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

   1 <?xml version="1.0" encoding="UTF-8"?>
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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>glViewport</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /></head><body><div class="refentry" title="glViewport"><a id="glViewport"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glViewport — set the viewport</p></div><div class="refsynopsisdiv" title="C Specification"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glViewport</b>(</code></td><td>GLint <var class="pdparam">x</var>, </td></tr><tr><td> </td><td>GLint <var class="pdparam">y</var>, </td></tr><tr><td> </td><td>GLsizei <var class="pdparam">width</var>, </td></tr><tr><td> </td><td>GLsizei <var class="pdparam">height</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Parameters"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>x</code></em>, </span><span class="term"><em class="parameter"><code>y</code></em></span></dt><dd><p>
   5                     Specify the lower left corner of the viewport rectangle,
   6                     in pixels. The initial value is (0,0).
   7                 </p></dd><dt><span class="term"><em class="parameter"><code>width</code></em>, </span><span class="term"><em class="parameter"><code>height</code></em></span></dt><dd><p>
   8                     Specify the width and height
   9                     of the viewport.
  10                     When a GL context is first attached to a window,
  11                     <em class="parameter"><code>width</code></em> and <em class="parameter"><code>height</code></em> are set to the dimensions of that
  12                     window.
  13                 </p></dd></dl></div></div><div class="refsect1" title="Description"><a id="description"></a><h2>Description</h2><p>
  14             <code class="function">glViewport</code> specifies the affine transformation of
  15             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">x</mml:mi></mml:math>
  16             and
  17             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">y</mml:mi></mml:math>
  18             from
  19             normalized device coordinates to window coordinates.
  20             Let
  21             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  22
  23                 <mml:mfenced open="(" close=")">
  24                     <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
  25                     <mml:mi mathvariant="italic">nd</mml:mi>
  26                     </mml:msub>
  27                     <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
  28                     <mml:mi mathvariant="italic">nd</mml:mi>
  29                     </mml:msub>
  30                 </mml:mfenced>
  31             </mml:math>
  32             be normalized device coordinates.
  33             Then the window coordinates
  34             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  35
  36                 <mml:mfenced open="(" close=")">
  37                     <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
  38                     <mml:mi mathvariant="italic">w</mml:mi>
  39                     </mml:msub>
  40                     <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
  41                     <mml:mi mathvariant="italic">w</mml:mi>
  42                     </mml:msub>
  43                 </mml:mfenced>
  44             </mml:math>
  45             are computed as follows:
  46         </p><p>
  47             </p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  48
  49                 <mml:mrow>
  50                     <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
  51                     <mml:mi mathvariant="italic">w</mml:mi>
  52                     </mml:msub>
  53                     <mml:mo>=</mml:mo>
  54                     <mml:mrow>
  55                         <mml:mfenced open="(" close=")">
  56                             <mml:mrow>
  57                                 <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
  58                                 <mml:mi mathvariant="italic">nd</mml:mi>
  59                                 </mml:msub>
  60                                 <mml:mo>+</mml:mo>
  61                                 <mml:mn>1</mml:mn>
  62                             </mml:mrow>
  63                         </mml:mfenced>
  64                         <mml:mo>⁢</mml:mo>
  65                         <mml:mfenced open="(" close=")">
  66                             <mml:mfrac>
  67                                 <mml:mi mathvariant="italic">width</mml:mi>
  68                                 <mml:mn>2</mml:mn>
  69                             </mml:mfrac>
  70                         </mml:mfenced>
  71                         <mml:mo>+</mml:mo>
  72                         <mml:mi mathvariant="italic">x</mml:mi>
  73                     </mml:mrow>
  74                 </mml:mrow>
  75             </mml:math></div><p>
  76         </p><p>
  77             </p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  78
  79                 <mml:mrow>
  80                     <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
  81                     <mml:mi mathvariant="italic">w</mml:mi>
  82                     </mml:msub>
  83                     <mml:mo>=</mml:mo>
  84                     <mml:mrow>
  85                         <mml:mfenced open="(" close=")">
  86                             <mml:mrow>
  87                                 <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
  88                                 <mml:mi mathvariant="italic">nd</mml:mi>
  89                                 </mml:msub>
  90                                 <mml:mo>+</mml:mo>
  91                                 <mml:mn>1</mml:mn>
  92                             </mml:mrow>
  93                         </mml:mfenced>
  94                         <mml:mo>⁢</mml:mo>
  95                         <mml:mfenced open="(" close=")">
  96                             <mml:mfrac>
  97                                 <mml:mi mathvariant="italic">height</mml:mi>
  98                                 <mml:mn>2</mml:mn>
  99                             </mml:mfrac>
 100                         </mml:mfenced>
 101                         <mml:mo>+</mml:mo>
 102                         <mml:mi mathvariant="italic">y</mml:mi>
 103                     </mml:mrow>
 104                 </mml:mrow>
 105             </mml:math></div><p>
 106         </p><p>
 107             Viewport width and height are silently clamped
 108             to a range that depends on the implementation.
 109             To query this range, call <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument
 110             <code class="constant">GL_MAX_VIEWPORT_DIMS</code>.
 111         </p></div><div class="refsect1" title="Errors"><a id="errors"></a><h2>Errors</h2><p>
 112             <code class="constant">GL_INVALID_VALUE</code> is generated if either <em class="parameter"><code>width</code></em> or <em class="parameter"><code>height</code></em> is negative.
 113         </p></div><div class="refsect1" title="Associated Gets"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
 114             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_VIEWPORT</code>
 115         </p><p>
 116             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_MAX_VIEWPORT_DIMS</code>
 117         </p></div><div class="refsect1" title="See Also"><a id="seealso"></a><h2>See Also</h2><p>
 118             <a class="citerefentry" href="glDepthRange.xml"><span class="citerefentry"><span class="refentrytitle">glDepthRange</span></span></a>
 119         </p></div><div class="refsect1" title="Copyright"><a id="Copyright"></a><h2>Copyright</h2><p>
 120             Copyright <span class="trademark"></span>© 1991-2006
 121             Silicon Graphics, Inc. This document is licensed under the SGI
 122             Free Software B License. For details, see
 123             <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
 124         </p></div></div></body></html>