |
134 | <term><constant>GL_POLYGON_SMOOTH_HINT</constant></term> | |
135 | <listitem> | |
136 | <para> | |
137 | </para> | |
138 | <para> | |
139 | Indicates the sampling quality of antialiased polygons. | |
140 | Hinting <constant>GL_NICEST</constant> can result in more pixel fragments being generated | |
141 | during rasterization, | |
142 | if a larger filter function is applied. | |
143 | </para> | |
144 | </listitem> | |
145 | </varlistentry> | |
146 | <varlistentry> | |
147 | <term><constant>GL_TEXTURE_COMPRESSION_HINT</constant></term> | |
148 | <listitem> | |
149 | <para> | |
150 | </para> | |
151 | <para> | |
152 | Indicates the quality and performance of the compressing texture images. | |
153 | Hinting <constant>GL_FASTEST</constant> indicates that texture images should be compressed | |
154 | as quickly as possible, while <constant>GL_NICEST</constant> indicates that texture images | |
155 | should be compressed with as little image quality loss as possible. | |
156 | <constant>GL_NICEST</constant> should be selected if the texture is to be retrieved by | |
157 | <citerefentry><refentrytitle>glGetCompressedTexImage</refentrytitle></citerefentry> for reuse. | |
158 | </para> | |
159 | </listitem> | |
160 | </varlistentry> | |
161 | </variablelist> | |
162 | </refsect1> | |
163 | <refsect1 id="notes"><title>Notes</title> | |
164 | <para> | |
165 | The interpretation of hints depends on the implementation. | |
166 | Some implementations ignore <function>glHint</function> settings. | |
167 | </para> | |
168 | </refsect1> | |
169 | <refsect1 id="errors"><title>Errors</title> | |
170 | <para> | |
171 | <constant>GL_INVALID_ENUM</constant> is generated if either <parameter>target</parameter> or <parameter>mode</parameter> is not | |
172 | an accepted value. | |
173 | </para> | |
174 | </refsect1> | |
175 | <refsect1 id="Copyright"><title>Copyright</title> | |
176 | <para> | |
177 | Copyright <trademark class="copyright"></trademark> 1991-2006 | |
178 | Silicon Graphics, Inc. This document is licensed under the SGI | |
179 | Free Software B License. For details, see | |
180 | <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>. | |
181 | </para> | |
182 | </refsect1> | |
183 | </refentry> |