upstream-doc/man2/xhtml/glTexGen.xml

   1 <?xml version="1.0" encoding="UTF-8"?>
   2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd">
   3 <!-- saved from url=(0013)about:internet -->
   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" /><title>glTexGen</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glTexGen"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glTexGen — control the generation of texture coordinates</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">glTexGeni</b>(</code></td><td>GLenum  </td><td><var class="pdparam">coord</var>, </td></tr><tr><td> </td><td>GLenum  </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLint  </td><td><var class="pdparam">param</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">glTexGenf</b>(</code></td><td>GLenum  </td><td><var class="pdparam">coord</var>, </td></tr><tr><td> </td><td>GLenum  </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLfloat  </td><td><var class="pdparam">param</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">glTexGend</b>(</code></td><td>GLenum  </td><td><var class="pdparam">coord</var>, </td></tr><tr><td> </td><td>GLenum  </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLdouble  </td><td><var class="pdparam">param</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>coord</code></em></span></dt><dd><p>
   5                     Specifies a texture coordinate.
   6                     Must be one of <code class="constant">GL_S</code>, <code class="constant">GL_T</code>, <code class="constant">GL_R</code>, or <code class="constant">GL_Q</code>.
   7                 </p></dd><dt><span class="term"><em class="parameter"><code>pname</code></em></span></dt><dd><p>
   8                     Specifies the symbolic name of the texture-coordinate generation function.
   9                     Must be <code class="constant">GL_TEXTURE_GEN_MODE</code>.
  10                 </p></dd><dt><span class="term"><em class="parameter"><code>param</code></em></span></dt><dd><p>
  11                     Specifies a single-valued texture generation parameter,
  12                     one of <code class="constant">GL_OBJECT_LINEAR</code>, <code class="constant">GL_EYE_LINEAR</code>, <code class="constant">GL_SPHERE_MAP</code>,
  13                     <code class="constant">GL_NORMAL_MAP</code>, or <code class="constant">GL_REFLECTION_MAP</code>.
  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">glTexGeniv</b>(</code></td><td>GLenum  </td><td><var class="pdparam">coord</var>, </td></tr><tr><td> </td><td>GLenum  </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>const GLint *  </td><td><var class="pdparam">params</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">glTexGenfv</b>(</code></td><td>GLenum  </td><td><var class="pdparam">coord</var>, </td></tr><tr><td> </td><td>GLenum  </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>const GLfloat *  </td><td><var class="pdparam">params</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">glTexGendv</b>(</code></td><td>GLenum  </td><td><var class="pdparam">coord</var>, </td></tr><tr><td> </td><td>GLenum  </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>const GLdouble *  </td><td><var class="pdparam">params</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>coord</code></em></span></dt><dd><p>
  15                     Specifies a texture coordinate.
  16                     Must be one of <code class="constant">GL_S</code>, <code class="constant">GL_T</code>, <code class="constant">GL_R</code>, or <code class="constant">GL_Q</code>.
  17                 </p></dd><dt><span class="term"><em class="parameter"><code>pname</code></em></span></dt><dd><p>
  18                     Specifies the symbolic name of the texture-coordinate generation function
  19                     or function parameters.
  20                     Must be
  21                     <code class="constant">GL_TEXTURE_GEN_MODE</code>,
  22                     <code class="constant">GL_OBJECT_PLANE</code>, or
  23                     <code class="constant">GL_EYE_PLANE</code>.
  24                 </p></dd><dt><span class="term"><em class="parameter"><code>params</code></em></span></dt><dd><p>
  25                     Specifies a pointer to an array of texture generation parameters.
  26                     If <em class="parameter"><code>pname</code></em> is <code class="constant">GL_TEXTURE_GEN_MODE</code>,
  27                     then the array must contain a single symbolic constant,
  28                     one of
  29                     <code class="constant">GL_OBJECT_LINEAR</code>,
  30                     <code class="constant">GL_EYE_LINEAR</code>,
  31                     <code class="constant">GL_SPHERE_MAP</code>,
  32                     <code class="constant">GL_NORMAL_MAP</code>, or
  33                     <code class="constant">GL_REFLECTION_MAP</code>.
  34                     Otherwise,
  35                     <em class="parameter"><code>params</code></em> holds the coefficients for the texture-coordinate generation function
  36                     specified by <em class="parameter"><code>pname</code></em>.
  37                 </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
  38             <code class="function">glTexGen</code> selects a texture-coordinate generation function
  39             or supplies coefficients for one of the functions.
  40             <em class="parameter"><code>coord</code></em> names one of the (<span class="emphasis"><em>s</em></span>, <span class="emphasis"><em>t</em></span>, <span class="emphasis"><em>r</em></span>, <span class="emphasis"><em>q</em></span>) texture
  41             coordinates; it must be one of the symbols
  42             <code class="constant">GL_S</code>,
  43             <code class="constant">GL_T</code>,
  44             <code class="constant">GL_R</code>, or
  45             <code class="constant">GL_Q</code>.
  46             <em class="parameter"><code>pname</code></em> must be one of three symbolic constants:
  47             <code class="constant">GL_TEXTURE_GEN_MODE</code>,
  48             <code class="constant">GL_OBJECT_PLANE</code>, or
  49             <code class="constant">GL_EYE_PLANE</code>.
  50             If <em class="parameter"><code>pname</code></em> is <code class="constant">GL_TEXTURE_GEN_MODE</code>,
  51             then <em class="parameter"><code>params</code></em> chooses a mode,
  52             one of
  53             <code class="constant">GL_OBJECT_LINEAR</code>,
  54             <code class="constant">GL_EYE_LINEAR</code>,
  55             <code class="constant">GL_SPHERE_MAP</code>,
  56             <code class="constant">GL_NORMAL_MAP</code>, or
  57             <code class="constant">GL_REFLECTION_MAP</code>.
  58             If <em class="parameter"><code>pname</code></em> is either <code class="constant">GL_OBJECT_PLANE</code> or <code class="constant">GL_EYE_PLANE</code>,
  59             <em class="parameter"><code>params</code></em> contains coefficients for the corresponding
  60             texture generation function.
  61         </p><p>
  62             If the texture generation function is <code class="constant">GL_OBJECT_LINEAR</code>,
  63             the function
  64         </p><p>
  65             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  66
  67                 <mml:mrow>
  68                     <mml:mi mathvariant="italic">g</mml:mi>
  69                     <mml:mo>=</mml:mo>
  70                     <mml:mrow>
  71                         <mml:mrow>
  72                             <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
  73                             <mml:mn>1</mml:mn>
  74                             </mml:msub>
  75                             <mml:mo>×</mml:mo>
  76                             <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
  77                             <mml:mi mathvariant="italic">o</mml:mi>
  78                             </mml:msub>
  79                         </mml:mrow>
  80                         <mml:mo>+</mml:mo>
  81                         <mml:mrow>
  82                             <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
  83                             <mml:mn>2</mml:mn>
  84                             </mml:msub>
  85                             <mml:mo>×</mml:mo>
  86                             <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
  87                             <mml:mi mathvariant="italic">o</mml:mi>
  88                             </mml:msub>
  89                         </mml:mrow>
  90                         <mml:mo>+</mml:mo>
  91                         <mml:mrow>
  92                             <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
  93                             <mml:mn>3</mml:mn>
  94                             </mml:msub>
  95                             <mml:mo>×</mml:mo>
  96                             <mml:msub><mml:mi mathvariant="italic">z</mml:mi>
  97                             <mml:mi mathvariant="italic">o</mml:mi>
  98                             </mml:msub>
  99                         </mml:mrow>
 100                         <mml:mo>+</mml:mo>
 101                         <mml:mrow>
 102                             <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 103                             <mml:mn>4</mml:mn>
 104                             </mml:msub>
 105                             <mml:mo>×</mml:mo>
 106                             <mml:msub><mml:mi mathvariant="italic">w</mml:mi>
 107                             <mml:mi mathvariant="italic">o</mml:mi>
 108                             </mml:msub>
 109                         </mml:mrow>
 110                     </mml:mrow>
 111                 </mml:mrow>
 112             </mml:math>
 113         </p><p>
 114             is used, where
 115             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">g</mml:mi></mml:math>
 116             is the value computed for the coordinate named in <em class="parameter"><code>coord</code></em>,
 117             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 118
 119                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 120                 <mml:mn>1</mml:mn>
 121                 </mml:msub>
 122             </mml:math>,
 123             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 124
 125                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 126                 <mml:mn>2</mml:mn>
 127                 </mml:msub>
 128             </mml:math>,
 129             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 130
 131                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 132                 <mml:mn>3</mml:mn>
 133                 </mml:msub>
 134             </mml:math>,
 135             and
 136             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 137
 138                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 139                 <mml:mn>4</mml:mn>
 140                 </mml:msub>
 141             </mml:math>
 142             are the four values supplied in <em class="parameter"><code>params</code></em>, and
 143             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 144
 145                 <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 146                 <mml:mi mathvariant="italic">o</mml:mi>
 147                 </mml:msub>
 148             </mml:math>,
 149             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 150
 151                 <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 152                 <mml:mi mathvariant="italic">o</mml:mi>
 153                 </mml:msub>
 154             </mml:math>,
 155             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 156
 157                 <mml:msub><mml:mi mathvariant="italic">z</mml:mi>
 158                 <mml:mi mathvariant="italic">o</mml:mi>
 159                 </mml:msub>
 160             </mml:math>,
 161             and
 162             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 163
 164                 <mml:msub><mml:mi mathvariant="italic">w</mml:mi>
 165                 <mml:mi mathvariant="italic">o</mml:mi>
 166                 </mml:msub>
 167             </mml:math>
 168             are the object coordinates of the vertex.
 169             This function can be used, for example, to texture-map terrain using sea level
 170             as a reference plane
 171             (defined by
 172             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 173
 174                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 175                 <mml:mn>1</mml:mn>
 176                 </mml:msub>
 177             </mml:math>,
 178             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 179
 180                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 181                 <mml:mn>2</mml:mn>
 182                 </mml:msub>
 183             </mml:math>,
 184             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 185
 186                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 187                 <mml:mn>3</mml:mn>
 188                 </mml:msub>
 189             </mml:math>,
 190             and
 191             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 192
 193                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 194                 <mml:mn>4</mml:mn>
 195                 </mml:msub>
 196             </mml:math>).
 197             The altitude of a terrain vertex is computed by the <code class="constant">GL_OBJECT_LINEAR</code>
 198             coordinate generation function as its distance from sea level;
 199             that altitude can then be used to index the texture image to map white snow
 200             onto peaks and green grass onto foothills.
 201         </p><p>
 202             If the texture generation function is <code class="constant">GL_EYE_LINEAR</code>, the function
 203         </p><p>
 204             </p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 205
 206                 <mml:mrow>
 207                     <mml:mi mathvariant="italic">g</mml:mi>
 208                     <mml:mo>=</mml:mo>
 209                     <mml:mrow>
 210                         <mml:mrow>
 211                             <mml:msup><mml:mfenced open="" close="">
 212                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 213                                 <mml:mn>1</mml:mn>
 214                                 </mml:msub>
 215                             </mml:mfenced>
 216                             <mml:mo>″</mml:mo>
 217                             </mml:msup>
 218                             <mml:mo>×</mml:mo>
 219                             <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 220                             <mml:mi mathvariant="italic">e</mml:mi>
 221                             </mml:msub>
 222                         </mml:mrow>
 223                         <mml:mo>+</mml:mo>
 224                         <mml:mrow>
 225                             <mml:msup><mml:mfenced open="" close="">
 226                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 227                                 <mml:mn>2</mml:mn>
 228                                 </mml:msub>
 229                             </mml:mfenced>
 230                             <mml:mo>″</mml:mo>
 231                             </mml:msup>
 232                             <mml:mo>×</mml:mo>
 233                             <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 234                             <mml:mi mathvariant="italic">e</mml:mi>
 235                             </mml:msub>
 236                         </mml:mrow>
 237                         <mml:mo>+</mml:mo>
 238                         <mml:mrow>
 239                             <mml:msup><mml:mfenced open="" close="">
 240                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 241                                 <mml:mn>3</mml:mn>
 242                                 </mml:msub>
 243                             </mml:mfenced>
 244                             <mml:mo>″</mml:mo>
 245                             </mml:msup>
 246                             <mml:mo>×</mml:mo>
 247                             <mml:msub><mml:mi mathvariant="italic">z</mml:mi>
 248                             <mml:mi mathvariant="italic">e</mml:mi>
 249                             </mml:msub>
 250                         </mml:mrow>
 251                         <mml:mo>+</mml:mo>
 252                         <mml:mrow>
 253                             <mml:msup><mml:mfenced open="" close="">
 254                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 255                                 <mml:mn>4</mml:mn>
 256                                 </mml:msub>
 257                             </mml:mfenced>
 258                             <mml:mo>″</mml:mo>
 259                             </mml:msup>
 260                             <mml:mo>×</mml:mo>
 261                             <mml:msub><mml:mi mathvariant="italic">w</mml:mi>
 262                             <mml:mi mathvariant="italic">e</mml:mi>
 263                             </mml:msub>
 264                         </mml:mrow>
 265                     </mml:mrow>
 266                 </mml:mrow>
 267             </mml:math></div><p>
 268         </p><p>
 269             is used, where
 270         </p><p>
 271             </p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 272
 273                 <mml:mrow>
 274                     <mml:mfenced open="(" close=")">
 275                         <mml:mrow>
 276                             <mml:msup><mml:mfenced open="" close="">
 277                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 278                                 <mml:mn>1</mml:mn>
 279                                 </mml:msub>
 280                             </mml:mfenced>
 281                             <mml:mo>″</mml:mo>
 282                             </mml:msup>
 283                             <mml:mo>⁢</mml:mo>
 284                             <mml:msup><mml:mfenced open="" close="">
 285                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 286                                 <mml:mn>2</mml:mn>
 287                                 </mml:msub>
 288                             </mml:mfenced>
 289                             <mml:mo>″</mml:mo>
 290                             </mml:msup>
 291                             <mml:mo>⁢</mml:mo>
 292                             <mml:msup><mml:mfenced open="" close="">
 293                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 294                                 <mml:mn>3</mml:mn>
 295                                 </mml:msub>
 296                             </mml:mfenced>
 297                             <mml:mo>″</mml:mo>
 298                             </mml:msup>
 299                             <mml:mo>⁢</mml:mo>
 300                             <mml:msup><mml:mfenced open="" close="">
 301                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 302                                 <mml:mn>4</mml:mn>
 303                                 </mml:msub>
 304                             </mml:mfenced>
 305                             <mml:mo>″</mml:mo>
 306                             </mml:msup>
 307                         </mml:mrow>
 308                     </mml:mfenced>
 309                     <mml:mo>=</mml:mo>
 310                     <mml:mrow>
 311                         <mml:mfenced open="(" close=")">
 312                             <mml:mrow>
 313                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 314                                 <mml:mn>1</mml:mn>
 315                                 </mml:msub>
 316                                 <mml:mo>⁢</mml:mo>
 317                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 318                                 <mml:mn>2</mml:mn>
 319                                 </mml:msub>
 320                                 <mml:mo>⁢</mml:mo>
 321                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 322                                 <mml:mn>3</mml:mn>
 323                                 </mml:msub>
 324                                 <mml:mo>⁢</mml:mo>
 325                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 326                                 <mml:mn>4</mml:mn>
 327                                 </mml:msub>
 328                             </mml:mrow>
 329                         </mml:mfenced>
 330                         <mml:mo>⁢</mml:mo>
 331                         <mml:msup><mml:mi mathvariant="italic">M</mml:mi>
 332                         <mml:mn>-1</mml:mn>
 333                         </mml:msup>
 334                     </mml:mrow>
 335                 </mml:mrow>
 336             </mml:math></div><p>
 337         </p><p>
 338             and
 339             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 340
 341                 <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 342                 <mml:mi mathvariant="italic">e</mml:mi>
 343                 </mml:msub>
 344             </mml:math>,
 345             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 346
 347                 <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 348                 <mml:mi mathvariant="italic">e</mml:mi>
 349                 </mml:msub>
 350             </mml:math>,
 351             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 352
 353                 <mml:msub><mml:mi mathvariant="italic">z</mml:mi>
 354                 <mml:mi mathvariant="italic">e</mml:mi>
 355                 </mml:msub>
 356             </mml:math>,
 357             and
 358             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 359
 360                 <mml:msub><mml:mi mathvariant="italic">w</mml:mi>
 361                 <mml:mi mathvariant="italic">e</mml:mi>
 362                 </mml:msub>
 363             </mml:math>
 364             are the eye coordinates of the vertex,
 365             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 366
 367                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 368                 <mml:mn>1</mml:mn>
 369                 </mml:msub>
 370             </mml:math>,
 371             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 372
 373                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 374                 <mml:mn>2</mml:mn>
 375                 </mml:msub>
 376             </mml:math>,
 377             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 378
 379                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 380                 <mml:mn>3</mml:mn>
 381                 </mml:msub>
 382             </mml:math>,
 383             and
 384             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 385
 386                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 387                 <mml:mn>4</mml:mn>
 388                 </mml:msub>
 389             </mml:math>
 390             are the values supplied in <em class="parameter"><code>params</code></em>, and
 391             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">M</mml:mi></mml:math>
 392             is the modelview matrix when <code class="function">glTexGen</code> is invoked.
 393             If
 394             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">M</mml:mi></mml:math>
 395             is poorly conditioned or singular,
 396             texture coordinates generated by the resulting function may be inaccurate
 397             or undefined.
 398         </p><p>
 399             Note that the values in <em class="parameter"><code>params</code></em> define a reference plane in eye coordinates.
 400             The modelview matrix that is applied to them may not be the same one
 401             in effect when the polygon vertices are transformed.
 402             This function establishes a field of texture coordinates
 403             that can produce dynamic contour lines on moving objects.
 404         </p><p>
 405             If the texture generation function is <code class="constant">GL_SPHERE_MAP</code> and <em class="parameter"><code>coord</code></em> is either
 406             <code class="constant">GL_S</code> or
 407             <code class="constant">GL_T</code>,
 408             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">s</mml:mi></mml:math>
 409             and
 410             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">t</mml:mi></mml:math>
 411             texture coordinates are generated as follows.
 412             Let <span class="emphasis"><em>u</em></span> be the unit vector pointing from the origin to the polygon vertex
 413             (in eye coordinates).
 414             Let <span class="emphasis"><em>n</em></span> sup prime be the current normal,
 415             after transformation to eye coordinates.
 416             Let
 417         </p><p>
 418             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 419
 420                 <mml:mrow>
 421                     <mml:mi mathvariant="italic">f</mml:mi>
 422                     <mml:mo>=</mml:mo>
 423                     <mml:msup><mml:mfenced open="(" close=")">
 424                         <mml:mrow>
 425                             <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 426                             <mml:mi mathvariant="italic">x</mml:mi>
 427                             </mml:msub>
 428                             <mml:mo>⁢</mml:mo>
 429                             <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 430                             <mml:mi mathvariant="italic">y</mml:mi>
 431                             </mml:msub>
 432                             <mml:mo>⁢</mml:mo>
 433                             <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 434                             <mml:mi mathvariant="italic">z</mml:mi>
 435                             </mml:msub>
 436                         </mml:mrow>
 437                     </mml:mfenced>
 438                     <mml:mi mathvariant="italic">T</mml:mi>
 439                     </mml:msup>
 440                 </mml:mrow>
 441             </mml:math>
 442             be the reflection vector such that
 443         </p><p>
 444             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 445
 446                 <mml:mrow>
 447                     <mml:mi mathvariant="italic">f</mml:mi>
 448                     <mml:mo>=</mml:mo>
 449                     <mml:mrow>
 450                         <mml:mi mathvariant="italic">u</mml:mi>
 451                         <mml:mo>-</mml:mo>
 452                         <mml:mn>2</mml:mn>
 453                         <mml:mo>⁢</mml:mo>
 454                         <mml:msup><mml:mi mathvariant="italic">n</mml:mi>
 455                         <mml:mo>″</mml:mo>
 456                         </mml:msup>
 457                         <mml:mo>⁢</mml:mo>
 458                         <mml:msup><mml:mfenced open="" close="">
 459                             <mml:msup><mml:mi mathvariant="italic">n</mml:mi>
 460                             <mml:mo>″</mml:mo>
 461                             </mml:msup>
 462                         </mml:mfenced>
 463                         <mml:mi mathvariant="italic">T</mml:mi>
 464                         </mml:msup>
 465                         <mml:mo>⁢</mml:mo>
 466                         <mml:mi mathvariant="italic">u</mml:mi>
 467                     </mml:mrow>
 468                 </mml:mrow>
 469             </mml:math>
 470         </p><p>
 471             Finally, let
 472             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 473
 474                 <mml:mrow>
 475                     <mml:mi mathvariant="italic">m</mml:mi>
 476                     <mml:mo>=</mml:mo>
 477                     <mml:mrow>
 478                         <mml:mn>2</mml:mn>
 479                         <mml:mo>⁢</mml:mo>
 480                         <mml:msqrt>
 481                             <mml:mfenced open="(" close=")">
 482                                 <mml:mrow>
 483                                     <mml:msup><mml:mfenced open="" close="">
 484                                         <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 485                                         <mml:mi mathvariant="italic">x</mml:mi>
 486                                         </mml:msub>
 487                                     </mml:mfenced>
 488                                     <mml:mn>2</mml:mn>
 489                                     </mml:msup>
 490                                     <mml:mo>+</mml:mo>
 491                                     <mml:msup><mml:mfenced open="" close="">
 492                                         <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 493                                         <mml:mi mathvariant="italic">y</mml:mi>
 494                                         </mml:msub>
 495                                     </mml:mfenced>
 496                                     <mml:mn>2</mml:mn>
 497                                     </mml:msup>
 498                                     <mml:mo>+</mml:mo>
 499                                     <mml:msup><mml:mfenced open="(" close=")">
 500                                         <mml:mrow>
 501                                             <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 502                                             <mml:mi mathvariant="italic">z</mml:mi>
 503                                             </mml:msub>
 504                                             <mml:mo>+</mml:mo>
 505                                             <mml:mn>1</mml:mn>
 506                                         </mml:mrow>
 507                                     </mml:mfenced>
 508                                     <mml:mn>2</mml:mn>
 509                                     </mml:msup>
 510                                 </mml:mrow>
 511                             </mml:mfenced>
 512                         </mml:msqrt>
 513                     </mml:mrow>
 514                 </mml:mrow>
 515             </mml:math>.
 516             Then the values assigned to the
 517             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">s</mml:mi></mml:math>
 518             and
 519             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">t</mml:mi></mml:math>
 520             texture coordinates are
 521         </p><p>
 522             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 523
 524                 <mml:mrow>
 525                     <mml:mi mathvariant="italic">s</mml:mi>
 526                     <mml:mo>=</mml:mo>
 527                     <mml:mrow>
 528                         <mml:mfrac>
 529                             <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 530                             <mml:mi mathvariant="italic">x</mml:mi>
 531                             </mml:msub>
 532                             <mml:mi mathvariant="italic">m</mml:mi>
 533                         </mml:mfrac>
 534                         <mml:mo>+</mml:mo>
 535                         <mml:mfrac>
 536                             <mml:mn>1</mml:mn>
 537                             <mml:mn>2</mml:mn>
 538                         </mml:mfrac>
 539                     </mml:mrow>
 540                 </mml:mrow>
 541             </mml:math>
 542         </p><p>
 543             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 544
 545                 <mml:mrow>
 546                     <mml:mi mathvariant="italic">t</mml:mi>
 547                     <mml:mo>=</mml:mo>
 548                     <mml:mrow>
 549                         <mml:mfrac>
 550                             <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 551                             <mml:mi mathvariant="italic">y</mml:mi>
 552                             </mml:msub>
 553                             <mml:mi mathvariant="italic">m</mml:mi>
 554                         </mml:mfrac>
 555                         <mml:mo>+</mml:mo>
 556                         <mml:mfrac>
 557                             <mml:mn>1</mml:mn>
 558                             <mml:mn>2</mml:mn>
 559                         </mml:mfrac>
 560                     </mml:mrow>
 561                 </mml:mrow>
 562             </mml:math>
 563         </p><p>
 564             To enable or disable a texture-coordinate generation function, call
 565             <a href="glEnable.xml"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a> or <a href="glDisable.xml"><span class="citerefentry"><span class="refentrytitle">glDisable</span></span></a>
 566             with one of the symbolic texture-coordinate names
 567             (<code class="constant">GL_TEXTURE_GEN_S</code>,
 568             <code class="constant">GL_TEXTURE_GEN_T</code>,
 569             <code class="constant">GL_TEXTURE_GEN_R</code>, or
 570             <code class="constant">GL_TEXTURE_GEN_Q</code>) as the argument.
 571             When enabled,
 572             the specified texture coordinate is computed
 573             according to the generating function associated with that coordinate.
 574             When disabled,
 575             subsequent vertices take the specified texture coordinate
 576             from the current set of texture coordinates. Initially, all texture
 577             generation functions are set to <code class="constant">GL_EYE_LINEAR</code> and are disabled.
 578             Both
 579             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">s</mml:mi></mml:math>
 580             plane equations are (1, 0, 0, 0),
 581             both
 582             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">t</mml:mi></mml:math>
 583             plane equations are (0, 1, 0, 0),
 584             and all
 585             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">r</mml:mi></mml:math>
 586             and
 587             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">q</mml:mi></mml:math>
 588             plane equations are (0, 0, 0, 0).
 589         </p><p>
 590             When the <code class="code">ARB_multitexture</code> extension is supported, <code class="function">glTexGen</code> sets the
 591             texture generation parameters for the currently active texture unit,
 592             selected with <a href="glActiveTexture.xml"><span class="citerefentry"><span class="refentrytitle">glActiveTexture</span></span></a>.
 593         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
 594             <code class="constant">GL_INVALID_ENUM</code> is generated when <em class="parameter"><code>coord</code></em> or <em class="parameter"><code>pname</code></em> is not an
 595             accepted defined value,
 596             or when <em class="parameter"><code>pname</code></em> is <code class="constant">GL_TEXTURE_GEN_MODE</code> and <em class="parameter"><code>params</code></em> is not an
 597             accepted defined value.
 598         </p><p>
 599             <code class="constant">GL_INVALID_ENUM</code> is generated when <em class="parameter"><code>pname</code></em> is <code class="constant">GL_TEXTURE_GEN_MODE</code>,
 600             <em class="parameter"><code>params</code></em> is <code class="constant">GL_SPHERE_MAP</code>,
 601             and <em class="parameter"><code>coord</code></em> is either <code class="constant">GL_R</code> or <code class="constant">GL_Q</code>.
 602         </p><p>
 603             <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glTexGen</code>
 604             is executed between the execution of <a href="glBegin.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a>
 605             and the corresponding execution of <a href="glEnd.xml"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>.
 606         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
 607             <a href="glGetTexGen.xml"><span class="citerefentry"><span class="refentrytitle">glGetTexGen</span></span></a>
 608         </p><p>
 609             <a href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_TEXTURE_GEN_S</code>
 610         </p><p>
 611             <a href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_TEXTURE_GEN_T</code>
 612         </p><p>
 613             <a href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_TEXTURE_GEN_R</code>
 614         </p><p>
 615             <a href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_TEXTURE_GEN_Q</code>
 616         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
 617             <a href="glActiveTexture.xml"><span class="citerefentry"><span class="refentrytitle">glActiveTexture</span></span></a>,
 618             <a href="glCopyPixels.xml"><span class="citerefentry"><span class="refentrytitle">glCopyPixels</span></span></a>,
 619             <a href="glCopyTexImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage2D</span></span></a>,
 620             <a href="glCopyTexSubImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage1D</span></span></a>,
 621             <a href="glCopyTexSubImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage2D</span></span></a>,
 622             <a href="glCopyTexSubImage3D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage3D</span></span></a>,
 623             <a href="glTexEnv.xml"><span class="citerefentry"><span class="refentrytitle">glTexEnv</span></span></a>,
 624             <a href="glTexImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage1D</span></span></a>,
 625             <a href="glTexImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage2D</span></span></a>,
 626             <a href="glTexImage3D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage3D</span></span></a>,
 627             <a href="glTexParameter.xml"><span class="citerefentry"><span class="refentrytitle">glTexParameter</span></span></a>,
 628             <a href="glTexSubImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glTexSubImage1D</span></span></a>,
 629             <a href="glTexSubImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glTexSubImage2D</span></span></a>,
 630             <a href="glTexSubImage3D.xml"><span class="citerefentry"><span class="refentrytitle">glTexSubImage3D</span></span></a>
 631         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
 632             Copyright <span class="trademark"></span>© 1991-2006
 633             Silicon Graphics, Inc. This document is licensed under the SGI
 634             Free Software B License. For details, see
 635             <a href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
 636         </p></div></div></body></html>