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1<html> 2 3<head><title>Mesa FAQ</title></head> 4 5<BODY text="#000000" bgcolor="#55bbff" link="#111188"> 6 7 8<center> 9<h1>Mesa Frequently Asked Questions</h1> 10Last updated: 27 April 2004 11</center> 12 13<br> 14<br> 15<h2>Index</h2> 16<a href="#part1">1. High-level Questions and Answers</a> 17<br> 18<a href="#part2">2. Compilation and Installation Problems</a> 19<br> 20<a href="#part3">3. Runtime / Rendering Problems</a> 21<br> 22<a href="#part4">4. Developer Questions</a> 23<br> 24<br> 25<br> 26 27 28 29<a name="part1"> 30</a><h1><a name="part1">1. High-level Questions and Answers</a></h1> 31 32<h2><a name="part1">1.1 What is Mesa?</a></h2> 33<p> 34<a name="part1">Mesa is an open-source implementation of the OpenGL specification. 35OpenGL is a programming library for writing interactive 3D applications. 36See the </a><a href="http://www.opengl.org/">OpenGL website</a> for more 37information. 38</p> 39<p> 40Mesa 5.x supports the OpenGL 1.4 specification. 41</p> 42 43 44<h2>1.2 Does Mesa support/use graphics hardware?</h2> 45<p> 46Yes. Specifically, Mesa serves as the OpenGL core for the open-source 47XFree86/DRI OpenGL drivers. See the <a href="http://dri.sf.net/">DRI 48website</a> for more information. 49</p> 50<p> 51There have been other hardware drivers for Mesa over the years (such as 52the 3Dfx Glide/Voodoo driver, an old S3 driver, etc) but the DRI drivers 53are the modern ones. 54</p> 55 56<h2>1.3 What purpose does Mesa (software-based rendering) serve today?</h2> 57<p> 58Hardware-accelerated OpenGL implementations are available for most popular 59operating systems today. 60Still, Mesa serves at least these purposes: 61</p> 62<ul> 63<li>Mesa is used as the core of the open-source XFree86/DRI hardware drivers. 64</li> 65<li>Mesa is quite portable and allows OpenGL to be used on systems 66 that have no other OpenGL solution. 67</li> 68<li>Software rendering with Mesa serves as a reference for validating the 69 hardware drivers. 70</li> 71<li>A software implementation of OpenGL is useful for experimentation, 72 such as testing new rendering techniques. 73</li> 74<li>Mesa can render images with deep color channels: 16-bit integer 75 and 32-bit floating point color channels are supported. 76 This capability is only now appearing in hardware. 77</li> 78<li>Mesa's internal limits (max lights, clip planes, texture size, etc) can be 79 changed for special needs (hardware limits are hard to overcome). 80</li> 81</ul> 82 83<h2>1.4 How do I upgrade my DRI installation to use a new Mesa release?</h2> 84<p> 85You don't! A copy of the Mesa source code lives inside the XFree86/DRI source 86tree and gets compiled into the individual DRI driver modules. 87If you try to install Mesa over an XFree86/DRI installation, you'll lose 88hardware rendering (because stand-alone Mesa's libGL.so is different than 89the XFree86 libGL.so). 90</p> 91<p> 92The DRI developers will incorporate the latest release of Mesa into the 93DRI drivers when the time is right. 94</p> 95<p> 96To upgrade, either look for a new release of <a href="http://www.xfree86.org" 97target="_parent">XFree86</a> or visit the 98<a href="http://dri.sf.net" target="_parent">DRI website</a> to see 99if there's newer drivers. 100</p> 101 102 103<h2>1.5 Are there other open-source implementations of OpenGL?</h2> 104<p> 105Yes, SGI's <a href="http://oss.sgi.com/projects/ogl-sample/index.html" 106target="_parent"> 107OpenGL Sample Implemenation (SI)</a> is available. 108The SI was written during the time that OpenGL was originally designed. 109Unfortunately, development of the SI has stagnated. 110Mesa is much more up to date with modern features and extensions. 111</p> 112 113<p> 114<a href="http://ogl-es.sourceforge.net" target="_parent">Vincent</a> is 115an open-source implementation of OpenGL ES for mobile devices. 116 117<p> 118<a href="http://www.dsbox.com/minigl.html" target="_parent">miniGL</a> 119is a subset of OpenGL for PalmOS devices. 120 121<p> 122<a href="http://fabrice.bellard.free.fr/TinyGL/" 123target="_parent">TinyGL</a> is a subset of OpenGL. 124</p> 125 126<p> 127<a href="http://softgl.studierstube.org/" target="_parent">SoftGL</a> 128is an OpenGL subset for mobile devices. 129</p> 130 131<p> 132<a href="http://chromium.sourceforge.net/" target="_parent">Chromium</a> 133isn't a conventional OpenGL implementation (it's layered upon OpenGL), 134but it does export the OpenGL API. It allows tiled rendering, sort-last 135rendering, etc. 136</p> 137 138 139<p> 140There may be other open OpenGL implementations, but Mesa is the most 141popular and feature-complete. 142</p> 143 144<br> 145<br> 146 147 148<a name="part2"> 149</a><h1><a name="part2">2. Compilation and Installation Problems</a></h1> 150 151 152<h2><a name="part2">2.1 What's the easiest way to install Mesa?</a></h2> 153<p> 154<a name="part2">If you're using a Linux-based system, your distro CD most likely already 155has Mesa packages (like RPM or DEB) which you can easily install. 156</a></p> 157 158 159<h2><a name="part2">2.2 Running <code>configure; make</code> Doesn't Work</a></h2> 160<p> 161<a name="part2">Unfortunately, the GNU autoconf/automake/libtool system doesn't seem to work 162too well on non GNU/Linux systems, even after installing gmake, gcc, etc. 163For that reason, Mesa's <b>old-style</b> makefile system is still included. 164The old-style system uses good old traditional Makefiles. Try the following: 165</a></p><pre><a name="part2"> cd Mesa-x.y.z 166 cp Makefile.X11 Makefile 167 make 168</a></pre> 169<a name="part2">You'll see a list of system configurations from which to choose. 170For example: 171</a><pre><a name="part2"> make linux-x86 172</a></pre> 173<p> 174<a name="part2">If you're experienced with GNU autoconf/automake/libtool and think you can help 175with maintence, contact the Mesa developers. 176FYI, the Mesa developers generally don't use the autoconf/automake system. 177We're especially annoyed with the fact that a +5000-line script (libtool) 178is needed to make shared libraries (ugh). 179</a></p> 180 181<h2><a name="part2">2.3 Mesa still doesn't compile</a></h2> 182<p> 183<a name="part2">If the old-style Makefile system doesn't work either, make sure you have 184the most recent version of Mesa. 185Otherwise, file a bug report or post to the Mesa3d-users mailing list. 186Give as much info as possible when describing your problem. 187</a></p> 188 189 190<h2><a name="part2">2.4 I get undefined symbols such as bgnpolygon, v3f, etc...</a></h2> 191<p> 192<a name="part2">You're application is written in IRIS GL, not OpenGL. 193IRIS GL was the predecessor to OpenGL and is a different thing (almost) 194entirely. 195Mesa's not the solution. 196</a></p> 197 198 199<h2><a name="part2">2.5 Where is the GLUT library?</a></h2> 200<p> 201<a name="part2">GLUT (OpenGL Utility Toolkit) is in the separate MesaDemos-x.y.z.tar.gz file. 202If you don't already have GLUT installed, you should grab the MesaDemos 203package and unpack it before compiling Mesa. 204</a></p> 205 206 207 208<h2><a name="part2">2.6 What's the proper place for the libraries and headers?</a></h2> 209<p> 210<a name="part2">On Linux-based systems you'll want to follow the 211</a><a href="http://oss.sgi.com/projects/ogl-sample/ABI/index.html" 212target="_parent">Linux ABI</a> standard. 213Basically you'll want the following: 214</p> 215<ul> 216<li>/usr/include/GL/gl.h - the main OpenGL header 217</li><li>/usr/include/GL/glu.h - the OpenGL GLU (utility) header 218</li><li>/usr/include/GL/glx.h - the OpenGL GLX header 219</li><li>/usr/include/GL/glext.h - the OpenGL extensions header 220</li><li>/usr/include/GL/glxext.h - the OpenGL GLX extensions header 221</li><li>/usr/include/GL/osmesa.h - the Mesa off-screen rendering header 222</li><li>/usr/lib/libGL.so - a symlink to libGL.so.1 223</li><li>/usr/lib/libGL.so.1 - a symlink to libGL.so.1.xyz 224</li><li>/usr/lib/libGL.so.xyz - the actual OpenGL/Mesa library. xyz denotes the 225Mesa version number. 226</li><li>/usr/lib/libGLU.so - a symlink to libGLU.so.1 227</li><li>/usr/lib/libGLU.so.1 - a symlink to libGLU.so.1.3.xyz 228</li><li>/usr/lib/libGLU.so.xyz - the OpenGL Utility library. xyz denotes the Mesa 229version number. 230</li></ul> 231<p> 232After installing XFree86 and the DRI drivers, some of these files 233may be symlinks into the /usr/X11R6/ tree. 234</p> 235<p> 236The old-style Makefile system doesn't install the Mesa libraries; it's 237up to you to copy them (and the headers) to the right place. 238</p> 239<p> 240The GLUT header and library should go in the same directories. 241</p> 242<br> 243<br> 244 245 246<a name="part3"> 247</a><h1><a name="part3">3. Runtime / Rendering Problems</a></h1> 248 249<h2><a name="part3">3.1 Rendering is slow / why isn't my graphics hardware being used?</a></h2> 250<p> 251<a name="part3">Stand-alone Mesa (downloaded as MesaLib-x.y.z.tar.gz) doesn't have any 252support for hardware acceleration (with the exception of the 3DFX Voodoo 253driver). 254</a></p> 255<p> 256<a name="part3">What you really want is a DRI or NVIDIA (or another vendor's OpenGL) driver 257for your particular hardware. 258</a></p> 259<p> 260<a name="part3">You can run the <code>glxinfo</code> program to learn about your OpenGL 261library. 262Look for the GL_VENDOR and GL_RENDERER values. 263That will identify who's OpenGL library you're using and what sort of 264hardware it has detected. 265</a></p> 266<p> 267<a name="part3">If your DRI-based driver isn't working, go to the 268</a><a href="http://dri.sf.net/" target="_parent">DRI website</a> for trouble-shooting information. 269</p> 270 271 272<h2>3.2 I'm seeing errors in depth (Z) buffering. Why?</h2> 273<p> 274Make sure the ratio of the far to near clipping planes isn't too great. 275Look 276<a href="http://www.sgi.com/software/opengl/advanced97/notes/node18.html" 277target="_parent"> 278here</a> for details. 279</p> 280<p> 281Mesa uses a 16-bit depth buffer by default which is smaller and faster 282to clear than a 32-bit buffer but not as accurate. 283If you need a deeper you can modify the parameters to 284<code> glXChooseVisual</code> in your code. 285</p> 286 287 288<h2>3.3 Why Isn't depth buffering working at all?</h2> 289<p> 290Be sure you're requesting a depth buffered-visual. If you set the MESA_DEBUG 291environment variable it will warn you about trying to enable depth testing 292when you don't have a depth buffer. 293</p> 294<p>Specifically, make sure <code>glutInitDisplayMode</code> is being called 295with <code>GLUT_DEPTH</code> or <code>glXChooseVisual</code> is being 296called with a non-zero value for GLX_DEPTH_SIZE. 297</p> 298<p>This discussion applies to stencil buffers, accumulation buffers and 299alpha channels too. 300</p> 301 302 303<h2>3.4 Why does glGetString() always return NULL?</h2> 304<p> 305Be sure you have an active/current OpenGL rendering context before 306calling glGetString. 307</p> 308 309 310<h2>3.5 GL_POINTS and GL_LINES don't touch the right pixels</h2> 311<p> 312If you're trying to draw a filled region by using GL_POINTS or GL_LINES 313and seeing holes or gaps it's because of a float-to-int rounding problem. 314But this is not a bug. 315See Appendix H of the OpenGL Programming Guide - "OpenGL Correctness Tips". 316Basically, applying a translation of (0.375, 0.375, 0.0) to your coordinates 317will fix the problem. 318</p> 319 320<br> 321<br> 322 323 324<a name="part4"> 325</a><h1><a name="part4">4. Developer Questions</a></h1> 326 327<h2><a name="part4">4.1 How can I contribute?</a></h2> 328<p> 329<a name="part4">First, join the Mesa3d-dev mailing list. That's where Mesa development 330is discussed. 331</a></p> 332<p> 333<a name="part4">The </a><a href="http://www.opengl.org/developers/documentation/specs.html" target="_parent"> 334OpenGL Specification</a> is the bible for OpenGL implemention work. 335You should read it. 336</p> 337<p>Most of the Mesa development work involves implementing new OpenGL 338extensions, writing hardware drivers (for the DRI), and code optimization. 339</p> 340 341<h2>4.2 How do I write a new device driver?</h2> 342<p> 343Unfortunately, writing a device driver isn't easy. 344It requires detailed understanding of OpenGL, the Mesa code, and your 345target hardware/operating system. 3463D graphics are not simple. 347</p> 348<p> 349The best way to get started is to use an existing driver as your starting 350point. 351For a software driver, the X11 and OSMesa drivers are good examples. 352For a hardware driver, the Radeon and R200 DRI drivers are good examples. 353</p> 354<p>The DRI website has more information about writing hardware drivers. 355The process isn't well document because the Mesa driver interface changes 356over time, and we seldome have spare time for writing documentation. 357That being said, many people have managed to figure out the process. 358</p> 359<p> 360Joining the appropriate mailing lists and asking questions (and searching 361the archives) is a good way to get information. 362</p> 363 364 365<h2>4.3 Why isn't GL_EXT_texture_compression_s3tc implemented in Mesa and/or the DRI drivers?</h2> 366<p> 367The <a href="http://oss.sgi.com/projects/ogl-sample/registry/EXT/texture_compression_s3tc.txt" target="_parent">specification for the extension</a> 368indicates that there are intellectual property (IP) and/or patent issues 369to be dealt with. 370</p> 371<p>We've been unsucessful in getting a response from S3 (or whoever owns 372the IP nowadays) to indicate whether or not an open source project can 373implement the extension (specifically the compression/decompression 374algorithms). 375</p> 376<p> 377Until we can get official permission to do so, this extension will not 378be implemented in Mesa. 379</p> 380 381 382</body> 383</html> 384