HCoop / clinton / guile-figl.git / blame
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1 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd"> |
| 2 | <!-- saved from url=(0013)about:internet --> | |
| 3 | <?xml-stylesheet type="text/xsl" href="mathml.xsl"?><html xmlns="http://www.w3.org/1999/xhtml" xmlns:pref="http://www.w3.org/2002/Math/preference" pref:renderer="mathplayer-dl"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>glHint</title><meta name="generator" content="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> | |
| 13 | are accepted. | |
| 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> | |
| 30 | </p><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> | |
| 33 | </p><p> | |
| 34 | The most correct, | |
| 35 | or highest quality, | |
| 36 | option should be chosen. | |
| 37 | </p></dd><dt><span class="term"><code class="constant">GL_DONT_CARE</code></span></dt><dd><p> | |
| 38 | </p><p> | |
| 39 | No preference. | |
| 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, | |
| 45 | are as follows: | |
| 46 | </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GL_FOG_HINT</code></span></dt><dd><p> | |
| 47 | </p><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> | |
| 54 | </p><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> | |
| 58 | </p><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> | |
| 61 | </p><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> | |
| 66 | </p><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> | |
| 73 | </p><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> | |
| 78 | </p><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 | |
| 81 | during rasterization, | |
| 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> | |
| 84 | </p><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. | |
| 94 | </p><p> | |
| 95 | <code class="constant">GL_TEXTURE_COMPRESSION_HINT</code> is available only if the GL version is 1.3 | |
| 96 | or greater. | |
| 97 | </p><p> | |
| 98 | <code class="constant">GL_GENERATE_MIPMAP_HINT</code> is available only if the GL version is 1.4 | |
| 99 | or greater. | |
| 100 | </p><p> | |
| 101 | <code class="constant">GL_FRAGMENT_SHADER_DERIVATIVE_HINT</code> is available only if the GL version is 2.0 | |
| 102 | or greater. | |
| 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 | |
| 105 | an accepted value. | |
| 106 | </p><p> | |
| 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> |