faq.html revision 1.1.1.2
1 1.1 mrg <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2 1.1 mrg <html lang="en"> 3 1.1 mrg <head> 4 1.1 mrg <meta http-equiv="content-type" content="text/html; charset=utf-8"> 5 1.1 mrg <title>Mesa FAQ</title> 6 1.1 mrg <link rel="stylesheet" type="text/css" href="mesa.css"> 7 1.1 mrg </head> 8 1.1 mrg <body> 9 1.1 mrg 10 1.1 mrg <div class="header"> 11 1.1 mrg <h1>The Mesa 3D Graphics Library</h1> 12 1.1 mrg </div> 13 1.1 mrg 14 1.1 mrg <iframe src="contents.html"></iframe> 15 1.1 mrg <div class="content"> 16 1.1 mrg 17 1.1 mrg <h1>Mesa Frequently Asked Questions</h1> 18 1.1.1.2 mrg Last updated: 19 September 2018 19 1.1 mrg 20 1.1 mrg <br> 21 1.1 mrg <br> 22 1.1 mrg <h2>Index</h2> 23 1.1.1.2 mrg <ol> 24 1.1.1.2 mrg <li><a href="#part1">High-level Questions and Answers</a></li> 25 1.1.1.2 mrg <li><a href="#part2">Compilation and Installation Problems</a></li> 26 1.1.1.2 mrg <li><a href="#part3">Runtime / Rendering Problems</a></li> 27 1.1.1.2 mrg <li><a href="#part4">Developer Questions</a></li> 28 1.1.1.2 mrg </ol> 29 1.1 mrg <br> 30 1.1 mrg <br> 31 1.1 mrg 32 1.1 mrg 33 1.1 mrg 34 1.1 mrg <h1 id="part1">1. High-level Questions and Answers</h1> 35 1.1 mrg 36 1.1 mrg <h2>1.1 What is Mesa?</h2> 37 1.1 mrg <p> 38 1.1 mrg Mesa is an open-source implementation of the OpenGL specification. 39 1.1 mrg OpenGL is a programming library for writing interactive 3D applications. 40 1.1.1.2 mrg See the <a href="https://www.opengl.org/">OpenGL website</a> for more 41 1.1 mrg information. 42 1.1 mrg </p> 43 1.1 mrg <p> 44 1.1 mrg Mesa 9.x supports the OpenGL 3.1 specification. 45 1.1 mrg </p> 46 1.1 mrg 47 1.1 mrg 48 1.1 mrg <h2>1.2 Does Mesa support/use graphics hardware?</h2> 49 1.1 mrg <p> 50 1.1 mrg Yes. Specifically, Mesa serves as the OpenGL core for the open-source DRI 51 1.1 mrg drivers for X.org. 52 1.1 mrg </p> 53 1.1 mrg <ul> 54 1.1.1.2 mrg <li>See the <a href="https://dri.freedesktop.org/">DRI website</a> 55 1.1 mrg for more information.</li> 56 1.1.1.2 mrg <li>See <a href="https://01.org/linuxgraphics">01.org</a> 57 1.1 mrg for more information about Intel drivers.</li> 58 1.1.1.2 mrg <li>See <a href="https://nouveau.freedesktop.org">nouveau.freedesktop.org</a> 59 1.1 mrg for more information about Nouveau drivers.</li> 60 1.1.1.2 mrg <li>See <a href="https://www.x.org/wiki/RadeonFeature">www.x.org/wiki/RadeonFeature</a> 61 1.1 mrg for more information about Radeon drivers.</li> 62 1.1 mrg </ul> 63 1.1 mrg 64 1.1 mrg <h2>1.3 What purpose does Mesa serve today?</h2> 65 1.1 mrg <p> 66 1.1 mrg Hardware-accelerated OpenGL implementations are available for most popular 67 1.1 mrg operating systems today. 68 1.1 mrg Still, Mesa serves at least these purposes: 69 1.1 mrg </p> 70 1.1 mrg <ul> 71 1.1 mrg <li>Mesa is used as the core of the open-source X.org DRI 72 1.1 mrg hardware drivers. 73 1.1 mrg </li> 74 1.1 mrg <li>Mesa is quite portable and allows OpenGL to be used on systems 75 1.1 mrg that have no other OpenGL solution. 76 1.1 mrg </li> 77 1.1 mrg <li>Software rendering with Mesa serves as a reference for validating the 78 1.1 mrg hardware drivers. 79 1.1 mrg </li> 80 1.1 mrg <li>A software implementation of OpenGL is useful for experimentation, 81 1.1 mrg such as testing new rendering techniques. 82 1.1 mrg </li> 83 1.1 mrg <li>Mesa can render images with deep color channels: 16-bit integer 84 1.1 mrg and 32-bit floating point color channels are supported. 85 1.1 mrg This capability is only now appearing in hardware. 86 1.1 mrg </li> 87 1.1 mrg <li>Mesa's internal limits (max lights, clip planes, texture size, etc) can be 88 1.1 mrg changed for special needs (hardware limits are hard to overcome). 89 1.1 mrg </li> 90 1.1 mrg </ul> 91 1.1 mrg 92 1.1 mrg 93 1.1 mrg <h2>1.4 What's the difference between "Stand-Alone" Mesa and the DRI drivers?</h2> 94 1.1 mrg <p> 95 1.1 mrg <em>Stand-alone Mesa</em> is the original incarnation of Mesa. 96 1.1 mrg On systems running the X Window System it does all its rendering through 97 1.1 mrg the Xlib API: 98 1.1 mrg </p> 99 1.1 mrg <ul> 100 1.1 mrg <li>The GLX API is supported, but it's really just an emulation of the 101 1.1 mrg real thing. 102 1.1 mrg <li>The GLX wire protocol is not supported and there's no OpenGL extension 103 1.1 mrg loaded by the X server. 104 1.1 mrg <li>There is no hardware acceleration. 105 1.1 mrg <li>The OpenGL library, libGL.so, contains everything (the programming API, 106 1.1 mrg the GLX functions and all the rendering code). 107 1.1 mrg </ul> 108 1.1 mrg <p> 109 1.1 mrg Alternately, Mesa acts as the core for a number of OpenGL hardware drivers 110 1.1 mrg within the DRI (Direct Rendering Infrastructure): 111 1.1 mrg <ul> 112 1.1 mrg <li>The libGL.so library provides the GL and GLX API functions, a GLX 113 1.1 mrg protocol encoder, and a device driver loader. 114 1.1 mrg <li>The device driver modules (such as r200_dri.so) contain a built-in 115 1.1 mrg copy of the core Mesa code. 116 1.1 mrg <li>The X server loads the GLX module. 117 1.1 mrg The GLX module decodes incoming GLX protocol and dispatches the commands 118 1.1 mrg to a rendering module. 119 1.1 mrg For the DRI, this module is basically a software Mesa renderer. 120 1.1 mrg </ul> 121 1.1 mrg 122 1.1 mrg 123 1.1 mrg 124 1.1 mrg <h2>1.5 How do I upgrade my DRI installation to use a new Mesa release?</h2> 125 1.1 mrg <p> 126 1.1 mrg This wasn't easy in the past. 127 1.1 mrg Now, the DRI drivers are included in the Mesa tree and can be compiled 128 1.1 mrg separately from the X server. 129 1.1 mrg Just follow the Mesa <a href="install.html">compilation instructions</a>. 130 1.1 mrg </p> 131 1.1 mrg 132 1.1 mrg 133 1.1 mrg <h2>1.6 Are there other open-source implementations of OpenGL?</h2> 134 1.1 mrg <p> 135 1.1 mrg Yes, SGI's <a href="http://oss.sgi.com/projects/ogl-sample/index.html"> 136 1.1 mrg OpenGL Sample Implementation (SI)</a> is available. 137 1.1 mrg The SI was written during the time that OpenGL was originally designed. 138 1.1 mrg Unfortunately, development of the SI has stagnated. 139 1.1 mrg Mesa is much more up to date with modern features and extensions. 140 1.1 mrg </p> 141 1.1 mrg 142 1.1 mrg <p> 143 1.1.1.2 mrg <a href="https://sourceforge.net/projects/ogl-es/">Vincent</a> is 144 1.1 mrg an open-source implementation of OpenGL ES for mobile devices. 145 1.1 mrg 146 1.1 mrg <p> 147 1.1 mrg <a href="http://www.dsbox.com/minigl.html">miniGL</a> 148 1.1 mrg is a subset of OpenGL for PalmOS devices. 149 1.1 mrg 150 1.1 mrg <p> 151 1.1 mrg <a href="http://bellard.org/TinyGL/">TinyGL</a> 152 1.1 mrg is a subset of OpenGL. 153 1.1 mrg </p> 154 1.1 mrg 155 1.1 mrg <p> 156 1.1.1.2 mrg <a href="https://sourceforge.net/projects/softgl/">SoftGL</a> 157 1.1 mrg is an OpenGL subset for mobile devices. 158 1.1 mrg </p> 159 1.1 mrg 160 1.1 mrg <p> 161 1.1 mrg <a href="http://chromium.sourceforge.net/">Chromium</a> 162 1.1 mrg isn't a conventional OpenGL implementation (it's layered upon OpenGL), 163 1.1 mrg but it does export the OpenGL API. It allows tiled rendering, sort-last 164 1.1 mrg rendering, etc. 165 1.1 mrg </p> 166 1.1 mrg 167 1.1 mrg <p> 168 1.1 mrg <a href="http://www.ticalc.org/archives/files/fileinfo/361/36173.html">ClosedGL</a> 169 1.1 mrg is an OpenGL subset library for TI graphing calculators. 170 1.1 mrg </p> 171 1.1 mrg 172 1.1 mrg <p> 173 1.1 mrg There may be other open OpenGL implementations, but Mesa is the most 174 1.1 mrg popular and feature-complete. 175 1.1 mrg </p> 176 1.1 mrg 177 1.1 mrg 178 1.1 mrg 179 1.1 mrg <br> 180 1.1 mrg <br> 181 1.1 mrg 182 1.1 mrg 183 1.1 mrg <h1 id="part2">2. Compilation and Installation Problems</h1> 184 1.1 mrg 185 1.1 mrg 186 1.1 mrg <h2>2.1 What's the easiest way to install Mesa?</h2> 187 1.1 mrg <p> 188 1.1 mrg If you're using a Linux-based system, your distro CD most likely already 189 1.1 mrg has Mesa packages (like RPM or DEB) which you can easily install. 190 1.1 mrg </p> 191 1.1 mrg 192 1.1 mrg 193 1.1 mrg <h2>2.2 I get undefined symbols such as bgnpolygon, v3f, etc...</h2> 194 1.1 mrg <p> 195 1.1 mrg You're application is written in IRIS GL, not OpenGL. 196 1.1 mrg IRIS GL was the predecessor to OpenGL and is a different thing (almost) 197 1.1 mrg entirely. 198 1.1 mrg Mesa's not the solution. 199 1.1 mrg </p> 200 1.1 mrg 201 1.1 mrg 202 1.1 mrg <h2>2.3 Where is the GLUT library?</h2> 203 1.1 mrg <p> 204 1.1 mrg GLUT (OpenGL Utility Toolkit) is no longer in the separate MesaGLUT-x.y.z.tar.gz file. 205 1.1 mrg If you don't already have GLUT installed, you should grab 206 1.1 mrg <a href="http://freeglut.sourceforge.net/">freeglut</a>. 207 1.1 mrg </p> 208 1.1 mrg 209 1.1 mrg 210 1.1 mrg <h2>2.4 Where is the GLw library?</h2> 211 1.1 mrg <p> 212 1.1.1.2 mrg GLw (OpenGL widget library) is now available from a separate <a href="https://cgit.freedesktop.org/mesa/glw/">git repository</a>. Unless you're using very old Xt/Motif applications with OpenGL, you shouldn't need it. 213 1.1 mrg </p> 214 1.1 mrg 215 1.1 mrg 216 1.1 mrg <h2>2.5 What's the proper place for the libraries and headers?</h2> 217 1.1 mrg <p> 218 1.1 mrg On Linux-based systems you'll want to follow the 219 1.1 mrg <a href="http://oss.sgi.com/projects/ogl-sample/ABI/index.html">Linux ABI</a> standard. 220 1.1 mrg Basically you'll want the following: 221 1.1 mrg </p> 222 1.1 mrg <ul> 223 1.1 mrg <li>/usr/include/GL/gl.h - the main OpenGL header 224 1.1 mrg </li><li>/usr/include/GL/glu.h - the OpenGL GLU (utility) header 225 1.1 mrg </li><li>/usr/include/GL/glx.h - the OpenGL GLX header 226 1.1 mrg </li><li>/usr/include/GL/glext.h - the OpenGL extensions header 227 1.1 mrg </li><li>/usr/include/GL/glxext.h - the OpenGL GLX extensions header 228 1.1 mrg </li><li>/usr/include/GL/osmesa.h - the Mesa off-screen rendering header 229 1.1 mrg </li><li>/usr/lib/libGL.so - a symlink to libGL.so.1 230 1.1 mrg </li><li>/usr/lib/libGL.so.1 - a symlink to libGL.so.1.xyz 231 1.1 mrg </li><li>/usr/lib/libGL.so.xyz - the actual OpenGL/Mesa library. xyz denotes the 232 1.1 mrg Mesa version number. 233 1.1 mrg </li></ul> 234 1.1 mrg <p> 235 1.1.1.2 mrg When configuring Mesa, there are three meson options that affect the install 236 1.1 mrg location that you should take care with: <code>--prefix</code>, 237 1.1.1.2 mrg <code>--libdir</code>, and <code>-D dri-drivers-path</code>. To install Mesa 238 1.1 mrg into the system location where it will be available for all programs to use, set 239 1.1 mrg <code>--prefix=/usr</code>. Set <code>--libdir</code> to where your Linux 240 1.1 mrg distribution installs system libraries, usually either <code>/usr/lib</code> or 241 1.1.1.2 mrg <code>/usr/lib64</code>. Set <code>-D dri-drivers-path</code> to the directory 242 1.1 mrg where your Linux distribution installs DRI drivers. To find your system's DRI 243 1.1 mrg driver directory, try executing <code>find /usr -type d -name dri</code>. For 244 1.1 mrg example, if the <code>find</code> command listed <code>/usr/lib64/dri</code>, 245 1.1.1.2 mrg then set <code>-D dri-drivers-path=/usr/lib64/dri</code>. 246 1.1 mrg </p> 247 1.1 mrg <p> 248 1.1 mrg After determining the correct values for the install location, configure Mesa 249 1.1.1.2 mrg with <code>meson configure --prefix=/usr --libdir=xxx -D dri-drivers-path=xxx</code> 250 1.1.1.2 mrg and then install with <code>sudo ninja install</code>. 251 1.1 mrg </p> 252 1.1 mrg <br> 253 1.1 mrg <br> 254 1.1 mrg 255 1.1 mrg 256 1.1 mrg <h1 id="part3">3. Runtime / Rendering Problems</h1> 257 1.1 mrg 258 1.1 mrg <h2>3.1 Rendering is slow / why isn't my graphics hardware being used?</h2> 259 1.1 mrg <p> 260 1.1 mrg If Mesa can't use its hardware accelerated drivers it falls back on one of its software renderers. 261 1.1 mrg (eg. classic swrast, softpipe or llvmpipe) 262 1.1 mrg </p> 263 1.1 mrg <p> 264 1.1 mrg You can run the <code>glxinfo</code> program to learn about your OpenGL 265 1.1 mrg library. 266 1.1 mrg Look for the <code>OpenGL vendor</code> and <code>OpenGL renderer</code> values. 267 1.1 mrg That will identify who's OpenGL library with which driver you're using and what sort of 268 1.1 mrg hardware it has detected. 269 1.1 mrg </p> 270 1.1 mrg <p> 271 1.1 mrg If you're using a hardware accelerated driver you want <code>direct rendering: Yes</code>. 272 1.1 mrg </p> 273 1.1 mrg <p> 274 1.1 mrg If your DRI-based driver isn't working, go to the 275 1.1.1.2 mrg <a href="https://dri.freedesktop.org/">DRI website</a> for trouble-shooting information. 276 1.1 mrg </p> 277 1.1 mrg 278 1.1 mrg 279 1.1 mrg <h2>3.2 I'm seeing errors in depth (Z) buffering. Why?</h2> 280 1.1 mrg <p> 281 1.1 mrg Make sure the ratio of the far to near clipping planes isn't too great. 282 1.1 mrg Look 283 1.1.1.2 mrg <a href="https://www.opengl.org/resources/faq/technical/depthbuffer.htm#0040">here</a> 284 1.1 mrg for details. 285 1.1 mrg </p> 286 1.1 mrg <p> 287 1.1 mrg Mesa uses a 16-bit depth buffer by default which is smaller and faster 288 1.1 mrg to clear than a 32-bit buffer but not as accurate. 289 1.1 mrg If you need a deeper you can modify the parameters to 290 1.1 mrg <code> glXChooseVisual</code> in your code. 291 1.1 mrg </p> 292 1.1 mrg 293 1.1 mrg 294 1.1 mrg <h2>3.3 Why Isn't depth buffering working at all?</h2> 295 1.1 mrg <p> 296 1.1 mrg Be sure you're requesting a depth buffered-visual. If you set the MESA_DEBUG 297 1.1 mrg environment variable it will warn you about trying to enable depth testing 298 1.1 mrg when you don't have a depth buffer. 299 1.1 mrg </p> 300 1.1 mrg <p>Specifically, make sure <code>glutInitDisplayMode</code> is being called 301 1.1 mrg with <code>GLUT_DEPTH</code> or <code>glXChooseVisual</code> is being 302 1.1 mrg called with a non-zero value for GLX_DEPTH_SIZE. 303 1.1 mrg </p> 304 1.1 mrg <p>This discussion applies to stencil buffers, accumulation buffers and 305 1.1 mrg alpha channels too. 306 1.1 mrg </p> 307 1.1 mrg 308 1.1 mrg 309 1.1 mrg <h2>3.4 Why does glGetString() always return NULL?</h2> 310 1.1 mrg <p> 311 1.1 mrg Be sure you have an active/current OpenGL rendering context before 312 1.1 mrg calling glGetString. 313 1.1 mrg </p> 314 1.1 mrg 315 1.1 mrg 316 1.1 mrg <h2>3.5 GL_POINTS and GL_LINES don't touch the right pixels</h2> 317 1.1 mrg <p> 318 1.1 mrg If you're trying to draw a filled region by using GL_POINTS or GL_LINES 319 1.1 mrg and seeing holes or gaps it's because of a float-to-int rounding problem. 320 1.1 mrg But this is not a bug. 321 1.1 mrg See Appendix H of the OpenGL Programming Guide - "OpenGL Correctness Tips". 322 1.1 mrg Basically, applying a translation of (0.375, 0.375, 0.0) to your coordinates 323 1.1 mrg will fix the problem. 324 1.1 mrg </p> 325 1.1 mrg 326 1.1 mrg <br> 327 1.1 mrg <br> 328 1.1 mrg 329 1.1 mrg 330 1.1 mrg <h1 id="part4">4. Developer Questions</h1> 331 1.1 mrg 332 1.1 mrg <h2>4.1 How can I contribute?</h2> 333 1.1 mrg <p> 334 1.1 mrg First, join the <a href="lists.html">mesa-dev mailing list</a>. 335 1.1 mrg That's where Mesa development is discussed. 336 1.1 mrg </p> 337 1.1 mrg <p> 338 1.1.1.2 mrg The <a href="https://www.opengl.org/documentation"> 339 1.1 mrg OpenGL Specification</a> is the bible for OpenGL implementation work. 340 1.1 mrg You should read it. 341 1.1 mrg </p> 342 1.1 mrg <p>Most of the Mesa development work involves implementing new OpenGL 343 1.1 mrg extensions, writing hardware drivers (for the DRI), and code optimization. 344 1.1 mrg </p> 345 1.1 mrg 346 1.1 mrg <h2>4.2 How do I write a new device driver?</h2> 347 1.1 mrg <p> 348 1.1 mrg Unfortunately, writing a device driver isn't easy. 349 1.1 mrg It requires detailed understanding of OpenGL, the Mesa code, and your 350 1.1 mrg target hardware/operating system. 351 1.1 mrg 3D graphics are not simple. 352 1.1 mrg </p> 353 1.1 mrg <p> 354 1.1 mrg The best way to get started is to use an existing driver as your starting 355 1.1 mrg point. 356 1.1 mrg For a classic hardware driver, the i965 driver is a good example. 357 1.1 mrg For a Gallium3D hardware driver, the r300g, r600g and the i915g are good examples. 358 1.1 mrg </p> 359 1.1 mrg <p>The DRI website has more information about writing hardware drivers. 360 1.1 mrg The process isn't well document because the Mesa driver interface changes 361 1.1 mrg over time, and we seldom have spare time for writing documentation. 362 1.1 mrg That being said, many people have managed to figure out the process. 363 1.1 mrg </p> 364 1.1 mrg <p> 365 1.1 mrg Joining the appropriate mailing lists and asking questions (and searching 366 1.1 mrg the archives) is a good way to get information. 367 1.1 mrg </p> 368 1.1 mrg 369 1.1 mrg 370 1.1 mrg <h2>4.3 Why isn't GL_EXT_texture_compression_s3tc implemented in Mesa?</h2> 371 1.1 mrg <p> 372 1.1.1.2 mrg Oh but it is! Prior to 2nd October 2017, the Mesa project did not include s3tc 373 1.1.1.2 mrg support due to intellectual property (IP) and/or patent issues around the s3tc 374 1.1.1.2 mrg algorithm. 375 1.1.1.2 mrg </p> 376 1.1.1.2 mrg <p> 377 1.1.1.2 mrg As of Mesa 17.3.0, Mesa now officially supports s3tc, as the patent has expired. 378 1.1 mrg </p> 379 1.1 mrg <p> 380 1.1.1.2 mrg In versions prior to this, a 3rd party <a href="https://dri.freedesktop.org/wiki/S3TC"> 381 1.1.1.2 mrg plug-in library</a> was required. 382 1.1 mrg </p> 383 1.1 mrg 384 1.1 mrg </div> 385 1.1 mrg </body> 386 1.1 mrg </html> 387
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