upstream-doc/man2/glTexGen.xml

   1 <?xml version="1.0" encoding="UTF-8"?>
   2 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
   3               "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
   4 <refentry id="glTexGen">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>1991-2006</year>
   9                 <holder>Silicon Graphics, Inc.</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>glTexGen</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>glTexGen</refname>
  17         <refpurpose>control the generation of texture coordinates</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>C Specification</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>void <function>glTexGeni</function></funcdef>
  23                 <paramdef>GLenum <parameter>coord</parameter></paramdef>
  24                 <paramdef>GLenum <parameter>pname</parameter></paramdef>
  25                 <paramdef>GLint <parameter>param</parameter></paramdef>
  26             </funcprototype>
  27         </funcsynopsis>
  28         <funcsynopsis>
  29             <funcprototype>
  30                 <funcdef>void <function>glTexGenf</function></funcdef>
  31                 <paramdef>GLenum <parameter>coord</parameter></paramdef>
  32                 <paramdef>GLenum <parameter>pname</parameter></paramdef>
  33                 <paramdef>GLfloat <parameter>param</parameter></paramdef>
  34             </funcprototype>
  35         </funcsynopsis>
  36         <funcsynopsis>
  37             <funcprototype>
  38                 <funcdef>void <function>glTexGend</function></funcdef>
  39                 <paramdef>GLenum <parameter>coord</parameter></paramdef>
  40                 <paramdef>GLenum <parameter>pname</parameter></paramdef>
  41                 <paramdef>GLdouble <parameter>param</parameter></paramdef>
  42             </funcprototype>
  43         </funcsynopsis>
  44     </refsynopsisdiv>
  45     <!-- eqn: ignoring delim $$ -->
  46     <refsect1 id="parameters"><title>Parameters</title>
  47         <variablelist>
  48         <varlistentry>
  49             <term><parameter>coord</parameter></term>
  50             <listitem>
  51                 <para>
  52                     Specifies a texture coordinate.
  53                     Must be one of <constant>GL_S</constant>, <constant>GL_T</constant>, <constant>GL_R</constant>, or <constant>GL_Q</constant>.
  54                 </para>
  55             </listitem>
  56         </varlistentry>
  57         <varlistentry>
  58             <term><parameter>pname</parameter></term>
  59             <listitem>
  60                 <para>
  61                     Specifies the symbolic name of the texture-coordinate generation function.
  62                     Must be <constant>GL_TEXTURE_GEN_MODE</constant>.
  63                 </para>
  64             </listitem>
  65         </varlistentry>
  66         <varlistentry>
  67             <term><parameter>param</parameter></term>
  68             <listitem>
  69                 <para>
  70                     Specifies a single-valued texture generation parameter,
  71                     one of <constant>GL_OBJECT_LINEAR</constant>, <constant>GL_EYE_LINEAR</constant>, <constant>GL_SPHERE_MAP</constant>,
  72                     <constant>GL_NORMAL_MAP</constant>, or <constant>GL_REFLECTION_MAP</constant>.
  73                 </para>
  74             </listitem>
  75         </varlistentry>
  76         </variablelist>
  77     </refsect1>
  78     <refsynopsisdiv><title>C Specification</title>
  79         <funcsynopsis>
  80             <funcprototype>
  81                 <funcdef>void <function>glTexGeniv</function></funcdef>
  82                 <paramdef>GLenum <parameter>coord</parameter></paramdef>
  83                 <paramdef>GLenum <parameter>pname</parameter></paramdef>
  84                 <paramdef>const GLint * <parameter>params</parameter></paramdef>
  85             </funcprototype>
  86         </funcsynopsis>
  87         <funcsynopsis>
  88             <funcprototype>
  89                 <funcdef>void <function>glTexGenfv</function></funcdef>
  90                 <paramdef>GLenum <parameter>coord</parameter></paramdef>
  91                 <paramdef>GLenum <parameter>pname</parameter></paramdef>
  92                 <paramdef>const GLfloat * <parameter>params</parameter></paramdef>
  93             </funcprototype>
  94         </funcsynopsis>
  95         <funcsynopsis>
  96             <funcprototype>
  97                 <funcdef>void <function>glTexGendv</function></funcdef>
  98                 <paramdef>GLenum <parameter>coord</parameter></paramdef>
  99                 <paramdef>GLenum <parameter>pname</parameter></paramdef>
 100                 <paramdef>const GLdouble * <parameter>params</parameter></paramdef>
 101             </funcprototype>
 102         </funcsynopsis>
 103     </refsynopsisdiv>
 104     <refsect1 id="parameters2"><title>Parameters</title>
 105         <variablelist>
 106         <varlistentry>
 107             <term><parameter>coord</parameter></term>
 108             <listitem>
 109                 <para>
 110                     Specifies a texture coordinate.
 111                     Must be one of <constant>GL_S</constant>, <constant>GL_T</constant>, <constant>GL_R</constant>, or <constant>GL_Q</constant>.
 112                 </para>
 113             </listitem>
 114         </varlistentry>
 115         <varlistentry>
 116             <term><parameter>pname</parameter></term>
 117             <listitem>
 118                 <para>
 119                     Specifies the symbolic name of the texture-coordinate generation function
 120                     or function parameters.
 121                     Must be
 122                     <constant>GL_TEXTURE_GEN_MODE</constant>,
 123                     <constant>GL_OBJECT_PLANE</constant>, or
 124                     <constant>GL_EYE_PLANE</constant>.
 125                 </para>
 126             </listitem>
 127         </varlistentry>
 128         <varlistentry>
 129             <term><parameter>params</parameter></term>
 130             <listitem>
 131                 <para>
 132                     Specifies a pointer to an array of texture generation parameters.
 133                     If <parameter>pname</parameter> is <constant>GL_TEXTURE_GEN_MODE</constant>,
 134                     then the array must contain a single symbolic constant,
 135                     one of
 136                     <constant>GL_OBJECT_LINEAR</constant>,
 137                     <constant>GL_EYE_LINEAR</constant>,
 138                     <constant>GL_SPHERE_MAP</constant>,
 139                     <constant>GL_NORMAL_MAP</constant>, or
 140                     <constant>GL_REFLECTION_MAP</constant>.
 141                     Otherwise,
 142                     <parameter>params</parameter> holds the coefficients for the texture-coordinate generation function
 143                     specified by <parameter>pname</parameter>.
 144                 </para>
 145             </listitem>
 146         </varlistentry>
 147         </variablelist>
 148     </refsect1>
 149     <refsect1 id="description"><title>Description</title>
 150         <para>
 151             <function>glTexGen</function> selects a texture-coordinate generation function
 152             or supplies coefficients for one of the functions.
 153             <parameter>coord</parameter> names one of the (<emphasis>s</emphasis>, <emphasis>t</emphasis>, <emphasis>r</emphasis>, <emphasis>q</emphasis>) texture
 154             coordinates; it must be one of the symbols
 155             <constant>GL_S</constant>,
 156             <constant>GL_T</constant>,
 157             <constant>GL_R</constant>, or
 158             <constant>GL_Q</constant>.
 159             <parameter>pname</parameter> must be one of three symbolic constants:
 160             <constant>GL_TEXTURE_GEN_MODE</constant>,
 161             <constant>GL_OBJECT_PLANE</constant>, or
 162             <constant>GL_EYE_PLANE</constant>.
 163             If <parameter>pname</parameter> is <constant>GL_TEXTURE_GEN_MODE</constant>,
 164             then <parameter>params</parameter> chooses a mode,
 165             one of
 166             <constant>GL_OBJECT_LINEAR</constant>,
 167             <constant>GL_EYE_LINEAR</constant>,
 168             <constant>GL_SPHERE_MAP</constant>,
 169             <constant>GL_NORMAL_MAP</constant>, or
 170             <constant>GL_REFLECTION_MAP</constant>.
 171             If <parameter>pname</parameter> is either <constant>GL_OBJECT_PLANE</constant> or <constant>GL_EYE_PLANE</constant>,
 172             <parameter>params</parameter> contains coefficients for the corresponding
 173             texture generation function.
 174         </para>
 175         <para>
 176             If the texture generation function is <constant>GL_OBJECT_LINEAR</constant>,
 177             the function
 178         </para>
 179         <para>
 180             <inlineequation><mml:math>
 181                 <!-- eqn: g  =  p sub 1 * x sub o  +  p sub 2 * y sub o  +  p sub 3 * z sub o  +  p sub 4 * w sub o:-->
 182                 <mml:mrow>
 183                     <mml:mi mathvariant="italic">g</mml:mi>
 184                     <mml:mo>=</mml:mo>
 185                     <mml:mrow>
 186                         <mml:mrow>
 187                             <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 188                             <mml:mn>1</mml:mn>
 189                             </mml:msub>
 190                             <mml:mo>&times;</mml:mo>
 191                             <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 192                             <mml:mi mathvariant="italic">o</mml:mi>
 193                             </mml:msub>
 194                         </mml:mrow>
 195                         <mml:mo>+</mml:mo>
 196                         <mml:mrow>
 197                             <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 198                             <mml:mn>2</mml:mn>
 199                             </mml:msub>
 200                             <mml:mo>&times;</mml:mo>
 201                             <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 202                             <mml:mi mathvariant="italic">o</mml:mi>
 203                             </mml:msub>
 204                         </mml:mrow>
 205                         <mml:mo>+</mml:mo>
 206                         <mml:mrow>
 207                             <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 208                             <mml:mn>3</mml:mn>
 209                             </mml:msub>
 210                             <mml:mo>&times;</mml:mo>
 211                             <mml:msub><mml:mi mathvariant="italic">z</mml:mi>
 212                             <mml:mi mathvariant="italic">o</mml:mi>
 213                             </mml:msub>
 214                         </mml:mrow>
 215                         <mml:mo>+</mml:mo>
 216                         <mml:mrow>
 217                             <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 218                             <mml:mn>4</mml:mn>
 219                             </mml:msub>
 220                             <mml:mo>&times;</mml:mo>
 221                             <mml:msub><mml:mi mathvariant="italic">w</mml:mi>
 222                             <mml:mi mathvariant="italic">o</mml:mi>
 223                             </mml:msub>
 224                         </mml:mrow>
 225                     </mml:mrow>
 226                 </mml:mrow>
 227             </mml:math></inlineequation>
 228         </para>
 229         <para>
 230             is used, where
 231             <inlineequation><mml:math><mml:mi mathvariant="italic">g</mml:mi></mml:math></inlineequation>
 232             is the value computed for the coordinate named in <parameter>coord</parameter>,
 233             <inlineequation><mml:math>
 234                 <!-- eqn: p sub 1:-->
 235                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 236                 <mml:mn>1</mml:mn>
 237                 </mml:msub>
 238             </mml:math></inlineequation>,
 239             <inlineequation><mml:math>
 240                 <!-- eqn: p sub 2:-->
 241                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 242                 <mml:mn>2</mml:mn>
 243                 </mml:msub>
 244             </mml:math></inlineequation>,
 245             <inlineequation><mml:math>
 246                 <!-- eqn: p sub 3:-->
 247                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 248                 <mml:mn>3</mml:mn>
 249                 </mml:msub>
 250             </mml:math></inlineequation>,
 251             and
 252             <inlineequation><mml:math>
 253                 <!-- eqn: p sub 4:-->
 254                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 255                 <mml:mn>4</mml:mn>
 256                 </mml:msub>
 257             </mml:math></inlineequation>
 258             are the four values supplied in <parameter>params</parameter>, and
 259             <inlineequation><mml:math>
 260                 <!-- eqn: x sub o:-->
 261                 <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 262                 <mml:mi mathvariant="italic">o</mml:mi>
 263                 </mml:msub>
 264             </mml:math></inlineequation>,
 265             <inlineequation><mml:math>
 266                 <!-- eqn: y sub o:-->
 267                 <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 268                 <mml:mi mathvariant="italic">o</mml:mi>
 269                 </mml:msub>
 270             </mml:math></inlineequation>,
 271             <inlineequation><mml:math>
 272                 <!-- eqn: z sub o:-->
 273                 <mml:msub><mml:mi mathvariant="italic">z</mml:mi>
 274                 <mml:mi mathvariant="italic">o</mml:mi>
 275                 </mml:msub>
 276             </mml:math></inlineequation>,
 277             and
 278             <inlineequation><mml:math>
 279                 <!-- eqn: w sub o:-->
 280                 <mml:msub><mml:mi mathvariant="italic">w</mml:mi>
 281                 <mml:mi mathvariant="italic">o</mml:mi>
 282                 </mml:msub>
 283             </mml:math></inlineequation>
 284             are the object coordinates of the vertex.
 285             This function can be used, for example, to texture-map terrain using sea level
 286             as a reference plane
 287             (defined by
 288             <inlineequation><mml:math>
 289                 <!-- eqn: p sub 1:-->
 290                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 291                 <mml:mn>1</mml:mn>
 292                 </mml:msub>
 293             </mml:math></inlineequation>,
 294             <inlineequation><mml:math>
 295                 <!-- eqn: p sub 2:-->
 296                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 297                 <mml:mn>2</mml:mn>
 298                 </mml:msub>
 299             </mml:math></inlineequation>,
 300             <inlineequation><mml:math>
 301                 <!-- eqn: p sub 3:-->
 302                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 303                 <mml:mn>3</mml:mn>
 304                 </mml:msub>
 305             </mml:math></inlineequation>,
 306             and
 307             <inlineequation><mml:math>
 308                 <!-- eqn: p sub 4:-->
 309                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 310                 <mml:mn>4</mml:mn>
 311                 </mml:msub>
 312             </mml:math></inlineequation>).
 313             The altitude of a terrain vertex is computed by the <constant>GL_OBJECT_LINEAR</constant>
 314             coordinate generation function as its distance from sea level;
 315             that altitude can then be used to index the texture image to map white snow
 316             onto peaks and green grass onto foothills.
 317         </para>
 318         <para>
 319             If the texture generation function is <constant>GL_EYE_LINEAR</constant>, the function
 320         </para>
 321         <para>
 322             <informalequation><mml:math>
 323                 <!-- eqn: g  =      {p sub 1} sup prime * x sub e  +      {p sub 2} sup prime * y sub e  +      {p sub 3} sup prime * z sub e  +      {p sub 4} sup prime * w sub e:-->
 324                 <mml:mrow>
 325                     <mml:mi mathvariant="italic">g</mml:mi>
 326                     <mml:mo>=</mml:mo>
 327                     <mml:mrow>
 328                         <mml:mrow>
 329                             <mml:msup><mml:mfenced open="" close="">
 330                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 331                                 <mml:mn>1</mml:mn>
 332                                 </mml:msub>
 333                             </mml:mfenced>
 334                             <mml:mo>&Prime;</mml:mo>
 335                             </mml:msup>
 336                             <mml:mo>&times;</mml:mo>
 337                             <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 338                             <mml:mi mathvariant="italic">e</mml:mi>
 339                             </mml:msub>
 340                         </mml:mrow>
 341                         <mml:mo>+</mml:mo>
 342                         <mml:mrow>
 343                             <mml:msup><mml:mfenced open="" close="">
 344                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 345                                 <mml:mn>2</mml:mn>
 346                                 </mml:msub>
 347                             </mml:mfenced>
 348                             <mml:mo>&Prime;</mml:mo>
 349                             </mml:msup>
 350                             <mml:mo>&times;</mml:mo>
 351                             <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 352                             <mml:mi mathvariant="italic">e</mml:mi>
 353                             </mml:msub>
 354                         </mml:mrow>
 355                         <mml:mo>+</mml:mo>
 356                         <mml:mrow>
 357                             <mml:msup><mml:mfenced open="" close="">
 358                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 359                                 <mml:mn>3</mml:mn>
 360                                 </mml:msub>
 361                             </mml:mfenced>
 362                             <mml:mo>&Prime;</mml:mo>
 363                             </mml:msup>
 364                             <mml:mo>&times;</mml:mo>
 365                             <mml:msub><mml:mi mathvariant="italic">z</mml:mi>
 366                             <mml:mi mathvariant="italic">e</mml:mi>
 367                             </mml:msub>
 368                         </mml:mrow>
 369                         <mml:mo>+</mml:mo>
 370                         <mml:mrow>
 371                             <mml:msup><mml:mfenced open="" close="">
 372                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 373                                 <mml:mn>4</mml:mn>
 374                                 </mml:msub>
 375                             </mml:mfenced>
 376                             <mml:mo>&Prime;</mml:mo>
 377                             </mml:msup>
 378                             <mml:mo>&times;</mml:mo>
 379                             <mml:msub><mml:mi mathvariant="italic">w</mml:mi>
 380                             <mml:mi mathvariant="italic">e</mml:mi>
 381                             </mml:msub>
 382                         </mml:mrow>
 383                     </mml:mrow>
 384                 </mml:mrow>
 385             </mml:math></informalequation>
 386         </para>
 387         <para>
 388             is used, where
 389         </para>
 390         <para>
 391             <informalequation><mml:math>
 392                 <!-- eqn: left (   {p sub 1} sup prime   {p sub 2} sup prime   {p sub 3} sup prime   {p sub 4} sup prime right )  =  left ( p sub 1   p sub 2   p sub 3   p sub 4 right )  M sup -1:-->
 393                 <mml:mrow>
 394                     <mml:mfenced open="(" close=")">
 395                         <mml:mrow>
 396                             <mml:msup><mml:mfenced open="" close="">
 397                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 398                                 <mml:mn>1</mml:mn>
 399                                 </mml:msub>
 400                             </mml:mfenced>
 401                             <mml:mo>&Prime;</mml:mo>
 402                             </mml:msup>
 403                             <mml:mo>&it;</mml:mo>
 404                             <mml:msup><mml:mfenced open="" close="">
 405                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 406                                 <mml:mn>2</mml:mn>
 407                                 </mml:msub>
 408                             </mml:mfenced>
 409                             <mml:mo>&Prime;</mml:mo>
 410                             </mml:msup>
 411                             <mml:mo>&it;</mml:mo>
 412                             <mml:msup><mml:mfenced open="" close="">
 413                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 414                                 <mml:mn>3</mml:mn>
 415                                 </mml:msub>
 416                             </mml:mfenced>
 417                             <mml:mo>&Prime;</mml:mo>
 418                             </mml:msup>
 419                             <mml:mo>&it;</mml:mo>
 420                             <mml:msup><mml:mfenced open="" close="">
 421                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 422                                 <mml:mn>4</mml:mn>
 423                                 </mml:msub>
 424                             </mml:mfenced>
 425                             <mml:mo>&Prime;</mml:mo>
 426                             </mml:msup>
 427                         </mml:mrow>
 428                     </mml:mfenced>
 429                     <mml:mo>=</mml:mo>
 430                     <mml:mrow>
 431                         <mml:mfenced open="(" close=")">
 432                             <mml:mrow>
 433                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 434                                 <mml:mn>1</mml:mn>
 435                                 </mml:msub>
 436                                 <mml:mo>&it;</mml:mo>
 437                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 438                                 <mml:mn>2</mml:mn>
 439                                 </mml:msub>
 440                                 <mml:mo>&it;</mml:mo>
 441                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 442                                 <mml:mn>3</mml:mn>
 443                                 </mml:msub>
 444                                 <mml:mo>&it;</mml:mo>
 445                                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 446                                 <mml:mn>4</mml:mn>
 447                                 </mml:msub>
 448                             </mml:mrow>
 449                         </mml:mfenced>
 450                         <mml:mo>&it;</mml:mo>
 451                         <mml:msup><mml:mi mathvariant="italic">M</mml:mi>
 452                         <mml:mn>-1</mml:mn>
 453                         </mml:msup>
 454                     </mml:mrow>
 455                 </mml:mrow>
 456             </mml:math></informalequation>
 457         </para>
 458         <para>
 459             and
 460             <inlineequation><mml:math>
 461                 <!-- eqn: x sub e:-->
 462                 <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 463                 <mml:mi mathvariant="italic">e</mml:mi>
 464                 </mml:msub>
 465             </mml:math></inlineequation>,
 466             <inlineequation><mml:math>
 467                 <!-- eqn: y sub e:-->
 468                 <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 469                 <mml:mi mathvariant="italic">e</mml:mi>
 470                 </mml:msub>
 471             </mml:math></inlineequation>,
 472             <inlineequation><mml:math>
 473                 <!-- eqn: z sub e:-->
 474                 <mml:msub><mml:mi mathvariant="italic">z</mml:mi>
 475                 <mml:mi mathvariant="italic">e</mml:mi>
 476                 </mml:msub>
 477             </mml:math></inlineequation>,
 478             and
 479             <inlineequation><mml:math>
 480                 <!-- eqn: w sub e:-->
 481                 <mml:msub><mml:mi mathvariant="italic">w</mml:mi>
 482                 <mml:mi mathvariant="italic">e</mml:mi>
 483                 </mml:msub>
 484             </mml:math></inlineequation>
 485             are the eye coordinates of the vertex,
 486             <inlineequation><mml:math>
 487                 <!-- eqn: p sub 1:-->
 488                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 489                 <mml:mn>1</mml:mn>
 490                 </mml:msub>
 491             </mml:math></inlineequation>,
 492             <inlineequation><mml:math>
 493                 <!-- eqn: p sub 2:-->
 494                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 495                 <mml:mn>2</mml:mn>
 496                 </mml:msub>
 497             </mml:math></inlineequation>,
 498             <inlineequation><mml:math>
 499                 <!-- eqn: p sub 3:-->
 500                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 501                 <mml:mn>3</mml:mn>
 502                 </mml:msub>
 503             </mml:math></inlineequation>,
 504             and
 505             <inlineequation><mml:math>
 506                 <!-- eqn: p sub 4:-->
 507                 <mml:msub><mml:mi mathvariant="italic">p</mml:mi>
 508                 <mml:mn>4</mml:mn>
 509                 </mml:msub>
 510             </mml:math></inlineequation>
 511             are the values supplied in <parameter>params</parameter>, and
 512             <inlineequation><mml:math><mml:mi mathvariant="italic">M</mml:mi></mml:math></inlineequation>
 513             is the modelview matrix when <function>glTexGen</function> is invoked.
 514             If
 515             <inlineequation><mml:math><mml:mi mathvariant="italic">M</mml:mi></mml:math></inlineequation>
 516             is poorly conditioned or singular,
 517             texture coordinates generated by the resulting function may be inaccurate
 518             or undefined.
 519         </para>
 520         <para>
 521             Note that the values in <parameter>params</parameter> define a reference plane in eye coordinates.
 522             The modelview matrix that is applied to them may not be the same one
 523             in effect when the polygon vertices are transformed.
 524             This function establishes a field of texture coordinates
 525             that can produce dynamic contour lines on moving objects.
 526         </para>
 527         <para>
 528             If the texture generation function is <constant>GL_SPHERE_MAP</constant> and <parameter>coord</parameter> is either
 529             <constant>GL_S</constant> or
 530             <constant>GL_T</constant>,
 531             <inlineequation><mml:math><mml:mi mathvariant="italic">s</mml:mi></mml:math></inlineequation>
 532             and
 533             <inlineequation><mml:math><mml:mi mathvariant="italic">t</mml:mi></mml:math></inlineequation>
 534             texture coordinates are generated as follows.
 535             Let <emphasis>u</emphasis> be the unit vector pointing from the origin to the polygon vertex
 536             (in eye coordinates).
 537             Let <emphasis>n</emphasis> sup prime be the current normal,
 538             after transformation to eye coordinates.
 539             Let
 540         </para>
 541         <para>
 542             <inlineequation><mml:math>
 543                 <!-- eqn: f  =  ( f sub x  f sub y  f sub z ) sup T:-->
 544                 <mml:mrow>
 545                     <mml:mi mathvariant="italic">f</mml:mi>
 546                     <mml:mo>=</mml:mo>
 547                     <mml:msup><mml:mfenced open="(" close=")">
 548                         <mml:mrow>
 549                             <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 550                             <mml:mi mathvariant="italic">x</mml:mi>
 551                             </mml:msub>
 552                             <mml:mo>&it;</mml:mo>
 553                             <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 554                             <mml:mi mathvariant="italic">y</mml:mi>
 555                             </mml:msub>
 556                             <mml:mo>&it;</mml:mo>
 557                             <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 558                             <mml:mi mathvariant="italic">z</mml:mi>
 559                             </mml:msub>
 560                         </mml:mrow>
 561                     </mml:mfenced>
 562                     <mml:mi mathvariant="italic">T</mml:mi>
 563                     </mml:msup>
 564                 </mml:mrow>
 565             </mml:math></inlineequation>
 566             be the reflection vector such that
 567         </para>
 568         <para>
 569             <inlineequation><mml:math>
 570                 <!-- eqn: f  =   u  -  2 n sup prime {n sup prime} sup T u:-->
 571                 <mml:mrow>
 572                     <mml:mi mathvariant="italic">f</mml:mi>
 573                     <mml:mo>=</mml:mo>
 574                     <mml:mrow>
 575                         <mml:mi mathvariant="italic">u</mml:mi>
 576                         <mml:mo>-</mml:mo>
 577                         <mml:mn>2</mml:mn>
 578                         <mml:mo>&it;</mml:mo>
 579                         <mml:msup><mml:mi mathvariant="italic">n</mml:mi>
 580                         <mml:mo>&Prime;</mml:mo>
 581                         </mml:msup>
 582                         <mml:mo>&it;</mml:mo>
 583                         <mml:msup><mml:mfenced open="" close="">
 584                             <mml:msup><mml:mi mathvariant="italic">n</mml:mi>
 585                             <mml:mo>&Prime;</mml:mo>
 586                             </mml:msup>
 587                         </mml:mfenced>
 588                         <mml:mi mathvariant="italic">T</mml:mi>
 589                         </mml:msup>
 590                         <mml:mo>&it;</mml:mo>
 591                         <mml:mi mathvariant="italic">u</mml:mi>
 592                     </mml:mrow>
 593                 </mml:mrow>
 594             </mml:math></inlineequation>
 595         </para>
 596         <para>
 597             Finally, let
 598             <inlineequation><mml:math>
 599                 <!-- eqn: m  =  2 sqrt ({f sub x} sup 2  +  {f sub y} sup 2  +  (f sub z  +  1) sup 2):-->
 600                 <mml:mrow>
 601                     <mml:mi mathvariant="italic">m</mml:mi>
 602                     <mml:mo>=</mml:mo>
 603                     <mml:mrow>
 604                         <mml:mn>2</mml:mn>
 605                         <mml:mo>&it;</mml:mo>
 606                         <mml:msqrt>
 607                             <mml:mfenced open="(" close=")">
 608                                 <mml:mrow>
 609                                     <mml:msup><mml:mfenced open="" close="">
 610                                         <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 611                                         <mml:mi mathvariant="italic">x</mml:mi>
 612                                         </mml:msub>
 613                                     </mml:mfenced>
 614                                     <mml:mn>2</mml:mn>
 615                                     </mml:msup>
 616                                     <mml:mo>+</mml:mo>
 617                                     <mml:msup><mml:mfenced open="" close="">
 618                                         <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 619                                         <mml:mi mathvariant="italic">y</mml:mi>
 620                                         </mml:msub>
 621                                     </mml:mfenced>
 622                                     <mml:mn>2</mml:mn>
 623                                     </mml:msup>
 624                                     <mml:mo>+</mml:mo>
 625                                     <mml:msup><mml:mfenced open="(" close=")">
 626                                         <mml:mrow>
 627                                             <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 628                                             <mml:mi mathvariant="italic">z</mml:mi>
 629                                             </mml:msub>
 630                                             <mml:mo>+</mml:mo>
 631                                             <mml:mn>1</mml:mn>
 632                                         </mml:mrow>
 633                                     </mml:mfenced>
 634                                     <mml:mn>2</mml:mn>
 635                                     </mml:msup>
 636                                 </mml:mrow>
 637                             </mml:mfenced>
 638                         </mml:msqrt>
 639                     </mml:mrow>
 640                 </mml:mrow>
 641             </mml:math></inlineequation>.
 642             Then the values assigned to the
 643             <inlineequation><mml:math><mml:mi mathvariant="italic">s</mml:mi></mml:math></inlineequation>
 644             and
 645             <inlineequation><mml:math><mml:mi mathvariant="italic">t</mml:mi></mml:math></inlineequation>
 646             texture coordinates are
 647         </para>
 648         <para>
 649             <inlineequation><mml:math>
 650                 <!-- eqn: s  =  f sub x over m  +  1 over 2:-->
 651                 <mml:mrow>
 652                     <mml:mi mathvariant="italic">s</mml:mi>
 653                     <mml:mo>=</mml:mo>
 654                     <mml:mrow>
 655                         <mml:mfrac>
 656                             <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 657                             <mml:mi mathvariant="italic">x</mml:mi>
 658                             </mml:msub>
 659                             <mml:mi mathvariant="italic">m</mml:mi>
 660                         </mml:mfrac>
 661                         <mml:mo>+</mml:mo>
 662                         <mml:mfrac>
 663                             <mml:mn>1</mml:mn>
 664                             <mml:mn>2</mml:mn>
 665                         </mml:mfrac>
 666                     </mml:mrow>
 667                 </mml:mrow>
 668             </mml:math></inlineequation>
 669         </para>
 670         <para>
 671             <inlineequation><mml:math>
 672                 <!-- eqn: t  =  f sub y over m  +  1 over 2:-->
 673                 <mml:mrow>
 674                     <mml:mi mathvariant="italic">t</mml:mi>
 675                     <mml:mo>=</mml:mo>
 676                     <mml:mrow>
 677                         <mml:mfrac>
 678                             <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 679                             <mml:mi mathvariant="italic">y</mml:mi>
 680                             </mml:msub>
 681                             <mml:mi mathvariant="italic">m</mml:mi>
 682                         </mml:mfrac>
 683                         <mml:mo>+</mml:mo>
 684                         <mml:mfrac>
 685                             <mml:mn>1</mml:mn>
 686                             <mml:mn>2</mml:mn>
 687                         </mml:mfrac>
 688                     </mml:mrow>
 689                 </mml:mrow>
 690             </mml:math></inlineequation>
 691         </para>
 692         <para>
 693             To enable or disable a texture-coordinate generation function, call
 694             <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> or <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry>
 695             with one of the symbolic texture-coordinate names
 696             (<constant>GL_TEXTURE_GEN_S</constant>,
 697             <constant>GL_TEXTURE_GEN_T</constant>,
 698             <constant>GL_TEXTURE_GEN_R</constant>, or
 699             <constant>GL_TEXTURE_GEN_Q</constant>) as the argument.
 700             When enabled,
 701             the specified texture coordinate is computed
 702             according to the generating function associated with that coordinate.
 703             When disabled,
 704             subsequent vertices take the specified texture coordinate
 705             from the current set of texture coordinates. Initially, all texture
 706             generation functions are set to <constant>GL_EYE_LINEAR</constant> and are disabled.
 707             Both
 708             <inlineequation><mml:math><mml:mi mathvariant="italic">s</mml:mi></mml:math></inlineequation>
 709             plane equations are (1, 0, 0, 0),
 710             both
 711             <inlineequation><mml:math><mml:mi mathvariant="italic">t</mml:mi></mml:math></inlineequation>
 712             plane equations are (0, 1, 0, 0),
 713             and all
 714             <inlineequation><mml:math><mml:mi mathvariant="italic">r</mml:mi></mml:math></inlineequation>
 715             and
 716             <inlineequation><mml:math><mml:mi mathvariant="italic">q</mml:mi></mml:math></inlineequation>
 717             plane equations are (0, 0, 0, 0).
 718         </para>
 719         <para>
 720             When the <code>ARB_multitexture</code> extension is supported, <function>glTexGen</function> sets the
 721             texture generation parameters for the currently active texture unit,
 722             selected with <citerefentry><refentrytitle>glActiveTexture</refentrytitle></citerefentry>.
 723         </para>
 724     </refsect1>
 725     <refsect1 id="errors"><title>Errors</title>
 726         <para>
 727             <constant>GL_INVALID_ENUM</constant> is generated when <parameter>coord</parameter> or <parameter>pname</parameter> is not an
 728             accepted defined value,
 729             or when <parameter>pname</parameter> is <constant>GL_TEXTURE_GEN_MODE</constant> and <parameter>params</parameter> is not an
 730             accepted defined value.
 731         </para>
 732         <para>
 733             <constant>GL_INVALID_ENUM</constant> is generated when <parameter>pname</parameter> is <constant>GL_TEXTURE_GEN_MODE</constant>,
 734             <parameter>params</parameter> is <constant>GL_SPHERE_MAP</constant>,
 735             and <parameter>coord</parameter> is either <constant>GL_R</constant> or <constant>GL_Q</constant>.
 736         </para>
 737         <para>
 738             <constant>GL_INVALID_OPERATION</constant> is generated if <function>glTexGen</function>
 739             is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
 740             and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
 741         </para>
 742     </refsect1>
 743     <refsect1 id="associatedgets"><title>Associated Gets</title>
 744         <para>
 745             <citerefentry><refentrytitle>glGetTexGen</refentrytitle></citerefentry>
 746         </para>
 747         <para>
 748             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_TEXTURE_GEN_S</constant>
 749         </para>
 750         <para>
 751             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_TEXTURE_GEN_T</constant>
 752         </para>
 753         <para>
 754             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_TEXTURE_GEN_R</constant>
 755         </para>
 756         <para>
 757             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_TEXTURE_GEN_Q</constant>
 758         </para>
 759     </refsect1>
 760     <refsect1 id="seealso"><title>See Also</title>
 761         <para>
 762             <citerefentry><refentrytitle>glActiveTexture</refentrytitle></citerefentry>,
 763             <citerefentry><refentrytitle>glCopyPixels</refentrytitle></citerefentry>,
 764             <citerefentry><refentrytitle>glCopyTexImage2D</refentrytitle></citerefentry>,
 765             <citerefentry><refentrytitle>glCopyTexSubImage1D</refentrytitle></citerefentry>,
 766             <citerefentry><refentrytitle>glCopyTexSubImage2D</refentrytitle></citerefentry>,
 767             <citerefentry><refentrytitle>glCopyTexSubImage3D</refentrytitle></citerefentry>,
 768             <citerefentry><refentrytitle>glTexEnv</refentrytitle></citerefentry>,
 769             <citerefentry><refentrytitle>glTexImage1D</refentrytitle></citerefentry>,
 770             <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>,
 771             <citerefentry><refentrytitle>glTexImage3D</refentrytitle></citerefentry>,
 772             <citerefentry><refentrytitle>glTexParameter</refentrytitle></citerefentry>,
 773             <citerefentry><refentrytitle>glTexSubImage1D</refentrytitle></citerefentry>,
 774             <citerefentry><refentrytitle>glTexSubImage2D</refentrytitle></citerefentry>,
 775             <citerefentry><refentrytitle>glTexSubImage3D</refentrytitle></citerefentry>
 776         </para>
 777     </refsect1>
 778     <refsect1 id="Copyright"><title>Copyright</title>
 779         <para>
 780             Copyright <trademark class="copyright"></trademark> 1991-2006
 781             Silicon Graphics, Inc. This document is licensed under the SGI
 782             Free Software B License. For details, see
 783             <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
 784         </para>
 785     </refsect1>
 786 </refentry>