docs/subset-A.html

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   2 <html>
   3 <head>
   4   <title>Mini GLX Specification</title>
   5 </head>
   6 <body>
   7 <span style="font-style: italic;"></span><span
   8  style="font-weight: bold;"></span>
   9 <h1>
  10 <center>Mesa Subset Specification</center>
  11 </h1>
  12 <h2>
  13 <center>
  14 <h3>Tungsten Graphics, Inc.</h3>
  15 <h3>February 26, 2003<br>
  16 </h3>
  17 </center>
  18 </h2>
  19 <p> Copyright &copy; 2002-2003 by <a
  20  href="http://www.tungstengraphics.com/">Tungsten Graphics, Inc.</a>,
  21 Cedar Park, Texas. All Rights Reserved. <br>
  22 <br>
  23 Permission is granted to make and distribute verbatim copies of this
  24 document provided the copyright notice and this permission notice are
  25 preserved on all copies.<br>
  26 </p>
  27 <p> OpenGL is a trademark of <a href="http://www.sgi.com">Silicon
  28 Graphics, Inc.</a>.</p>
  29 <h1>1. Introduction</h1>
  30 This document describes a subset of the Mesa implemented by Tungsten
  31 Graphics, Inc. for embedded devices. &nbsp;Prior to reading this
  32 document the reader should be familiar with the OpenGL 1.2.1
  33 specification dated April 1, 1999 (available from <a
  34  href="http://www.opengl.org/developers/documentation/specs.html">http://www.opengl.org/developers/documentation/specs.html</a>.)
  35 &nbsp;Experience with OpenGL programming is highly advisable.<a
  36  href="http://www.opengl.org/developers/documentation/specs.html"><br>
  37 </a><br>
  38 Tungsten Graphics, Inc. is working with industry standards
  39 organizations +in an attempt to standardize this Mesa subset and any
  40 other possible subsets +as a result of this work. <br>
  41 <br>
  42 Appendix A contains a list of issues of which some may not be resolved.<br>
  43 <br>
  44 To summarize, the following major features of Mesa are omitted from the
  45 subset:<br>
  46 <ul>
  47   <li>Vertex arrays</li>
  48   <li>Texture coordinate generation</li>
  49   <li>Lighting</li>
  50   <li>Point size</li>
  51   <li>Polygon stipple</li>
  52   <li>DrawPixels, CopyPixels, PixelZoom</li>
  53   <li>1-D and 3-D textures</li>
  54   <li>CopyTex[Sub]Image</li>
  55   <li>Fog</li>
  56   <li>Depth test</li>
  57   <li>Color Index mode</li>
  58   <li>Accumulation buffer</li>
  59   <li>Feedback mode</li>
  60   <li>Evaluators</li>
  61   <li>Push/Pop attributes</li>
  62   <li>Display lists<br>
  63   </li>
  64 </ul>
  65 <p>Further reductions are made at a lower level of detail.<br>
  66 </p>
  67 <p>Mesa function names are printed in <span style="font-weight: bold;">bold
  68 face</span>. &nbsp;Function parameters are printed in <span
  69  style="font-style: italic;">italics</span>.<br>
  70 </p>
  71 <p>The Tungsten Graphics, Inc. Mesa subset library is hereafter
  72 referred to as <span style="font-style: italic;">the subset.</span><br>
  73 <br>
  74 </p>
  75 <h1>2. Primitive Specification</h1>
  76 <h2>2.1 glBegin, glEnd and glVertex Commands</h2>
  77 The basic rendering primitives are points, lines and triangles.
  78 &nbsp;Quadrilaterals and polygons are composed of triangles.
  79 &nbsp;Primitives are drawn with the <span style="font-weight: bold;">glBegin</span>
  80 and <span style="font-weight: bold;">glEnd</span> commands and a subset
  81 of the <span style="font-weight: bold;">glVertex</span> commands:<br>
  82 <br>
  83 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glBegin</span>(GLenum<span
  84  style="font-style: italic;">mode</span>)<br>
  85 void <span style="font-weight: bold;">glEnd</span>(void)<br>
  86 <br>
  87 void <span style="font-weight: bold;">glVertex2f</span>(GLfloat <span
  88  style="font-style: italic;">x</span>, GLfloat <span
  89  style="font-style: italic;">y</span>)<br>
  90 void <span style="font-weight: bold;">glVertex2fv</span>(const GLfloat
  91 *<span style="font-style: italic;">v</span>)<br>
  92 void <span style="font-weight: bold;">glVertex3f</span>(GLfloat <span
  93  style="font-style: italic;">x</span>, GLfloat <span
  94  style="font-style: italic;">y</span>, GLfloat <span
  95  style="font-style: italic;">z</span>)<br>
  96 void <span style="font-weight: bold;">glVertex3fv</span>(const GLfloat
  97 *<span style="font-style: italic;">v</span>)<br>
  98 </div>
  99 <br>
 100 The <span style="font-style: italic;">mode</span> parameter to <span
 101  style="font-weight: bold;">glBegin</span> may be one of the following<br>
 102 <br>
 103 <div style="margin-left: 40px;">GL_POINTS - a series of individual
 104 points<br>
 105 GL_LINES - a series of disjoint line segments<br>
 106 GL_LINE_STRIP - series of connected line segments<br>
 107 GL_LINE_LOOP - a closed loop of line segments<br>
 108 GL_TRIANGLES - a series of individual triangles<br>
 109 GL_TRIANGLE_STRIP - a connected strip of triangles<br>
 110 GL_TRIANGLE_FAN - a sequence of triangles all sharing a common vertex<br>
 111 GL_QUADS - a sequence of individual quadrilaterals<br>
 112 GL_QUAD_STRIP - a connected strip of quadrilaterals<br>
 113 GL_POLYGON - a closed, convex polygon<br>
 114 <br>
 115 </div>
 116 <br>
 117 The <span style="font-weight: bold;">glVertex</span> commands take two
 118 or three floating point coordinates, or a pointer to an array of two or
 119 three floating point coordinates. &nbsp;Vertices are actually 4-element
 120 homogeneous coordinates. &nbsp;The fourth component, unspecified by the
 121 subset's <span style="font-weight: bold;">glVertex</span> commands, is
 122 one.<br>
 123 <br>
 124 <span style="font-weight: bold;"></span>
 125 <h2>2.2 Other Per-vertex Commands<br>
 126 </h2>
 127 The <span style="font-weight: bold;">glColor</span> and <span
 128  style="font-weight: bold;">glTexCoord</span> commands may be used to
 129 specify colors and texture coordinates for each vertex:<br>
 130 <br>
 131 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glColor3f</span>(GLfloat<span
 132  style="font-style: italic;">red</span>, GLfloat <span
 133  style="font-style: italic;">green</span>, GLfloat <span
 134  style="font-style: italic;">blue</span>)<br>
 135 void <span style="font-weight: bold;">glColor3fv</span>(const GLfloat *<span
 136  style="font-style: italic;">rgb</span>)<br>
 137 void <span style="font-weight: bold;">glColor4f</span>(GLfloat <span
 138  style="font-style: italic;">red,</span> GLfloat <span
 139  style="font-style: italic;">green,</span> GLfloat <span
 140  style="font-style: italic;">blue,</span> GLfloat <span
 141  style="font-style: italic;">alpha</span>)<br>
 142 void <span style="font-weight: bold;">glColor4fv</span>(const GLfloat *<span
 143  style="font-style: italic;">rgba</span>)<br>
 144 void <span style="font-weight: bold;">glTexCoord2f</span>(GLfloat <span
 145  style="font-style: italic;">s</span>, GLfloat<span
 146  style="font-style: italic;"> t</span>)<br>
 147 void <span style="font-weight: bold;">glTexCoord2fv</span>(const
 148 GLfloat *<span style="font-style: italic;">c</span>)<br>
 149 <br>
 150 </div>
 151 The <span style="font-weight: bold;">glColor</span> commands specify
 152 the color and optionally, the alpha value, for subsequent vertices.
 153 &nbsp;For the <span style="font-weight: bold;">glColor3</span> commands,
 154 alpha is set to one.<br>
 155 <br>
 156 The <span style="font-weight: bold;">glTexCoord2</span> commands
 157 specify the texture coordinate for subsequent vertices. &nbsp;Texture
 158 coordinates are actually four-component coordinates: (s, t, r, q).
 159 &nbsp;The <span style="font-weight: bold;">glTexCoord2</span> commands
 160 set s and t explicitly. &nbsp;The r and q components are zero and one,
 161 respectively.<br>
 162 <br>
 163 <span style="font-weight: bold;"></span>Only <span
 164  style="font-weight: bold;">glVertex, glColor</span> and <span
 165  style="font-weight: bold;">glTexCoord</span> commands are allowed
 166 between <span style="font-weight: bold;">glBegin</span> and <span
 167  style="font-weight: bold;">glEnd.</span> &nbsp;Calling any other
 168 command between <span style="font-weight: bold;">glBegin</span> and <span
 169  style="font-weight: bold;">glEnd</span> will result in the error
 170 GL_INVALID_OPERATION.<br>
 171 <br>
 172 <h2>2.3 Unsupported Commands</h2>
 173 None of the following commands related to primitive specification are
 174 supported by the subset:<br>
 175 <br>
 176 <div style="margin-left: 40px;">Per-Vertex commands:<br>
 177 </div>
 178 <div style="margin-left: 40px;">
 179 <div style="margin-left: 40px;"><span style="font-weight: bold;">glVertex2d,
 180 glVertex2i, glVertex2s, glVertex3d, glVertex3i, glVertex3s, glVertex4d,
 181 glVertex4i, glVertex4s, glVertex2dv, glVertex2iv, glVertex2sv,
 182 glVertex3dv, glVertex3iv, glVertex3sv, glVertex4dv, glVertex4iv,
 183 glVertex4sv,<br>
 184 glNormal3b, glNormal3d, glNormal3f, glNormal3i, glNormal3s, </span><span
 185  style="font-weight: bold;">glNormal3bv, glNormal3dv, glNormal3fv,
 186 glNormal3iv, glNormal3sv,<br>
 187 glIndexd, glIndexf, glIndexi, glIndexs, glIndexub, glIndexdv,
 188 glIndexfv, glIndexiv, glIndexsv, glIndexubv,<br>
 189 glColor3b, glColor3d, glColor3i, glColor3s, glColor3ub, glColor3ui,
 190 glColor3us, </span><span style="font-weight: bold;">glColor3bv,
 191 glColor3dv, glColor3iv, glColor3sv, glColor3ubv, glColor3uiv,
 192 glColor3usv,</span><span style="font-weight: bold;"> lColor4b,
 193 glColor4d, glColor4i, glColor4s, glColor4ub, glColor4ui, glColor4us, </span><span
 194  style="font-weight: bold;">glColor4bv, glColor4dv, glColor4iv,
 195 glColor4sv, glColor4ubv, glColor4uiv, glColor4usv,<br>
 196 </span><span style="font-weight: bold;">glTexCoord1d, glTexCoord1f,
 197 glTexCoord1i, glTexCoord1s, glTexCoord2d, glTexCoord2i, glTexCoord2s,
 198 glTexCoord3d, glTexCoord3f, glTexCoord3i, glTexCoord3s, glTexCoord4d,
 199 glTexCoord4f, glTexCoord4i, glTexCoord4s, glTexCoord1dv, glTexCoord1fv,
 200 glTexCoord1iv, glTexCoord1sv, glTexCoord2dv, glTexCoord2iv,
 201 glTexCoord2sv, glTexCoord3dv, glTexCoord3fv, glTexCoord3iv,
 202 glTexCoord3sv, glTexCoord4dv, glTexCoord4fv, glTexCoord4iv,
 203 glTexCoord4sv,<br>
 204 glEdgeFlag, glEdgeFlagv</span><br style="font-weight: bold;">
 205 <br>
 206 </div>
 207 Vertex array commands:<br>
 208 <div style="margin-left: 40px;"><span style="font-weight: bold;">glVertexPointer,
 209 glColorPointer, glIndexPointer, glTexCoordPointer, glEdgeFlagPointer,
 210 glNormalPointer, glInterleavedArrays, glArrayElement, glDrawArrays,
 211 glDrawElements, glDrawRangeElements, glEnableClientState,
 212 glDisableClientState</span><br>
 213 </div>
 214 </div>
 215 <div style="margin-left: 40px;"><br>
 216 Rectangle commands:<br>
 217 <div style="margin-left: 40px;"><span style="font-weight: bold;">glRects,
 218 glRecti, glRectf, glRectd, glRectsv, glRectiv, glRectfv, glRectdv,<br>
 219 <br>
 220 </span></div>
 221 </div>
 222 <div style="margin-left: 40px;">Lighting commands:<br>
 223 </div>
 224 <div style="margin-left: 80px;"><span style="font-weight: bold;">glMaterialf,
 225 glMateriali, glMaterialfv, glMaterialiv<br>
 226 </span><br>
 227 </div>
 228 <div style="margin-left: 40px;"> Evaluator commands:<br>
 229 <div style="margin-left: 40px;"><span style="font-weight: bold;">glEvalCoord1d,
 230 glEvalCoord1f, glEvalCoord1dv, glEvalCoord1fv,&nbsp;</span><span
 231  style="font-weight: bold;">glEvalCoord2d, glEvalCoord2f,
 232 glEvalCoord2dv, glEvalCoord2fv,<br>
 233 </span><span style="font-weight: bold;">glEvalPoint1, glEvalPoint2</span><br>
 234 <br>
 235 </div>
 236 </div>
 237 <h1>3. Coordinate Transformation</h1>
 238 <h2>3.1 Vertex Transformation</h2>
 239 Vertex coordinates are transformed by the current modelview and
 240 projection matrices then mapped to window coordinates as specified by
 241 the viewport. &nbsp;The following coordinate transformation commands are
 242 supported by the subset<br>
 243 <br>
 244 <div style="margin-left: 40px; font-weight: bold;">glMatrixMode<span
 245  style="font-weight: normal;">(GLenum <span style="font-style: italic;">mode</span>)</span><br>
 246 glLoadIdentity<span style="font-weight: normal;">(void)</span><br>
 247 glPushMatrix<span style="font-weight: normal;">(void)</span><br>
 248 glPopMatrix<span style="font-weight: normal;">(void)</span><br>
 249 glLoadMatrixf<span style="font-weight: normal;">(const GLfloat *<span
 250  style="font-style: italic;">m</span>)</span><br>
 251 glMultMatrixf<span style="font-weight: normal;">(const GLfloat *<span
 252  style="font-style: italic;">m</span>)</span><br>
 253 glRotatef<span style="font-weight: normal;">(GLfloat <span
 254  style="font-style: italic;">angle</span>, GLfloat <span
 255  style="font-style: italic;">x</span>, GLfloat <span
 256  style="font-style: italic;">y</span>, GLfloat <span
 257  style="font-style: italic;">z</span>)</span><br>
 258 glTranslatef<span style="font-weight: normal;">(GLfloat <span
 259  style="font-style: italic;">x</span>, GLfloat <span
 260  style="font-style: italic;">y</span>, GLfloat <span
 261  style="font-style: italic;">z</span>)</span><br>
 262 glScalef<span style="font-weight: normal;">(GLfloat <span
 263  style="font-style: italic;">x</span>, GLfloat <span
 264  style="font-style: italic;">y</span>, GLfloat <span
 265  style="font-style: italic;">z</span>)<br>
 266 <span style="font-weight: bold;">glFrustum(</span>GLdouble <span
 267  style="font-style: italic;">left,</span> GLdouble <span
 268  style="font-style: italic;">right,</span> GLdouble <span
 269  style="font-style: italic;">bottom,</span> GLdouble <span
 270  style="font-style: italic;">top,</span> GLdouble <span
 271  style="font-style: italic;">near,</span> GLdouble <span
 272  style="font-style: italic;">far</span>)</span><br>
 273 <span style="font-weight: normal;"><span style="font-weight: bold;">glOrtho(</span>GLdouble<span
 274  style="font-style: italic;"> left,</span> GLdouble <span
 275  style="font-style: italic;">right,</span> GLdouble <span
 276  style="font-style: italic;">bottom,</span> GLdouble <span
 277  style="font-style: italic;">top,</span> GLdouble <span
 278  style="font-style: italic;">near,</span> GLdouble <span
 279  style="font-style: italic;">far</span>)</span><br>
 280 glViewport<span style="font-weight: normal;">(GLint <span
 281  style="font-style: italic;">x</span>, GLint <span
 282  style="font-style: italic;">y</span>, GLsize <span
 283  style="font-style: italic;">width,</span> GLsizei <span
 284  style="font-style: italic;">height</span>)</span><br>
 285 </div>
 286 <br>
 287 The <span style="font-weight: bold;">glMatrixMode</span> command
 288 specifies the <span style="font-style: italic;">current matrix.</span>
 289 &nbsp;The mode parameter may be GL_MODELVIEW or GL_PROJECTION to specify
 290 the modelview matrix or projection matrix. &nbsp;Subsequent matrix
 291 commands will effect the current matrix. &nbsp;Also associated with the
 292 modelview and projection matrices are a modelview matrix stack and
 293 projection matrix stack.<br>
 294 <br>
 295 The <span style="font-weight: bold;">glLoadIdentity</span> command
 296 replaces the current matrix with the identity matrix. &nbsp;The matrix
 297 elements are specified in column-major order.<br>
 298 <br>
 299 The <span style="font-weight: bold;">glPushMatrix</span> command pushes
 300 a copy of the current matrix onto either the modelview matrix stack or
 301 the projection matrix stack. &nbsp;The <span style="font-weight: bold;">glPopMatrix</span>
 302 command replaces the current matrix with a copy of the top matrix off
 303 the modelview matrix stack or projection matrix stack, the pops the
 304 stack. &nbsp;Matrix stacks are useful for traversing and rendering
 305 hierarchical models.<br>
 306 <br>
 307 The <span style="font-weight: bold;">glMultMatrixf</span> command
 308 post-multiplies the current matrix by the specified matrix. &nbsp;The
 309 matrix elements are specified in column-major order.<br>
 310 <br>
 311 The <span style="font-weight: bold;">glRotatef</span> command
 312 post-multiplies the current matrix by a rotation matrix defined by the
 313 angle and rotation axis defined by x, y and z.<br>
 314 <br>
 315 The <span style="font-weight: bold;">glTranslatef</span> command
 316 post-multiplies the current matrix by a translation matrix defined by
 317 the <span style="font-style: italic;">x</span>, <span
 318  style="font-style: italic;">y</span> and <span
 319  style="font-style: italic;">z</span> translation parameters.<br>
 320 <span style="font-weight: bold;"></span><br>
 321 The <span style="font-weight: bold;">glScalef</span> command
 322 post-multiplies the current matrix by a scaling matrix defined by the <span
 323  style="font-style: italic;">x</span>, <span
 324  style="font-style: italic;">y</span> and <span
 325  style="font-style: italic;">z</span> scale factors.<br>
 326 <span style="font-weight: bold;"></span><br>
 327 The <span style="font-weight: bold;">glFrustum</span> command
 328 post-multiplies the current matrix by a perspective projection matrix.
 329 &nbsp;The <span style="font-style: italic;">near</span> and <span
 330  style="font-style: italic;">far</span> values specify the position of
 331 the hither and yon Z-axis clipping planes. &nbsp;The <span
 332  style="font-style: italic;">left, right, bottom</span> and <span
 333  style="font-style: italic;">top</span> parameters are the X and Y
 334 extents at the near clipping plane. &nbsp;<span
 335  style="font-weight: bold;">glFrustum</span> is normally used to modify
 336 the projection matrix.<br>
 337 <br>
 338 The <span style="font-weight: bold;">glOrtho</span> command
 339 post-multiplies the current matrix by an orthographic projection matrix.
 340 &nbsp;The <span style="font-style: italic;">near</span> and <span
 341  style="font-style: italic;">far</span> values specify the position of
 342 the hither and yon Z-axis clipping planes. &nbsp;The <span
 343  style="font-style: italic;">left, right, bottom</span> and <span
 344  style="font-style: italic;">top</span> parameters specify the X and
 345 Y-axis clipping planes. &nbsp;<span style="font-weight: bold;">glOrtho</span>
 346 is normally used to modify the projection matrix.<br>
 347 <br>
 348 The <span style="font-weight: bold;">glViewport</span> command
 349 specifies the mapping of coordinates from normalized device coordinates
 350 to window coordinates. &nbsp;The <span style="font-style: italic;">x</span>
 351 and <span style="font-style: italic;">y</span> parameters specify the
 352 viewport's lower-left corner in the window and the <span
 353  style="font-style: italic;">width</span> and <span
 354  style="font-style: italic;">height</span> parameters specify the size
 355 of the viewport. &nbsp;<span style="font-weight: bold;">glViewport</span>
 356 does not effect the current matrix.<br>
 357 <br>
 358 A coordinate transformed to window coordinates is hereafter known as (x<sub>w</sub>,
 359 y<sub>w</sub>, z<sub>w</sub>).<br>
 360 <br>
 361 <h2>3.2 Clipping</h2>
 362 View-volume clipping automatically discards or trims primitives which
 363 lie completely or partially outside of the view volume specified by <span
 364  style="font-weight: bold;">glFrustum</span> and <span
 365  style="font-weight: bold;">glOrtho</span>. &nbsp;Note that the <span
 366  style="font-weight: bold;">glViewport</span> command does not define a
 367 clipping region.<br>
 368 <br>
 369 Clipping occurs in <span style="font-style: italic;">clip coordinate
 370 space - </span>the coordinates produced after applying the projection
 371 matrix.<br>
 372 <br>
 373 <h2>3.3 Current Raster Position</h2>
 374 The current raster position specifies the location for drawing images
 375 with <span style="font-weight: bold;">glBitmap.</span> &nbsp;The current
 376 raster position is set with the commands:<br>
 377 <br>
 378 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glRasterPos2f</span>(GLfloat<span
 379  style="font-style: italic;">x</span>, GLfloat <span
 380  style="font-style: italic;">y</span>)<br>
 381 void <span style="font-weight: bold;">glRasterPos2fv</span>(const
 382 GLfloat *<span style="font-style: italic;">v</span>)<br>
 383 void <span style="font-weight: bold;">glRasterPos2i</span>(GLint <span
 384  style="font-style: italic;">x</span>, GLint <span
 385  style="font-style: italic;">y</span>)<br>
 386 void <span style="font-weight: bold;">glRasterPos2iv</span>(const
 387 GLint *<span style="font-style: italic;">v</span>)<br>
 388 </div>
 389 <br>
 390 <span style="font-weight: bold;">glRasterPos</span> specifies a
 391 4-component coordinate (x, y, 0, 1). &nbsp;The coordinate is processed
 392 like a vertex; it is transformed by the modelview matrix, the projection
 393 matrix and mapped to the viewport. &nbsp;The resulting window coordinate
 394 is stored as the current raster position. &nbsp;The coordinate is
 395 clipped-tested against the frustum like a vertex. &nbsp;If the
 396 coordinate is clipped, then the current raster position becomes invalid
 397 and subsequent <span style="font-weight: bold;">glBitmap</span> commands
 398 have no effect.<br>
 399 <br>
 400 <span style="font-weight: bold;">glRasterPos</span> also updates the
 401 current raster color and current raster texture coordinates. &nbsp;The
 402 current raster color is updated (copied) from the current color (as
 403 specified by <span style="font-weight: bold;">glColor</span>).
 404 &nbsp;The current raster texture coordinate is updated (copied) from the
 405 current texture coordinate (as specified by <span
 406  style="font-weight: bold;">glTexCoord</span>).<br>
 407 <br>
 408 <h2>3.4 Unsupported Commands</h2>
 409 The following commands related to vertex transformation are not
 410 supported by the subset:<br>
 411 <br>
 412 <div style="margin-left: 40px;">User-defined clip plane commands:<br>
 413 <div style="margin-left: 40px;"><span style="font-weight: bold;">glClipPlane</span><br>
 414 </div>
 415 <span style="font-weight: bold;"></span></div>
 416 <br>
 417 <div style="margin-left: 40px;">Lighting and material commands:</div>
 418 <div style="margin-left: 80px;"><span style="font-weight: bold;">glLightModeli,
 419 glLightModelf,&nbsp;</span><span style="font-weight: bold;">glLightModeliv,
 420 glLightModelfv,</span><span style="font-weight: bold;"> glLightf,
 421 glLighti, glLightfv, glLightiv, glColorMaterial</span><br>
 422 </div>
 423 <br>
 424 <div style="margin-left: 40px;">Automatic texture coordinate generation
 425 commands:<br>
 426 </div>
 427 <div style="margin-left: 40px;">
 428 <div style="margin-left: 40px;"><span style="font-weight: bold;">glTexGend,
 429 glTexGenf, glTexGeni, </span><span style="font-weight: bold;">glTexGendv,
 430 glTexGenfv, glTexGeniv, </span><br>
 431 <br style="font-weight: bold;">
 432 </div>
 433 Double-valued commands:<br>
 434 <div style="margin-left: 40px;"><span style="font-weight: bold;">glLoadMatrixd,
 435 glMultMatrixd, glRotated, glTranslated, glScaled</span><br
 436  style="font-weight: bold;">
 437 </div>
 438 <br>
 439 Depth Range command:<br>
 440 <div style="margin-left: 40px;"><span style="font-weight: bold;">glDepthRange</span>
 441 (the near value is always 0.0 and the far value is always 1.0)<br>
 442 </div>
 443 <br>
 444 Extra RasterPos commands:<br>
 445 <div style="margin-left: 40px;"><span style="font-weight: bold;">glRasterPos2d,
 446 glRasterPos2s, glRasterPos3d, glRasterPos3f, glRasterPos3i,
 447 glRasterPos3s, glRasterPos4d, glRasterPos4f, glRasterPos4i,
 448 glRasterPos4s, glRasterPos2dv, glRasterPos2sv, glRasterPos3dv,
 449 glRasterPos3fv, glRasterPos3iv, glRasterPos3sv, glRasterPos4dv,
 450 glRasterPos4fv, glRasterPos4iv, glRasterPos4sv</span><br>
 451 </div>
 452 <br>
 453 <br>
 454 </div>
 455 <h1>4. Rasterization</h1>
 456 This section describes the commands and options for drawing points,
 457 lines, triangles and bitmaps. &nbsp;<span style="font-style: italic;">Rasterization</span>
 458 is the term for the process which produces fragments from the geometric
 459 description of a primitive (a point, line, polygon or bitmap). &nbsp;For
 460 example, given the two coordinates for the end-points of a line segment,
 461 rasterization determines which pixels in the frame buffer are modified
 462 to <span style="font-style: italic;">draw</span> the line. &nbsp;A
 463 fragment is a tuple which consists of a window coordinate, colors and
 464 texture coordinates. &nbsp;The fragments produced by rasterization are
 465 subsequently processed by the per-fragment operations described later.<br>
 466 <br>
 467 <h2>4.1 Point Rasterization</h2>
 468 Points are rendered with the command sequence <span
 469  style="font-weight: bold;">glBegin</span>(GL_POINTS), <span
 470  style="font-weight: bold;">glVertex</span>, ... <span
 471  style="font-weight: bold;">glEnd</span>. &nbsp;The window coordinate (x<sub>w</sub>,
 472 y<sub>w</sub>, z<sub>w</sub>) is truncated to rasterize the point.
 473 &nbsp;The truncated coordinate with its associated color and texture
 474 coordinate is sent as a single fragment to the per-fragment processing
 475 stages.<br>
 476 <br>
 477 The <span style="font-weight: bold;">glPointSize</span> command is not
 478 supported; only 1-pixel points are supported.<br>
 479 <br>
 480 Point smoothing (antialiasing) is also not supported.<br>
 481 <br>
 482 <h2>4.2 Line Rasterization</h2>
 483 Lines are rendered with the command sequence <span
 484  style="font-weight: bold;">glBegin</span>(<span
 485  style="font-style: italic;">mode</span>), <span
 486  style="font-weight: bold;">glVertex</span>, <span
 487  style="font-weight: bold;">glVertex</span>, ... <span
 488  style="font-weight: bold;">glEnd</span> where <span
 489  style="font-style: italic;">mode</span> is one of GL_LINES,
 490 GL_LINE_STRIP or GL_LINE_LOOP. &nbsp;Lines are rasterized as described
 491 in the OpenGL specification. &nbsp;Note that OpenGL specifies the <span
 492  style="font-style: italic;">half-open</span> convention for drawing
 493 lines: the last fragment in a line segment is omitted so that endpoint
 494 pixels shared by two line segments will only be drawn once instead of
 495 twice.<br>
 496 <br>
 497 <h3>4.2.1 Line Width</h3>
 498 The width of lines can be controlled by<br>
 499 <br>
 500 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glLineWidth</span>(GLfloat<span
 501  style="font-style: italic;">width</span>)<br>
 502 </div>
 503 <br>
 504 where <span style="font-style: italic;">width</span> is the line width
 505 in pixels. &nbsp;The width defaults to 1.0. &nbsp;Attempting to set the
 506 width to a value less than or equal to zero will raise the error
 507 GL_INVALID_VALUE.<br>
 508 <br>
 509 <h3>4.2.2 Line Stipple<br>
 510 </h3>
 511 Lines may be stippled (i.e. dashed) with the command<br>
 512 <br>
 513 <div style="margin-left: 40px;"><span style="font-weight: bold;">glLineStipple</span>(GLint<span
 514  style="font-style: italic;">factor</span>, GLushort <span
 515  style="font-style: italic;">pattern</span>)<br>
 516 </div>
 517 <br>
 518 <span style="font-style: italic;">pattern</span> describes an on/off
 519 pattern for the fragments produced by rasterization and <span
 520  style="font-style: italic;">factor</span> specifies how many subsequent
 521 fragments are kept or culled for each pattern bit. &nbsp;Line stippling
 522 can be enabled or disabled by the commands <span
 523  style="font-weight: bold;">glEnable</span>(GL_LINE_STIPPLE) and <span
 524  style="font-weight: bold;">glDisable</span>(GL_LINE_STIPPLE).<br>
 525 <br>
 526 <h3>4.2.3 Line Antialiasing</h3>
 527 Lines may be antialiased. &nbsp;For antialiased lines, each fragment
 528 produced by rasterization is assigned a <span
 529  style="font-style: italic;">coverage value</span> which describes how
 530 much of the fragment's area is considered to be <span
 531  style="font-style: italic;">inside</span> the line. &nbsp;Later, the
 532 alpha value of each fragment is multiplied by the coverage value.
 533 &nbsp;By blending the fragments into the frame buffer, the edges of
 534 lines appear smoothed.<br>
 535 <br>
 536 Line antialiasing can be enabled or disabled with the commands <span
 537  style="font-weight: bold;">glEnable</span>(GL_LINE_SMOOTH) and <span
 538  style="font-weight: bold;">glDisable</span>(GL_LINE_SMOOTH).<br>
 539 <br>
 540 <h2>4.3 Polygon Rasterization</h2>
 541 Polygons, quadrilaterals and triangles share the same polygon
 542 rasterization options. <br>
 543 <br>
 544 Triangles are rendered by the command sequence <span
 545  style="font-weight: bold;">glBegin</span><span
 546  style="font-style: italic;"><span style="font-style: italic;">(mode</span></span>),<span
 547  style="font-weight: bold;">glVertex</span>, <span
 548  style="font-weight: bold;">glVertex</span>, ... <span
 549  style="font-weight: bold;">glEnd</span> where <span
 550  style="font-style: italic;">mode</span> may be one of GL_TRIANGLES,
 551 GL_TRIANGLE_STRIP or GL_TRIANGLE_FAN.<span style="font-weight: bold;"></span>
 552 &nbsp;For GL_TRIANGLES mode, the number of vertices should be a multiple
 553 of three - extra vertices will be ignored. &nbsp;For GL_TRIANGLE_STRIP
 554 and GL_TRIANGLE_FAN, at least three vertices should be specified.
 555 &nbsp;If less than three are specified, nothing is drawn. &nbsp;<br>
 556 <br>
 557 Quadrilaterals are <span style="font-weight: bold;"></span>rendered by
 558 the command sequence <span style="font-weight: bold;">glBegin</span>(<span
 559  style="font-style: italic;"><span style="font-style: italic;">mode</span></span>),<span
 560  style="font-weight: bold;">glVertex</span>, <span
 561  style="font-weight: bold;">glVertex</span>, ... <span
 562  style="font-weight: bold;">glEnd</span> where <span
 563  style="font-style: italic;">mode</span> may be one of GL_QUADS or
 564 GL_QUAD_STRIP.<span style="font-weight: bold;"></span> &nbsp; For
 565 GL_QUADS, the number of vertices should be a multiple of four - extra
 566 vertices will be ignored. &nbsp;For GL_QUAD_STRIP, the number of
 567 vertices should be even and at least four. &nbsp;Extra vertices (one)
 568 will be ignored.<br>
 569 <br>
 570 Convex polygons are <span style="font-weight: bold;"></span>rendered
 571 by the command sequence <span style="font-weight: bold;">glBegin</span><span
 572  style="font-style: italic;"><span style="font-style: italic;"></span></span>(GL_POLYGON),<span
 573  style="font-weight: bold;">glVertex</span>, <span
 574  style="font-weight: bold;">glVertex</span>, ... <span
 575  style="font-weight: bold;">glEnd</span>.<span
 576  style="font-style: italic;"></span><span style="font-weight: bold;"></span>
 577 &nbsp;If less than three vertices are specified, nothing is drawn.<br>
 578 <br>
 579 <h3>4.3.1 Polygon Orientation</h3>
 580 The <span style="font-style: italic;">winding order</span> of vertices
 581 (clockwise or counter-clockwise) is significant. &nbsp;It is used to
 582 determine the <span style="font-style: italic;">front-facing</span> or <span
 583  style="font-style: italic;">back-facing</span> orientation of polygons.
 584 &nbsp;By default, a front-facing polygon's vertices are in
 585 counter-clockwise order (in window coordinates). &nbsp;Figures 2.4 and
 586 2.5 of the OpenGL 1.2.1 specification illustrate the winding order for
 587 front-facing triangles and quadrilaterals, respectively.<br>
 588 <br>
 589 The command<br>
 590 <br>
 591 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glFrontFace</span>(GLenum<span
 592  style="font-style: italic;"> mode</span>)<br>
 593 </div>
 594 <br>
 595 specifies whether clockwise or counter-clockwise winding indicates a
 596 front-facing polygon. &nbsp;If <span style="font-style: italic;">mode</span>
 597 is GL_CW then polygons with clockwise winding are front-facing. &nbsp;If <span
 598  style="font-style: italic;">mode</span> is GL_CCW then polygons with
 599 counter-clockwise winding are front-facing. &nbsp;The default value is
 600 GL_CCW. &nbsp;If <span style="font-style: italic;">mode</span> is not
 601 GL_CCW or GL_CW then the error GL_INVALID_ENUM will be raised.<span
 602  style="font-style: italic;"></span><span style="font-style: italic;"></span><br>
 603 <br>
 604 <h3>4.3.2 Polygon Culling</h3>
 605 Polygons may be culled (discarded) depending on whether they are
 606 front-facing or back-facing. &nbsp;The command<br>
 607 <br>
 608 <div style="margin-left: 40px;">void<span style="font-weight: bold;">
 609 glCullFace</span>(GLenum <span style="font-style: italic;">mode</span>)<br>
 610 </div>
 611 <br>
 612 specifies whether front-facing, back-facing or all polygons should be
 613 culled. &nbsp;If <span style="font-style: italic;">mode</span> is
 614 GL_FRONT then front-facing polygons will be culled. &nbsp;If <span
 615  style="font-style: italic;">mode</span> is GL_BACK then back-facing
 616 polygons will be culled. Otherwise, if <span style="font-style: italic;">mode</span>
 617 is GL_FRONT_AND_BACK then all polygons will be culled. &nbsp;Any other
 618 value for <span style="font-style: italic;">mode</span> will raise the
 619 error GL_INVALID_ENUM.<br>
 620 <br>
 621 Polygon culling is enabled and disabled with the commands <span
 622  style="font-weight: bold;">glEnable</span>(GL_CULL_FACE) and <span
 623  style="font-weight: bold;">glDisable</span>(GL_CULL_FACE),
 624 respectively.<br>
 625 <br>
 626 <h3>4.3.3 Polygon Antialiasing</h3>
 627 Polygons may be antialiased in order to smooth their edges.
 628 &nbsp;Polygon antialiasing is enabled and disabled with the commands <span
 629  style="font-weight: bold;">glEnable</span>(GL_POLYGON_SMOOTH) and <span
 630  style="font-weight: bold;">glDisable</span>(GL_POLYGON_SMOOTH).<br>
 631 <br>
 632 When polygon antialiasing is enabled each fragment produced by polygon,
 633 triangle and quadrilateral rasterization will be given a <span
 634  style="font-style: italic;">coverage</span> value which indicates how
 635 much of the fragment is covered by the polygon. &nbsp;Fragments
 636 completely inside the polygon have coverage 1.0. &nbsp;Fragments
 637 completely outside the polygon have zero coverage (in theory).
 638 &nbsp;Fragments which intersect the polygon's edge have a coverage value
 639 in the range (0, 1).<br>
 640 <br>
 641 The fragment's alpha value is multiplied by the coverage value.
 642 &nbsp;By enabling the appropriate blending mode, polygon edges will
 643 appear smoothed.<br>
 644 <br>
 645 <h2>4.4 Shading</h2>
 646 The command<br>
 647 <br>
 648 <div style="margin-left: 40px;"> void <span style="font-weight: bold;">glShadeModel</span>(GLenum<span
 649  style="font-style: italic;">mode</span>)<br>
 650 </div>
 651 <br>
 652 determines whether colors are interpolated between vertices during
 653 rasterization. &nbsp;If <span style="font-style: italic;">mode</span> is
 654 GL_FLAT then vertex colors are not interpolated. &nbsp;The color used
 655 for drawing lines, triangles and quadrilaterals is that of the last
 656 vertex used to specify each primitive. &nbsp;For polygons, the color of
 657 the first vertex specifies the color for the entire polygon. &nbsp;If <span
 658  style="font-style: italic;">mode</span> is GL_SMOOTH then vertex colors
 659 are linearly interpolated to produce the fragment colors.<br>
 660 <br>
 661 <h2>4.5 Bitmap Rasterization</h2>
 662 A bitmap is a monochromatic, binary image in which each image element
 663 (or pixel) is represented by one bit. &nbsp;Fragments are only generated
 664 for the bits (pixels) which are set.  &nbsp;Bitmaps are commonly used to
 665 draw text (glyphs) and markers.<br>
 666 <br>
 667 A bitmap is drawn with the command<br>
 668 <br>
 669 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glBitmap</span>(GLsizei<span
 670  style="font-style: italic;">width</span>, GLsizei <span
 671  style="font-style: italic;">height</span>, GLfloat <span
 672  style="font-style: italic;">xOrig</span>, GLfloat <span
 673  style="font-style: italic;">yOrig</span>, GLfloat <span
 674  style="font-style: italic;">xMove</span>, GLfloat <span
 675  style="font-style: italic;">yMove</span>, const &nbsp;GLubyte *<span
 676  style="font-style: italic;">image</span>)<br>
 677 </div>
 678 <br>
 679 <span style="font-style: italic;">width </span>and <span
 680  style="font-style: italic;">height</span> specify the image size in
 681 pixels. &nbsp;<span style="font-style: italic;">xOrig</span> and <span
 682  style="font-style: italic;">yOrig</span> specify the bitmap origin.
 683 &nbsp;<span style="font-style: italic;">xMove</span> and <span
 684  style="font-style: italic;">yMove</span> are added to the current
 685 raster position after the bitmap is rasterized. &nbsp;<span
 686  style="font-style: italic;">image</span> is a pointer to the bitmap
 687 data.<br>
 688 <br>
 689 If the current raster position is not valid, <span
 690  style="font-weight: bold;">glBitmap</span> has no effect.<br>
 691 <br>
 692 <h3>4.5.1 Bitmap Unpacking</h3>
 693 The first step in bitmap rendering is <span style="font-style: italic;">unpacking.
 694 &nbsp;</span>Unpacking is the process of extracting image data from
 695 client memory subject to byte swapping, non-default row strides, etc.
 696 &nbsp;The unpacking parameters are specified with the command<br>
 697 <br>
 698 <div style="margin-left: 40px;">void<span style="font-weight: bold;">
 699 glPixelStorei</span>(GLenum pname, GLint value)<br>
 700 </div>
 701 <span style="font-style: italic;"></span><br>
 702 The following unpacking parameters may be set:<br>
 703 <br>
 704 <table cellpadding="2" cellspacing="2" border="1"
 705  style="text-align: left; width: 90%; margin-left: auto; margin-right: auto;">
 706   <tbody>
 707     <tr>
 708       <td style="vertical-align: top;">Parameter (<span
 709  style="font-style: italic;">pname</span>)<br>
 710       </td>
 711       <td style="vertical-align: top;">Value (<span
 712  style="font-style: italic;">value</span>)<br>
 713       </td>
 714       <td style="vertical-align: top;">Default<br>
 715       </td>
 716     </tr>
 717     <tr>
 718       <td style="vertical-align: top;">GL_UNPACK_ROW_LENGTH<br>
 719       </td>
 720       <td style="vertical-align: top;">Width of the image in memory, in
 721 pixels.<br>
 722       </td>
 723       <td style="vertical-align: top;">0<br>
 724       </td>
 725     </tr>
 726     <tr>
 727       <td style="vertical-align: top;">GL_UNPACK_LSB_FIRST<br>
 728       </td>
 729       <td style="vertical-align: top;">GL_FALSE indicates that the most
 730 significant bit is unpacked first from each byte. &nbsp;GL_TRUE
 731 indicates that the least significant bit is unpacked first from each
 732 byte. <br>
 733       </td>
 734       <td style="vertical-align: top;">GL_FALSE<br>
 735       </td>
 736     </tr>
 737   </tbody>
 738 </table>
 739 <br>
 740 <br>
 741 The GL_UNPACK_ROW_LENGTH specifies the stride (in pixels) for advancing
 742 from one row of the image to the next.&nbsp; If it's zero, the <span
 743  style="font-style: italic;">width</span> parameter to <span
 744  style="font-weight: bold;">glBitmap</span> specifies the width of the
 745 image in memory.<br>
 746 <br>
 747 GL_UNPACK_LSB_FIRST determines whether the least significant or most
 748 significant bit in each byte is unpacked first. &nbsp;Unpacking occurs
 749 in left to right order (in image space).<br>
 750 <br>
 751 The value of bit (i, j) of the image (where i is the image row and j is
 752 the image column) is found as follows:<br>
 753 <br>
 754 <div style="margin-left: 40px;">rowLength = (GL_UNPACK_ROW_LENGTH != 0)
 755 ? GL_UNPACK_ROW_LENGTH : <span style="font-style: italic;">width</span>;<br>
 756 <br>
 757 byte = <span style="font-style: italic;">image</span>[((rowLength + 7)
 758 / 8) * i + j / 8];<br>
 759 <br>
 760 if (GL_UNPACK_LSB_FIRST != 0)<br>
 761 &nbsp;&nbsp;&nbsp; bitMask = 1 &lt;&lt; (j % 8);<br>
 762 else<br>
 763 &nbsp;&nbsp;&nbsp; bitMask = 128 &gt;&gt; (j % 8);<br>
 764 <br>
 765 if (byte &amp; bitMask)<br>
 766 &nbsp;&nbsp;&nbsp; bit = 1;<br>
 767 else<br>
 768 &nbsp;&nbsp;&nbsp; bit = 0;<br>
 769 <br>
 770 </div>
 771 <span style="font-style: italic;"><span style="font-style: italic;"></span></span>
 772 <h3>4.5.2 Rasterization</h3>
 773 If the current raster position is (x<sub>rp</sub>, y<sub>rp</sub>, z<sub>rp</sub>,
 774 w<sub>rp</sub>), then the bitmap is rasterized according to the
 775 following algorithm:<br>
 776 <br>
 777 for (j = 0; j &lt; <span style="font-style: italic;">height</span>;
 778 j++) {<br>
 779 &nbsp;&nbsp;&nbsp; for (i = 0; i &lt; <span style="font-style: italic;">width</span>;
 780 i++) {<br>
 781 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; if (bit(i,j)) {<br>
 782 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; fragment.x =
 783 floor(x<sub>rp</sub> - <span style="font-style: italic;">xOrig</span>)
 784 + i;<br>
 785 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; fragment.y =
 786 floor(y<sub>rp</sub> - <span style="font-style: italic;">yOrig</span>)
 787 + j;<br>
 788 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; fragment.color
 789 = GL_CURRENT_RASTER_COLOR;<br>
 790 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;
 791 fragment.texture = GL_CURRENT_RASTER_TEXTURE_COORDS;<br>
 792 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;
 793 ProcessFragment(fragment)<br>
 794 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;}<br>
 795 &nbsp;&nbsp;&nbsp; }<br>
 796 }<br>
 797 <br>
 798 After the bitmap has been rendered the current raster position is
 799 updated as follows:<br>
 800 <br>
 801 <div style="margin-left: 40px;">x<sub>rp</sub> = x<sub>rp</sub> + <span
 802  style="font-style: italic;">xMove</span><br>
 803 y<sub>rp</sub> = y<sub>rp</sub> + <span style="font-style: italic;">yMove</span><br>
 804 </div>
 805 <br>
 806 <h3>4.5.3 Per-fragment Operations</h3>
 807 XXX supported? &nbsp;See issue in appendix A.<br>
 808 <br>
 809 <h2>4.6 Unsupported Commands</h2>
 810 The following commands related to rasterization are not supported by
 811 the subset.<br>
 812 <br>
 813 <div style="margin-left: 40px;">Point commands:<br>
 814 <div style="margin-left: 40px;"><span style="font-weight: bold;">glPointSize</span><br>
 815 </div>
 816 <br>
 817 Polygon commands:<br>
 818 <div style="margin-left: 40px; font-weight: bold;">glPolygonStipple<br>
 819 glPolygonOffset<br>
 820 glPolygonMode<br>
 821 <br>
 822 </div>
 823 </div>
 824 <div style="margin-left: 40px;">Pixel storage commands:<br>
 825 </div>
 826 <div style="font-weight: bold; margin-left: 80px;">glPixelStoref<br>
 827 </div>
 828 <br>
 829 <br>
 830 <h1>5. Texture Mapping<br>
 831 </h1>
 832 There are four elements to texture mapping: texture coordinate
 833 specification, texture image specification, texture sampling and texture
 834 application.<br>
 835 <br>
 836 Texture mapping is enabled and disabled with the commands <span
 837  style="font-weight: bold;">glEnable</span>(GL_TEXTURE_2D) and <span
 838  style="font-weight: bold;">glDisable</span>(GL_TEXTURE_2D).<br>
 839 <br>
 840 <h2>5.1 Texture Image Specification</h2>
 841 A texture image is specified with the command:<br>
 842 <br>
 843 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glTexImage2D</span>(GLenum<span
 844  style="font-style: italic;"> target</span>, GLint <span
 845  style="font-style: italic;">level</span>, GLint <span
 846  style="font-style: italic;">internalFormat,</span> GLsizei <span
 847  style="font-style: italic;">width,</span> GLsizei <span
 848  style="font-style: italic;">height,</span> GLint <span
 849  style="font-style: italic;">border,</span> GLenum <span
 850  style="font-style: italic;">format,</span> GLenum <span
 851  style="font-style: italic;">type,</span> const GLvoid *<span
 852  style="font-style: italic;">pixels</span> )<br>
 853 </div>
 854 <br>
 855 <span style="font-style: italic;">target</span> must be GL_TEXTURE_2D.
 856 &nbsp;<span style="font-style: italic;">level </span>indicates the
 857 mipmap level for mipmap textures. &nbsp;<span style="font-style: italic;">internalFormat</span>
 858 is a hint to indicate the preferred internal storage format for the
 859 texture. &nbsp;<span style="font-style: italic;">width</span> and <span
 860  style="font-style: italic;">height </span>indicate the image size in
 861 pixels (or texels). &nbsp;<span style="font-style: italic;">border </span>must
 862 be zero. &nbsp;<span style="font-style: italic;">format</span> and <span
 863  style="font-style: italic;">type</span> describe the pixel format and
 864 data type for the incoming image. &nbsp;<span style="font-style: italic;">pixels</span>
 865 points to the incoming texture image. &nbsp;These parameters are
 866 described in more detail below.<br>
 867 <br>
 868 <h3>5.1.1 Texture Image Size and Mipmaps</h3>
 869 <h3><span style="font-style: italic;"></span></h3>
 870 Texture images must have dimensions (width and height) that are powers
 871 of two. For example: 256 x 256, 32 x 1024, 1 x 8, etc. &nbsp;That is, it
 872 must be the case that <span style="font-style: italic;">width </span>=
 873 2<sup>n</sup> and <span style="font-style: italic;">height</span> = 2<sup>m</sup>
 874 for some positive integers n and m.<br>
 875 <br>
 876 Mipmapping is a method of antialiasing or filtering textures to improve
 877 their appearance. &nbsp;A mipmap is a set of images consisting of a base
 878 image and a set of filtered, reduced-resolution images. &nbsp;If the
 879 base image (<span style="font-style: italic;">level</span>=0) is of
 880 width 2<sup>n</sup> and height 2<sup>m</sup> then the level 1 image must
 881 be of width 2<sup>n-1</sup> and height 2<sup>m-1</sup>. &nbsp;Each mipmap
 882 level is half the width and height of the previous level, or at least
 883 one. &nbsp;The last mipmap level has a width and height of one.<br>
 884 <br>
 885 The following is an example of a mipmap's image levels:<br>
 886 <br>
 887 <table cellpadding="2" cellspacing="2" border="1"
 888  style="text-align: left; width: 50%; margin-left: auto; margin-right: auto;">
 889   <tbody>
 890     <tr>
 891       <td style="vertical-align: top;">mipmap level<br>
 892       </td>
 893       <td style="vertical-align: top;">width<br>
 894       </td>
 895       <td style="vertical-align: top;">height<br>
 896       </td>
 897     </tr>
 898     <tr>
 899       <td style="vertical-align: top;">0<br>
 900       </td>
 901       <td style="vertical-align: top;">256<br>
 902       </td>
 903       <td style="vertical-align: top;">64<br>
 904       </td>
 905     </tr>
 906     <tr>
 907       <td style="vertical-align: top;">1<br>
 908       </td>
 909       <td style="vertical-align: top;">128<br>
 910       </td>
 911       <td style="vertical-align: top;">32<br>
 912       </td>
 913     </tr>
 914     <tr>
 915       <td style="vertical-align: top;">2<br>
 916       </td>
 917       <td style="vertical-align: top;">64<br>
 918       </td>
 919       <td style="vertical-align: top;">16<br>
 920       </td>
 921     </tr>
 922     <tr>
 923       <td style="vertical-align: top;">3<br>
 924       </td>
 925       <td style="vertical-align: top;">32<br>
 926       </td>
 927       <td style="vertical-align: top;">8<br>
 928       </td>
 929     </tr>
 930     <tr>
 931       <td style="vertical-align: top;">4<br>
 932       </td>
 933       <td style="vertical-align: top;">16<br>
 934       </td>
 935       <td style="vertical-align: top;">4<br>
 936       </td>
 937     </tr>
 938     <tr>
 939       <td style="vertical-align: top;">5<br>
 940       </td>
 941       <td style="vertical-align: top;">8<br>
 942       </td>
 943       <td style="vertical-align: top;">2<br>
 944       </td>
 945     </tr>
 946     <tr>
 947       <td style="vertical-align: top;">6<br>
 948       </td>
 949       <td style="vertical-align: top;">4<br>
 950       </td>
 951       <td style="vertical-align: top;">1<br>
 952       </td>
 953     </tr>
 954     <tr>
 955       <td style="vertical-align: top;">7<br>
 956       </td>
 957       <td style="vertical-align: top;">2<br>
 958       </td>
 959       <td style="vertical-align: top;">1<br>
 960       </td>
 961     </tr>
 962     <tr>
 963       <td style="vertical-align: top;">8<br>
 964       </td>
 965       <td style="vertical-align: top;">1<br>
 966       </td>
 967       <td style="vertical-align: top;">1<br>
 968       </td>
 969     </tr>
 970   </tbody>
 971 </table>
 972 <br>
 973 If the <span style="font-style: italic;">width</span> or <span
 974  style="font-style: italic;">height</span> parameters are not powers of
 975 two, the error GL_INVALID_VALUE is raised. &nbsp;If the image levels in
 976 a mipmap do not satisfy the restrictions listed above the texture is
 977 considered to be <span style="font-style: italic;">inconsistent</span>
 978 and the system will behave as if the texturing is disabled.<br>
 979 <br>
 980 <h3>5.1.2 Texture Image Formats and Unpacking</h3>
 981 The <span style="font-weight: bold;">glTexImage2D</span> command's <span
 982  style="font-style: italic;"><span style="font-weight: bold;"></span></span><span
 983  style="font-style: italic;">format</span> and <span
 984  style="font-style: italic;">type</span> parameters describe the format
 985 of the incoming texture image.&nbsp; Accepted values for <span
 986  style="font-style: italic;">format</span> are GL_INTENSITY, GL_RGB and
 987 GL_RGBA. &nbsp;The <span style="font-style: italic;">type</span>
 988 parameter must be GL_UNSIGNED_BYTE. &nbsp;Pixel component values are
 989 thus in the range 0 through 255.<br>
 990 <br>
 991 If <span style="font-style: italic;">format</span> is GL_INTENSITY then
 992 the image has one byte per pixel which specifies the pixel's red, green,
 993 blue and alpha values.<span style="font-style: italic;"></span><br>
 994 <br>
 995 If <span style="font-style: italic;">format</span> is GL_RGB then the
 996 image has three bytes per pixel which specify the pixel's red, green and
 997 blue values (in that order). &nbsp;The alpha value defaults to 255.<br>
 998 <br>
 999 If <span style="font-style: italic;">format</span> is GL_RGBA then the
1000 image has four bytes per pixel which specify the pixel's red, green,
1001 blue and alpha values (in that order).<br>
1002 <br>
1003 The command<br>
1004 <br>
1005 <div style="margin-left: 40px;">void<span style="font-weight: bold;">
1006 glPixelStorei</span>(GLenum <span style="font-style: italic;">pname</span>,
1007 GLint <span style="font-style: italic;">value</span>)<br>
1008 </div>
1009 <br>
1010 controls the unpacking of texture image data from client memory. &nbsp;<span
1011  style="font-style: italic;">pname</span> may be GL_UNPACK_ROW_LENGTH to
1012 indicate the stride, in pixels, between subsequent rows of the image in
1013 client memory. &nbsp;If GL_UNPACK_ROW_LENGTH is zero (the default) then
1014 the <span style="font-style: italic;">width</span> parameter to <span
1015  style="font-weight: bold;">glTexImage2D </span>determines the stride.<span
1016  style="font-style: italic;"></span><br>
1017 <br>
1018 <h3>5.1.3 Internal Texture Format</h3>
1019 <span style="font-weight: bold;">glTexImage2D<span
1020  style="font-style: italic;"> </span></span>converts the incoming
1021 texture image to one of the supported internal texture formats.<br>
1022 <br>
1023 The <span style="font-style: italic;">internalFormat</span> parameter
1024 indicates the desired internal format for the texture and may be either
1025 GL_INTENSITY8, GL_RGB5 or GL_RGBA8.<br>
1026 <br>
1027 If <span style="font-style: italic;">internalFormat</span> is
1028 GL_INTENSITY8 then the texture has one byte per texel (texture element)
1029 which indicates the texel's intensity (or brightness). &nbsp;The
1030 intensity is obtained from the incoming image's red channel.<br>
1031 <br>
1032 If <span style="font-style: italic;">internalFormat</span> is GL_RGB5
1033 then the texture is stored with two bytes per texel: &nbsp;5 bits per
1034 red value, 5 bits per green value and 5 bits per blue value.<br>
1035 <br>
1036 If <span style="font-style: italic;">internalFormat </span>is
1037 GL_RGBA8 then the texture is stored with four bytes per texel: &nbsp;8
1038 bits for each of the red, green, &nbsp;blue and alpha values.<br>
1039 <br>
1040 The internal format is also significant to texture application (see
1041 section 5.4).<br>
1042 <br>
1043 <h2>5.2 Texture Coordinates</h2>
1044 Texture coordinates control the mapping from local polygon space to
1045 texture image space. &nbsp;Texture coordinates are set for each vertex
1046 with the <span style="font-weight: bold;">glTexCoord</span> commands.
1047 &nbsp;During line and polygon rasterization the vertex's texture
1048 coordinates are interpolated across the primitive to produce a texture
1049 coordinate for each fragment. &nbsp;The fragment texture coordinates are
1050 used to sample the current texture image.<br>
1051 <br>
1052 Texture coordinates are normally in the range [0, 1]. &nbsp;Values
1053 outside that range are processed according to the <span
1054  style="font-style: italic;">texture wrap mode</span>. &nbsp;The
1055 texture wrap mode is set with the command<br>
1056 <br>
1057 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glTexParameteri</span>(GLenum<span
1058  style="font-style: italic;"> target</span>, GLenum <span
1059  style="font-style: italic;">pname</span>, GLint <span
1060  style="font-style: italic;">value</span>)<br>
1061 <br>
1062 </div>
1063 <span style="font-style: italic;">target</span> must be GL_TEXTURE_2D.
1064 &nbsp;If <span style="font-style: italic;">pname</span> is
1065 GL_TEXTURE_WRAP_S or GL_TEXTURE_WRAP_T then <span
1066  style="font-style: italic;">value</span> must be either
1067 GL_CLAMP_TO_EDGE or GL_REPEAT.<br>
1068 <br>
1069 For GL_CLAMP_TO_EDGE, texture coordinates are effectively clamped to
1070 the interval [0, 1].<br>
1071 <br>
1072 For GL_REPEAT, the integer part of texture coordinates is ignored; only
1073 the fractional part of the texture coordinates is used. &nbsp;This
1074 allows texture images to repeated or tiled across an object.<br>
1075 <br>
1076 <h2>5.3 Texture Sampling</h2>
1077 Texture sampling is the process of using texture coordinates to extract
1078 a color from the texture image. &nbsp;Multiple, weighted samples may be
1079 taken from the texture and combined during the filtering step.<br>
1080 <br>
1081 During texture coordinate interpolation a <span
1082  style="font-style: italic;">level of detail</span> value (lambda) is
1083 computed for each fragment. &nbsp;For a mipmapped texture, lambda
1084 determines which level (or levels) of the mipmap will be sampled to
1085 obtain the texture color.<br>
1086 <br>
1087 If lambda indicates that multiple texels map to a single screen pixel,
1088 then the texture <span style="font-style: italic;">minification</span>
1089 filter will be used. &nbsp;Otherwise, if lambda indicates that a single
1090 texel maps to multiple screen pixels, then the texture <span
1091  style="font-style: italic;">magnification</span> filter will be used.<br>
1092 <span style="font-weight: bold;"></span><span
1093  style="font-style: italic;"></span><br>
1094 <h3>5.3.1 Texture Minification</h3>
1095 The texture minification filter is set with the <span
1096  style="font-weight: bold;">glTexParameteri </span><span
1097  style="font-style: italic;"></span><span style="font-weight: bold;"></span><span
1098  style="font-style: italic;"></span> command by setting <span
1099  style="font-style: italic;">target</span> to GL_TEXTURE_2D, setting <span
1100  style="font-style: italic;">pname</span> to GL_TEXTURE_MIN_FILTER and
1101 setting <span style="font-style: italic;">value</span> to GL_NEAREST,
1102 GL_LINEAR, GL_NEAREST_MIPMAP_NEAREST,&nbsp;
1103 GL_NEAREST_MIPMAP_LINEAR,&nbsp; &nbsp;GL_LINEAR_MIPMAP_NEAREST or
1104 GL_LINEAR_MIPMAP_LINEAR.<br>
1105 <br>
1106 GL_NEAREST samples the texel nearest the texture coordinate in the
1107 level 0 texture image.<br>
1108 <br>
1109 GL_LINEAR samples the four texels around the texture coordinate in the
1110 level 0 texture image. &nbsp;The four texels are linearly weighted to
1111 compute the final texel value.<br>
1112 <br>
1113 GL_NEAREST_MIPMAP_NEAREST samples the texel nearest the texture
1114 coordinate in the level N texture image. &nbsp;N is the level of detail
1115 and is computed by the partial derivatives of the texture coordinates
1116 with respect to the window coordinates.<br>
1117 <br>
1118 GL_NEAREST_MIPMAP_LINEAR samples two texels nearest the texture
1119 coordinates in the level N and N+1 texture images. &nbsp;The two texels
1120 are linearly weighted to compute the final texel value. &nbsp;N is the
1121 level of detail and is computed by the partial derivatives of the
1122 texture coordinates with respect to the window coordinates.<br>
1123 <br>
1124 GL_LINEAR_MIPMAP_NEAREST samples four texels around the texture
1125 coordinate in the level N texture image. &nbsp;The four texels are
1126 linearly weighted to compute the final texel value. &nbsp;N is the level
1127 of detail and is computed by the partial derivatives of the texture
1128 coordinates with respect to the window coordinates.<br>
1129 <br>
1130 GL_LINEAR_MIPMAP_LINEAR samples four texels around the texture
1131 coordinate in the level N texture image and four texels around the
1132 texture coordinate in the level N+1 texture image. &nbsp;The eight
1133 texels are linearly weighted to compute the final texel value. &nbsp;N
1134 is the level of detail and is computed by the partial derivatives of the
1135 texture coordinates with respect to the window coordinates.<br>
1136 <br>
1137 Filter modes other than GL_LINEAR and GL_NEAREST requires that the
1138 texture have a complete set of mipmaps. &nbsp;If the mipmap is
1139 incomplete, it is as if texturing is disabled.<br>
1140 &nbsp;<br>
1141 <h3>5.3.2 Texture Magnification</h3>
1142 The texture magnification filter is set with the <span
1143  style="font-weight: bold;">glTexParameteri </span><span
1144  style="font-style: italic;"></span><span style="font-weight: bold;"></span>command
1145 by setting <span style="font-style: italic;">target</span> to
1146 GL_TEXTURE_2D, setting <span style="font-style: italic;">pname</span> to
1147 GL_TEXTURE_MAG_FILTER and setting <span style="font-style: italic;">value</span>
1148 to GL_NEAREST or GL_LINEAR.<br>
1149 <br>
1150 GL_NEAREST samples the texel nearest the texture coordinate in the
1151 level 0 texture image.<br>
1152 <br>
1153 GL_LINEAR samples the four texels around the texture coordinate in the
1154 level 0 texture image. &nbsp;The four texels are linearly weighted to
1155 compute the final texel value.<br>
1156 <br>
1157 <h2>5.4 Texture Application</h2>
1158 The sampled texture value is combined with the incoming fragment color
1159 to produce a new fragment color. &nbsp;The fragment and texture colors
1160 are combined according to the texture environment mode and the current
1161 texture's base internal format. &nbsp;The texture environment mode is
1162 set with the command<br>
1163 <br>
1164 <div style="margin-left: 40px;">void<span style="font-weight: bold;">
1165 glTexEnvi</span>(GLenum <span style="font-style: italic;">target</span>,
1166 GLenum <span style="font-style: italic;">pname</span>, GLint <span
1167  style="font-style: italic;">value</span>)<br>
1168 </div>
1169 <br>
1170 <span style="font-style: italic;">target</span> must be GL_TEXTURE_ENV.
1171 &nbsp;If <span style="font-style: italic;">pname</span> is
1172 GL_TEXTURE_ENV_MODE then <span style="font-style: italic;">value</span>
1173 must be one of GL_REPLACE, GL_MODULATE, GL_DECAL, or GL_BLEND.<br>
1174 <br>
1175 There is also a <span style="font-style: italic;">texture environment
1176 color</span> that can factor into texture application. &nbsp;The texture
1177 environment color can be set with the command<br>
1178 <br>
1179 <div style="margin-left: 40px;">void<span style="font-weight: bold;">
1180 glTexEnvfv</span>(GLenum <span style="font-style: italic;">target</span>,
1181 GLenum <span style="font-style: italic;">pname</span>, const GLfloat *<span
1182  style="font-style: italic;">value</span>)<br>
1183 </div>
1184 <span style="font-style: italic;"></span><br>
1185 <span style="font-style: italic;">target</span> must be GL_TEXTURE_ENV.
1186 &nbsp;If <span style="font-style: italic;">pname</span> is
1187 GL_TEXTURE_ENV_COLOR then <span style="font-style: italic;">value </span>must
1188 point to an array of four values which specify the red, green, blue,
1189 and alpha values of the texture environment color. &nbsp;The values are
1190 clamped to the range [0, 1]. &nbsp;The default color is (0, 0, 0, 0).<br>
1191 <span style="font-style: italic;"></span><br>
1192 The following table describes the arithmetic used for each combination
1193 of environment mode and base internal format. &nbsp;(Rf, Gf, Bf, Af) is
1194 the incoming fragment color. &nbsp;(Rt, Gt, Bt, At) is the sampled
1195 texture color. &nbsp;Lt is the sampled texture luminance. &nbsp;<span
1196  style="font-style: italic;"></span>'It' is the sampled texture
1197 intensity. &nbsp;(Rc, Gc, Bc, Ac) is the texture environment color.
1198 &nbsp;(Rv, Gv, Bv, Av) is the resulting value.<br>
1199 <br>
1200 <br>
1201 <table cellpadding="2" cellspacing="2" border="1"
1202  style="text-align: left; width: 90%; margin-left: auto; margin-right: auto;">
1203   <tbody>
1204     <tr>
1205       <td style="vertical-align: top;">Base Internal Format<br>
1206       </td>
1207       <td style="vertical-align: top;">GL_REPLACE<br>
1208       </td>
1209       <td style="vertical-align: top;">GL_MODULATE<br>
1210       </td>
1211       <td style="vertical-align: top;">GL_DECAL<br>
1212       </td>
1213       <td style="vertical-align: top;">GL_BLEND<br>
1214       </td>
1215     </tr>
1216     <tr>
1217       <td style="vertical-align: top;">GL_INTENSITY<br>
1218       </td>
1219       <td style="vertical-align: top;">Rv = It<br>
1220 Gv = It<br>
1221 Bv = It<br>
1222 Bf = It<br>
1223       </td>
1224       <td style="vertical-align: top;">Rv = Rf * It<br>
1225 Gv = Gf * It<br>
1226 Bv = Bf * It<br>
1227 Av = Af * It</td>
1228       <td style="vertical-align: top;">undefined<br>
1229       </td>
1230       <td style="vertical-align: top;">Rv = Rf*(1-It) + Rc*It<br>
1231 Gv = Gf*(1-It) + Gc*It<br>
1232 Bv = Bf*(1-It) + Bc*It<br>
1233 Av = Af*(1-It) + Ac*It</td>
1234     </tr>
1235     <tr>
1236       <td style="vertical-align: top;">GL_RGB<br>
1237       </td>
1238       <td style="vertical-align: top;">Rv = Rt<br>
1239 Gv = Gt<br>
1240 Bv = Bt<br>
1241 Av = Af<br>
1242       </td>
1243       <td style="vertical-align: top;">Rv = Rf * Rt<br>
1244 Gv = Gf * Gt<br>
1245 Bv = Bf * Bt<br>
1246 Av = Af<br>
1247       </td>
1248       <td style="vertical-align: top;">Rv = Rt<br>
1249 Gv = Gt<br>
1250 Bv = Bt<br>
1251 Av = Af</td>
1252       <td style="vertical-align: top;">Rv = Rf*(1-Rt) + Rc*Rt<br>
1253 Gv = Gf*(1-Gt) + Gc*Gt<br>
1254 Bv = Bf*(1-Bt) + Bc*Bt<br>
1255 Av = Af</td>
1256     </tr>
1257     <tr>
1258       <td style="vertical-align: top;">GL_RGBA<br>
1259       </td>
1260       <td style="vertical-align: top;">Rv = Rt<br>
1261 Gv = Gt<br>
1262 Bv = Bt<br>
1263 Av = At<br>
1264       </td>
1265       <td style="vertical-align: top;">Rv = Rf * Rt<br>
1266 Gv = Gf * Gt<br>
1267 Bv = Bf * Bt<br>
1268 Av = Af * At</td>
1269       <td style="vertical-align: top;">Rv = Rf*(1-At) + Rt*At<br>
1270 Gv = Gf*(1-At) + Gt*At<br>
1271 Bv = Bf*(1-At) + Bt*At<br>
1272 Av = Af<br>
1273       </td>
1274       <td style="vertical-align: top;">Rv = Rf*(1-Rt) + Rc*Rt<br>
1275 Gv = Gf*(1-Gt) + Gc*Gt<br>
1276 Bv = Bf*(1-Bt) + Bc*Bt<br>
1277 Av = Af*At</td>
1278     </tr>
1279   </tbody>
1280 </table>
1281 <br>
1282 <br>
1283 <br>
1284 <h2>5.5 Texture Objects</h2>
1285 Texture objects encapsulate a set of texture images (mipmap) and
1286 related state into a named object. &nbsp;This facilitates use of
1287 multiple textures in an application. &nbsp;Texture objects are named
1288 with GLuints (unsigned integers). &nbsp;There is a default texture
1289 object with the name/identifier zero which can never be deleted.<br>
1290 <br>
1291 <h3>5.5.1 Creating Texture Objects</h3>
1292 A texture object is created by binding a new GLuint identifier to the
1293 GL_TEXTURE_2D target with the command:<br>
1294 <br>
1295 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glBindTexture</span>(GLenum<span
1296  style="font-style: italic;"> target</span>, GLuint <span
1297  style="font-style: italic;">textureID</span>)<br>
1298 </div>
1299 <br>
1300 <span style="font-style: italic;">target</span> must be GL_TEXTURE_2D.
1301 &nbsp;<span style="font-style: italic;">textureID</span> may be any
1302 unsigned integer. &nbsp;If <span style="font-style: italic;">textureID</span>
1303 does not name an existing texture object, a new texture object with that
1304 ID will be created, initialized to the default state. &nbsp;Whether the
1305 ID is new or existed previously, that named texture object is bound as
1306 the <span style="font-style: italic;">current texture object</span>.
1307 &nbsp;Subsequent <span style="font-weight: bold;">glTexParameter </span>and<span
1308  style="font-weight: bold;">glTexImage2D<span
1309  style="font-style: italic;"> </span></span>calls will effect the
1310 current texture object.<br>
1311 <span style="font-style: italic;"></span><span
1312  style="font-weight: bold;"><span style="font-style: italic;"> </span></span><br>
1313 <h3>5.5.2 Deleting Texture Objects</h3>
1314 One or more texture objects may be deleted with the command:<br>
1315 <br>
1316 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glDeleteTextures</span>(GLsizei<span
1317  style="font-style: italic;">n</span>, const GLuint *<span
1318  style="font-style: italic;">textureIDs</span>)<br>
1319 </div>
1320 <br>
1321 <span style="font-style: italic;">textureIDs</span> is an array of <span
1322  style="font-style: italic;">n</span> texture IDs. &nbsp;The named
1323 texture objects will be deleted. &nbsp;If the current texture object is
1324 deleted the default texture object (number 0) will be bound as the
1325 current texture object.<br>
1326 <br>
1327 <h3>5.5.3 Allocating Texture Object Identifiers</h3>
1328 A list of new, unused texture IDs can be obtained by calling the command<br>
1329 <br>
1330 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glGenTextures</span>(GLsizei<span
1331  style="font-style: italic;"> n</span>, GLuint *<span
1332  style="font-style: italic;">textureIDs</span>)<br>
1333 </div>
1334 <br>
1335 An array of <span style="font-style: italic;">n</span> unused texture
1336 IDs will be returned in the <span style="font-style: italic;">textureIDs</span>
1337 array.<br>
1338 <br>
1339 <br>
1340 <h1>6. Per-fragment Operations</h1>
1341 The fragments produced by rasterization are subjected to a number of
1342 operations which either modify the fragment or test the fragment
1343 (discarding the fragment if the test fails.) &nbsp;This chapter
1344 describes the per-fragment operations. &nbsp;They are presented in the
1345 order in which they're performed. &nbsp;If a fragment fails a test it is
1346 discarded and not subjected to subsequent tests or modifications.<br>
1347 <br>
1348 <h2>6.1 Scissor Test</h2>
1349 The scissor test limits rendering to a 2-D rectangular region of the
1350 framebuffer. &nbsp;The command<br>
1351 <br>
1352 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glScissor</span>(GLint<span
1353  style="font-style: italic;">x</span>, GLint <span
1354  style="font-style: italic;">y</span>, GLsizei <span
1355  style="font-style: italic;">width</span>, GLsizei<span
1356  style="font-style: italic;"> height</span>)<br>
1357 </div>
1358 <br>
1359 defines a clipping region with the lower-left corner at (<span
1360  style="font-style: italic;">x, y</span>) and the given <span
1361  style="font-style: italic;">width</span> and <span
1362  style="font-style: italic;">height</span>. &nbsp;The scissor test is
1363 enabled and disabled with the command <span style="font-weight: bold;">glEnable</span>(GL_SCISSOR_TEST)
1364 and <span style="font-weight: bold;">glDisable</span>(GL_SCISSOR_TEST).<br>
1365 <br>
1366 If the incoming fragment's position is (x<sub>f</sub>, y<sub>f</sub>)
1367 then the fragment will pass the test if <span
1368  style="font-style: italic;">x</span> &lt;= x<sub>f</sub> &lt; <span
1369  style="font-style: italic;">x</span> + <span
1370  style="font-style: italic;">width</span> and <span
1371  style="font-style: italic;">y</span> &lt;= y<sub>f</sub> &lt; <span
1372  style="font-style: italic;">y</span> + <span
1373  style="font-style: italic;">height. &nbsp;</span>Otherwise, the
1374 fragment is discarded.<br>
1375 <br>
1376 If <span style="font-style: italic;">width</span> or <span
1377  style="font-style: italic;">height</span> is less than zero the error
1378 GL_INVALID_VALUE is raised. &nbsp;The default scissor rectangle bounds
1379 are (0, 0, w, h) where w is the initial window width and h is the
1380 initial window height. &nbsp;The scissor test is disabled by default.<br>
1381 <br>
1382 <h2>6.2 Alpha Test</h2>
1383 The alpha test compares the fragment's alpha value against a reference
1384 value and discards the fragment if the comparison fails. &nbsp;The test
1385 is specified by the command<br>
1386 <br>
1387 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glAlphaFunc</span>(GLenum<span
1388  style="font-style: italic;">mode</span>, GLclampf <span
1389  style="font-style: italic;">reference</span>)<br>
1390 </div>
1391 <br>
1392 <span style="font-style: italic;">mode</span> specifies an inequality
1393 and <span style="font-style: italic;">reference</span> specifies a value
1394 to compare against. &nbsp;The following table lists all possible
1395 modes&nbsp;<span style="font-style: italic;"></span>and the
1396 corresponding test:<br>
1397 <br>
1398 <table cellpadding="2" cellspacing="2" border="1"
1399  style="text-align: left; width: 50%; margin-left: auto; margin-right: auto;">
1400   <tbody>
1401     <tr>
1402       <td style="vertical-align: top;">Comparison mode<br>
1403       </td>
1404       <td style="vertical-align: top;">The test passes if<br>
1405       </td>
1406     </tr>
1407     <tr>
1408       <td style="vertical-align: top;">GL_LESS<br>
1409       </td>
1410       <td style="vertical-align: top;">alpha &lt; <span
1411  style="font-style: italic;">reference</span><br>
1412       </td>
1413     </tr>
1414     <tr>
1415       <td style="vertical-align: top;">GL_LEQUAL<br>
1416       </td>
1417       <td style="vertical-align: top;">alpha &lt;= <span
1418  style="font-style: italic;">reference</span></td>
1419     </tr>
1420     <tr>
1421       <td style="vertical-align: top;">GL_GREATER<br>
1422       </td>
1423       <td style="vertical-align: top;">alpha &gt; <span
1424  style="font-style: italic;">reference</span></td>
1425     </tr>
1426     <tr>
1427       <td style="vertical-align: top;">GL_GEQUAL<br>
1428       </td>
1429       <td style="vertical-align: top;">alpha &gt;= <span
1430  style="font-style: italic;">reference</span></td>
1431     </tr>
1432     <tr>
1433       <td style="vertical-align: top;">GL_EQUAL<br>
1434       </td>
1435       <td style="vertical-align: top;">alpha == <span
1436  style="font-style: italic;">reference</span></td>
1437     </tr>
1438     <tr>
1439       <td style="vertical-align: top;">GL_NOTEQUAL<br>
1440       </td>
1441       <td style="vertical-align: top;">alpha != <span
1442  style="font-style: italic;">reference</span></td>
1443     </tr>
1444     <tr>
1445       <td style="vertical-align: top;">GL_NEVER<br>
1446       </td>
1447       <td style="vertical-align: top;">never pass<br>
1448       </td>
1449     </tr>
1450     <tr>
1451       <td style="vertical-align: top;">GL_ALWAYS<br>
1452       </td>
1453       <td style="vertical-align: top;">always passes<br>
1454       </td>
1455     </tr>
1456   </tbody>
1457 </table>
1458 <br>
1459 The <span style="font-style: italic;">reference</span> parameter is
1460 clamped to the range [0, 1].<br>
1461 <br>
1462 The alpha test is enabled and disabled with the commands <span
1463  style="font-weight: bold;">glEnable</span>(GL_ALPHA_TEST) and <span
1464  style="font-weight: bold;">glDisable</span>(GL_ALPHA_TEST).<br>
1465 <br>
1466 The default mode is GL_ALWAYS and the default reference value is 0.<br>
1467 <br>
1468 <h2>6.3 Stencil Test</h2>
1469 The stencil buffer stores an N-bit integer value for each pixel in the
1470 frame buffer. &nbsp;The stencil test compares the stencil buffer value
1471 at the fragment's position to a reference value and possibly discards
1472 the fragment based on the outcome. &nbsp;Furthermore, the stencil buffer
1473 value may be updated or modified depending on the outcome. &nbsp;If
1474 there is no stencil buffer the stencil test is bypassed.<br>
1475 <br>
1476 Stenciling is controlled by the commands<br>
1477 <br>
1478 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glStencilFunc</span>(GLenum<span
1479  style="font-style: italic;">func</span>, GLint <span
1480  style="font-style: italic;">ref</span>, GLuint <span
1481  style="font-style: italic;">mask</span>)<br>
1482 void <span style="font-weight: bold;">glStencilOp</span>(GLenum <span
1483  style="font-style: italic;">stencilFail</span>, GLenum <span
1484  style="font-style: italic;">depthTestFail</span>, GLenum <span
1485  style="font-style: italic;">depthTestPass</span>)<br>
1486 </div>
1487 <br>
1488 The <span style="font-weight: bold;">glStencilFunc<span
1489  style="font-style: italic;"> </span></span>command controls the
1490 stencil test while <span style="font-weight: bold;">glStencilOp</span>
1491 command controls the how the stencil buffer is updated/modified after
1492 the test.<br>
1493 <br>
1494 <span style="font-style: italic;">ref</span> is clamped to the range [0,
1495 2<sup>N</sup>-1] where N is the number of bits per stencil value in the
1496 stencil buffer.<span style="font-style: italic;"></span><br>
1497 <br>
1498 The following table lists all possible values for the <span
1499  style="font-style: italic;">func</span> parameter and when the stencil
1500 test will pass. &nbsp;Both the stencil buffer value and the stencil
1501 reference value are bit-wise ANDed with the <span
1502  style="font-style: italic;">mask</span> parameter before the test.<br>
1503 <br>
1504 <span style="font-style: italic;"></span><span
1505  style="font-style: italic;"></span><span style="font-style: italic;"></span>
1506 <table
1507  style="text-align: left; margin-left: auto; margin-right: auto; width: 70%;"
1508  border="1" cellspacing="2" cellpadding="2">
1509   <tbody>
1510     <tr>
1511       <td style="vertical-align: top;">Stencil <span
1512  style="font-style: italic;">func</span> value<br>
1513       </td>
1514       <td style="vertical-align: top;">Stencil test passes if<br>
1515       </td>
1516     </tr>
1517     <tr>
1518       <td style="vertical-align: top;">GL_LESS<br>
1519       </td>
1520       <td style="vertical-align: top;"><span style="font-style: italic;">(ref</span>&amp;<span
1521  style="font-style: italic;">mask)</span> &lt; (stencil buffer value
1522 &amp; <span style="font-style: italic;">mask)</span><br>
1523       </td>
1524     </tr>
1525     <tr>
1526       <td style="vertical-align: top;">GL_LEQUAL<br>
1527       </td>
1528       <td style="vertical-align: top;"><span style="font-style: italic;">(ref</span>
1529 &amp; <span style="font-style: italic;">mask) </span>&lt;= (stencil
1530 buffer value &amp; <span style="font-style: italic;">mask)</span></td>
1531     </tr>
1532     <tr>
1533       <td style="vertical-align: top;">GL_GREATER<br>
1534       </td>
1535       <td style="vertical-align: top;"><span style="font-style: italic;">(ref</span>
1536 &amp; <span style="font-style: italic;">mask) </span>&gt; (stencil
1537 buffer value &amp; <span style="font-style: italic;">mask)</span></td>
1538     </tr>
1539     <tr>
1540       <td style="vertical-align: top;">GL_GEQUAL<br>
1541       </td>
1542       <td style="vertical-align: top;"><span style="font-style: italic;">(ref</span>
1543 &amp; <span style="font-style: italic;">mask) </span>&gt;= (stencil
1544 buffer value &amp; <span style="font-style: italic;">mask)</span></td>
1545     </tr>
1546     <tr>
1547       <td style="vertical-align: top;">GL_EQUAL<br>
1548       </td>
1549       <td style="vertical-align: top;"><span style="font-style: italic;">(ref</span>
1550 &amp; <span style="font-style: italic;">mask) </span>== (stencil
1551 buffer value &amp; <span style="font-style: italic;">mask)</span></td>
1552     </tr>
1553     <tr>
1554       <td style="vertical-align: top;">GL_NOTEQUAL<br>
1555       </td>
1556       <td style="vertical-align: top;"><span style="font-style: italic;">(ref</span>
1557 &amp; <span style="font-style: italic;">mask) </span>!= (stencil
1558 buffer value &amp; <span style="font-style: italic;">mask)</span></td>
1559     </tr>
1560     <tr>
1561       <td style="vertical-align: top;">GL_NEVER<br>
1562       </td>
1563       <td style="vertical-align: top;">never passes<br>
1564       </td>
1565     </tr>
1566     <tr>
1567       <td style="vertical-align: top;">GL_ALWAYS<br>
1568       </td>
1569       <td style="vertical-align: top;">always passes<br>
1570       </td>
1571     </tr>
1572   </tbody>
1573 </table>
1574 <br>
1575 <span style="font-style: italic;"></span><br>
1576 If the stencil test passes, the fragment is passed to the next
1577 per-fragment operation. &nbsp;Otherwise, if the stencil test fails, the
1578 value in the stencil buffer is updated according to the value of the <span
1579  style="font-style: italic;">stencilFail</span> parameter to <span
1580  style="font-weight: bold;">glStencilOp</span>.<br>
1581 <br>
1582 <table cellpadding="2" cellspacing="2" border="1"
1583  style="text-align: left; width: 70%; margin-left: auto; margin-right: auto;">
1584   <tbody>
1585     <tr>
1586       <td style="vertical-align: top;"><span style="font-style: italic;">stencilFail</span>
1587 value<br>
1588       </td>
1589       <td style="vertical-align: top;">New stencil buffer value<br>
1590       </td>
1591     </tr>
1592     <tr>
1593       <td style="vertical-align: top;">GL_KEEP<br>
1594       </td>
1595       <td style="vertical-align: top;">originalValue<br>
1596       </td>
1597     </tr>
1598     <tr>
1599       <td style="vertical-align: top;">GL_ZERO<br>
1600       </td>
1601       <td style="vertical-align: top;">0<br>
1602       </td>
1603     </tr>
1604     <tr>
1605       <td style="vertical-align: top;">GL_INVERT<br>
1606       </td>
1607       <td style="vertical-align: top;">BitWiseInvert(originalValue)
1608 i.e. ~originalValue<br>
1609       </td>
1610     </tr>
1611     <tr>
1612       <td style="vertical-align: top;">GL_REPLACE<br>
1613       </td>
1614       <td style="vertical-align: top;"><span style="font-style: italic;">ref</span><br>
1615       </td>
1616     </tr>
1617     <tr>
1618       <td style="vertical-align: top;">GL_INCR<br>
1619       </td>
1620       <td style="vertical-align: top;">originalValue + 1, clamped to
1621 [0, 2<sup>N</sup>-1]</td>
1622     </tr>
1623     <tr>
1624       <td style="vertical-align: top;">GL_DECR<br>
1625       </td>
1626       <td style="vertical-align: top;">originalValue - 1, clamped to
1627 [0, 2<sup>N</sup>-1]</td>
1628     </tr>
1629   </tbody>
1630 </table>
1631 <span style="font-style: italic;"></span><span
1632  style="font-style: italic;"></span><br>
1633 <br>
1634 The <span style="font-style: italic;">depthTestFail</span> and <span
1635  style="font-style: italic;">depthTestPass</span> parameters to <span
1636  style="font-weight: bold;">glStencilOp</span> are ignored. &nbsp;Values
1637 for <span style="font-style: italic;">func</span> and <span
1638  style="font-style: italic;">stencilFail</span> other than those listed
1639 in the table will cause the error GL_INVALID_ENUM to be raised.<br>
1640 <br>
1641 The stencil test is enabled and disabled with the commands <span
1642  style="font-weight: bold;">glEnable</span>(GL_STENCIL_TEST) and <span
1643  style="font-weight: bold;">glDisable</span>(GL_STENCIL_TEST).<br>
1644 <br>
1645 The default stencil function is GL_ALWAYS. &nbsp;The default stencil
1646 reference value is 0. &nbsp;The default stencil mask is ~0. &nbsp;The
1647 default stencil fail operation is GL_KEEP.<br>
1648 <br>
1649 Values written into the stencil buffer are masked with the command<br>
1650 <br>
1651 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glStencilMask</span>(GLuint<span
1652  style="font-style: italic;">mask</span>)<br>
1653 </div>
1654 <br>
1655 Only the bits which are set in <span style="font-style: italic;">mask</span>
1656 will be modified in the stencil buffer when written to. &nbsp;If each
1657 stencil buffer value has N bits, only the least significant N bits of <span
1658  style="font-style: italic;">mask</span> are relevant. &nbsp;The default
1659 stencil mask is ~0.<br>
1660 <br>
1661 <h2>6.4 Blending and Logicop</h2>
1662 Blending or a logic operation combines the incoming fragment color with
1663 the destination frame buffer color according to a blending equation or
1664 bit-wise Boolean logical operation.<br>
1665 <br>
1666 Blending is enabled and disabled with the commands <span
1667  style="font-weight: bold;">glEnable</span>(GL_BLEND) and <span
1668  style="font-weight: bold;">glDisable</span>(GL_BLEND).<br>
1669 <br>
1670 The logic operation is enabled and disabled with the commands <span
1671  style="font-weight: bold;">glEnable</span>(GL_LOGIC_OP) and <span
1672  style="font-weight: bold;">glDisable</span>(GL_LOGIC_OP).<br>
1673 <br>
1674 If both blending and the logic operation are enabled, the logic
1675 operation has higher priority; blending is bypassed.<br>
1676 <br>
1677 <h3>6.4.1 Logic Op</h3>
1678 The command<br>
1679 <br>
1680 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glLogicop</span>(GLenum<span
1681  style="font-style: italic;">mode</span>)<br>
1682 <br>
1683 </div>
1684 Specifies the Boolean logic operation for combining the incoming
1685 fragment color with the destination frame buffer color. &nbsp;Both the
1686 incoming fragment color and destination frame buffer colors are
1687 interpreted as four-tuples of unsigned integer color components in the
1688 range [0, 2<sup>N</sup>-1] where N is the number of bits per color
1689 channel. &nbsp;N may not be the same for all color channels.<br>
1690 <br>
1691 The following table lists all values for <span
1692  style="font-style: italic;">mode</span> and the boolean arithmetic used
1693 to combine the incoming fragment color value (src)<span
1694  style="font-style: italic;"></span><span style="font-style: italic;"></span><span
1695  style="font-style: italic;"></span><span style="font-style: italic;"></span><span
1696  style="font-style: italic;"></span> with the destination framebuffer
1697 color value (dst). &nbsp;Standard ANSI C operators used.<br>
1698 <br>
1699 <table cellpadding="2" cellspacing="2" border="1"
1700  style="text-align: left; width: 50%; margin-left: auto; margin-right: auto;">
1701   <tbody>
1702     <tr>
1703       <td style="vertical-align: top;">LogicOp <span
1704  style="font-style: italic;">mode</span><br>
1705       </td>
1706       <td style="vertical-align: top;">Resulting channel value<br>
1707       </td>
1708     </tr>
1709     <tr>
1710       <td style="vertical-align: top;">GL_CLEAR<br>
1711       </td>
1712       <td style="vertical-align: top;">0<br>
1713       </td>
1714     </tr>
1715     <tr>
1716       <td style="vertical-align: top;">GL_SET<br>
1717       </td>
1718       <td style="vertical-align: top;">~0<br>
1719       </td>
1720     </tr>
1721     <tr>
1722       <td style="vertical-align: top;">GL_COPY<br>
1723       </td>
1724       <td style="vertical-align: top;">src<br>
1725       </td>
1726     </tr>
1727     <tr>
1728       <td style="vertical-align: top;">GL_COPY_INVERTED<br>
1729       </td>
1730       <td style="vertical-align: top;">~s<br>
1731       </td>
1732     </tr>
1733     <tr>
1734       <td style="vertical-align: top;">GL_NOOP<br>
1735       </td>
1736       <td style="vertical-align: top;">dst<br>
1737       </td>
1738     </tr>
1739     <tr>
1740       <td style="vertical-align: top;">GL_INVERT<br>
1741       </td>
1742       <td style="vertical-align: top;">~dst<br>
1743       </td>
1744     </tr>
1745     <tr>
1746       <td style="vertical-align: top;">GL_AND<br>
1747       </td>
1748       <td style="vertical-align: top;">src &amp; dst<br>
1749       </td>
1750     </tr>
1751     <tr>
1752       <td style="vertical-align: top;">GL_NAND<br>
1753       </td>
1754       <td style="vertical-align: top;">~(src &amp; dst)<br>
1755       </td>
1756     </tr>
1757     <tr>
1758       <td style="vertical-align: top;">GL_AND_REVERSE<br>
1759       </td>
1760       <td style="vertical-align: top;">src &amp; ~dst<br>
1761       </td>
1762     </tr>
1763     <tr>
1764       <td style="vertical-align: top;">GL_AND_INVERTED<br>
1765       </td>
1766       <td style="vertical-align: top;">~src &amp; dst<br>
1767       </td>
1768     </tr>
1769     <tr>
1770       <td style="vertical-align: top;">GL_OR<br>
1771       </td>
1772       <td style="vertical-align: top;">src | dst<br>
1773       </td>
1774     </tr>
1775     <tr>
1776       <td style="vertical-align: top;">GL_NOR<br>
1777       </td>
1778       <td style="vertical-align: top;">~(src | dst)<br>
1779       </td>
1780     </tr>
1781     <tr>
1782       <td style="vertical-align: top;">GL_OR_REVERSE<br>
1783       </td>
1784       <td style="vertical-align: top;">src | ~dst<br>
1785       </td>
1786     </tr>
1787     <tr>
1788       <td style="vertical-align: top;">GL_OR_INVERTED<br>
1789       </td>
1790       <td style="vertical-align: top;">~src | dst<br>
1791       </td>
1792     </tr>
1793     <tr>
1794       <td style="vertical-align: top;">GL_XOR<br>
1795       </td>
1796       <td style="vertical-align: top;">src ^ dst<br>
1797       </td>
1798     </tr>
1799     <tr>
1800       <td style="vertical-align: top;">GL_EQUIV<br>
1801       </td>
1802       <td style="vertical-align: top;">~(src ^ dst)<br>
1803       </td>
1804     </tr>
1805   </tbody>
1806 </table>
1807 <br>
1808 The fragment's color is replaced by the result of the logic operation.<br>
1809 <br>
1810 Specifying any value for <span style="font-style: italic;">mode</span>
1811 other than those listed in the above table will cause the error
1812 GL_INVALID_ENUM to be raised.<br>
1813 <br>
1814 The default value for <span style="font-style: italic;">mode</span> is
1815 GL_COPY. &nbsp;The logic operation is disabled by default.<br>
1816 <br>
1817 <h3>6.4.2 Blending</h3>
1818 The command<br>
1819 <br>
1820 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glBlendFunc</span>(GLenum<span
1821  style="font-style: italic;">srcTerm</span>, GLenum <span
1822  style="font-style: italic;">dstTerm</span>)<br>
1823 </div>
1824 <br>
1825 specifies the terms of the blending equation. &nbsp;If Cf = (Rf, Gf,
1826 Bf, Af) is the incoming fragment color and Cb = (Rb, Gb, Bb, Ab) is the
1827 frame buffer color, then the resulting color Cv = (Rv, Gv, Bv, Av) is
1828 computed by:<br>
1829 <br>
1830 <div style="margin-left: 40px;">Cv = Cf * <span
1831  style="font-style: italic;">srcTerm</span> + Cb * <span
1832  style="font-style: italic;">dstTerm</span><br>
1833 <span style="font-style: italic;"></span></div>
1834 <span style="font-style: italic;"> </span><br>
1835 All possible values for <span style="font-style: italic;">srcTerm</span>
1836 and the corresponding arithmetic term are listed in the following table:<br>
1837 <br>
1838 <table cellpadding="2" cellspacing="2" border="1"
1839  style="text-align: left; width: 70%; margin-left: auto; margin-right: auto;">
1840   <tbody>
1841     <tr>
1842       <td style="vertical-align: top;"><span style="font-style: italic;">srcTerm</span><br>
1843       </td>
1844       <td style="vertical-align: top;"><span style="font-style: italic;">srcTerm</span>Arithmetic<br>
1845       </td>
1846     </tr>
1847     <tr>
1848       <td style="vertical-align: top;">GL_ZERO<br>
1849       </td>
1850       <td style="vertical-align: top;">(0, 0, 0, 0)<br>
1851       </td>
1852     </tr>
1853     <tr>
1854       <td style="vertical-align: top;">GL_ONE<br>
1855       </td>
1856       <td style="vertical-align: top;">(1, 1, 1, 1)<br>
1857       </td>
1858     </tr>
1859     <tr>
1860       <td style="vertical-align: top;">GL_DST_COLOR<br>
1861       </td>
1862       <td style="vertical-align: top;">(Rb, Gb, Bb, Ab)<br>
1863       </td>
1864     </tr>
1865     <tr>
1866       <td style="vertical-align: top;">GL_ONE_MINUS_DST_COLOR<br>
1867       </td>
1868       <td style="vertical-align: top;">(1-Rb, 1-Gb, 1-Bb, 1-Ab)<br>
1869       </td>
1870     </tr>
1871     <tr>
1872       <td style="vertical-align: top;">GL_SRC_ALPHA<br>
1873       </td>
1874       <td style="vertical-align: top;">(Af, Af, Af, AF)<br>
1875       </td>
1876     </tr>
1877     <tr>
1878       <td style="vertical-align: top;">GL_ONE_MINUS_SRC_ALPHA<br>
1879       </td>
1880       <td style="vertical-align: top;">(1-Af, 1-Af, 1-Af, 1-Af)<br>
1881       </td>
1882     </tr>
1883     <tr>
1884       <td style="vertical-align: top;">GL_DST_ALPHA<br>
1885       </td>
1886       <td style="vertical-align: top;">(Ab, Ab, Ab, Ab)<br>
1887       </td>
1888     </tr>
1889     <tr>
1890       <td style="vertical-align: top;">GL_ONE_MINUS_DST_ALPHA<br>
1891       </td>
1892       <td style="vertical-align: top;">(1-Ab, 1-Ab, 1-Ab, 1-Ab)<br>
1893       </td>
1894     </tr>
1895     <tr>
1896       <td style="vertical-align: top;">GL_SRC_ALPHA_SATURATE<br>
1897       </td>
1898       <td style="vertical-align: top;">(m, m, m, 1) where m = MIN(Af,
1899 1-Ab)<br>
1900       </td>
1901     </tr>
1902   </tbody>
1903 </table>
1904 <br>
1905 All possible values for <span style="font-style: italic;">srcTerm</span>
1906 and the corresponding arithmetic term are listed in the following table:<br>
1907 <br>
1908 <table cellpadding="2" cellspacing="2" border="1"
1909  style="text-align: left; width: 70%; margin-left: auto; margin-right: auto;">
1910   <tbody>
1911     <tr>
1912       <td style="vertical-align: top;"><span style="font-style: italic;">dstTerm</span><br>
1913       </td>
1914       <td style="vertical-align: top;"><span style="font-style: italic;">dstTerm</span>Arithmetic<br>
1915       </td>
1916     </tr>
1917     <tr>
1918       <td style="vertical-align: top;">GL_ZERO<br>
1919       </td>
1920       <td style="vertical-align: top;">(0, 0, 0, 0)<br>
1921       </td>
1922     </tr>
1923     <tr>
1924       <td style="vertical-align: top;">GL_ONE<br>
1925       </td>
1926       <td style="vertical-align: top;">(1, 1, 1, 1)<br>
1927       </td>
1928     </tr>
1929     <tr>
1930       <td style="vertical-align: top;">GL_SRC_COLOR<br>
1931       </td>
1932       <td style="vertical-align: top;">(Rf, Gf, Bf, Af)<br>
1933       </td>
1934     </tr>
1935     <tr>
1936       <td style="vertical-align: top;">GL_ONE_MINUS_SRC_COLOR<br>
1937       </td>
1938       <td style="vertical-align: top;">(1-Rf, 1-Gf, 1-Bf, 1-Af)<br>
1939       </td>
1940     </tr>
1941     <tr>
1942       <td style="vertical-align: top;">GL_SRC_ALPHA<br>
1943       </td>
1944       <td style="vertical-align: top;">(Af, Af, Af, AF)<br>
1945       </td>
1946     </tr>
1947     <tr>
1948       <td style="vertical-align: top;">GL_ONE_MINUS_SRC_ALPHA<br>
1949       </td>
1950       <td style="vertical-align: top;">(1-Af, 1-Af, 1-Af, 1-Af)<br>
1951       </td>
1952     </tr>
1953     <tr>
1954       <td style="vertical-align: top;">GL_DST_ALPHA<br>
1955       </td>
1956       <td style="vertical-align: top;">(Ab, Ab, Ab, Ab)<br>
1957       </td>
1958     </tr>
1959     <tr>
1960       <td style="vertical-align: top;">GL_ONE_MINUS_DST_ALPHA<br>
1961       </td>
1962       <td style="vertical-align: top;">(1-Ab, 1-Ab, 1-Ab, 1-Ab)<br>
1963       </td>
1964     </tr>
1965   </tbody>
1966 </table>
1967 <br>
1968 The fragment's color is replaced by the result of the blending equation.<br>
1969 <br>
1970 Values for <span style="font-style: italic;">srcTerm</span> and <span
1971  style="font-style: italic;">dstTerm</span> other than those listed in
1972 the table will cause the error GL_INVALID_ENUM to be raised.<br>
1973 <br>
1974 The default value for <span style="font-style: italic;">srcTerm</span>
1975 is GL_ONE. &nbsp;The default value for <span style="font-style: italic;">dstTerm</span>
1976 is GL_ZERO. &nbsp;Blending is disabled by default.<br>
1977 <br>
1978 <h2>6.5 Color Mask</h2>
1979 The final fragment color is written into the current color buffer at
1980 the end of the per-fragment operations. &nbsp;Normally, all color
1981 channels in the frame buffer are replaced with the final fragment color.
1982 &nbsp;However, the command<br>
1983 <br>
1984 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glColorMask</span>(GLboolean<span
1985  style="font-style: italic;">redMask</span>, GLboolean <span
1986  style="font-style: italic;">greenMask</span>, GLboolean <span
1987  style="font-style: italic;">blueMask</span>, GLboolean <span
1988  style="font-style: italic;">alphaMask</span>)<br>
1989 </div>
1990 <br>
1991 allows selective writing to individual color channels. &nbsp;If <span
1992  style="font-style: italic;">redMask</span> is GL_TRUE then writing to
1993 the red color channel is enabled, otherwise it's disabled.
1994 &nbsp;Similarly, the green, blue and alpha channels can also be masked.<br>
1995 <br>
1996 Initially all four mask values are GL_TRUE.<br>
1997 <br>
1998 Color masking is not enabled/disabled with the <span
1999  style="font-weight: bold;">glEnable</span>/<span
2000  style="font-weight: bold;">glDisable</span> commands.<br>
2001 <br>
2002 <h1>7. Frame Buffer Operations</h1>
2003 The frame buffer is considered to be a two-dimensional array of pixels.
2004 &nbsp;The frame buffer is also organized into layers or logical buffers.
2005 &nbsp;There may be a front color buffer, back color buffer and stencil
2006 buffer. &nbsp;A double-buffered frame buffer has both a front color
2007 buffer and back color buffer. &nbsp;A single-buffered framebuffer only
2008 has a front color buffer. &nbsp;Each pixel in a color buffer has a red,
2009 green and blue value and an optional alpha value.<br>
2010 <br>
2011 <h2>7.1 Clearing Buffers</h2>
2012 Buffers are cleared (set to uniform values) with the command<br>
2013 <br>
2014 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glClear</span>(GLbitfield<span
2015  style="font-style: italic;">buffers</span>)<br>
2016 </div>
2017 <br>
2018 <span style="font-style: italic;">buffers</span> is a bitmask for which
2019 the value may be the bitwise-OR of the values GL_COLOR_BUFFER_BIT and
2020 GL_STENCIL_BUFFER_BIT. &nbsp;If the GL_COLOR_BUFFER_BIT bit is
2021 specified, the current color buffer will be cleared. &nbsp;If the
2022 GL_STENCIL_BUFFER_BIT bit is specified, the stencil buffer will be
2023 cleared.<br>
2024 <br>
2025 The current color buffer is specified with the command<br>
2026 <br>
2027 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glDrawBuffer</span>(GLenum<span
2028  style="font-style: italic;"> buffer</span>)<br>
2029 </div>
2030 <br>
2031 <span style="font-style: italic;">buffer</span> may be either GL_FRONT,
2032 GL_BACK or GL_NONE. &nbsp;GL_FRONT indicates that the front color buffer
2033 will be modified by <span style="font-weight: bold;">glClear</span> and
2034 any drawing command. &nbsp;GL_BACK indicates that the back color buffer
2035 will be modified by <span style="font-weight: bold;">glClear</span> and
2036 any drawing command. &nbsp;GL_NONE indicates that neither color buffer
2037 will be modified by <span style="font-weight: bold;">glClear</span> or
2038 any drawing command. &nbsp;GL_BACK is only valid for double-buffered
2039 frame buffers.<br>
2040 <br>
2041 The current scissor rectangle, set by the <span
2042  style="font-weight: bold;">glScissor</span> command, effects <span
2043  style="font-weight: bold;">glClear</span><span
2044  style="font-style: italic;">,</span><span style="font-style: italic;"> </span>limiting
2045 the clear to the scissor rectangle, if it's enabled. &nbsp;Furthermore, <span
2046  style="font-weight: bold;"></span>only the color channels enabled by <span
2047  style="font-weight: bold;">glColorMask</span> will be effected by <span
2048  style="font-weight: bold;">glClear</span>(GL_COLOR_BUFFER_BIT).
2049 &nbsp;Likewise, only the stencil bits enabled by <span
2050  style="font-weight: bold;">glStencilMask</span> will be effected by <span
2051  style="font-weight: bold;">glClear</span>(GL_STENCIL_BUFFER_BIT).<br>
2052 <br>
2053 The current clear color is set with the command<br>
2054 <br>
2055 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glClearColor</span>(GLclampf<span
2056  style="font-style: italic;">red</span>, GLclampf <span
2057  style="font-style: italic;">green</span>, GLclampf <span
2058  style="font-style: italic;">blue</span>, GLclampf <span
2059  style="font-style: italic;">alpha</span>)<br>
2060 </div>
2061 <br>
2062 Subsequent calls to <span style="font-weight: bold;">glClear</span>
2063 will use the color (<span style="font-style: italic;">red, green, blue,
2064 alpha</span>) to clear the front or back color buffers.<br>
2065 <span style="font-style: italic;"></span><br>
2066 The current stencil clear value is set with the command<br>
2067 <br>
2068 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glClearStencil</span>(GLint<span
2069  style="font-style: italic;">clearValue</span>)<br>
2070 </div>
2071 <br>
2072 If the stencil buffer is N bits deep, the least significant N bits of <span
2073  style="font-style: italic;">clearValue</span> will be used to clear the
2074 stencil buffer.<br>
2075 <br>
2076 <br>
2077 <h1>8. Other Features</h1>
2078 <h2>8.1 Frame Buffer Readback</h2>
2079 A rectangular region of pixels can be read from the frame buffer and
2080 placed in client memory with the command<br>
2081 <br>
2082 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glReadPixels</span>(GLint<span
2083  style="font-style: italic;">x</span>, GLint <span
2084  style="font-style: italic;">y</span>, GLsizei <span
2085  style="font-style: italic;">width</span>, GLsizei <span
2086  style="font-style: italic;">height</span>, GLenum <span
2087  style="font-style: italic;">format</span>, GLenum <span
2088  style="font-style: italic;">type</span>, GLvoid *<span
2089  style="font-style: italic;">data</span>)<br>
2090 </div>
2091 <br>
2092 <span style="font-style: italic;">x</span> and <span
2093  style="font-style: italic;">y</span> specify the coordinate of the
2094 lower-left corner of the region to read and <span
2095  style="font-style: italic;">width</span> and <span
2096  style="font-style: italic;">height</span> specify the size of the
2097 rectangular region to read. &nbsp;<span style="font-style: italic;">format</span>
2098 specifies the format of image data and must be either GL_RGB or
2099 GL_RGBA.&nbsp; <span style="font-style: italic;">type</span> specify the
2100 data type of the image data and must be either GL_UNSIGNED_BYTE or
2101 GL_FLOAT. &nbsp;Other values for <span style="font-style: italic;">format</span>
2102 or <span style="font-style: italic;">type</span> will cause the error
2103 GL_INVALID_ENUM to be raised.<br>
2104 <br>
2105 The framebuffer may contain 3-component colors (red, green, blue) or
2106 4-component colors (red, green, blue, alpha). &nbsp;If an alpha channel
2107 is not present, alpha values default to 1.0.<br>
2108 <br>
2109 The frame buffer color components (red, green, blue, alpha) are either
2110 converted to 8-bit unsigned integers in the range[0, 255] if <span
2111  style="font-style: italic;">type </span>is GL_UNSIGNED_BYTE or
2112 converted to floating point values in the range [0, 1] if <span
2113  style="font-style: italic;">type</span> is GL_FLOAT. &nbsp;The (red,
2114 green, blue, alpha) tuples are then stored as GL_RGB triplets (by
2115 dropping the alpha component) or GL_RGBA quadruples in client memory.<br>
2116 <br>
2117 Image data is <span style="font-style: italic;">packed</span> into
2118 client memory according to the pixel packing parameters which are set by
2119 the command<br>
2120 <br>
2121 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glPixelStorei</span>(GLenum<span
2122  style="font-style: italic;"> pname</span>, GLint <span
2123  style="font-style: italic;">value</span>)<br>
2124 </div>
2125 <br>
2126 <span style="font-style: italic;">pname</span> must be
2127 GL_PACK_ROW_LENGTH. &nbsp;<span style="font-style: italic;">value</span>
2128 indicates the stride (in pixels) between subsequent rows in the
2129 destination image. &nbsp;If GL_PACK_ROW_LENGTH is zero (the default)
2130 then the <span style="font-style: italic;">width</span> parameter to <span
2131  style="font-weight: bold;">glReadPixels</span> indicates the row stride.<br>
2132 <br>
2133 Pixel readback takes place as follows:<br>
2134 <br>
2135 <div style="margin-left: 40px;">if (GL_PACK_ROW_LENGTH == 0)<br>
2136 &nbsp;&nbsp;&nbsp; rowLength = <span style="font-style: italic;">width</span>;<br>
2137 else<br>
2138 &nbsp;&nbsp;&nbsp; rowLength = GL_PACK_ROW_LENGTH<br>
2139 <br>
2140 if (<span style="font-style: italic;">format</span> == GL_RGB) {<br>
2141 &nbsp;&nbsp;&nbsp; for (i = 0; i &lt; <span style="font-style: italic;">height</span>;
2142 i++) {<br>
2143 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; for (j = 0; j &lt; <span
2144  style="font-style: italic;">width</span>; j++) {<br>
2145 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; k = (i *
2146 rowLength + j) * 3;<br>
2147 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; <span
2148  style="font-style: italic;">data</span>[k+0] = FrameBuffer(<span
2149  style="font-style: italic;">x</span> + j, <span
2150  style="font-style: italic;">y</span> + i).red;<br>
2151 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp; &nbsp; &nbsp;&nbsp; <span
2152  style="font-style: italic;">data</span>[k+1] = FrameBuffer(<span
2153  style="font-style: italic;">x</span> + j, <span
2154  style="font-style: italic;">y</span> + i).green;<br>
2155 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; <span
2156  style="font-style: italic;">data</span>[k+2] = FrameBuffer(<span
2157  style="font-style: italic;">x</span> + j, <span
2158  style="font-style: italic;">y</span> + i).blue;<span
2159  style="font-style: italic;"></span><br>
2160 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; }<br>
2161 &nbsp;&nbsp;&nbsp; }<br>
2162 }<br>
2163 else {<br>
2164 &nbsp;&nbsp;&nbsp; for (i = 0; i &lt; <span style="font-style: italic;">height</span>;
2165 i++) {<br>
2166 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; for (j = 0; j &lt; <span
2167  style="font-style: italic;">width</span>; j++) {<br>
2168 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; k = (i *
2169 rowLength + j) * 4;<br>
2170 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; <span
2171  style="font-style: italic;">data</span>[k+0] = FrameBuffer(<span
2172  style="font-style: italic;">x</span> + j, <span
2173  style="font-style: italic;">y</span> + i).red;<br>
2174 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp; &nbsp; &nbsp;&nbsp; <span
2175  style="font-style: italic;">data</span>[k+1] = FrameBuffer(<span
2176  style="font-style: italic;">x</span> + j, <span
2177  style="font-style: italic;">y</span> + i).green;<br>
2178 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; <span
2179  style="font-style: italic;">data</span>[k+2] = FrameBuffer(<span
2180  style="font-style: italic;">x</span> + j, <span
2181  style="font-style: italic;">y</span> + i).blue;<span
2182  style="font-style: italic;"></span><br>
2183 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; <span
2184  style="font-style: italic;">data</span>[k+3] = FrameBuffer(<span
2185  style="font-style: italic;">x</span> + j, <span
2186  style="font-style: italic;">y</span> + i).alpha;<span
2187  style="font-style: italic;"></span><br>
2188 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; }<br>
2189 &nbsp;&nbsp;&nbsp; }<br>
2190 }<br>
2191 </div>
2192 <br>
2193 The function FrameBuffer(<span style="font-style: italic;">c, r</span>)
2194 returns the pixel in the frame buffer at column <span
2195  style="font-style: italic;">c</span> of row <span
2196  style="font-style: italic;">r. &nbsp;</span><span
2197  style="font-style: italic;">data</span> is considered to be either a
2198 GLubyte pointer or a GLfloat pointer, depending on the <span
2199  style="font-style: italic;">type</span> parameter. &nbsp;Similarly, the
2200 FrameBuffer function returns either GLubyte values in the range [0, 255]
2201 or GLfloat values in the range [0,1], depending on the <span
2202  style="font-style: italic;">type</span> parameter.<br>
2203 <br>
2204 Pixels may be read from either the front or back color buffer.
2205 &nbsp;The command<br>
2206 <br>
2207 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glReadBuffer</span>(GLenum<span
2208  style="font-style: italic;">buffer</span>)<br>
2209 </div>
2210 <br>
2211 specifies the source for reading images with <span
2212  style="font-weight: bold;">glReadPixels</span>. &nbsp;If <span
2213  style="font-style: italic;">buffer</span> is GL_FRONT then front color
2214 buffer is the source. &nbsp;If <span style="font-style: italic;">buffer</span>
2215 is GL_BACK then the back color buffer is the source. &nbsp;It is illegal
2216 to specify GL_BACK when the color buffer is not double buffered.
2217 &nbsp;Any invalid value for <span style="font-style: italic;">buffer</span>
2218 will raise the error GL_INVALID_ENUM.<br>
2219 <br>
2220 The default read source is GL_BACK if the frame buffer is double
2221 buffered. &nbsp;Otherwise, the default read source is GL_FRONT.<br>
2222 <br>
2223 <h2>8.2 Selection Mode</h2>
2224 Selection mode is typically used to implement <span
2225  style="font-style: italic;">picking</span>: determining which
2226 primitive(s) are present at particular window positions. &nbsp;The
2227 command<br>
2228 <br>
2229 <div style="margin-left: 40px;">GLint <span style="font-weight: bold;">glRenderMode</span>(GLenum<span
2230  style="font-style: italic;">mode</span>)<br>
2231 </div>
2232 <br>
2233 is used to enable selection mode. &nbsp;If <span
2234  style="font-style: italic;">mode</span> is GL_SELECTION the graphics
2235 library is put into selection mode. &nbsp;If <span
2236  style="font-style: italic;">mode</span> is GL_RENDER the graphic
2237 library is put into normal rendering mode. &nbsp;Any other value for <span
2238  style="font-style: italic;">mode</span> will raise the error
2239 GL_INVALID_ENUM.<br>
2240 <br>
2241 When in selection mode rendering commands will not effect the
2242 framebuffer. &nbsp;Instead, a record of the primitives that would have
2243 been drawn is placed in the <span style="font-style: italic;">selection</span> <span
2244  style="font-style: italic;">buffer</span>. &nbsp;The selection buffer
2245 is specified with the command<br>
2246 <br>
2247 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glSelectionBuffer</span>(GLsizei<span
2248  style="font-style: italic;">n</span>, GLuint *<span
2249  style="font-style: italic;">buffer</span>)<br>
2250 </div>
2251 <span style="font-style: italic;"></span><span
2252  style="font-style: italic;"><br>
2253 buffer</span> is an array of <span style="font-style: italic;">n</span>
2254 unsigned integers. &nbsp;No more than <span style="font-style: italic;">n</span>
2255 values will be placed in the buffer.<br>
2256 <br>
2257 The <span style="font-style: italic;">name stack</span> is a stack
2258 (LIFO) of unsigned integer names. &nbsp;The following commands
2259 manipulate the name stack:<br>
2260 <br>
2261 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glInitNames</span>(void)<br>
2262 void <span style="font-weight: bold;">glPushName</span>(GLuint <span
2263  style="font-style: italic;">name</span>)<br>
2264 void <span style="font-weight: bold;">glPopName</span>(void)<br>
2265 void <span style="font-weight: bold;">glLoadName</span>(GLuint <span
2266  style="font-style: italic;">name</span>)<br>
2267 </div>
2268 <br>
2269 <span style="font-weight: bold;">glInitNames</span> resets the name
2270 stack to an empty state. &nbsp;<span style="font-weight: bold;">glPushName<span
2271  style="font-style: italic;"> </span></span>pushes the given <span
2272  style="font-style: italic;">name</span> value onto the stack. &nbsp;<span
2273  style="font-weight: bold;">glPopName</span> pops the top name from the
2274 stack. &nbsp;<span style="font-weight: bold;">glLoadName<span
2275  style="font-style: italic;"> </span></span>replaces the top value on
2276 the stack with the specified <span style="font-style: italic;">name</span>.
2277 &nbsp;Stack underflow and overflow conditions cause the errors
2278 GL_STACK_OVERFLOW and GL_STACK_UNDERFLOW to be raised.<br>
2279 <br>
2280 While in selection mode, primitives (points, lines, polygons) are
2281 transformed and clip-tested normally. &nbsp;Primitives which aren't
2282 discarded by clipping cause the <span style="font-style: italic;">hit</span> <span
2283  style="font-style: italic;">data</span> to be updated. &nbsp;The hit
2284 data consists of three pieces of information: a hit flag, a minimum Z
2285 value and a maximum Z value. &nbsp;First, the hit flag is set.
2286 &nbsp;Then, for each of the primitive's vertices, the vertex Z value is
2287 compared to the minimum and maximum Z values. &nbsp;The minimum Z value
2288 is updated if the vertex's Z value is less than the minimum Z value.
2289 &nbsp;The maximum Z value is updated if the vertex's Z value is greater
2290 than the maximum Z value.<br>
2291 <br>
2292 When any of <span style="font-weight: bold;">glInitNames</span><span
2293  style="font-style: italic;"><span style="font-style: italic;">, </span></span><span
2294  style="font-weight: bold;">glPushName</span>, <span
2295  style="font-weight: bold;">glPopName</span>, <span
2296  style="font-weight: bold;">glLoadName</span> or <span
2297  style="font-weight: bold;">glRenderMode</span> are called and the hit
2298 flag is set, a <span style="font-style: italic;">hit record</span> is
2299 written to the selection buffer.<br>
2300 <br>
2301 A hit record consists of a sequence of unsigned integers. &nbsp;The
2302 first value is the size of the name stack. &nbsp;The second value is the
2303 minimum Z value multiplied by 2<sup>32</sup>-1. &nbsp;The third value is
2304 the maximum Z value multiplied by 2<sup>32</sup>-1. &nbsp;The remaining
2305 values are the values in the name stack, in bottom to top order.
2306 &nbsp;The hit flag is cleared after a hit record is written to the
2307 selection buffer. &nbsp;Hit records are places sequentially into the
2308 selection buffer until it is full or selection mode is terminated.<br>
2309 <br>
2310 Selection mode is terminated by calling <span
2311  style="font-weight: bold;">glRenderMode</span>(GL_RENDER). &nbsp; The
2312 return value of <span style="font-weight: bold;">glRenderMode</span>
2313 will be -1 if the selection buffer overflowed. &nbsp;Otherwise, the
2314 return value will indicate the number of values written into the
2315 selection buffer.<br>
2316 <br>
2317 <h2>8.3 Synchronization</h2>
2318 The command<br>
2319 <br>
2320 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glFlush</span>(void)<br>
2321 </div>
2322 <br>
2323 makes the graphics library to flush all pending graphics commands.
2324 &nbsp;The command<br>
2325 <div style="margin-left: 40px;"><br>
2326 void <span style="font-weight: bold;">glFinish</span>(void)<br>
2327 </div>
2328 <br>
2329 makes the graphics library flush the command queue and wait until those
2330 commands are completed. &nbsp;<span style="font-weight: bold;">glFlush</span>
2331 will not return until all previous graphics commands have been fully
2332 completed.<br>
2333 <br>
2334 These commands are typically used to force completion of rendering to
2335 the front color buffer. &nbsp;Otherwise, rendering to the front color
2336 buffer may not appear. &nbsp;The <span style="font-style: italic;">swapbuffers</span>
2337 command (part of the window system binding library) does an implicit
2338 flush before swapping the front and back color buffers. &nbsp;The <span
2339  style="font-weight: bold;">glReadPixels</span> command also does an
2340 implicit flush before reading pixel data from the frame buffer.<br>
2341 <br>
2342 <h1>9. State Queries</h1>
2343 The current value of nearly all library state variables can be queried.
2344 &nbsp;This chapter describes the commands used for querying the value of
2345 state variables.<br>
2346 <br>
2347 <h2>9.1 General State Queries</h2>
2348 The command<br>
2349 <br>
2350 <div style="margin-left: 40px;">void <span style="font-weight: bold;">glGetFloatv</span>(GLenum<span
2351  style="font-style: italic;">pname</span>, GLfloat *<span
2352  style="font-style: italic;">values</span>)<br>
2353 </div>
2354 <br>
2355 returns the value(s) of the state variable specified by <span
2356  style="font-style: italic;">pname</span>. &nbsp;The following table
2357 lists all accepted values for <span style="font-style: italic;">pname</span>
2358 and a description of the value(s). &nbsp;Specifying any other value for <span
2359  style="font-style: italic;">pname</span> causes the error
2360 GL_INVALID_ENUM to be raised.<br>
2361 <br>
2362 <table cellpadding="2" cellspacing="2" border="1"
2363  style="text-align: left; width: 90%; margin-left: auto; margin-right: auto;">
2364   <tbody>
2365     <tr>
2366       <td style="vertical-align: top;">Variable (<span
2367  style="font-style: italic;">pname)</span><br>
2368       </td>
2369       <td style="vertical-align: top;">Number of values<br>
2370       </td>
2371       <td style="vertical-align: top;">Value(s) Description<br>
2372       </td>
2373     </tr>
2374     <tr>
2375       <td style="vertical-align: top;">GL_ALPHA_BITS<br>
2376       </td>
2377       <td style="vertical-align: top;">1<br>
2378       </td>
2379       <td style="vertical-align: top;">Number of bits per alpha value
2380 in the frame buffer.<br>
2381       </td>
2382     </tr>
2383     <tr>
2384       <td style="vertical-align: top;">GL_ALPHA_TEST<br>
2385       </td>
2386       <td style="vertical-align: top;">1<br>
2387       </td>
2388       <td style="vertical-align: top;">Zero if the alpha test is
2389 disabled.<br>
2390 One if the alpha test is enabled.<br>
2391       </td>
2392     </tr>
2393     <tr>
2394       <td style="vertical-align: top;">GL_ALPHA_TEST_FUNC<br>
2395       </td>
2396       <td style="vertical-align: top;">1<br>
2397       </td>
2398       <td style="vertical-align: top;">The alpha test function.<br>
2399       </td>
2400     </tr>
2401     <tr>
2402       <td style="vertical-align: top;">GL_BLEND<br>
2403       </td>
2404       <td style="vertical-align: top;">1<br>
2405       </td>
2406       <td style="vertical-align: top;">Zero if blending is disabled.<br>
2407 One if blending is enabled.<br>
2408       </td>
2409     </tr>
2410     <tr>
2411       <td style="vertical-align: top;">GL_BLEND_DST<br>
2412       </td>
2413       <td style="vertical-align: top;">1<br>
2414       </td>
2415       <td style="vertical-align: top;">Blend destination function/term.<br>
2416       </td>
2417     </tr>
2418     <tr>
2419       <td style="vertical-align: top;">GL_BLEND_SRC<br>
2420       </td>
2421       <td style="vertical-align: top;">1<br>
2422       </td>
2423       <td style="vertical-align: top;">Blend source function/term.<br>
2424       </td>
2425     </tr>
2426     <tr>
2427       <td style="vertical-align: top;">GL_BLUE_BITS<br>
2428       </td>
2429       <td style="vertical-align: top;">1<br>
2430       </td>
2431       <td style="vertical-align: top;">Number of bits per blue value in
2432 the frame buffer.<br>
2433       </td>
2434     </tr>
2435     <tr>
2436       <td style="vertical-align: top;">GL_COLOR_CLEAR_VALUE<br>
2437       </td>
2438       <td style="vertical-align: top;">4<br>
2439       </td>
2440       <td style="vertical-align: top;">Clear color (red, green, blue,
2441 alpha).<br>
2442       </td>
2443     </tr>
2444     <tr>
2445       <td style="vertical-align: top;">GL_COLOR_WRITE_MASK<br>
2446       </td>
2447       <td style="vertical-align: top;">4<br>
2448       </td>
2449       <td style="vertical-align: top;">Color buffer writemask (red,
2450 green, blue, alpha).<br>
2451 Zero if writing is disabled.<br>
2452 One if writing is enabled.<br>
2453       </td>
2454     </tr>
2455     <tr>
2456       <td style="vertical-align: top;">GL_CULL_FACE<br>
2457       </td>
2458       <td style="vertical-align: top;">1<br>
2459       </td>
2460       <td style="vertical-align: top;">Zero if polygon culling is
2461 disabled.<br>
2462 One if polygon culling is enabled.<br>
2463       </td>
2464     </tr>
2465     <tr>
2466       <td style="vertical-align: top;">GL_CULL_FACE_MODE<br>
2467       </td>
2468       <td style="vertical-align: top;">1<br>
2469       </td>
2470       <td style="vertical-align: top;">Polygon cull mode: GL_FRONT,
2471 GL_BACK or GL_FRONT_AND_BACK.<br>
2472       </td>
2473     </tr>
2474     <tr>
2475       <td style="vertical-align: top;">GL_CURRENT_COLOR<br>
2476       </td>
2477       <td style="vertical-align: top;">4<br>
2478       </td>
2479       <td style="vertical-align: top;">Current color (red, green, blue,
2480 alpha).<br>
2481       </td>
2482     </tr>
2483     <tr>
2484       <td style="vertical-align: top;">GL_CURRENT_RASTER_COLOR<br>
2485       </td>
2486       <td style="vertical-align: top;">4<br>
2487       </td>
2488       <td style="vertical-align: top;">Current raster position color
2489 (red, green, blue, alpha).<br>
2490       </td>
2491     </tr>
2492     <tr>
2493       <td style="vertical-align: top;">GL_CURRENT_RASTER_TEXTURE_COORDS<br>
2494       </td>
2495       <td style="vertical-align: top;">4<br>
2496       </td>
2497       <td style="vertical-align: top;">Current raster position texture
2498 coordinates (s, t, r, q).<br>
2499       </td>
2500     </tr>
2501     <tr>
2502       <td style="vertical-align: top;">GL_CURRENT_RASTER_POSITION<br>
2503       </td>
2504       <td style="vertical-align: top;">4<br>
2505       </td>
2506       <td style="vertical-align: top;">Current raster position (x, y,
2507 z, w).<br>
2508       </td>
2509     </tr>
2510     <tr>
2511       <td style="vertical-align: top;">GL_CURRENT_POSITION_VALID<br>
2512       </td>
2513       <td style="vertical-align: top;">1<br>
2514       </td>
2515       <td style="vertical-align: top;">Zero if current raster position
2516 is invalid.<br>
2517 One if current raster position is valid.<br>
2518       </td>
2519     </tr>
2520     <tr>
2521       <td style="vertical-align: top;">GL_CURRENT_TEXTURE_COORDS<br>
2522       </td>
2523       <td style="vertical-align: top;">4<br>
2524       </td>
2525       <td style="vertical-align: top;">Current texture coordinates (s,
2526 t, r, q)<br>
2527       </td>
2528     </tr>
2529     <tr>
2530       <td style="vertical-align: top;">GL_DOUBLEBUFFER<br>
2531       </td>
2532       <td style="vertical-align: top;">1<br>
2533       </td>
2534       <td style="vertical-align: top;">Zero if color buffer is
2535 single-buffered.<br>
2536 One if color buffer is double-buffered.<br>
2537       </td>
2538     </tr>
2539     <tr>
2540       <td style="vertical-align: top;">GL_DRAW_BUFFER<br>
2541       </td>
2542       <td style="vertical-align: top;">1<br>
2543       </td>
2544       <td style="vertical-align: top;">Current color draw buffer:
2545 GL_FRONT or GL_BACK.<br>
2546       </td>
2547     </tr>
2548     <tr>
2549       <td style="vertical-align: top;">GL_FRONT_FACE</td>
2550       <td style="vertical-align: top;">1<br>
2551       </td>
2552       <td style="vertical-align: top;">Polygon front-face winding:
2553 GL_CW or GL_CCW.<br>
2554       </td>
2555     </tr>
2556     <tr>
2557       <td style="vertical-align: top;">GL_GREEN_BITS<br>
2558       </td>
2559       <td style="vertical-align: top;">1<br>
2560       </td>
2561       <td style="vertical-align: top;">Number of bits per green value
2562 in the frame buffer.<br>
2563       </td>
2564     </tr>
2565     <tr>
2566       <td style="vertical-align: top;">GL_LINE_SMOOTH<br>
2567       </td>
2568       <td style="vertical-align: top;">1<br>
2569       </td>
2570       <td style="vertical-align: top;">Zero if line smoothing is
2571 disabled.<br>
2572 One if line smoothing is enabled.<br>
2573       </td>
2574     </tr>
2575     <tr>
2576       <td style="vertical-align: top;">GL_LINE_STIPPLE<br>
2577       </td>
2578       <td style="vertical-align: top;">1<br>
2579       </td>
2580       <td style="vertical-align: top;">Zero if line stippling is
2581 disabled.<br>
2582 One if line stippling is enabled.<br>
2583       </td>
2584     </tr>
2585     <tr>
2586       <td style="vertical-align: top;">GL_LINE_STIPPLE_PATTERN<br>
2587       </td>
2588       <td style="vertical-align: top;">1<br>
2589       </td>
2590       <td style="vertical-align: top;">Line stipple pattern.<br>
2591       </td>
2592     </tr>
2593     <tr>
2594       <td style="vertical-align: top;">GL_LINE_STIPPLE_REPEAT<br>
2595       </td>
2596       <td style="vertical-align: top;">1<br>
2597       </td>
2598       <td style="vertical-align: top;">Line stipple repeat factor.<br>
2599       </td>
2600     </tr>
2601     <tr>
2602       <td style="vertical-align: top;">GL_LINE_WIDTH<br>
2603       </td>
2604       <td style="vertical-align: top;">1<br>
2605       </td>
2606       <td style="vertical-align: top;">Line width in pixels.<br>
2607       </td>
2608     </tr>
2609     <tr>
2610       <td style="vertical-align: top;">GL_LINE_WIDTH_GRANULARITY<br>
2611       </td>
2612       <td style="vertical-align: top;">1<br>
2613       </td>
2614       <td style="vertical-align: top;">Aliased line width granularity.<br>
2615       </td>
2616     </tr>
2617     <tr>
2618       <td style="vertical-align: top;">GL_LINE_WIDTH_RANGE<br>
2619       </td>
2620       <td style="vertical-align: top;">2<br>
2621       </td>
2622       <td style="vertical-align: top;">Minimum and maximum aliased line
2623 widths.<br>
2624       </td>
2625     </tr>
2626     <tr>
2627       <td style="vertical-align: top;">GL_ALIASED_LINE_WIDTH_RANGE<br>
2628       </td>
2629       <td style="vertical-align: top;">2<br>
2630       </td>
2631       <td style="vertical-align: top;">Minimum and maximum antialiased
2632 line widths.</td>
2633     </tr>
2634     <tr>
2635       <td style="vertical-align: top;">GL_COLOR_LOGIC_OP<br>
2636       </td>
2637       <td style="vertical-align: top;">1<br>
2638       </td>
2639       <td style="vertical-align: top;">Zero if logicop is disabled.<br>
2640 One if logicop is enabled.<br>
2641       </td>
2642     </tr>
2643     <tr>
2644       <td style="vertical-align: top;">GL_LOGIC_OP_MODE<br>
2645       </td>
2646       <td style="vertical-align: top;">1<br>
2647       </td>
2648       <td style="vertical-align: top;">Logicop function.<br>
2649       </td>
2650     </tr>
2651     <tr>
2652       <td style="vertical-align: top;">GL_MATRIX_MODE<br>
2653       </td>
2654       <td style="vertical-align: top;">1<br>
2655       </td>
2656       <td style="vertical-align: top;">Matrix mode: GL_MODELVIEW or
2657 GL_PROJECTION.<br>
2658       </td>
2659     </tr>
2660     <tr>
2661       <td style="vertical-align: top;">GL_MAX_MODELVIEW_STACK_DEPTH<br>
2662       </td>
2663       <td style="vertical-align: top;">1<br>
2664       </td>
2665       <td style="vertical-align: top;">Maximum size of the modelview
2666 matrix stack.<br>
2667       </td>
2668     </tr>
2669     <tr>
2670       <td style="vertical-align: top;">GL_MAX_NAME_STACK_DEPTH<br>
2671       </td>
2672       <td style="vertical-align: top;">1<br>
2673       </td>
2674       <td style="vertical-align: top;">Maximum size of the selection
2675 name stack.<br>
2676       </td>
2677     </tr>
2678     <tr>
2679       <td style="vertical-align: top;">GL_MAX_PROJECTION_STACK_DEPTH<br>
2680       </td>
2681       <td style="vertical-align: top;">1<br>
2682       </td>
2683       <td style="vertical-align: top;">Maximum size of the projection
2684 matrix stack.<br>
2685       </td>
2686     </tr>
2687     <tr>
2688       <td style="vertical-align: top;">GL_MAX_TEXTURE_SIZE<br>
2689       </td>
2690       <td style="vertical-align: top;">1<br>
2691       </td>
2692       <td style="vertical-align: top;">Maximum 2D texture image width
2693 and height.<br>
2694       </td>
2695     </tr>
2696     <tr>
2697       <td style="vertical-align: top;">GL_MAX_VIEWPORT_DIMS<br>
2698       </td>
2699       <td style="vertical-align: top;">2</td>
2700       <td style="vertical-align: top;">Maximum viewport width and
2701 height in pixels.<br>
2702       </td>
2703     </tr>
2704     <tr>
2705       <td style="vertical-align: top;">GL_MODELVIEW_MATRIX<br>
2706       </td>
2707       <td style="vertical-align: top;">16<br>
2708       </td>
2709       <td style="vertical-align: top;">Current/top modelview matrix
2710 values.<br>
2711       </td>
2712     </tr>
2713     <tr>
2714       <td style="vertical-align: top;">GL_MODELVIEW_MATRIX_STACK_DEPTH<br>
2715       </td>
2716       <td style="vertical-align: top;">1<br>
2717       </td>
2718       <td style="vertical-align: top;">Current size of the modelview
2719 matrix stack.<br>
2720       </td>
2721     </tr>
2722     <tr>
2723       <td style="vertical-align: top;">GL_NAME_STACK_DEPTH<br>
2724       </td>
2725       <td style="vertical-align: top;">1<br>
2726       </td>
2727       <td style="vertical-align: top;">Current size of the selection
2728 name stack.<br>
2729       </td>
2730     </tr>
2731     <tr>
2732       <td style="vertical-align: top;">GL_PACK_ROW_LENGTH<br>
2733       </td>
2734       <td style="vertical-align: top;">1<br>
2735       </td>
2736       <td style="vertical-align: top;">Pixel packing row length.<br>
2737       </td>
2738     </tr>
2739     <tr>
2740       <td style="vertical-align: top;">GL_POLYGON_SMOOTH<br>
2741       </td>
2742       <td style="vertical-align: top;">1<br>
2743       </td>
2744       <td style="vertical-align: top;">Zero if polygon smoothing is
2745 disabled.<br>
2746 One if polygon smoothing is enabled.<br>
2747       </td>
2748     </tr>
2749     <tr>
2750       <td style="vertical-align: top;">GL_PROJECTION_MATRIX<br>
2751       </td>
2752       <td style="vertical-align: top;">16<br>
2753       </td>
2754       <td style="vertical-align: top;">Current/top projection matrix
2755 values.<br>
2756       </td>
2757     </tr>
2758     <tr>
2759       <td style="vertical-align: top;">GL_PROJECTION_STACK_DEPTH<br>
2760       </td>
2761       <td style="vertical-align: top;">1<br>
2762       </td>
2763       <td style="vertical-align: top;">Current size of projection
2764 matrix stack.<br>
2765       </td>
2766     </tr>
2767     <tr>
2768       <td style="vertical-align: top;">GL_READ_BUFFER<br>
2769       </td>
2770       <td style="vertical-align: top;">1<br>
2771       </td>
2772       <td style="vertical-align: top;">Current read buffer: GL_FRONT or
2773 GL_BACK.<br>
2774       </td>
2775     </tr>
2776     <tr>
2777       <td style="vertical-align: top;">GL_RED_BITS<br>
2778       </td>
2779       <td style="vertical-align: top;">1<br>
2780       </td>
2781       <td style="vertical-align: top;">Number of bits per red value in
2782 the frame buffer.<br>
2783       </td>
2784     </tr>
2785     <tr>
2786       <td style="vertical-align: top;">GL_RENDER_MODE<br>
2787       </td>
2788       <td style="vertical-align: top;">1<br>
2789       </td>
2790       <td style="vertical-align: top;">Current rendering mode:
2791 GL_RENDER or GL_SELECTION.<br>
2792       </td>
2793     </tr>
2794     <tr>
2795       <td style="vertical-align: top;">GL_RGBA_MODE<br>
2796       </td>
2797       <td style="vertical-align: top;">1<br>
2798       </td>
2799       <td style="vertical-align: top;">Always one.<br>
2800       </td>
2801     </tr>
2802     <tr>
2803       <td style="vertical-align: top;">GL_SCISSOR_BOX<br>
2804       </td>
2805       <td style="vertical-align: top;">4<br>
2806       </td>
2807       <td style="vertical-align: top;">Scissor box (x, y, width,
2808 height).<br>
2809       </td>
2810     </tr>
2811     <tr>
2812       <td style="vertical-align: top;">GL_SCISSOR_TEST<br>
2813       </td>
2814       <td style="vertical-align: top;">1<br>
2815       </td>
2816       <td style="vertical-align: top;">Zero if scissor test is disabled.<br>
2817 One if scissor test is enabled.<br>
2818       </td>
2819     </tr>
2820     <tr>
2821       <td style="vertical-align: top;">GL_SELECTION_BUFFER_SIZE<br>
2822       </td>
2823       <td style="vertical-align: top;">1<br>
2824       </td>
2825       <td style="vertical-align: top;">Size of selection buffer.<br>
2826       </td>
2827     </tr>
2828     <tr>
2829       <td style="vertical-align: top;">GL_SHADE_MODEL<br>
2830       </td>
2831       <td style="vertical-align: top;">1<br>
2832       </td>
2833       <td style="vertical-align: top;">Shade model: GL_FLAT or
2834 GL_SMOOTH.<br>
2835       </td>
2836     </tr>
2837     <tr>
2838       <td style="vertical-align: top;">GL_STENCIL_BITS<br>
2839       </td>
2840       <td style="vertical-align: top;">1<br>
2841       </td>
2842       <td style="vertical-align: top;">Number of bits per stencil value
2843 in the frame buffer.<br>
2844       </td>
2845     </tr>
2846     <tr>
2847       <td style="vertical-align: top;">GL_STENCIL_CLEAR_VALUE<br>
2848       </td>
2849       <td style="vertical-align: top;">1<br>
2850       </td>
2851       <td style="vertical-align: top;">Stencil buffer clear value.<br>
2852       </td>
2853     </tr>
2854     <tr>
2855       <td style="vertical-align: top;">GL_STENCIL_FAIL<br>
2856       </td>
2857       <td style="vertical-align: top;">1<br>
2858       </td>
2859       <td style="vertical-align: top;">Stencil fail operation.<br>
2860       </td>
2861     </tr>
2862     <tr>
2863       <td style="vertical-align: top;">GL_STENCIL_FUNC<br>
2864       </td>
2865       <td style="vertical-align: top;">1<br>
2866       </td>
2867       <td style="vertical-align: top;">Stencil function.<br>
2868       </td>
2869     </tr>
2870     <tr>
2871       <td style="vertical-align: top;">GL_STENCIL_REF<br>
2872       </td>
2873       <td style="vertical-align: top;">1<br>
2874       </td>
2875       <td style="vertical-align: top;">Stencil reference value.<br>
2876       </td>
2877     </tr>
2878     <tr>
2879       <td style="vertical-align: top;">GL_STENCIL_TEST<br>
2880       </td>
2881       <td style="vertical-align: top;">1<br>
2882       </td>
2883       <td style="vertical-align: top;">Zero if stencil test is disabled.<br>
2884 One if stencil test is enabled.<br>
2885       </td>
2886     </tr>
2887     <tr>
2888       <td style="vertical-align: top;">GL_STENCIL_VALUE_MASK<br>
2889       </td>
2890       <td style="vertical-align: top;">1<br>
2891       </td>
2892       <td style="vertical-align: top;">Stencil mask value.<br>
2893       </td>
2894     </tr>
2895     <tr>
2896       <td style="vertical-align: top;">GL_STENCIL_WRITE_MASK<br>
2897       </td>
2898       <td style="vertical-align: top;">1<br>
2899       </td>
2900       <td style="vertical-align: top;">Stencil buffer write mask.<br>
2901       </td>
2902     </tr>
2903     <tr>
2904       <td style="vertical-align: top;">GL_TEXTURE_2D<br>
2905       </td>
2906       <td style="vertical-align: top;">1<br>
2907       </td>
2908       <td style="vertical-align: top;">Zero if 2D texture mapping is
2909 disabled.<br>
2910 One if 2D texture mapping is enabled.<br>
2911       </td>
2912     </tr>
2913     <tr>
2914       <td style="vertical-align: top;">GL_TEXTURE_BINDING_2D</td>
2915       <td style="vertical-align: top;">1<br>
2916       </td>
2917       <td style="vertical-align: top;">Name of currently bound 2D
2918 texture object.<br>
2919       </td>
2920     </tr>
2921     <tr>
2922       <td style="vertical-align: top;">GL_TEXTURE_ENV_COLOR<br>
2923       </td>
2924       <td style="vertical-align: top;">4<br>
2925       </td>
2926       <td style="vertical-align: top;">Texture environment color (red,
2927 green, blue, alpha).<br>
2928       </td>
2929     </tr>
2930     <tr>
2931       <td style="vertical-align: top;">GL_TEXTURE_ENV_MODE<br>
2932       </td>
2933       <td style="vertical-align: top;">1<br>
2934       </td>
2935       <td style="vertical-align: top;">Texture environment mode.<br>
2936       </td>
2937     </tr>
2938     <tr>
2939       <td style="vertical-align: top;">GL_UNPACK_ROW_LENGTH<br>
2940       </td>
2941       <td style="vertical-align: top;">1<br>
2942       </td>
2943       <td style="vertical-align: top;">Pixel unpacking row length.<br>
2944       </td>
2945     </tr>
2946     <tr>
2947       <td style="vertical-align: top;">GL_UNPACK_LSB_FIRST<br>
2948       </td>
2949       <td style="vertical-align: top;">1<br>
2950       </td>
2951       <td style="vertical-align: top;">Zero if most significant bit is
2952 unpacked first for bitmaps.<br>
2953 One if least significant bit is unpacked first for bitmaps.<br>
2954       </td>
2955     </tr>
2956     <tr>
2957       <td style="vertical-align: top;">GL_VIEWPORT<br>
2958       </td>
2959       <td style="vertical-align: top;">4<br>
2960       </td>
2961       <td style="vertical-align: top;">Current viewport (x, y, width,
2962 height).<br>
2963       </td>
2964     </tr>
2965   </tbody>
2966 </table>
2967 <br>
2968 <br>
2969 <h2>9.2 String Queries</h2>
2970 The command<br>
2971 <br>
2972 <div style="margin-left: 40px;">const GLubyte *<span
2973  style="font-weight: bold;">glGetString</span>(GLenum <span
2974  style="font-style: italic;">name</span>)<br>
2975 </div>
2976 <br>
2977 is used to query string-valued values. &nbsp;The legal values for <span
2978  style="font-style: italic;">name</span> are described in the following
2979 table:<br>
2980 <br>
2981 <table cellpadding="2" cellspacing="2" border="1"
2982  style="text-align: left; width: 80%; margin-left: auto; margin-right: auto;">
2983   <tbody>
2984     <tr>
2985       <td style="vertical-align: top;"><span style="font-style: italic;">name</span><br>
2986       </td>
2987       <td style="vertical-align: top;">Return value<br>
2988       </td>
2989     </tr>
2990     <tr>
2991       <td style="vertical-align: top;">GL_VERSION<br>
2992       </td>
2993       <td style="vertical-align: top;">The library version, such as
2994 "1.2".<br>
2995       </td>
2996     </tr>
2997     <tr>
2998       <td style="vertical-align: top;">GL_RENDERER<br>
2999       </td>
3000       <td style="vertical-align: top;">The renderer, such as "Mesa DRI
3001 Radeon".<br>
3002       </td>
3003     </tr>
3004     <tr>
3005       <td style="vertical-align: top;">GL_VENDOR<br>
3006       </td>
3007       <td style="vertical-align: top;">The vendor of this
3008 implementation, such as "Tungsten Graphics, Inc."<br>
3009       </td>
3010     </tr>
3011     <tr>
3012       <td style="vertical-align: top;">GL_EXTENSIONS<br>
3013       </td>
3014       <td style="vertical-align: top;">A white-space separated list of
3015 the supported extensions. </td>
3016     </tr>
3017   </tbody>
3018 </table>
3019 <br>
3020 <h2>9.3 Error Queries</h2>
3021 The command<br>
3022 <br>
3023 <div style="margin-left: 40px;">GLenum <span style="font-weight: bold;">glGetError</span>(void)<br>
3024 </div>
3025 <br>
3026 returns the current error code. &nbsp;The current error code will be
3027 set by a GL command when an error condition has been detected. &nbsp;If
3028 the current error code is already set, subsequent errors will not be
3029 recorded. &nbsp;The error code is reset/cleared to GL_NO_ERROR when <span
3030  style="font-weight: bold;">glGetError</span> returns. &nbsp;The
3031 following error codes are possible:<br>
3032 <br>
3033 <table cellpadding="2" cellspacing="2" border="1"
3034  style="text-align: left; width: 80%; margin-left: auto; margin-right: auto;">
3035   <tbody>
3036     <tr>
3037       <td style="vertical-align: top;">Error code<br>
3038       </td>
3039       <td style="vertical-align: top;">Meaning<br>
3040       </td>
3041     </tr>
3042     <tr>
3043       <td style="vertical-align: top;">GL_NO_ERROR<br>
3044       </td>
3045       <td style="vertical-align: top;">No error has been recorded.<br>
3046       </td>
3047     </tr>
3048     <tr>
3049       <td style="vertical-align: top;">GL_INVALID_ENUM<br>
3050       </td>
3051       <td style="vertical-align: top;">An enum parameter had an invalid
3052 value.<br>
3053       </td>
3054     </tr>
3055     <tr>
3056       <td style="vertical-align: top;">GL_INVALID_VALUE<br>
3057       </td>
3058       <td style="vertical-align: top;">A numeric parameter had an
3059 invalid value.<br>
3060       </td>
3061     </tr>
3062     <tr>
3063       <td style="vertical-align: top;">GL_INVALID_OPERATION<br>
3064       </td>
3065       <td style="vertical-align: top;">A function was called when not
3066 legal to do so.<br>
3067       </td>
3068     </tr>
3069     <tr>
3070       <td style="vertical-align: top;">GL_STACK_OVERFLOW<br>
3071       </td>
3072       <td style="vertical-align: top;">The current transformation
3073 matrix stack is full.<br>
3074       </td>
3075     </tr>
3076     <tr>
3077       <td style="vertical-align: top;">GL_STACK_UNDERFLOW<br>
3078       </td>
3079       <td style="vertical-align: top;">The current transformation
3080 matrix stack is empty.<br>
3081       </td>
3082     </tr>
3083     <tr>
3084       <td style="vertical-align: top;">GL_OUT_OF_MEMORY<br>
3085       </td>
3086       <td style="vertical-align: top;">The system ran out of dynamic
3087 memory.<br>
3088       </td>
3089     </tr>
3090   </tbody>
3091 </table>
3092 <br>
3093 <br>
3094 <h1>10. Unsupported Features</h1>
3095 This section lists other features and functions which are not supported
3096 and not previously discussed.<br>
3097 <br>
3098 <h2>10.1 Feedback Mode</h2>
3099 Feedback mode and the following related functions are not supported.<br>
3100 <br>
3101 <div style="margin-left: 40px;"><span style="font-weight: bold;">glFeedbackBuffer</span><br>
3102 <span style="font-weight: bold;">glPassThrough</span><br>
3103 </div>
3104 <br>
3105 <h2>10.2 1D and 3D Textures<br>
3106 </h2>
3107 Only 2D texture images are supported. &nbsp;The following functions
3108 used to specify 1D and 3D texture images are not supported:<br>
3109 <br>
3110 <div style="margin-left: 40px;"><span style="font-weight: bold;">glTexImage1D</span><br
3111  style="font-weight: bold;">
3112 <span style="font-weight: bold;">glTexImage3D</span><br
3113  style="font-weight: bold;">
3114 <span style="font-weight: bold;">glTexSubImage1D</span><br
3115  style="font-weight: bold;">
3116 <span style="font-weight: bold;"> glTexSubImage3D</span><br
3117  style="font-weight: bold;">
3118 <span style="font-weight: bold;">glCopyTexImage1D</span><br
3119  style="font-weight: bold;">
3120 <span style="font-weight: bold;"> glCopyTexSubImage1D</span><br
3121  style="font-weight: bold;">
3122 <span style="font-weight: bold;"> glCopyTexSubImage3D</span><br>
3123 </div>
3124 <br>
3125 <h2>10.3 Alternate Texture Image Commands<br>
3126 </h2>
3127 Texture images may only be specified with <span
3128  style="font-weight: bold;">glTexImage2D</span>. &nbsp;The following
3129 alternate texture image commands are not supported:<br>
3130 <br>
3131 <div style="margin-left: 40px; font-weight: bold;">glTexSubImage2D<br>
3132 glCopyTexImage2D<br>
3133 glCopyTexSubImage2D<br>
3134 </div>
3135 <br>
3136 <h2>10.4 Proxy Textures</h2>
3137 Proxy textures are not supported and the GL_PROXY_TEXTURE_2D token is
3138 not supported by any function.<br>
3139 <br>
3140 <br>
3141 <h2>10.5 Other Texture Commands</h2>
3142 The following commands related to texture mapping are not supported by
3143 the subset:<br>
3144 <br>
3145 <div style="margin-left: 40px; font-weight: bold;"> glPrioritizeTextures<br>
3146 glAreTexturesResident<br>
3147 glIsTexture<br>
3148 glTexEnviv<br>
3149 glTexEnvf<br>
3150 glTexParameterf<br>
3151 glTexParameteriv<br>
3152 glTexParameterfv<br>
3153 </div>
3154 <br>
3155 <br>
3156 <h2>10.6 Copy and Draw Pixels<br>
3157 </h2>
3158 The following commands are not supported:<br>
3159 <br>
3160 <div style="margin-left: 40px;"><span style="font-weight: bold;">glDrawPixels<br>
3161 glCopyPixels<br>
3162 glPixelZoom<br>
3163 <br>
3164 </span></div>
3165 <h2>10.7 Color Index Mode<br>
3166 </h2>
3167 Color index mode and the following related commands are not supported:<br>
3168 <br>
3169 <span style="font-weight: bold;"></span>
3170 <div style="margin-left: 40px;"><span style="font-weight: bold;">glIndexub<br>
3171 </span><span style="font-weight: bold;">glIndexi</span><br>
3172 <span style="font-weight: bold;">glIndexs<br>
3173 glIndexf<br>
3174 glIndexd<br>
3175 </span><span style="font-weight: bold;">glIndexubv<br>
3176 </span><span style="font-weight: bold;">glIndexiv</span><br>
3177 <span style="font-weight: bold;">glIndexsv<br>
3178 glIndexfv<br>
3179 glIndexdv</span><span style="font-weight: bold;"><br>
3180 glIndexMask<br>
3181 </span><span style="font-weight: bold;">glClearIndex<br>
3182 glIndexPointer</span><br style="font-weight: bold;">
3183 <br>
3184 </div>
3185 <h2>10.8 Pixel Transfer Operations</h2>
3186 The pixel transfer operations (scale, bias, look-up table, etc) are not
3187 supported and the following commands are omitted:<br>
3188 <br style="font-weight: bold;">
3189 <div style="margin-left: 40px;"><span style="font-weight: bold;">glPixelTransferf</span><br
3190  style="font-weight: bold;">
3191 <span style="font-weight: bold;">glPixelTransferi</span><br
3192  style="font-weight: bold;">
3193 <span style="font-weight: bold;">glPixelMapfv</span><br
3194  style="font-weight: bold;">
3195 <span style="font-weight: bold;">glPixelMapuiv</span><br
3196  style="font-weight: bold;">
3197 <span style="font-weight: bold;">glPixelMapusv</span><br
3198  style="font-weight: bold;">
3199 <span style="font-weight: bold;">glGetPixelMapfv</span><br
3200  style="font-weight: bold;">
3201 <span style="font-weight: bold;">glGetPixelMapuiv</span><br
3202  style="font-weight: bold;">
3203 <span style="font-weight: bold;">glGetPixelMapusv</span><br>
3204 </div>
3205 <br>
3206 <h2>10.9 Hints</h2>
3207 Hints and the following related command is not supported:<br>
3208 <br>
3209 <div style="margin-left: 40px;"><span style="font-weight: bold;">glHint<br>
3210 </span><br>
3211 </div>
3212 <h2>10.10 State Query Commands<br>
3213 </h2>
3214 The following state query commands are not supported:<br>
3215 <br>
3216 <div style="margin-left: 40px; font-weight: bold;">glGetBooleanv<br>
3217 glGetIntegerv<br>
3218 glGetDoublev<br>
3219 glGetPointerv<br>
3220 glGetTexEnvi<br>
3221 glGetTexEnvf<br>
3222 glGetTexParameteriv<br>
3223 glGetTexParameterfv<br>
3224 glGetTexLevelParameteriv<br>
3225 glGetTexLevelParameterfv<br>
3226 glGetTexImage<br>
3227 glGetClipPlane<br>
3228 </div>
3229 <br>
3230 <h2>10.11 Attribute Stacks</h2>
3231 State attribute stacks and the following related commands are not
3232 supported:<br>
3233 <br>
3234 <div style="margin-left: 40px;"><span style="font-weight: bold;">glPushAttrib</span><br
3235  style="font-weight: bold;">
3236 <span style="font-weight: bold;">glPopAtttrib</span><br>
3237 <br style="font-weight: bold;">
3238 </div>
3239 <h2>10.12 Double-Valued Functions</h2>
3240 All functions which take double-precision floating point values, but
3241 for which there is an equivalent single-precision valued function, are
3242 omitted. &nbsp;This includes, but is not limited to:<br>
3243 <br>
3244 <div style="margin-left: 40px;"><span style="font-weight: bold;">glVertex2d</span><br
3245  style="font-weight: bold;">
3246 <span style="font-weight: bold;">glVertex2dv</span><br
3247  style="font-weight: bold;">
3248 <span style="font-weight: bold;">glVertex3d</span><br
3249  style="font-weight: bold;">
3250 <span style="font-weight: bold;"> glVertex3dv</span><br
3251  style="font-weight: bold;">
3252 <span style="font-weight: bold;">glVertex4d</span><br
3253  style="font-weight: bold;">
3254 <span style="font-weight: bold;"> glVertex4dv</span><br
3255  style="font-weight: bold;">
3256 <span style="font-weight: bold;">glColor3d</span><br
3257  style="font-weight: bold;">
3258 <span style="font-weight: bold;">glColor3d</span><span
3259  style="font-weight: bold;">v</span><br style="font-weight: bold;">
3260 <span style="font-weight: bold;">glColor4d</span><br
3261  style="font-weight: bold;">
3262 <span style="font-weight: bold;"> glColor4dv</span><br
3263  style="font-weight: bold;">
3264 <span style="font-weight: bold;">glTexCoord1d</span><br
3265  style="font-weight: bold;">
3266 <span style="font-weight: bold;">glTexCoord1d</span><span
3267  style="font-weight: bold;">v</span><br style="font-weight: bold;">
3268 <span style="font-weight: bold;">glTexCoord2d</span><br
3269  style="font-weight: bold;">
3270 <span style="font-weight: bold;"> glTexCoord2dv</span><br
3271  style="font-weight: bold;">
3272 <span style="font-weight: bold;">glTexCoord3d</span><br
3273  style="font-weight: bold;">
3274 <span style="font-weight: bold;"> glTexCoord3dv</span><br
3275  style="font-weight: bold;">
3276 <span style="font-weight: bold;">glTexCoord4d</span><br
3277  style="font-weight: bold;">
3278 <span style="font-weight: bold;"> glTexCoord4dv</span><br
3279  style="font-weight: bold;">
3280 <span style="font-weight: bold;">glRasterPos2d</span><br
3281  style="font-weight: bold;">
3282 <span style="font-weight: bold;"> glRasterPos2dv</span><br
3283  style="font-weight: bold;">
3284 <span style="font-weight: bold;">glRasterPos3d</span><br
3285  style="font-weight: bold;">
3286 <span style="font-weight: bold;"> glRasterPos3dv</span><br
3287  style="font-weight: bold;">
3288 <span style="font-weight: bold;">glRasterPos4d</span><br
3289  style="font-weight: bold;">
3290 <span style="font-weight: bold;"> glRasterPos4dv</span><br
3291  style="font-weight: bold;">
3292 <span style="font-weight: bold;">glLoadMatrixd</span><br
3293  style="font-weight: bold;">
3294 <span style="font-weight: bold;">glMultMatrixd</span><br
3295  style="font-weight: bold;">
3296 <span style="font-weight: bold;">glScaled</span><br
3297  style="font-weight: bold;">
3298 <span style="font-weight: bold;">glRotated</span><br
3299  style="font-weight: bold;">
3300 <span style="font-weight: bold;">glTranslated<br>
3301 glRectd<br>
3302 glRectdv<br>
3303 </span> <span style="font-weight: bold;"><br>
3304 </span> </div>
3305 <h2>10.13 Evaluators</h2>
3306 Evaluators and the following related commands are not supported:<br>
3307 <br>
3308 <div style="margin-left: 40px;"><span style="font-weight: bold;">glMap1f</span><br
3309  style="font-weight: bold;">
3310 <span style="font-weight: bold;">glMap2d</span><br
3311  style="font-weight: bold;">
3312 <span style="font-weight: bold;">glMap2f</span><br
3313  style="font-weight: bold;">
3314 <span style="font-weight: bold;">glGetMapdv</span><br
3315  style="font-weight: bold;">
3316 <span style="font-weight: bold;">glGetMapfv</span><br
3317  style="font-weight: bold;">
3318 <span style="font-weight: bold;">glGetMapiv</span><br
3319  style="font-weight: bold;">
3320 <span style="font-weight: bold;">glEvalCoord1d</span><br
3321  style="font-weight: bold;">
3322 <span style="font-weight: bold;">glEvalCoord1f</span><br
3323  style="font-weight: bold;">
3324 <span style="font-weight: bold;">glEvalCoord1dv</span><br
3325  style="font-weight: bold;">
3326 <span style="font-weight: bold;">glEvalCoord1fv</span><br
3327  style="font-weight: bold;">
3328 <span style="font-weight: bold;">glEvalCoord2d</span><br
3329  style="font-weight: bold;">
3330 <span style="font-weight: bold;">glEvalCoord2f</span><br
3331  style="font-weight: bold;">
3332 <span style="font-weight: bold;">glEvalCoord2dv</span><br
3333  style="font-weight: bold;">
3334 <span style="font-weight: bold;">glEvalCoord2fv</span><br
3335  style="font-weight: bold;">
3336 <span style="font-weight: bold;">glMapGrid1d</span><br
3337  style="font-weight: bold;">
3338 <span style="font-weight: bold;">glMapGrid1f</span><br
3339  style="font-weight: bold;">
3340 <span style="font-weight: bold;">glMapGrid2d</span><br
3341  style="font-weight: bold;">
3342 <span style="font-weight: bold;">glMapGrid2f</span><br
3343  style="font-weight: bold;">
3344 <span style="font-weight: bold;">glEvalPoint1</span><br
3345  style="font-weight: bold;">
3346 <span style="font-weight: bold;">glEvalPoint2</span><br
3347  style="font-weight: bold;">
3348 <span style="font-weight: bold;">glEvalMesh1</span><br
3349  style="font-weight: bold;">
3350 <span style="font-weight: bold;">glEvalMesh2</span><br
3351  style="font-weight: bold;">
3352 </div>
3353 <br>
3354 <h2>10.14 Display Lists</h2>
3355 Display lists and the following related commands are not supported:<br>
3356 <br>
3357 <div style="margin-left: 40px; font-weight: bold;">glIsList<br>
3358 glDeleteLists<br>
3359 glGenLists<br>
3360 glNewList<br>
3361 glEndList<br>
3362 glCallList<br>
3363 glCallLists<br>
3364 glListBase<br>
3365 </div>
3366 <br>
3367 <h2>10.15 Accumulation Buffer</h2>
3368 The accumulation buffer and the following related commands are not
3369 supported:<br>
3370 <br style="font-weight: bold;">
3371 <div style="margin-left: 40px;"><span style="font-weight: bold;">glAccum</span><br
3372  style="font-weight: bold;">
3373 <span style="font-weight: bold;">glClearAccum</span><br>
3374 </div>
3375 <br>
3376 <h2>10.16 Fog</h2>
3377 Fog and the following related commands are not supported:<br>
3378 <br>
3379 <div style="margin-left: 40px; font-weight: bold;"> glFogi<br>
3380 glFogf<br>
3381 glFogiv<br>
3382 glFogfv<br>
3383 </div>
3384 <br>
3385 <h2>10.17 Depth Test</h2>
3386 Depth testing and the following related commands are not supported:<br>
3387 <br>
3388 <div style="margin-left: 40px;"><span style="font-weight: bold;">glDepthFunc</span><br
3389  style="font-weight: bold;">
3390 <span style="font-weight: bold;">glDepthMask</span><br
3391  style="font-weight: bold;">
3392 <span style="font-weight: bold;">glDepthRange</span><br
3393  style="font-weight: bold;">
3394 <span style="font-weight: bold;">glClearDepth</span><br>
3395 </div>
3396 <br>
3397 <h2>10.18 Imaging Subset</h2>
3398 The OpenGL imaging subset (which implements features such as
3399 convolution, histogram, min/max recording, color matrix and color
3400 tables) is not supported.<br>
3401 <br>
3402 <br>
3403 <h1>Appendix A: Issues</h1>
3404 This appendix lists documentation and subset issues with their current
3405 status. &nbsp;For items which are still open, the documentation (above)
3406 follows the recommended solution.<br>
3407 <br>
3408 <h2>A.1 Vertex Arrays</h2>
3409 Should vertex arrays be supported? &nbsp;Is there a performance
3410 advantage?<br>
3411 <br>
3412 RESOLUTION: No, there isn't enough of a performance advantage to
3413 justify them.<br>
3414 <br>
3415 <h2>A.2 Polygon Antialiasing and Edge Flags</h2>
3416 Should edge flags be supported for antialiasing?<br>
3417 <br>
3418 Edge flags don't effect antialiasing, at least not normally. &nbsp;A
3419 number of approaches to antialiasing have been summarized in email.<br>
3420 <br>
3421 RECOMMENDATION: don't support edge flags. &nbsp;They don't effect
3422 polygon antialiasing.<br>
3423 <br>
3424 RESOLUTION: closed, as of 26 Feb 2003.<br>
3425 <br>
3426 <h2>A.3 glRasterPos vs. glWindowPos</h2>
3427 Should glRasterPos and/or glWindowPos commands be supported?<br>
3428 <br>
3429 RESOLUTION: Closed: implement glRasterPos commands, but not glWindowPos
3430 commands.<br>
3431 <br>
3432 <h2>A.4 GL_IBM_rasterpos_clip extension</h2>
3433 Should the GL_IBM_rasterpos_clip extension be implemented?<br>
3434 <br>
3435 RESOLUTION: &nbsp;No. &nbsp;It's not required.<br>
3436 <br>
3437 <h2>A.5 Image Formats and Types</h2>
3438 Which image formats and types should be supported for <span
3439  style="font-weight: bold;">glTexImage2D</span> and <span
3440  style="font-weight: bold;">glReadPixels</span>?<br>
3441 <br>
3442 OpenGL specifies a <span style="font-weight: bold;">large</span>
3443 variety of image formats and data types. &nbsp;Only a few are commonly
3444 used.<br>
3445 <br>
3446 RECOMMENDATION: &nbsp;we propose a subset:<br>
3447 <br>
3448 For <span style="font-weight: bold;">glTexImage2D</span> only allow <span
3449  style="font-style: italic;">type</span>=GL_UNSIGNED_BYTE and <span
3450  style="font-style: italic;">format</span>=GL_RGBA, GL_RGB,
3451 GL_INTENSITY. &nbsp; Only allow <span style="font-style: italic;">internalFormat</span>
3452 to be GL_RGBA, GL_RGB or GL_INTENSITY as well.&nbsp; Basically, only
3453 support image formats/types that are directly supported by the Radeon
3454 hardware. &nbsp;This will allow <span style="font-weight: bold;">glTexImage2D</span>
3455 to basically just use <span style="font-weight: bold;">memcpy</span> to
3456 copy texture images.<br>
3457 <br>
3458 For <span style="font-weight: bold;">glReadPixels</span>, only allow <span
3459  style="font-style: italic;">type</span> = GL_UNSIGNED_BYTE or GL_FLOAT.
3460 &nbsp;Only allow <span style="font-style: italic;">format</span> =
3461 GL_RGB or GL_RGBA. &nbsp;This is just enough to support the OpenGL
3462 conformance tests.<br>
3463 <br>
3464 RESOLUTION: open<br>
3465 <br>
3466 <h2>A.6 Texture Environment Modes</h2>
3467 Which texture environment modes should be supported? &nbsp;OpenGL 1.2
3468 has GL_REPLACE, GL_MODULATE, GL_DECAL and GL_BLEND. &nbsp;GL_DECAL isn't
3469 defined for all base internal texture formats. &nbsp;GL_ADD is another
3470 useful mode. &nbsp;Perhaps drop GL_DECAL mode and add GL_ADD mode.<br>
3471 <br>
3472 RECOMMENDATION: implement the standard modes GL_REPLACE, GL_MODULATE,
3473 GL_DECAL and GL_BLEND.<br>
3474 <br>
3475 RESOLUTION: open<br>
3476 <br>
3477 <h2>A.7 Truncated Mipmaps and LOD Control</h2>
3478 Should we support the GL_TEXTURE_BASE_LEVEL, GL_TEXTURE_MAX_LEVEL,
3479 GL_TEXTURE_MIN_LOD and GL_TEXTURE_MAX_LOD texture parameters?<br>
3480 <br>
3481 RECOMMENDATION: &nbsp;We propose omitting these features at this time,
3482 in the interest of simplifying the driver.<br>
3483 <br>
3484 RESOLUTION: open<br>
3485 <br>
3486 <h2>A.8 Texture Priorities and Residency</h2>
3487 Should the subset support texture priorities via <span
3488  style="font-weight: bold;">glPrioritizeTextures</span> and the <span
3489  style="font-weight: bold;">glAreTexturesResident</span> command?<br>
3490 <br>
3491 RECOMMENDATION: &nbsp;Few applications use these features and
3492 functions. &nbsp;We propose omitting them to simplify the driver.<br>
3493 <br>
3494 RESOLUTION: open<br>
3495 <br>
3496 <h2>A.9 Pixel Pack/Unpack Alignment Control</h2>
3497 Should we support the GL_PACK_ALIGNMENT and GL_UNPACK_ALIGNMENT options?<br>
3498 <br>
3499 These are used to align pixel data addresses to 1, 2 and 4-byte
3500 multiples for <span style="font-weight: bold;">glBitmap, glTexImage2D</span>
3501 and <span style="font-weight: bold;">glReadPixels</span>. &nbsp;These
3502 aren't strictly needed since the user can provide a 1, 2 or 4-byte
3503 aligned address and appropriate GL_PACK_ROW_LENGTH or
3504 GL_UNPACK_ROW_LENGTH values instead.<br>
3505 <br>
3506 RECOMMENDATION: &nbsp;We recommend omitting them to simplify the driver.<br>
3507 <br>
3508 RESOLUTION: open<br>
3509 <br>
3510 <h2>A.10 Pixel Pack/Unpack Skip Rows/Pixels Control</h2>
3511 Should we support the GL_UNPACK_SKIP_PIXELS, GL_UNPACK_SKIP_ROWS,
3512 GL_PACK_SKIP_PIXELS and GL_PACK_SKIP_ROWS options for pixel
3513 unpacking/packing?<br>
3514 <br>
3515 These options aren't really needed since the user can adjust the start
3516 address and GL_PACK/UNPACK_ROW_LENGTH parameters to achieve the same
3517 effect.<br>
3518 <br>
3519 RECOMMENDATION: &nbsp;omit these parameters.<br>
3520 <br>
3521 RESOLUTION: open<br>
3522 <br>
3523 <h2>A.11 Texture State Queries</h2>
3524 Should we support the command <span style="font-weight: bold;">glGetTexEnvi/fv,
3525 glGetTexParameteri/fv</span> and <span style="font-weight: bold;">glGetTexLevelParameteri/fv</span>?<br>
3526 <br>
3527 RECOMMENDATION: &nbsp;No.&nbsp;They're seldom needed and their
3528 implementation is several hundred lines of code in length.<br>
3529 <br>
3530 RESOLUTION: &nbsp;open<br>
3531 <br>
3532 <h2>A.12 glGetIntegerv, glGetBooleanv and glGetDoublev</h2>
3533 Should we support the commands <span style="font-weight: bold;">glGetIntegerv,
3534 glGetBooleanv </span>and <span style="font-weight: bold;">glGetDoublev</span>
3535 in addition to <span style="font-weight: bold;">glGetFloatv</span>?<br>
3536 <br>
3537 RECOMMENDATION: &nbsp;Omit the boolean, integer and double-valued
3538 functions. All state values which can be queried by these commands can
3539 be expressed as floating point values and queried with <span
3540  style="font-weight: bold;">glGetFloatv</span>. &nbsp;The
3541 implementation of the other three commands involves many lines of code.<br>
3542 <br>
3543 RESOLUTION: &nbsp;open<br>
3544 <br>
3545 <h2>A.13 glBitmap and Per-Fragment Operations</h2>
3546 Should bitmaps rendered with <span style="font-weight: bold;">glBitmap</span>
3547 be subjected to the per-fragment operations?<br>
3548 <br>
3549 If bitmaps are implemented with points it will be easy to implement the
3550 per-fragment operations. &nbsp;Otherwise, it could be difficult.<br>
3551 <br>
3552 RECOMMENDATION: &nbsp;Implement glBitmap by drawing points/pixels with
3553 the hardware. &nbsp;This will make supporting the per-fragments
3554 trivially easy. &nbsp;Also, it makes portrait-mode display relatively
3555 easy.<br>
3556 <br>
3557 RESOLUTION: &nbsp;open<br>
3558 <br>
3559 <h2>A.14 Reduced gl.h Header File</h2>
3560 Should we produce a reduced gl.h header file which only defines the
3561 tokens and functions which are implemented by the subset?<br>
3562 <br>
3563 RECOMMENDATION: yes. &nbsp;It would be a useful reference to
3564 programmers to quickly determine which functions and tokens are
3565 supported.<br>
3566 <br>
3567 RESOLUTION: open<br>
3568 <br>
3569 <h2>A.15 glPolygonMode</h2>
3570 Is <span style="font-weight: bold;">glPolygonMode</span> needed?<br>
3571 <br>
3572 RECOMMENDATION: No. &nbsp;Omit it.<br>
3573 <br>
3574 RESOLUTION: closed, as of 26 Feb 2003<br>
3575 <br>
3576 <br>
3577 <p> </p>
3578 </body>
3579 </html>