faq.html revision a376e339a5f7cb15de6c74556b1e1b219d84374a
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: 30 March 2003 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 96<h2>1.5 Are there other open-source implementations of OpenGL?</h2> 97<p> 98Yes, SGI's <a href="http://oss.sgi.com/projects/ogl-sample/index.html"> 99OpenGL Sample Implemenation (SI)</a> is available. 100The SI was written during the time that OpenGL was originally designed. 101Unfortunately, development of the SI has stagnated. 102Mesa is much more up to date with modern features and extensions. 103</p> 104<p> 105<a href="http://www.dsbox.com/minigl.html">miniGL</a> is a subset of OpenGL 106for PalmOS devices. 107 108<a href="http://fabrice.bellard.free.fr/TinyGL/">TinyGL</a> is another 109subset of OpenGL. 110</p> 111<p> 112There may be others but Mesa is the most popular and feature-complete. 113</p> 114 115<br> 116<br> 117 118 119<a name="part2"> 120</a><h1><a name="part2">2. Compilation and Installation Problems</a></h1> 121 122 123<h2><a name="part2">2.1 What's the easiest way to install Mesa?</a></h2> 124<p> 125<a name="part2">If you're using a Linux-based system, your distro CD most likely already 126has Mesa packages (like RPM or DEB) which you can easily install. 127</a></p> 128 129 130<h2><a name="part2">2.2 Running <code>configure; make</code> Doesn't Work</a></h2> 131<p> 132<a name="part2">Unfortunately, the GNU autoconf/automake/libtool system doesn't seem to work 133too well on non GNU/Linux systems, even after installing gmake, gcc, etc. 134For that reason, Mesa's <b>old-style</b> makefile system is still included. 135The old-style system uses good old traditional Makefiles. Try the following: 136</a></p><pre><a name="part2"> cd Mesa-x.y.z 137 cp Makefile.X11 Makefile 138 make 139</a></pre> 140<a name="part2">You'll see a list of system configurations from which to choose. 141For example: 142</a><pre><a name="part2"> make linux-x86 143</a></pre> 144<p> 145<a name="part2">If you're experienced with GNU autoconf/automake/libtool and think you can help 146with maintence, contact the Mesa developers. 147FYI, the Mesa developers generally don't use the autoconf/automake system. 148We're especially annoyed with the fact that a +5000-line script (libtool) 149is needed to make shared libraries (ugh). 150</a></p> 151 152<h2><a name="part2">2.3 Mesa still doesn't compile</a></h2> 153<p> 154<a name="part2">If the old-style Makefile system doesn't work either, make sure you have 155the most recent version of Mesa. 156Otherwise, file a bug report or post to the Mesa3d-users mailing list. 157Give as much info as possible when describing your problem. 158</a></p> 159 160 161<h2><a name="part2">2.4 I get undefined symbols such as bgnpolygon, v3f, etc...</a></h2> 162<p> 163<a name="part2">You're application is written in IRIS GL, not OpenGL. 164IRIS GL was the predecessor to OpenGL and is a different thing (almost) 165entirely. 166Mesa's not the solution. 167</a></p> 168 169 170<h2><a name="part2">2.5 Where is the GLUT library?</a></h2> 171<p> 172<a name="part2">GLUT (OpenGL Utility Toolkit) is in the separate MesaDemos-x.y.z.tar.gz file. 173If you don't already have GLUT installed, you should grab the MesaDemos 174package and unpack it before compiling Mesa. 175</a></p> 176 177 178 179<h2><a name="part2">2.6 What's the proper place for the libraries and headers?</a></h2> 180<p> 181<a name="part2">On Linux-based systems you'll want to follow the 182</a><a href="http://oss.sgi.com/projects/ogl-sample/ABI/index.html">Linux ABI</a> 183standard. 184Basically you'll want the following: 185</p> 186<ul> 187<li>/usr/include/GL/gl.h - the main OpenGL header 188</li><li>/usr/include/GL/glu.h - the OpenGL GLU (utility) header 189</li><li>/usr/include/GL/glx.h - the OpenGL GLX header 190</li><li>/usr/include/GL/glext.h - the OpenGL extensions header 191</li><li>/usr/include/GL/glxext.h - the OpenGL GLX extensions header 192</li><li>/usr/include/GL/osmesa.h - the Mesa off-screen rendering header 193</li><li>/usr/lib/libGL.so - a symlink to libGL.so.1 194</li><li>/usr/lib/libGL.so.1 - a symlink to libGL.so.1.xyz 195</li><li>/usr/lib/libGL.so.xyz - the actual OpenGL/Mesa library. xyz denotes the 196Mesa version number. 197</li><li>/usr/lib/libGLU.so - a symlink to libGLU.so.1 198</li><li>/usr/lib/libGLU.so.1 - a symlink to libGLU.so.1.3.xyz 199</li><li>/usr/lib/libGLU.so.xyz - the OpenGL Utility library. xyz denotes the Mesa 200version number. 201</li></ul> 202<p> 203After installing XFree86 and the DRI drivers, some of these files 204may be symlinks into the /usr/X11R6/ tree. 205</p> 206<p> 207The old-style Makefile system doesn't install the Mesa libraries; it's 208up to you to copy them (and the headers) to the right place. 209</p> 210<p> 211The GLUT header and library should go in the same directories. 212</p> 213<br> 214<br> 215 216 217<a name="part3"> 218</a><h1><a name="part3">3. Runtime / Rendering Problems</a></h1> 219 220<h2><a name="part3">3.1 Rendering is slow / why isn't my graphics hardware being used?</a></h2> 221<p> 222<a name="part3">Stand-alone Mesa (downloaded as MesaLib-x.y.z.tar.gz) doesn't have any 223support for hardware acceleration (with the exception of the 3DFX Voodoo 224driver). 225</a></p> 226<p> 227<a name="part3">What you really want is a DRI or NVIDIA (or another vendor's OpenGL) driver 228for your particular hardware. 229</a></p> 230<p> 231<a name="part3">You can run the <code>glxinfo</code> program to learn about your OpenGL 232library. 233Look for the GL_VENDOR and GL_RENDERER values. 234That will identify who's OpenGL library you're using and what sort of 235hardware it has detected. 236</a></p> 237<p> 238<a name="part3">If your DRI-based driver isn't working, go to the 239</a><a href="http://dri.sf.net/">DRI website</a> for trouble-shooting information. 240</p> 241 242 243<h2>3.2 I'm seeing errors in depth (Z) buffering. Why?</h2> 244<p> 245Make sure the ratio of the far to near clipping planes isn't too great. 246Look 247<a href="http://www.sgi.com/software/opengl/advanced97/notes/node18.html"> 248here</a> for details. 249</p> 250<p> 251Mesa uses a 16-bit depth buffer by default which is smaller and faster 252to clear than a 32-bit buffer but not as accurate. 253If you need a deeper you can modify the parameters to 254<code> glXChooseVisual</code> in your code. 255</p> 256 257 258<h2>3.3 Why Isn't depth buffering working at all?</h2> 259<p> 260Be sure you're requesting a depth buffered-visual. If you set the MESA_DEBUG 261environment variable it will warn you about trying to enable depth testing 262when you don't have a depth buffer. 263</p> 264<p>Specifically, make sure <code>glutInitDisplayMode</code> is being called 265with <code>GLUT_DEPTH</code> or <code>glXChooseVisual</code> is being 266called with a non-zero value for GLX_DEPTH_SIZE. 267</p> 268<p>This discussion applies to stencil buffers, accumulation buffers and 269alpha channels too. 270</p> 271 272 273<h2>3.4 Why does glGetString() always return NULL?</h2> 274<p> 275Be sure you have an active/current OpenGL rendering context before 276calling glGetString. 277</p> 278 279 280<h2>3.5 GL_POINTS and GL_LINES don't touch the right pixels</h2> 281<p> 282If you're trying to draw a filled region by using GL_POINTS or GL_LINES 283and seeing holes or gaps it's because of a float-to-int rounding problem. 284But this is not a bug. 285See Appendix H of the OpenGL Programming Guide - "OpenGL Correctness Tips". 286Basically, applying a translation of (0.375, 0.375, 0.0) to your coordinates 287will fix the problem. 288</p> 289 290<br> 291<br> 292 293 294<a name="part4"> 295</a><h1><a name="part4">4. Developer Questions</a></h1> 296 297<h2><a name="part4">4.1 How can I contribute?</a></h2> 298<p> 299<a name="part4">First, join the Mesa3d-dev mailing list. That's where Mesa development 300is discussed. 301</a></p> 302<p> 303<a name="part4">The </a><a href="http://www.opengl.org/developers/documentation/specs.html"> 304OpenGL Specification</a> is the bible for OpenGL implemention work. 305You should read it. 306</p> 307<p>Most of the Mesa development work involves implementing new OpenGL 308extensions, writing hardware drivers (for the DRI), and code optimization. 309</p> 310 311<h2>4.2 How do I write a new device driver?</h2> 312<p> 313Unfortunately, writing a device driver isn't easy. 314It requires detailed understanding of OpenGL, the Mesa code, and your 315target hardware/operating system. 3163D graphics are not simple. 317</p> 318<p> 319The best way to get started is to use an existing driver as your starting 320point. 321For a software driver, the X11 and OSMesa drivers are good examples. 322For a hardware driver, the Radeon and R200 DRI drivers are good examples. 323</p> 324<p>The DRI website has more information about writing hardware drivers. 325The process isn't well document because the Mesa driver interface changes 326over time, and we seldome have spare time for writing documentation. 327That being said, many people have managed to figure out the process. 328</p> 329<p> 330Joining the appropriate mailing lists and asking questions (and searching 331the archives) is a good way to get information. 332</p> 333 334 335</body> 336</html> 337