upstream-man-pages/man2/glMap1.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="glMap1">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>1991-2006</year>
   9                 <holder>Silicon Graphics, Inc.</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>glMap1</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>glMap1</refname>
  17         <refpurpose>define a one-dimensional evaluator</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>C Specification</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>void <function>glMap1f</function></funcdef>
  23                 <paramdef>GLenum <parameter>target</parameter></paramdef>
  24                 <paramdef>GLfloat <parameter>u1</parameter></paramdef>
  25                 <paramdef>GLfloat <parameter>u2</parameter></paramdef>
  26                 <paramdef>GLint <parameter>stride</parameter></paramdef>
  27                 <paramdef>GLint <parameter>order</parameter></paramdef>
  28                 <paramdef>const GLfloat * <parameter>points</parameter></paramdef>
  29             </funcprototype>
  30         </funcsynopsis>
  31         <funcsynopsis>
  32             <funcprototype>
  33                 <funcdef>void <function>glMap1d</function></funcdef>
  34                 <paramdef>GLenum <parameter>target</parameter></paramdef>
  35                 <paramdef>GLdouble <parameter>u1</parameter></paramdef>
  36                 <paramdef>GLdouble <parameter>u2</parameter></paramdef>
  37                 <paramdef>GLint <parameter>stride</parameter></paramdef>
  38                 <paramdef>GLint <parameter>order</parameter></paramdef>
  39                 <paramdef>const GLdouble * <parameter>points</parameter></paramdef>
  40             </funcprototype>
  41         </funcsynopsis>
  42     </refsynopsisdiv>
  43     <!-- eqn: ignoring delim $$ -->
  44     <refsect1 id="parameters"><title>Parameters</title>
  45         <variablelist>
  46         <varlistentry>
  47             <term><parameter>target</parameter></term>
  48             <listitem>
  49                 <para>
  50                     Specifies the kind of values that are generated by the evaluator.
  51                     Symbolic constants
  52                     <constant>GL_MAP1_VERTEX_3</constant>,
  53                     <constant>GL_MAP1_VERTEX_4</constant>,
  54                     <constant>GL_MAP1_INDEX</constant>,
  55                     <constant>GL_MAP1_COLOR_4</constant>,
  56                     <constant>GL_MAP1_NORMAL</constant>,
  57                     <constant>GL_MAP1_TEXTURE_COORD_1</constant>,
  58                     <constant>GL_MAP1_TEXTURE_COORD_2</constant>,
  59                     <constant>GL_MAP1_TEXTURE_COORD_3</constant>, and
  60                     <constant>GL_MAP1_TEXTURE_COORD_4</constant> are accepted.
  61                 </para>
  62             </listitem>
  63         </varlistentry>
  64         <varlistentry>
  65             <term><parameter>u1</parameter></term>
  66             <term><parameter>u2</parameter></term>
  67             <listitem>
  68                 <para>
  69                     Specify a linear mapping of
  70                     <inlineequation><mml:math><mml:mi mathvariant="italic">u</mml:mi></mml:math></inlineequation>,
  71                     as presented to <citerefentry><refentrytitle>glEvalCoord1</refentrytitle></citerefentry>,
  72                     to
  73                     <inlineequation><mml:math>
  74                         <!-- eqn: u hat:-->
  75                         <mml:mover><mml:mi mathvariant="italic">u</mml:mi><mml:mo>&Hat;</mml:mo></mml:mover>
  76                     </mml:math></inlineequation>,
  77                     the variable that is evaluated by the equations specified by this command.
  78                 </para>
  79             </listitem>
  80         </varlistentry>
  81         <varlistentry>
  82             <term><parameter>stride</parameter></term>
  83             <listitem>
  84                 <para>
  85                     Specifies the number of floats or doubles between
  86                     the beginning of one control point and the beginning of the next one
  87                     in the data structure referenced in <parameter>points</parameter>.
  88                     This allows control points to be embedded in arbitrary data structures.
  89                     The only constraint is that the values for a particular control point
  90                     must occupy contiguous memory locations.
  91                 </para>
  92             </listitem>
  93         </varlistentry>
  94         <varlistentry>
  95             <term><parameter>order</parameter></term>
  96             <listitem>
  97                 <para>
  98                     Specifies the number of control points.
  99                     Must be positive.
 100                 </para>
 101             </listitem>
 102         </varlistentry>
 103         <varlistentry>
 104             <term><parameter>points</parameter></term>
 105             <listitem>
 106                 <para>
 107                     Specifies a pointer to the array of control points.
 108                 </para>
 109             </listitem>
 110         </varlistentry>
 111         </variablelist>
 112     </refsect1>
 113     <refsect1 id="description"><title>Description</title>
 114         <para>
 115             Evaluators provide a way to use polynomial or rational polynomial mapping
 116             to produce vertices,
 117             normals,
 118             texture coordinates,
 119             and colors.
 120             The values produced by an evaluator are sent to further stages
 121             of GL processing just as if they had been presented using
 122             <citerefentry><refentrytitle>glVertex</refentrytitle></citerefentry>,
 123             <citerefentry><refentrytitle>glNormal</refentrytitle></citerefentry>,
 124             <citerefentry><refentrytitle>glTexCoord</refentrytitle></citerefentry>, and
 125             <citerefentry><refentrytitle>glColor</refentrytitle></citerefentry> commands,
 126             except that the generated values do not update the current normal,
 127             texture coordinates,
 128             or color.
 129         </para>
 130         <para>
 131             All polynomial or rational polynomial splines of any degree
 132             (up to the maximum degree supported by the GL implementation)
 133             can be described using evaluators.
 134             These include almost all splines used in computer graphics: B-splines,
 135             Bezier curves, Hermite splines, and so on.
 136         </para>
 137         <para>
 138             Evaluators define curves based on Bernstein polynomials.
 139             Define
 140             <inlineequation><mml:math>
 141                 <!-- eqn: p ( u hat):-->
 142                 <mml:mrow>
 143                     <mml:mi mathvariant="italic">p</mml:mi>
 144                     <mml:mo>&af;</mml:mo>
 145                     <mml:mfenced open="(" close=")">
 146                         <mml:mover><mml:mi mathvariant="italic">u</mml:mi><mml:mo>&Hat;</mml:mo></mml:mover>
 147                     </mml:mfenced>
 148                 </mml:mrow>
 149             </mml:math></inlineequation>
 150             as
 151         </para>
 152         <para>
 153             <informalequation><mml:math>
 154                 <!-- eqn: p ( u hat)   =   sum from {i = 0} to {n}   { {B sub i} sup n ( u hat ) R sub i }:-->
 155                 <mml:mrow>
 156                     <mml:mrow>
 157                         <mml:mi mathvariant="italic">p</mml:mi>
 158                         <mml:mo>&af;</mml:mo>
 159                         <mml:mfenced open="(" close=")">
 160                             <mml:mover><mml:mi mathvariant="italic">u</mml:mi><mml:mo>&Hat;</mml:mo></mml:mover>
 161                         </mml:mfenced>
 162                     </mml:mrow>
 163                     <mml:mo>=</mml:mo>
 164                     <mml:mrow>
 165                         <mml:munderover>
 166                             <mml:mo>&Sigma;</mml:mo>
 167                             <mml:mrow>
 168                                 <mml:mi mathvariant="italic">i</mml:mi>
 169                                 <mml:mo>=</mml:mo>
 170                                 <mml:mn>0</mml:mn>
 171                             </mml:mrow>
 172                             <mml:mi mathvariant="italic">n</mml:mi>
 173                         </mml:munderover>
 174                         <mml:mrow>
 175                             <mml:mrow>
 176                                 <mml:msup><mml:mfenced open="" close="">
 177                                     <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 178                                     <mml:mi mathvariant="italic">i</mml:mi>
 179                                     </mml:msub>
 180                                 </mml:mfenced>
 181                                 <mml:mi mathvariant="italic">n</mml:mi>
 182                                 </mml:msup>
 183                                 <mml:mo>&af;</mml:mo>
 184                                 <mml:mfenced open="(" close=")">
 185                                     <mml:mover><mml:mi mathvariant="italic">u</mml:mi><mml:mo>&Hat;</mml:mo></mml:mover>
 186                                 </mml:mfenced>
 187                             </mml:mrow>
 188                             <mml:mo>&it;</mml:mo>
 189                             <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 190                             <mml:mi mathvariant="italic">i</mml:mi>
 191                             </mml:msub>
 192                         </mml:mrow>
 193                     </mml:mrow>
 194                 </mml:mrow>
 195             </mml:math></informalequation>
 196         </para>
 197         <para>
 198         </para>
 199         <para>
 200             where
 201             <inlineequation><mml:math>
 202                 <!-- eqn: R sub i:-->
 203                 <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 204                 <mml:mi mathvariant="italic">i</mml:mi>
 205                 </mml:msub>
 206             </mml:math></inlineequation>
 207             is a control point and
 208             <inlineequation><mml:math>
 209                 <!-- eqn: {B sub i} sup n ( u hat):-->
 210                 <mml:mrow>
 211                     <mml:msup><mml:mfenced open="" close="">
 212                         <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 213                         <mml:mi mathvariant="italic">i</mml:mi>
 214                         </mml:msub>
 215                     </mml:mfenced>
 216                     <mml:mi mathvariant="italic">n</mml:mi>
 217                     </mml:msup>
 218                     <mml:mo>&af;</mml:mo>
 219                     <mml:mfenced open="(" close=")">
 220                         <mml:mover><mml:mi mathvariant="italic">u</mml:mi><mml:mo>&Hat;</mml:mo></mml:mover>
 221                     </mml:mfenced>
 222                 </mml:mrow>
 223             </mml:math></inlineequation>
 224             is the
 225             <inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>th
 226             Bernstein polynomial of degree
 227             <inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>
 228             (<parameter>order</parameter> =
 229             <inlineequation><mml:math>
 230                 <!-- eqn: n  +  1:-->
 231                 <mml:mrow>
 232                     <mml:mi mathvariant="italic">n</mml:mi>
 233                     <mml:mo>+</mml:mo>
 234                     <mml:mn>1</mml:mn>
 235                 </mml:mrow>
 236             </mml:math></inlineequation>):
 237         </para>
 238         <para>
 239             <inlineequation><mml:math>
 240                 <!-- eqn: {B sub i} sup n ( u hat)   =   left ( {cpile { n above i }} right ) {u hat} sup i { ( 1 - u hat) sup { n - i } }:-->
 241                 <mml:mrow>
 242                     <mml:mrow>
 243                         <mml:msup><mml:mfenced open="" close="">
 244                             <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 245                             <mml:mi mathvariant="italic">i</mml:mi>
 246                             </mml:msub>
 247                         </mml:mfenced>
 248                         <mml:mi mathvariant="italic">n</mml:mi>
 249                         </mml:msup>
 250                         <mml:mo>&af;</mml:mo>
 251                         <mml:mfenced open="(" close=")">
 252                             <mml:mover><mml:mi mathvariant="italic">u</mml:mi><mml:mo>&Hat;</mml:mo></mml:mover>
 253                         </mml:mfenced>
 254                     </mml:mrow>
 255                     <mml:mo>=</mml:mo>
 256                     <mml:mrow>
 257                         <mml:mfenced open="(" close=")">
 258                             <mml:mfenced open="" close="">
 259                                 <mml:mtable>
 260                                     <mml:mtr><mml:mtd>
 261                                         <mml:mi mathvariant="italic">n</mml:mi>
 262                                     </mml:mtd></mml:mtr>
 263                                     <mml:mtr><mml:mtd>
 264                                         <mml:mi mathvariant="italic">i</mml:mi>
 265                                     </mml:mtd></mml:mtr>
 266                                 </mml:mtable>
 267                             </mml:mfenced>
 268                         </mml:mfenced>
 269                         <mml:mo>&it;</mml:mo>
 270                         <mml:msup><mml:mfenced open="" close="">
 271                             <mml:mover><mml:mi mathvariant="italic">u</mml:mi><mml:mo>&Hat;</mml:mo></mml:mover>
 272                         </mml:mfenced>
 273                         <mml:mi mathvariant="italic">i</mml:mi>
 274                         </mml:msup>
 275                         <mml:mo>&it;</mml:mo>
 276                         <mml:mfenced open="" close="">
 277                             <mml:msup><mml:mfenced open="(" close=")">
 278                                 <mml:mrow>
 279                                     <mml:mn>1</mml:mn>
 280                                     <mml:mo>-</mml:mo>
 281                                     <mml:mover><mml:mi mathvariant="italic">u</mml:mi><mml:mo>&Hat;</mml:mo></mml:mover>
 282                                 </mml:mrow>
 283                             </mml:mfenced>
 284                             <mml:mfenced open="" close="">
 285                                 <mml:mrow>
 286                                     <mml:mi mathvariant="italic">n</mml:mi>
 287                                     <mml:mo>-</mml:mo>
 288                                     <mml:mi mathvariant="italic">i</mml:mi>
 289                                 </mml:mrow>
 290                             </mml:mfenced>
 291                             </mml:msup>
 292                         </mml:mfenced>
 293                     </mml:mrow>
 294                 </mml:mrow>
 295             </mml:math></inlineequation>
 296         </para>
 297         <para>
 298             Recall that
 299         </para>
 300         <para>
 301             <inlineequation><mml:math>
 302                 <!-- eqn: 0 sup 0  ==  1:-->
 303                 <mml:mrow>
 304                     <mml:msup><mml:mn>0</mml:mn>
 305                     <mml:mn>0</mml:mn>
 306                     </mml:msup>
 307                     <mml:mo>==</mml:mo>
 308                     <mml:mn>1</mml:mn>
 309                 </mml:mrow>
 310             </mml:math></inlineequation>
 311             and
 312             <inlineequation><mml:math>
 313                 <!-- eqn: left ( {cpile { n above 0 }} right )  ==  1:-->
 314                 <mml:mrow>
 315                     <mml:mfenced open="(" close=")">
 316                         <mml:mfenced open="" close="">
 317                             <mml:mtable>
 318                                 <mml:mtr><mml:mtd>
 319                                     <mml:mi mathvariant="italic">n</mml:mi>
 320                                 </mml:mtd></mml:mtr>
 321                                 <mml:mtr><mml:mtd>
 322                                     <mml:mn>0</mml:mn>
 323                                 </mml:mtd></mml:mtr>
 324                             </mml:mtable>
 325                         </mml:mfenced>
 326                     </mml:mfenced>
 327                     <mml:mo>==</mml:mo>
 328                     <mml:mn>1</mml:mn>
 329                 </mml:mrow>
 330             </mml:math></inlineequation>
 331         </para>
 332         <para>
 333             <function>glMap1</function> is used to define the basis and to specify what kind of values
 334             are produced.
 335             Once defined,
 336             a map can be enabled and disabled by calling <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry>
 337             with the map name, one of the nine predefined values for <parameter>target</parameter>
 338             described below.
 339             <citerefentry><refentrytitle>glEvalCoord1</refentrytitle></citerefentry> evaluates the one-dimensional maps that are enabled.
 340             When
 341             <citerefentry><refentrytitle>glEvalCoord1</refentrytitle></citerefentry> presents a value
 342             <inlineequation><mml:math><mml:mi mathvariant="italic">u</mml:mi></mml:math></inlineequation>,
 343             the Bernstein functions are evaluated using
 344             <inlineequation><mml:math>
 345                 <!-- eqn: u hat:-->
 346                 <mml:mover><mml:mi mathvariant="italic">u</mml:mi><mml:mo>&Hat;</mml:mo></mml:mover>
 347             </mml:math></inlineequation>,
 348             where
 349             <inlineequation><mml:math>
 350                 <!-- eqn: u hat   =   {u  -  u1} over {u2  -  u1}:-->
 351                 <mml:mrow>
 352                     <mml:mover><mml:mi mathvariant="italic">u</mml:mi><mml:mo>&Hat;</mml:mo></mml:mover>
 353                     <mml:mo>=</mml:mo>
 354                     <mml:mfrac>
 355                         <mml:mfenced open="" close="">
 356                             <mml:mrow>
 357                                 <mml:mi mathvariant="italic">u</mml:mi>
 358                                 <mml:mo>-</mml:mo>
 359                                 <mml:mi mathvariant="italic">u1</mml:mi>
 360                             </mml:mrow>
 361                         </mml:mfenced>
 362                         <mml:mfenced open="" close="">
 363                             <mml:mrow>
 364                                 <mml:mi mathvariant="italic">u2</mml:mi>
 365                                 <mml:mo>-</mml:mo>
 366                                 <mml:mi mathvariant="italic">u1</mml:mi>
 367                             </mml:mrow>
 368                         </mml:mfenced>
 369                     </mml:mfrac>
 370                 </mml:mrow>
 371             </mml:math></inlineequation>
 372         </para>
 373         <para>
 374             <parameter>target</parameter> is a symbolic constant that indicates what kind of control points
 375             are provided in <parameter>points</parameter>,
 376             and what output is generated when the map is evaluated.
 377             It can assume one of nine predefined values:
 378         </para>
 379         <variablelist>
 380             <varlistentry>
 381                 <term><constant>GL_MAP1_VERTEX_3</constant></term>
 382                 <listitem>
 383                     <para>
 384                         Each control point is three floating-point values representing
 385                         <inlineequation><mml:math><mml:mi mathvariant="italic">x</mml:mi></mml:math></inlineequation>,
 386                         <inlineequation><mml:math><mml:mi mathvariant="italic">y</mml:mi></mml:math></inlineequation>,
 387                         and
 388                         <inlineequation><mml:math><mml:mi mathvariant="italic">z</mml:mi></mml:math></inlineequation>.
 389                         Internal <citerefentry><refentrytitle>glVertex3</refentrytitle></citerefentry> commands are generated when the map is evaluated.
 390                     </para>
 391                 </listitem>
 392             </varlistentry>
 393             <varlistentry>
 394                 <term><constant>GL_MAP1_VERTEX_4</constant></term>
 395                 <listitem>
 396                     <para>
 397                         Each control point is four floating-point values representing
 398                         <inlineequation><mml:math><mml:mi mathvariant="italic">x</mml:mi></mml:math></inlineequation>,
 399                         <inlineequation><mml:math><mml:mi mathvariant="italic">y</mml:mi></mml:math></inlineequation>,
 400                         <inlineequation><mml:math><mml:mi mathvariant="italic">z</mml:mi></mml:math></inlineequation>,
 401                         and
 402                         <inlineequation><mml:math><mml:mi mathvariant="italic">w</mml:mi></mml:math></inlineequation>.
 403                         Internal <citerefentry><refentrytitle>glVertex4</refentrytitle></citerefentry> commands are generated when the map is evaluated.
 404                     </para>
 405                 </listitem>
 406             </varlistentry>
 407             <varlistentry>
 408                 <term><constant>GL_MAP1_INDEX</constant></term>
 409                 <listitem>
 410                     <para>
 411                         Each control point is a single floating-point value representing a color index.
 412                         Internal <citerefentry><refentrytitle>glIndex</refentrytitle></citerefentry> commands are generated when the map is evaluated
 413                         but the current index is not updated with the value of these <citerefentry><refentrytitle>glIndex</refentrytitle></citerefentry>
 414                         commands.
 415                     </para>
 416                 </listitem>
 417             </varlistentry>
 418             <varlistentry>
 419                 <term><constant>GL_MAP1_COLOR_4</constant></term>
 420                 <listitem>
 421                     <para>
 422                         Each control point is four floating-point values representing
 423                         red, green, blue, and alpha.
 424                         Internal <citerefentry><refentrytitle>glColor4</refentrytitle></citerefentry> commands are generated when the map is
 425                         evaluated but the current color is not updated with the value of these
 426                         <citerefentry><refentrytitle>glColor4</refentrytitle></citerefentry> commands.
 427                     </para>
 428                 </listitem>
 429             </varlistentry>
 430             <varlistentry>
 431                 <term><constant>GL_MAP1_NORMAL</constant></term>
 432                 <listitem>
 433                     <para>
 434                         Each control point is three floating-point values representing
 435                         the
 436                         <inlineequation><mml:math><mml:mi mathvariant="italic">x</mml:mi></mml:math></inlineequation>,
 437                         <inlineequation><mml:math><mml:mi mathvariant="italic">y</mml:mi></mml:math></inlineequation>,
 438                         and
 439                         <inlineequation><mml:math><mml:mi mathvariant="italic">z</mml:mi></mml:math></inlineequation>
 440                         components of a normal vector.
 441                         Internal <citerefentry><refentrytitle>glNormal</refentrytitle></citerefentry> commands are generated when the map is
 442                         evaluated but the current normal is not updated with the value of
 443                         these <citerefentry><refentrytitle>glNormal</refentrytitle></citerefentry> commands.
 444                     </para>
 445                 </listitem>
 446             </varlistentry>
 447             <varlistentry>
 448                 <term><constant>GL_MAP1_TEXTURE_COORD_1</constant></term>
 449                 <listitem>
 450                     <para>
 451                         Each control point is a single floating-point value representing
 452                         the
 453                         <inlineequation><mml:math><mml:mi mathvariant="italic">s</mml:mi></mml:math></inlineequation>
 454                         texture coordinate.
 455                         Internal
 456                         <citerefentry><refentrytitle>glTexCoord1</refentrytitle></citerefentry> commands are generated when the map is
 457                         evaluated but the current texture coordinates are not updated with the value
 458                         of these <citerefentry><refentrytitle>glTexCoord</refentrytitle></citerefentry> commands.
 459                     </para>
 460                 </listitem>
 461             </varlistentry>
 462             <varlistentry>
 463                 <term><constant>GL_MAP1_TEXTURE_COORD_2</constant></term>
 464                 <listitem>
 465                     <para>
 466                         Each control point is two floating-point values representing
 467                         the
 468                         <inlineequation><mml:math><mml:mi mathvariant="italic">s</mml:mi></mml:math></inlineequation>
 469                         and
 470                         <inlineequation><mml:math><mml:mi mathvariant="italic">t</mml:mi></mml:math></inlineequation>
 471                         texture coordinates.
 472                         Internal
 473                         <citerefentry><refentrytitle>glTexCoord2</refentrytitle></citerefentry> commands are generated when the map is
 474                         evaluated but the current texture coordinates are not updated with the value
 475                         of these <citerefentry><refentrytitle>glTexCoord</refentrytitle></citerefentry> commands.
 476                     </para>
 477                 </listitem>
 478             </varlistentry>
 479             <varlistentry>
 480                 <term><constant>GL_MAP1_TEXTURE_COORD_3</constant></term>
 481                 <listitem>
 482                     <para>
 483                         Each control point is three floating-point values representing
 484                         the
 485                         <inlineequation><mml:math><mml:mi mathvariant="italic">s</mml:mi></mml:math></inlineequation>,
 486                         <inlineequation><mml:math><mml:mi mathvariant="italic">t</mml:mi></mml:math></inlineequation>,
 487                         and
 488                         <inlineequation><mml:math><mml:mi mathvariant="italic">r</mml:mi></mml:math></inlineequation>
 489                         texture coordinates.
 490                         Internal <citerefentry><refentrytitle>glTexCoord3</refentrytitle></citerefentry> commands are generated when the map is
 491                         evaluated but the current texture coordinates are not updated with the value
 492                         of these <citerefentry><refentrytitle>glTexCoord</refentrytitle></citerefentry> commands.
 493                     </para>
 494                 </listitem>
 495             </varlistentry>
 496             <varlistentry>
 497                 <term><constant>GL_MAP1_TEXTURE_COORD_4</constant></term>
 498                 <listitem>
 499                     <para>
 500                         Each control point is four floating-point values representing
 501                         the
 502                         <inlineequation><mml:math><mml:mi mathvariant="italic">s</mml:mi></mml:math></inlineequation>,
 503                         <inlineequation><mml:math><mml:mi mathvariant="italic">t</mml:mi></mml:math></inlineequation>,
 504                         <inlineequation><mml:math><mml:mi mathvariant="italic">r</mml:mi></mml:math></inlineequation>,
 505                         and
 506                         <inlineequation><mml:math><mml:mi mathvariant="italic">q</mml:mi></mml:math></inlineequation>
 507                         texture coordinates.
 508                         Internal
 509                         <citerefentry><refentrytitle>glTexCoord4</refentrytitle></citerefentry> commands are generated when the map is evaluated but
 510                         the current texture coordinates are not updated with the value
 511                         of these <citerefentry><refentrytitle>glTexCoord</refentrytitle></citerefentry> commands.
 512                     </para>
 513                 </listitem>
 514             </varlistentry>
 515         </variablelist>
 516         <para>
 517             <parameter>stride</parameter>,
 518             <parameter>order</parameter>, and
 519             <parameter>points</parameter> define the array addressing for accessing the control points.
 520             <parameter>points</parameter> is the location of the first control point,
 521             which occupies one, two, three, or four contiguous memory locations,
 522             depending on which map is being defined.
 523             <parameter>order</parameter> is the number of control points in the array.
 524             <parameter>stride</parameter> specifies how many float or double locations to advance the internal
 525             memory pointer to reach the next control point.
 526         </para>
 527     </refsect1>
 528     <refsect1 id="notes"><title>Notes</title>
 529         <para>
 530             As is the case with all GL commands that accept pointers to data,
 531             it is as if the contents of <parameter>points</parameter> were copied by <function>glMap1</function> before <function>glMap1</function>
 532             returns.
 533             Changes to the contents of <parameter>points</parameter> have no effect after <function>glMap1</function> is called.
 534         </para>
 535     </refsect1>
 536     <refsect1 id="errors"><title>Errors</title>
 537         <para>
 538             <constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> is not an accepted value.
 539         </para>
 540         <para>
 541             <constant>GL_INVALID_VALUE</constant> is generated if <parameter>u1</parameter> is equal to <parameter>u2</parameter>.
 542         </para>
 543         <para>
 544             <constant>GL_INVALID_VALUE</constant> is generated if <parameter>stride</parameter> is less than the number
 545             of values in a control point.
 546         </para>
 547         <para>
 548             <constant>GL_INVALID_VALUE</constant> is generated if <parameter>order</parameter> is less than 1 or
 549             greater than the return value of <constant>GL_MAX_EVAL_ORDER</constant>.
 550         </para>
 551         <para>
 552             <constant>GL_INVALID_OPERATION</constant> is generated if <function>glMap1</function>
 553             is executed between the execution of
 554             <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
 555             and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
 556         </para>
 557         <para>
 558             <constant>GL_INVALID_OPERATION</constant> is generated if <function>glMap1</function> is called and the value
 559             of <constant>GL_ACTIVE_TEXTURE</constant> is not <constant>GL_TEXTURE0</constant>.
 560         </para>
 561     </refsect1>
 562     <refsect1 id="associatedgets"><title>Associated Gets</title>
 563         <para>
 564             <citerefentry><refentrytitle>glGetMap</refentrytitle></citerefentry>
 565         </para>
 566         <para>
 567             <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_MAX_EVAL_ORDER</constant>
 568         </para>
 569         <para>
 570             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_VERTEX_3</constant>
 571         </para>
 572         <para>
 573             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_VERTEX_4</constant>
 574         </para>
 575         <para>
 576             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_INDEX</constant>
 577         </para>
 578         <para>
 579             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_COLOR_4</constant>
 580         </para>
 581         <para>
 582             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_NORMAL</constant>
 583         </para>
 584         <para>
 585             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_TEXTURE_COORD_1</constant>
 586         </para>
 587         <para>
 588             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_TEXTURE_COORD_2</constant>
 589         </para>
 590         <para>
 591             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_TEXTURE_COORD_3</constant>
 592         </para>
 593         <para>
 594             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_TEXTURE_COORD_4</constant>
 595         </para>
 596     </refsect1>
 597     <refsect1 id="seealso"><title>See Also</title>
 598         <para>
 599             <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>,
 600             <citerefentry><refentrytitle>glColor</refentrytitle></citerefentry>,
 601             <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>,
 602             <citerefentry><refentrytitle>glEvalCoord</refentrytitle></citerefentry>,
 603             <citerefentry><refentrytitle>glEvalMesh</refentrytitle></citerefentry>,
 604             <citerefentry><refentrytitle>glEvalPoint</refentrytitle></citerefentry>,
 605             <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>,
 606             <citerefentry><refentrytitle>glMapGrid</refentrytitle></citerefentry>,
 607             <citerefentry><refentrytitle>glNormal</refentrytitle></citerefentry>,
 608             <citerefentry><refentrytitle>glTexCoord</refentrytitle></citerefentry>,
 609             <citerefentry><refentrytitle>glVertex</refentrytitle></citerefentry>
 610         </para>
 611     </refsect1>
 612     <refsect1 id="Copyright"><title>Copyright</title>
 613         <para>
 614             Copyright <trademark class="copyright"></trademark> 1991-2006
 615             Silicon Graphics, Inc. This document is licensed under the SGI
 616             Free Software B License. For details, see
 617             <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
 618         </para>
 619     </refsect1>
 620 </refentry>