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"text/html; charset=UTF-8" /><title>glHint
</title><meta name=
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"DocBook XSL Stylesheets V1.73.2" /></head><body><div class=
"refentry" lang=
"en" xml:
lang=
"en"><a id=
"glHint"></a><div class=
"titlepage"></div><div class=
"refnamediv"><h2>Name
</h2><p>glHint — specify implementation-specific hints
</p></div><div class=
"refsynopsisdiv"><h2>C Specification
</h2><div class=
"funcsynopsis"><table border=
"0" summary=
"Function synopsis" cellspacing=
"0" cellpadding=
"0"><tr><td><code class=
"funcdef">void
<b class=
"fsfunc">glHint
</b>(
</code></td><td>GLenum
</td><td><var class=
"pdparam">target
</var>,
</td></tr><tr><td> </td><td>GLenum
</td><td><var class=
"pdparam">mode
</var><code>)
</code>;
</td></tr></table></div></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"parameters"></a><h2>Parameters
</h2><div class=
"variablelist"><dl><dt><span class=
"term"><em class=
"parameter"><code>target
</code></em></span></dt><dd><p>
4 Specifies a symbolic constant indicating the behavior to be controlled.
5 <code class=
"constant">GL_FOG_HINT
</code>,
6 <code class=
"constant">GL_GENERATE_MIPMAP_HINT
</code>,
7 <code class=
"constant">GL_LINE_SMOOTH_HINT
</code>,
8 <code class=
"constant">GL_PERSPECTIVE_CORRECTION_HINT
</code>,
9 <code class=
"constant">GL_POINT_SMOOTH_HINT
</code>,
10 <code class=
"constant">GL_POLYGON_SMOOTH_HINT
</code>,
11 <code class=
"constant">GL_TEXTURE_COMPRESSION_HINT
</code>, and
12 <code class=
"constant">GL_FRAGMENT_SHADER_DERIVATIVE_HINT
</code>
14 </p></dd><dt><span class=
"term"><em class=
"parameter"><code>mode
</code></em></span></dt><dd><p>
15 Specifies a symbolic constant indicating the desired behavior.
16 <code class=
"constant">GL_FASTEST
</code>,
17 <code class=
"constant">GL_NICEST
</code>, and
18 <code class=
"constant">GL_DONT_CARE
</code> are accepted.
19 </p></dd></dl></div></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"description"></a><h2>Description
</h2><p>
20 Certain aspects of GL behavior,
21 when there is room for interpretation,
22 can be controlled with hints.
23 A hint is specified with two arguments.
24 <em class=
"parameter"><code>target
</code></em> is a symbolic
25 constant indicating the behavior to be controlled,
26 and
<em class=
"parameter"><code>mode
</code></em> is another symbolic constant indicating the desired
27 behavior. The initial value for each
<em class=
"parameter"><code>target
</code></em> is
<code class=
"constant">GL_DONT_CARE
</code>.
28 <em class=
"parameter"><code>mode
</code></em> can be one of the following:
29 </p><div class=
"variablelist"><dl><dt><span class=
"term"><code class=
"constant">GL_FASTEST
</code></span></dt><dd><p>
31 The most efficient option should be chosen.
32 </p></dd><dt><span class=
"term"><code class=
"constant">GL_NICEST
</code></span></dt><dd><p>
36 option should be chosen.
37 </p></dd><dt><span class=
"term"><code class=
"constant">GL_DONT_CARE
</code></span></dt><dd><p>
40 </p></dd></dl></div><p>
41 Though the implementation aspects that can be hinted are well defined,
42 the interpretation of the hints depends on the implementation.
43 The hint aspects that can be specified with
<em class=
"parameter"><code>target
</code></em>,
44 along with suggested semantics,
46 </p><div class=
"variablelist"><dl><dt><span class=
"term"><code class=
"constant">GL_FOG_HINT
</code></span></dt><dd><p>
48 Indicates the accuracy of fog calculation.
49 If per-pixel fog calculation is not efficiently supported
50 by the GL implementation,
51 hinting
<code class=
"constant">GL_DONT_CARE
</code> or
<code class=
"constant">GL_FASTEST
</code> can result in per-vertex
52 calculation of fog effects.
53 </p></dd><dt><span class=
"term"><code class=
"constant">GL_FRAGMENT_SHADER_DERIVATIVE_HINT
</code></span></dt><dd><p>
55 Indicates the accuracy of the derivative calculation for the GL shading language fragment processing built-in functions:
56 <code class=
"constant">dFdx
</code>,
<code class=
"constant">dFdy
</code>, and
<code class=
"constant">fwidth
</code>.
57 </p></dd><dt><span class=
"term"><code class=
"constant">GL_GENERATE_MIPMAP_HINT
</code></span></dt><dd><p>
59 Indicates the quality of filtering when generating mipmap images.
60 </p></dd><dt><span class=
"term"><code class=
"constant">GL_LINE_SMOOTH_HINT
</code></span></dt><dd><p>
62 Indicates the sampling quality of antialiased lines.
63 If a larger filter function is applied, hinting
<code class=
"constant">GL_NICEST
</code> can
64 result in more pixel fragments being generated during rasterization.
65 </p></dd><dt><span class=
"term"><code class=
"constant">GL_PERSPECTIVE_CORRECTION_HINT
</code></span></dt><dd><p>
67 Indicates the quality of color, texture coordinate, and fog coordinate
68 interpolation. If perspective-corrected parameter interpolation is not
69 efficiently supported by the GL implementation, hinting
<code class=
"constant">GL_DONT_CARE
</code>
70 or
<code class=
"constant">GL_FASTEST
</code> can result in simple linear interpolation of colors
71 and/or texture coordinates.
72 </p></dd><dt><span class=
"term"><code class=
"constant">GL_POINT_SMOOTH_HINT
</code></span></dt><dd><p>
74 Indicates the sampling quality of antialiased points.
75 If a larger filter function is applied, hinting
<code class=
"constant">GL_NICEST
</code> can
76 result in more pixel fragments being generated during rasterization.
77 </p></dd><dt><span class=
"term"><code class=
"constant">GL_POLYGON_SMOOTH_HINT
</code></span></dt><dd><p>
79 Indicates the sampling quality of antialiased polygons.
80 Hinting
<code class=
"constant">GL_NICEST
</code> can result in more pixel fragments being generated
82 if a larger filter function is applied.
83 </p></dd><dt><span class=
"term"><code class=
"constant">GL_TEXTURE_COMPRESSION_HINT
</code></span></dt><dd><p>
85 Indicates the quality and performance of the compressing texture images.
86 Hinting
<code class=
"constant">GL_FASTEST
</code> indicates that texture images should be compressed
87 as quickly as possible, while
<code class=
"constant">GL_NICEST
</code> indicates that texture images
88 should be compressed with as little image quality loss as possible.
89 <code class=
"constant">GL_NICEST
</code> should be selected if the texture is to be retrieved by
90 <a class=
"citerefentry" href=
"glGetCompressedTexImage.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glGetCompressedTexImage
</span></span></a> for reuse.
91 </p></dd></dl></div></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"notes"></a><h2>Notes
</h2><p>
92 The interpretation of hints depends on the implementation.
93 Some implementations ignore
<code class=
"function">glHint
</code> settings.
95 <code class=
"constant">GL_TEXTURE_COMPRESSION_HINT
</code> is available only if the GL version is
1.3
98 <code class=
"constant">GL_GENERATE_MIPMAP_HINT
</code> is available only if the GL version is
1.4
101 <code class=
"constant">GL_FRAGMENT_SHADER_DERIVATIVE_HINT
</code> is available only if the GL version is
2.0
103 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"errors"></a><h2>Errors
</h2><p>
104 <code class=
"constant">GL_INVALID_ENUM
</code> is generated if either
<em class=
"parameter"><code>target
</code></em> or
<em class=
"parameter"><code>mode
</code></em> is not
107 <code class=
"constant">GL_INVALID_OPERATION
</code> is generated if
<code class=
"function">glHint
</code>
108 is executed between the execution of
<a class=
"citerefentry" href=
"glBegin.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glBegin
</span></span></a>
109 and the corresponding execution of
<a class=
"citerefentry" href=
"glEnd.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glEnd
</span></span></a>.
110 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"Copyright"></a><h2>Copyright
</h2><p>
111 Copyright
<span class=
"trademark"></span>©
1991-
2006
112 Silicon Graphics, Inc. This document is licensed under the SGI
113 Free Software B License. For details, see
114 <a class=
"ulink" href=
"http://oss.sgi.com/projects/FreeB/" target=
"_top">http://oss.sgi.com/projects/FreeB/
</a>.
115 </p></div></div></body></html>