1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2 <html lang="en"> 3 <head> 4 <meta http-equiv="content-type" content="text/html; charset=utf-8"> 5 <title>Mini GLX Specification</title> 6 </head> 7 <body> 8 <span style="font-style: italic;"></span><span 9 style="font-weight: bold;"></span> 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 © 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. 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 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>. 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 Quadrilaterals and polygons are composed of triangles. 72 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. Vertices are actually 4-element 113 homogeneous coordinates. 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 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. Texture 151 coordinates are actually four-component coordinates: (s, t, r, q). 152 The <span style="font-weight: bold;">glTexCoord2</span> commands 153 set s and t explicitly. 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> 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, </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. 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 The mode parameter may be GL_MODELVIEW or GL_PROJECTION to specify 283 the modelview matrix or projection matrix. Subsequent matrix 284 commands will effect the current matrix. 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. 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. 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. 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. 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 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. 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. <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 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. 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. <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. 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. <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>. 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> 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). The coordinate is processed 385 like a vertex; it is transformed by the modelview matrix, the projection 386 matrix and mapped to the viewport. The resulting window coordinate 387 is stored as the current raster position. The coordinate is 388 clipped-tested against the frustum like a vertex. 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. The 395 current raster color is updated (copied) from the current color (as 396 specified by <span style="font-weight: bold;">glColor</span>). 397 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, </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. <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). 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. A 456 fragment is a tuple which consists of a window coordinate, colors and 457 texture coordinates. 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>. The window coordinate (x<sub>w</sub>, 465 y<sub>w</sub>, z<sub>w</sub>) is truncated to rasterize the point. 466 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. Lines are rasterized as described 484 in the OpenGL specification. 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. The width defaults to 1.0. 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. 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. 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. Later, the 525 alpha value of each fragment is multiplied by the coverage value. 526 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 For GL_TRIANGLES mode, the number of vertices should be a multiple 546 of three - extra vertices will be ignored. For GL_TRIANGLE_STRIP 547 and GL_TRIANGLE_FAN, at least three vertices should be specified. 548 If less than three are specified, nothing is drawn. <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> For 558 GL_QUADS, the number of vertices should be a multiple of four - extra 559 vertices will be ignored. For GL_QUAD_STRIP, the number of 560 vertices should be even and at least four. 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 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. 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 By default, a front-facing polygon's vertices are in 578 counter-clockwise order (in window coordinates). 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. If <span style="font-style: italic;">mode</span> 590 is GL_CW then polygons with clockwise winding are front-facing. If <span 591 style="font-style: italic;">mode</span> is GL_CCW then polygons with 592 counter-clockwise winding are front-facing. The default value is 593 GL_CCW. 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. 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. If <span style="font-style: italic;">mode</span> is 607 GL_FRONT then front-facing polygons will be culled. 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. 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 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. Fragments 629 completely inside the polygon have coverage 1.0. Fragments 630 completely outside the polygon have zero coverage (in theory). 631 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 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. If <span style="font-style: italic;">mode</span> is 647 GL_FLAT then vertex colors are not interpolated. The color used 648 for drawing lines, triangles and quadrilaterals is that of the last 649 vertex used to specify each primitive. For polygons, the color of 650 the first vertex specifies the color for the entire polygon. 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. Fragments are only generated 657 for the bits (pixels) which are set. 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 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. <span style="font-style: italic;">xOrig</span> and <span 675 style="font-style: italic;">yOrig</span> specify the bitmap origin. 676 <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. <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 </span>Unpacking is the process of extracting image data from 688 client memory subject to byte swapping, non-default row strides, etc. 689 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. 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. 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. 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 bitMask = 1 << (j % 8);<br> 755 else<br> 756 bitMask = 128 >> (j % 8);<br> 757 <br> 758 if (byte & bitMask)<br> 759 bit = 1;<br> 760 else<br> 761 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 < <span style="font-style: italic;">height</span>; 771 j++) {<br> 772 for (i = 0; i < <span style="font-style: italic;">width</span>; 773 i++) {<br> 774 if (bit(i,j)) {<br> 775 fragment.x = 776 floor(x<sub>rp</sub> - <span style="font-style: italic;">xOrig</span>) 777 + i;<br> 778 fragment.y = 779 floor(y<sub>rp</sub> - <span style="font-style: italic;">yOrig</span>) 780 + j;<br> 781 fragment.color 782 = GL_CURRENT_RASTER_COLOR;<br> 783 784 fragment.texture = GL_CURRENT_RASTER_TEXTURE_COORDS;<br> 785 786 ProcessFragment(fragment)<br> 787 }<br> 788 }<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? 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 <span style="font-style: italic;">level </span>indicates the 850 mipmap level for mipmap textures. <span style="font-style: italic;">internalFormat</span> 851 is a hint to indicate the preferred internal storage format for the 852 texture. <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). <span style="font-style: italic;">border </span>must 855 be zero. <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. <span style="font-style: italic;">pixels</span> 858 points to the incoming texture image. 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. 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. A mipmap is a set of images consisting of a base 871 image and a set of filtered, reduced-resolution images. 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>. Each mipmap 875 level is half the width and height of the previous level, or at least 876 one. 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. 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. Accepted values for <span 979 style="font-style: italic;">format</span> are GL_INTENSITY, GL_RGB and 980 GL_RGBA. The <span style="font-style: italic;">type</span> 981 parameter must be GL_UNSIGNED_BYTE. 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). 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. <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. 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). 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: 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: 8 1031 bits for each of the red, green, 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. Texture coordinates are set for each vertex 1039 with the <span style="font-weight: bold;">glTexCoord</span> commands. 1040 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. 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]. Values 1046 outside that range are processed according to the <span 1047 style="font-style: italic;">texture wrap mode</span>. 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 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. 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. 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. 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. 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, 1096 GL_NEAREST_MIPMAP_LINEAR, 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. 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. 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. The two texels 1113 are linearly weighted to compute the final texel value. 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. The four texels are 1119 linearly weighted to compute the final texel value. 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. The eight 1126 texels are linearly weighted to compute the final texel value. 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. If the mipmap is 1132 incomplete, it is as if texturing is disabled.<br> 1133 <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. 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. The fragment and texture colors 1153 are combined according to the texture environment mode and the current 1154 texture's base internal format. 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 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. 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 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. The values are 1183 clamped to the range [0, 1]. 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. (Rf, Gf, Bf, Af) is 1187 the incoming fragment color. (Rt, Gt, Bt, At) is the sampled 1188 texture color. Lt is the sampled texture luminance. <span 1189 style="font-style: italic;"></span>'It' is the sampled texture 1190 intensity. (Rc, Gc, Bc, Ac) is the texture environment color. 1191 (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. This facilitates use of 1280 multiple textures in an application. Texture objects are named 1281 with GLuints (unsigned integers). 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 <span style="font-style: italic;">textureID</span> may be any 1295 unsigned integer. 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. 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 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. The named 1316 texture objects will be deleted. 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.) This chapter 1337 describes the per-fragment operations. They are presented in the 1338 order in which they're performed. 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. 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>. 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> <= x<sub>f</sub> < <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> <= y<sub>f</sub> < <span 1365 style="font-style: italic;">y</span> + <span 1366 style="font-style: italic;">height. </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. 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. 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. 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. The following table lists all possible 1388 modes <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 < <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 <= <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 > <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 >= <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. 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. Furthermore, the stencil buffer 1466 value may be updated or modified depending on the outcome. 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. 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>&<span 1514 style="font-style: italic;">mask)</span> < (stencil buffer value 1515 & <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 & <span style="font-style: italic;">mask) </span><= (stencil 1523 buffer value & <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 & <span style="font-style: italic;">mask) </span>> (stencil 1530 buffer value & <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 & <span style="font-style: italic;">mask) </span>>= (stencil 1537 buffer value & <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 & <span style="font-style: italic;">mask) </span>== (stencil 1544 buffer value & <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 & <span style="font-style: italic;">mask) </span>!= (stencil 1551 buffer value & <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. 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. 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. The default stencil 1639 reference value is 0. The default stencil mask is ~0. 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. 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. 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. 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. 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). 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 & 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 & 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 & ~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 & 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. 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. 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. The default value for <span style="font-style: italic;">dstTerm</span> 1969 is GL_ZERO. 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. Normally, all color 1974 channels in the frame buffer are replaced with the final fragment color. 1975 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. 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 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 The frame buffer is also organized into layers or logical buffers. 1998 There may be a front color buffer, back color buffer and stencil 1999 buffer. A double-buffered frame buffer has both a front color 2000 buffer and back color buffer. A single-buffered framebuffer only 2001 has a front color buffer. 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. If the GL_COLOR_BUFFER_BIT bit is 2014 specified, the current color buffer will be cleared. 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. 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. 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. GL_NONE indicates that neither color buffer 2030 will be modified by <span style="font-weight: bold;">glClear</span> or 2031 any drawing command. 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. 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 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. <span style="font-style: italic;">format</span> 2091 specifies the format of image data and must be either GL_RGB or 2092 GL_RGBA. <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. 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). 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. 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. <span style="font-style: italic;">value</span> 2121 indicates the stride (in pixels) between subsequent rows in the 2122 destination image. 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 rowLength = <span style="font-style: italic;">width</span>;<br> 2130 else<br> 2131 rowLength = GL_PACK_ROW_LENGTH<br> 2132 <br> 2133 if (<span style="font-style: italic;">format</span> == GL_RGB) {<br> 2134 for (i = 0; i < <span style="font-style: italic;">height</span>; 2135 i++) {<br> 2136 for (j = 0; j < <span 2137 style="font-style: italic;">width</span>; j++) {<br> 2138 k = (i * 2139 rowLength + j) * 3;<br> 2140 <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 <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 <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 }<br> 2154 }<br> 2155 }<br> 2156 else {<br> 2157 for (i = 0; i < <span style="font-style: italic;">height</span>; 2158 i++) {<br> 2159 for (j = 0; j < <span 2160 style="font-style: italic;">width</span>; j++) {<br> 2161 k = (i * 2162 rowLength + j) * 4;<br> 2163 <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 <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 <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 <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 }<br> 2182 }<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. </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. 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 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>. If <span 2206 style="font-style: italic;">buffer</span> is GL_FRONT then front color 2207 buffer is the source. If <span style="font-style: italic;">buffer</span> 2208 is GL_BACK then the back color buffer is the source. It is illegal 2209 to specify GL_BACK when the color buffer is not double buffered. 2210 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. 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. 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. If <span 2227 style="font-style: italic;">mode</span> is GL_SELECTION the graphics 2228 library is put into selection mode. If <span 2229 style="font-style: italic;">mode</span> is GL_RENDER the graphic 2230 library is put into normal rendering mode. 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. 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>. 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. 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. 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. <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. <span 2266 style="font-weight: bold;">glPopName</span> pops the top name from the 2267 stack. <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 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. 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. The hit 2277 data consists of three pieces of information: a hit flag, a minimum Z 2278 value and a maximum Z value. First, the hit flag is set. 2279 Then, for each of the primitive's vertices, the vertex Z value is 2280 compared to the minimum and maximum Z values. The minimum Z value 2281 is updated if the vertex's Z value is less than the minimum Z value. 2282 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. The 2295 first value is the size of the name stack. The second value is the 2296 minimum Z value multiplied by 2<sup>32</sup>-1. The third value is 2297 the maximum Z value multiplied by 2<sup>32</sup>-1. The remaining 2298 values are the values in the name stack, in bottom to top order. 2299 The hit flag is cleared after a hit record is written to the 2300 selection buffer. 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). The 2305 return value of <span style="font-weight: bold;">glRenderMode</span> 2306 will be -1 if the selection buffer overflowed. 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 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. <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. Otherwise, rendering to the front color 2329 buffer may not appear. 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. 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 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>. The following table 2350 lists all accepted values for <span style="font-style: italic;">pname</span> 2351 and a description of the value(s). 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. 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. The current error code will be 3020 set by a GL command when an error condition has been detected. If 3021 the current error code is already set, subsequent errors will not be 3022 recorded. The error code is reset/cleared to GL_NO_ERROR when <span 3023 style="font-weight: bold;">glGetError</span> returns. 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. 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>. 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. 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. 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? 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. A 3412 number of approaches to antialiasing have been summarized in email.<br> 3413 <br> 3414 RECOMMENDATION: don't support edge flags. 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: No. 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. Only a few are commonly 3437 used.<br> 3438 <br> 3439 RECOMMENDATION: 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. Only allow <span style="font-style: italic;">internalFormat</span> 3445 to be GL_RGBA, GL_RGB or GL_INTENSITY as well. Basically, only 3446 support image formats/types that are directly supported by the Radeon 3447 hardware. 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 Only allow <span style="font-style: italic;">format</span> = 3454 GL_RGB or GL_RGBA. 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? OpenGL 1.2 3461 has GL_REPLACE, GL_MODULATE, GL_DECAL and GL_BLEND. GL_DECAL isn't 3462 defined for all base internal texture formats. GL_ADD is another 3463 useful mode. 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: 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: Few applications use these features and 3485 functions. 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>. 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: 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: 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: No. They're seldom needed and their 3521 implementation is several hundred lines of code in length.<br> 3522 <br> 3523 RESOLUTION: 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: 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>. The 3534 implementation of the other three commands involves many lines of code.<br> 3535 <br> 3536 RESOLUTION: 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. Otherwise, it could be difficult.<br> 3544 <br> 3545 RECOMMENDATION: Implement glBitmap by drawing points/pixels with 3546 the hardware. This will make supporting the per-fragments 3547 trivially easy. Also, it makes portrait-mode display relatively 3548 easy.<br> 3549 <br> 3550 RESOLUTION: 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. 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. 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> 3573
