docs/subset-A.html

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