upstream-man-pages/man3/xhtml/glHint.xml

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   4 <?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" /><link rel="stylesheet" type="text/css" href="opengl-man.css" /><title>glHint</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /></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"><p><code class="funcdef">void <b class="fsfunc">glHint</b>(</code>GLenum <var class="pdparam">target</var>, GLenum <var class="pdparam">mode</var><code>)</code>;</p></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>
   5                     Specifies a symbolic constant indicating the behavior to be controlled.
   6                     <code class="constant">GL_LINE_SMOOTH_HINT</code>,
   7                     <code class="constant">GL_POLYGON_SMOOTH_HINT</code>,
   8                     <code class="constant">GL_TEXTURE_COMPRESSION_HINT</code>, and
   9                     <code class="constant">GL_FRAGMENT_SHADER_DERIVATIVE_HINT</code>
  10                     are accepted.
  11                 </p></dd><dt><span class="term"><em class="parameter"><code>mode</code></em></span></dt><dd><p>
  12                     Specifies a symbolic constant indicating the desired behavior.
  13                     <code class="constant">GL_FASTEST</code>,
  14                     <code class="constant">GL_NICEST</code>, and
  15                     <code class="constant">GL_DONT_CARE</code> are accepted.
  16                 </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
  17             Certain aspects of GL behavior,
  18             when there is room for interpretation,
  19             can be controlled with hints.
  20             A hint is specified with two arguments.
  21             <em class="parameter"><code>target</code></em> is a symbolic
  22             constant indicating the behavior to be controlled,
  23             and <em class="parameter"><code>mode</code></em> is another symbolic constant indicating the desired
  24             behavior. The initial value for each <em class="parameter"><code>target</code></em> is <code class="constant">GL_DONT_CARE</code>.
  25             <em class="parameter"><code>mode</code></em> can be one of the following:
  26         </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GL_FASTEST</code></span></dt><dd><p>
  27                     </p><p>
  28                         The most efficient option should be chosen.
  29                     </p></dd><dt><span class="term"><code class="constant">GL_NICEST</code></span></dt><dd><p>
  30                     </p><p>
  31                         The most correct,
  32                         or highest quality,
  33                         option should be chosen.
  34                     </p></dd><dt><span class="term"><code class="constant">GL_DONT_CARE</code></span></dt><dd><p>
  35                     </p><p>
  36                         No preference.
  37                     </p></dd></dl></div><p>
  38             Though the implementation aspects that can be hinted are well defined,
  39             the interpretation of the hints depends on the implementation.
  40             The hint aspects that can be specified with <em class="parameter"><code>target</code></em>,
  41             along with suggested semantics,
  42             are as follows:
  43         </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GL_FRAGMENT_SHADER_DERIVATIVE_HINT</code></span></dt><dd><p>
  44                     </p><p>
  45                         Indicates the accuracy of the derivative calculation for the GL shading language fragment processing built-in functions:
  46                         <code class="constant">dFdx</code>, <code class="constant">dFdy</code>, and <code class="constant">fwidth</code>.
  47                     </p></dd><dt><span class="term"><code class="constant">GL_LINE_SMOOTH_HINT</code></span></dt><dd><p>
  48                     </p><p>
  49                         Indicates the sampling quality of antialiased lines.
  50                         If a larger filter function is applied, hinting <code class="constant">GL_NICEST</code> can
  51                         result in more pixel fragments being generated during rasterization.
  52                     </p></dd><dt><span class="term"><code class="constant">GL_POLYGON_SMOOTH_HINT</code></span></dt><dd><p>
  53                     </p><p>
  54                         Indicates the sampling quality of antialiased polygons.
  55                         Hinting <code class="constant">GL_NICEST</code> can result in more pixel fragments being generated
  56                         during rasterization,
  57                         if a larger filter function is applied.
  58                     </p></dd><dt><span class="term"><code class="constant">GL_TEXTURE_COMPRESSION_HINT</code></span></dt><dd><p>
  59                     </p><p>
  60                         Indicates the quality and performance of the compressing texture images.
  61                         Hinting <code class="constant">GL_FASTEST</code> indicates that texture images should be compressed
  62                         as quickly as possible, while <code class="constant">GL_NICEST</code> indicates that texture images
  63                         should be compressed with as little image quality loss as possible.
  64                         <code class="constant">GL_NICEST</code> should be selected if the texture is to be retrieved by
  65                         <a href="glGetCompressedTexImage.xml"><span class="citerefentry"><span class="refentrytitle">glGetCompressedTexImage</span></span></a> for reuse.
  66                     </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p>
  67             The interpretation of hints depends on the implementation.
  68             Some implementations ignore <code class="function">glHint</code> settings.
  69         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
  70             <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
  71             an accepted value.
  72         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
  73             Copyright <span class="trademark"></span>© 1991-2006
  74             Silicon Graphics, Inc. This document is licensed under the SGI
  75             Free Software B License. For details, see
  76             <a href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
  77         </p></div></div></body></html>