upstream-doc/man2/xhtml/glEvalCoord.xml

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   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>glEvalCoord</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glEvalCoord"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glEvalCoord — evaluate enabled one- and two-dimensional maps</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">glEvalCoord1f</b>(</code></td><td>GLfloat  </td><td><var class="pdparam">u</var><code>)</code>;</td></tr></table></div><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glEvalCoord1d</b>(</code></td><td>GLdouble  </td><td><var class="pdparam">u</var><code>)</code>;</td></tr></table></div><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glEvalCoord2f</b>(</code></td><td>GLfloat  </td><td><var class="pdparam">u</var>, </td></tr><tr><td> </td><td>GLfloat  </td><td><var class="pdparam">v</var><code>)</code>;</td></tr></table></div><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glEvalCoord2d</b>(</code></td><td>GLdouble  </td><td><var class="pdparam">u</var>, </td></tr><tr><td> </td><td>GLdouble  </td><td><var class="pdparam">v</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>u</code></em></span></dt><dd><p>
   4                     Specifies a value that is the domain coordinate
   5                     <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">u</mml:mi></mml:math>
   6                     to the basis function
   7                     defined in a previous <a class="citerefentry" href="glMap1.xml"><span class="citerefentry"><span class="refentrytitle">glMap1</span></span></a> or <a class="citerefentry" href="glMap2.xml"><span class="citerefentry"><span class="refentrytitle">glMap2</span></span></a> command.
   8                 </p></dd><dt><span class="term"><em class="parameter"><code>v</code></em></span></dt><dd><p>
   9                     Specifies a value that is the domain coordinate
  10                     <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">v</mml:mi></mml:math>
  11                     to the basis function
  12                     defined in a previous <a class="citerefentry" href="glMap2.xml"><span class="citerefentry"><span class="refentrytitle">glMap2</span></span></a> command.
  13                     This argument is not present in a <code class="function">glEvalCoord1</code> command.
  14                 </p></dd></dl></div></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">glEvalCoord1fv</b>(</code></td><td>const GLfloat *  </td><td><var class="pdparam">u</var><code>)</code>;</td></tr></table></div><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glEvalCoord1dv</b>(</code></td><td>const GLdouble *  </td><td><var class="pdparam">u</var><code>)</code>;</td></tr></table></div><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glEvalCoord2fv</b>(</code></td><td>const GLfloat *  </td><td><var class="pdparam">u</var><code>)</code>;</td></tr></table></div><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glEvalCoord2dv</b>(</code></td><td>const GLdouble *  </td><td><var class="pdparam">u</var><code>)</code>;</td></tr></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters2"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>u</code></em></span></dt><dd><p>
  15                     Specifies a pointer to an array containing
  16                     either one or two domain coordinates.
  17                     The first coordinate is
  18                     <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">u</mml:mi></mml:math>.
  19                     The second coordinate is
  20                     <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">v</mml:mi></mml:math>,
  21                     which is present only in <code class="function">glEvalCoord2</code> versions.
  22                 </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
  23             <code class="function">glEvalCoord1</code> evaluates enabled one-dimensional maps at argument
  24             <em class="parameter"><code>u</code></em>.
  25             <code class="function">glEvalCoord2</code> does the same for two-dimensional maps using
  26             two domain values,
  27             <em class="parameter"><code>u</code></em> and <em class="parameter"><code>v</code></em>.
  28             To define a map, call <a class="citerefentry" href="glMap1.xml"><span class="citerefentry"><span class="refentrytitle">glMap1</span></span></a> and <a class="citerefentry" href="glMap2.xml"><span class="citerefentry"><span class="refentrytitle">glMap2</span></span></a>; to enable and
  29             disable it, call <a class="citerefentry" href="glEnable.xml"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a> and <a class="citerefentry" href="glDisable.xml"><span class="citerefentry"><span class="refentrytitle">glDisable</span></span></a>.
  30         </p><p>
  31             When one of the <code class="function">glEvalCoord</code> commands is issued,
  32             all currently enabled maps of the indicated dimension are evaluated.
  33             Then,
  34             for each enabled map,
  35             it is as if the corresponding GL command had been issued with the
  36             computed value.
  37             That is,
  38             if <code class="constant">GL_MAP1_INDEX</code> or
  39             <code class="constant">GL_MAP2_INDEX</code> is enabled,
  40             a <a class="citerefentry" href="glIndex.xml"><span class="citerefentry"><span class="refentrytitle">glIndex</span></span></a> command is simulated.
  41             If <code class="constant">GL_MAP1_COLOR_4</code> or
  42             <code class="constant">GL_MAP2_COLOR_4</code> is enabled,
  43             a <a class="citerefentry" href="glColor.xml"><span class="citerefentry"><span class="refentrytitle">glColor</span></span></a> command is simulated.
  44             If <code class="constant">GL_MAP1_NORMAL</code> or <code class="constant">GL_MAP2_NORMAL</code> is enabled,
  45             a normal vector is produced,
  46             and if any of
  47             <code class="constant">GL_MAP1_TEXTURE_COORD_1</code>,
  48             <code class="constant">GL_MAP1_TEXTURE_COORD_2</code>,
  49             <code class="constant">GL_MAP1_TEXTURE_COORD_3</code>,
  50             <code class="constant">GL_MAP1_TEXTURE_COORD_4</code>,
  51             <code class="constant">GL_MAP2_TEXTURE_COORD_1</code>,
  52             <code class="constant">GL_MAP2_TEXTURE_COORD_2</code>,
  53             <code class="constant">GL_MAP2_TEXTURE_COORD_3</code>, or
  54             <code class="constant">GL_MAP2_TEXTURE_COORD_4</code> is enabled, then an appropriate <a class="citerefentry" href="glTexCoord.xml"><span class="citerefentry"><span class="refentrytitle">glTexCoord</span></span></a> command is simulated.
  55         </p><p>
  56             For color,
  57             color index,
  58             normal,
  59             and texture coordinates the GL uses evaluated values instead of current values for those evaluations
  60             that are enabled,
  61             and current values otherwise,
  62             However,
  63             the evaluated values do not update the current values.
  64             Thus, if <a class="citerefentry" href="glVertex.xml"><span class="citerefentry"><span class="refentrytitle">glVertex</span></span></a> commands are interspersed with <code class="function">glEvalCoord</code>
  65             commands, the color,
  66             normal,
  67             and texture coordinates associated with the <a class="citerefentry" href="glVertex.xml"><span class="citerefentry"><span class="refentrytitle">glVertex</span></span></a> commands are not
  68             affected by the values generated by the <code class="function">glEvalCoord</code> commands,
  69             but only by the most recent
  70             <a class="citerefentry" href="glColor.xml"><span class="citerefentry"><span class="refentrytitle">glColor</span></span></a>,
  71             <a class="citerefentry" href="glIndex.xml"><span class="citerefentry"><span class="refentrytitle">glIndex</span></span></a>,
  72             <a class="citerefentry" href="glNormal.xml"><span class="citerefentry"><span class="refentrytitle">glNormal</span></span></a>, and
  73             <a class="citerefentry" href="glTexCoord.xml"><span class="citerefentry"><span class="refentrytitle">glTexCoord</span></span></a> commands.
  74         </p><p>
  75             No commands are issued for maps that are not enabled.
  76             If more than one texture evaluation is enabled for a particular dimension
  77             (for example, <code class="constant">GL_MAP2_TEXTURE_COORD_1</code> and
  78             <code class="constant">GL_MAP2_TEXTURE_COORD_2</code>),
  79             then only the evaluation of the map that produces the larger
  80             number of coordinates
  81             (in this case, <code class="constant">GL_MAP2_TEXTURE_COORD_2</code>)
  82             is carried out.
  83             <code class="constant">GL_MAP1_VERTEX_4</code> overrides <code class="constant">GL_MAP1_VERTEX_3</code>,
  84             and
  85             <code class="constant">GL_MAP2_VERTEX_4</code> overrides <code class="constant">GL_MAP2_VERTEX_3</code>,
  86             in the same manner.
  87             If neither a three- nor a four-component vertex map is enabled for the
  88             specified dimension,
  89             the <code class="function">glEvalCoord</code> command is ignored.
  90         </p><p>
  91             If you have enabled automatic normal generation,
  92             by calling <a class="citerefentry" href="glEnable.xml"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a> with argument <code class="constant">GL_AUTO_NORMAL</code>,
  93             <code class="function">glEvalCoord2</code> generates surface normals analytically,
  94             regardless of the contents or enabling of the <code class="constant">GL_MAP2_NORMAL</code> map.
  95             Let
  96         </p><p>
  97             </p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  98
  99                 <mml:mrow>
 100                     <mml:mi mathvariant="bold">m</mml:mi>
 101                     <mml:mo>=</mml:mo>
 102                     <mml:mrow>
 103                         <mml:mfenced open="" close="">
 104                             <mml:mfrac>
 105                                 <mml:mfenced open="" close="">
 106                                     <mml:mrow>
 107                                         <mml:mo>∂</mml:mo>
 108                                         <mml:mi mathvariant="bold">p</mml:mi>
 109                                     </mml:mrow>
 110                                 </mml:mfenced>
 111                                 <mml:mfenced open="" close="">
 112                                     <mml:mrow>
 113                                         <mml:mo>∂</mml:mo>
 114                                         <mml:mi mathvariant="italic">u</mml:mi>
 115                                     </mml:mrow>
 116                                 </mml:mfenced>
 117                             </mml:mfrac>
 118                         </mml:mfenced>
 119                         <mml:mo>×</mml:mo>
 120                         <mml:mfenced open="" close="">
 121                             <mml:mfrac>
 122                                 <mml:mfenced open="" close="">
 123                                     <mml:mrow>
 124                                         <mml:mo>∂</mml:mo>
 125                                         <mml:mi mathvariant="bold">p</mml:mi>
 126                                     </mml:mrow>
 127                                 </mml:mfenced>
 128                                 <mml:mfenced open="" close="">
 129                                     <mml:mrow>
 130                                         <mml:mo>∂</mml:mo>
 131                                         <mml:mi mathvariant="italic">v</mml:mi>
 132                                     </mml:mrow>
 133                                 </mml:mfenced>
 134                             </mml:mfrac>
 135                         </mml:mfenced>
 136                     </mml:mrow>
 137                 </mml:mrow>
 138             </mml:math></div><p>
 139         </p><p>
 140             Then the generated normal
 141             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 142
 143                 <mml:mi mathvariant="bold">n</mml:mi>
 144             </mml:math>
 145             is
 146             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 147
 148                 <mml:mrow>
 149                     <mml:mi mathvariant="bold">n</mml:mi>
 150                     <mml:mo>=</mml:mo>
 151                     <mml:mfrac>
 152                         <mml:mi mathvariant="bold">m</mml:mi>
 153                         <mml:mfenced open="" close="">
 154                             <mml:mfenced open="&#x2225;" close="&#x2225;">
 155                                 <mml:mi mathvariant="bold">m</mml:mi>
 156                             </mml:mfenced>
 157                         </mml:mfenced>
 158                     </mml:mfrac>
 159                 </mml:mrow>
 160             </mml:math>
 161         </p><p>
 162             If automatic normal generation is disabled,
 163             the corresponding normal map <code class="constant">GL_MAP2_NORMAL</code>,
 164             if enabled,
 165             is used to produce a normal.
 166             If neither automatic normal generation nor a normal map is enabled,
 167             no normal is generated for
 168             <code class="function">glEvalCoord2</code> commands.
 169         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
 170             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP1_VERTEX_3</code>
 171         </p><p>
 172             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP1_VERTEX_4</code>
 173         </p><p>
 174             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP1_INDEX</code>
 175         </p><p>
 176             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP1_COLOR_4</code>
 177         </p><p>
 178             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP1_NORMAL</code>
 179         </p><p>
 180             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP1_TEXTURE_COORD_1</code>
 181         </p><p>
 182             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP1_TEXTURE_COORD_2</code>
 183         </p><p>
 184             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP1_TEXTURE_COORD_3</code>
 185         </p><p>
 186             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP1_TEXTURE_COORD_4</code>
 187         </p><p>
 188             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP2_VERTEX_3</code>
 189         </p><p>
 190             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP2_VERTEX_4</code>
 191         </p><p>
 192             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP2_INDEX</code>
 193         </p><p>
 194             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP2_COLOR_4</code>
 195         </p><p>
 196             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP2_NORMAL</code>
 197         </p><p>
 198             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP2_TEXTURE_COORD_1</code>
 199         </p><p>
 200             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP2_TEXTURE_COORD_2</code>
 201         </p><p>
 202             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP2_TEXTURE_COORD_3</code>
 203         </p><p>
 204             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_MAP2_TEXTURE_COORD_4</code>
 205         </p><p>
 206             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_AUTO_NORMAL</code>
 207         </p><p>
 208             <a class="citerefentry" href="glGetMap.xml"><span class="citerefentry"><span class="refentrytitle">glGetMap</span></span></a>
 209         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
 210             <a class="citerefentry" href="glBegin.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a>,
 211             <a class="citerefentry" href="glColor.xml"><span class="citerefentry"><span class="refentrytitle">glColor</span></span></a>,
 212             <a class="citerefentry" href="glEnable.xml"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a>,
 213             <a class="citerefentry" href="glEvalMesh.xml"><span class="citerefentry"><span class="refentrytitle">glEvalMesh</span></span></a>,
 214             <a class="citerefentry" href="glEvalPoint.xml"><span class="citerefentry"><span class="refentrytitle">glEvalPoint</span></span></a>,
 215             <a class="citerefentry" href="glIndex.xml"><span class="citerefentry"><span class="refentrytitle">glIndex</span></span></a>,
 216             <a class="citerefentry" href="glMap1.xml"><span class="citerefentry"><span class="refentrytitle">glMap1</span></span></a>,
 217             <a class="citerefentry" href="glMap2.xml"><span class="citerefentry"><span class="refentrytitle">glMap2</span></span></a>,
 218             <a class="citerefentry" href="glMapGrid.xml"><span class="citerefentry"><span class="refentrytitle">glMapGrid</span></span></a>,
 219             <a class="citerefentry" href="glNormal.xml"><span class="citerefentry"><span class="refentrytitle">glNormal</span></span></a>,
 220             <a class="citerefentry" href="glTexCoord.xml"><span class="citerefentry"><span class="refentrytitle">glTexCoord</span></span></a>,
 221             <a class="citerefentry" href="glVertex.xml"><span class="citerefentry"><span class="refentrytitle">glVertex</span></span></a>
 222         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
 223             Copyright <span class="trademark"></span>© 1991-2006
 224             Silicon Graphics, Inc. This document is licensed under the SGI
 225             Free Software B License. For details, see
 226             <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
 227         </p></div></div></body></html>