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