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3<head><title>Mesa FAQ</title></head>
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10<center>
11<h1>Mesa Frequently Asked Questions</h1>
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]12Last updated: 17 November 2004
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]13</center>
14
15<br>
16<br>
17<h2>Index</h2>
18<a href="#part1">1. High-level Questions and Answers</a>
19<br>
20<a href="#part2">2. Compilation and Installation Problems</a>
21<br>
22<a href="#part3">3. Runtime / Rendering Problems</a>
23<br>
24<a href="#part4">4. Developer Questions</a>
25<br>
26<br>
27<br>
28
29
30
31<a name="part1">
32</a><h1><a name="part1">1. High-level Questions and Answers</a></h1>
33
34<h2><a name="part1">1.1 What is Mesa?</a></h2>
35<p>
36<a name="part1">Mesa is an open-source implementation of the OpenGL specification.
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]37OpenGL is a programming library for writing interactive 3D applications.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]38See the </a><a href="http://www.opengl.org/">OpenGL website</a> for more
39information.
40</p>
41<p>
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]42Mesa 5.x supports the OpenGL 1.4 specification.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]43</p>
44
45
46<h2>1.2 Does Mesa support/use graphics hardware?</h2>
47<p>
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]48Yes. Specifically, Mesa serves as the OpenGL core for the open-source
49XFree86/DRI OpenGL drivers. See the <a href="http://dri.sf.net/">DRI
50website</a> for more information.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]51</p>
52<p>
53There have been other hardware drivers for Mesa over the years (such as
54the 3Dfx Glide/Voodoo driver, an old S3 driver, etc) but the DRI drivers
55are the modern ones.
56</p>
57
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]58<h2>1.3 What purpose does Mesa serve today?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]59<p>
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]60Hardware-accelerated OpenGL implementations are available for most popular
61operating systems today.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]62Still, Mesa serves at least these purposes:
63</p>
64<ul>
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]65<li>Mesa is used as the core of the open-source XFree86/DRI hardware drivers.
66</li>
67<li>Mesa is quite portable and allows OpenGL to be used on systems
68 that have no other OpenGL solution.
69</li>
70<li>Software rendering with Mesa serves as a reference for validating the
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]71 hardware drivers.
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]72</li>
73<li>A software implementation of OpenGL is useful for experimentation,
74 such as testing new rendering techniques.
75</li>
76<li>Mesa can render images with deep color channels: 16-bit integer
77 and 32-bit floating point color channels are supported.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]78 This capability is only now appearing in hardware.
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]79</li>
80<li>Mesa's internal limits (max lights, clip planes, texture size, etc) can be
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]81 changed for special needs (hardware limits are hard to overcome).
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]82</li>
83</ul>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]84
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]85
86<h2>1.4 What's the difference between"Stand-Alone" Mesa and the DRI drivers?</h2>
87<p>
88<em>Stand-alone Mesa</em> is the original incarnation of Mesa.
89On systems running the X Window System, it does all its rendering through
90the Xlib API.
91<ul>
92<li>The GLX API is supported, but it's really just an emulation of the
93 real thing.
94<li>The GLX wire protocol is not supported and there's no OpenGL extension
95 loaded by the X server.
96<li>There is no hardware acceleration.
97<li>The OpenGL library, libGL.so, contains everything (the programming API,
98 the GLX functions and all the rendering code).
99</ul>
100</p>
101<p>
102Alternately, Mesa acts as the core for a number of OpenGL hardware drivers
103within the DRI (Direct Rendering Infrastructure):
104<ul>
105<li>The libGL.so library provides the GL and GLX API functions, a GLX
106 protocol encoder, and a device driver loader.
107<li>The device driver modules (such as r200_dri.so) contain a built-in
108 copy of the core Mesa code.
109<li>The X server loads the GLX module.
110 The GLX module decodes incoming GLX protocol and dispatches the commands
111 to a rendering module.
112 For the DRI, this module is basically a software Mesa renderer.
113</ul>
114
115
116
117<h2>1.5 How do I upgrade my DRI installation to use a new Mesa release?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]118<p>
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]119You don't! A copy of the Mesa source code lives inside the XFree86/DRI source
120tree and gets compiled into the individual DRI driver modules.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]121If you try to install Mesa over an XFree86/DRI installation, you'll lose
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]122hardware rendering (because stand-alone Mesa's libGL.so is different than
123the XFree86 libGL.so).
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]124</p>
125<p>
126The DRI developers will incorporate the latest release of Mesa into the
127DRI drivers when the time is right.
128</p>
Brian Paul824a4fc2003-08-06 19:05:26 +0000[diff] [blame]129<p>
130To upgrade, either look for a new release of <a href="http://www.xfree86.org"
131target="_parent">XFree86</a> or visit the
132<a href="http://dri.sf.net" target="_parent">DRI website</a> to see
133if there's newer drivers.
134</p>
135
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]136
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]137<h2>1.6 Are there other open-source implementations of OpenGL?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]138<p>
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]139Yes, SGI's <a href="http://oss.sgi.com/projects/ogl-sample/index.html"
140target="_parent">
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]141OpenGL Sample Implemenation (SI)</a> is available.
142The SI was written during the time that OpenGL was originally designed.
143Unfortunately, development of the SI has stagnated.
144Mesa is much more up to date with modern features and extensions.
145</p>
Brian Paul186d4d82004-04-27 12:55:08 +0000[diff] [blame]146
147<p>
148<a href="http://ogl-es.sourceforge.net" target="_parent">Vincent</a> is
149an open-source implementation of OpenGL ES for mobile devices.
150
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]151<p>
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]152<a href="http://www.dsbox.com/minigl.html" target="_parent">miniGL</a>
153is a subset of OpenGL for PalmOS devices.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]154
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]155<p>
156<a href="http://fabrice.bellard.free.fr/TinyGL/"
157target="_parent">TinyGL</a> is a subset of OpenGL.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]158</p>
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]159
160<p>
161<a href="http://softgl.studierstube.org/" target="_parent">SoftGL</a>
162is an OpenGL subset for mobile devices.
163</p>
164
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]165<p>
Brian Paulacbc1e02003-11-26 18:10:31 +0000[diff] [blame]166<a href="http://chromium.sourceforge.net/" target="_parent">Chromium</a>
167isn't a conventional OpenGL implementation (it's layered upon OpenGL),
168but it does export the OpenGL API. It allows tiled rendering, sort-last
169rendering, etc.
170</p>
171
Brian Paulacbc1e02003-11-26 18:10:31 +0000[diff] [blame]172<p>
173There may be other open OpenGL implementations, but Mesa is the most
174popular and feature-complete.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]175</p>
176
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]177
178
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]179<br>
180<br>
181
182
183<a name="part2">
184</a><h1><a name="part2">2. Compilation and Installation Problems</a></h1>
185
186
187<h2><a name="part2">2.1 What's the easiest way to install Mesa?</a></h2>
188<p>
189<a name="part2">If you're using a Linux-based system, your distro CD most likely already
190has Mesa packages (like RPM or DEB) which you can easily install.
191</a></p>
192
193
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]194<h2><a name="part2">2.2 Running <code>configure; make</code> doesn't Work</a></h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]195<p>
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]196Mesa no longer supports GNU autoconf/automake. Why?
197<ul>
198<li>It seemed to seldom work on anything but Linux
199<li>The config files were hard to maintain and hard to understand
200<li>libtool caused a lot of grief
201</ul>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]202
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]203<p>
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]204Now, Mesa again uses a conventional Makefile system (as it did originally).
205Basically, each Makefile in the tree includes one of the configuration
206files from the config/ directory.
207The config files specify all the variables for a variety of popular systems.
208</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]209
210
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]211<h2><a name="part2">2.3 I get undefined symbols such as bgnpolygon, v3f, etc...</a></h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]212<p>
213<a name="part2">You're application is written in IRIS GL, not OpenGL.
214IRIS GL was the predecessor to OpenGL and is a different thing (almost)
215entirely.
216Mesa's not the solution.
217</a></p>
218
219
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]220<h2><a name="part2">2.4 Where is the GLUT library?</a></h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]221<p>
222<a name="part2">GLUT (OpenGL Utility Toolkit) is in the separate MesaDemos-x.y.z.tar.gz file.
223If you don't already have GLUT installed, you should grab the MesaDemos
224package and unpack it before compiling Mesa.
225</a></p>
226
227
228
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]229<h2><a name="part2">2.5 What's the proper place for the libraries and headers?</a></h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]230<p>
231<a name="part2">On Linux-based systems you'll want to follow the
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]232</a><a href="http://oss.sgi.com/projects/ogl-sample/ABI/index.html"
233target="_parent">Linux ABI</a> standard.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]234Basically you'll want the following:
235</p>
236<ul>
237<li>/usr/include/GL/gl.h - the main OpenGL header
238</li><li>/usr/include/GL/glu.h - the OpenGL GLU (utility) header
239</li><li>/usr/include/GL/glx.h - the OpenGL GLX header
240</li><li>/usr/include/GL/glext.h - the OpenGL extensions header
241</li><li>/usr/include/GL/glxext.h - the OpenGL GLX extensions header
242</li><li>/usr/include/GL/osmesa.h - the Mesa off-screen rendering header
243</li><li>/usr/lib/libGL.so - a symlink to libGL.so.1
244</li><li>/usr/lib/libGL.so.1 - a symlink to libGL.so.1.xyz
245</li><li>/usr/lib/libGL.so.xyz - the actual OpenGL/Mesa library. xyz denotes the
246Mesa version number.
247</li><li>/usr/lib/libGLU.so - a symlink to libGLU.so.1
248</li><li>/usr/lib/libGLU.so.1 - a symlink to libGLU.so.1.3.xyz
249</li><li>/usr/lib/libGLU.so.xyz - the OpenGL Utility library. xyz denotes the Mesa
250version number.
251</li></ul>
252<p>
253After installing XFree86 and the DRI drivers, some of these files
254may be symlinks into the /usr/X11R6/ tree.
255</p>
256<p>
257The old-style Makefile system doesn't install the Mesa libraries; it's
258up to you to copy them (and the headers) to the right place.
259</p>
260<p>
261The GLUT header and library should go in the same directories.
262</p>
263<br>
264<br>
265
266
267<a name="part3">
268</a><h1><a name="part3">3. Runtime / Rendering Problems</a></h1>
269
270<h2><a name="part3">3.1 Rendering is slow / why isn't my graphics hardware being used?</a></h2>
271<p>
272<a name="part3">Stand-alone Mesa (downloaded as MesaLib-x.y.z.tar.gz) doesn't have any
273support for hardware acceleration (with the exception of the 3DFX Voodoo
274driver).
275</a></p>
276<p>
277<a name="part3">What you really want is a DRI or NVIDIA (or another vendor's OpenGL) driver
278for your particular hardware.
279</a></p>
280<p>
281<a name="part3">You can run the <code>glxinfo</code> program to learn about your OpenGL
282library.
283Look for the GL_VENDOR and GL_RENDERER values.
284That will identify who's OpenGL library you're using and what sort of
285hardware it has detected.
286</a></p>
287<p>
288<a name="part3">If your DRI-based driver isn't working, go to the
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]289</a><a href="http://dri.sf.net/" target="_parent">DRI website</a> for trouble-shooting information.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]290</p>
291
292
293<h2>3.2 I'm seeing errors in depth (Z) buffering. Why?</h2>
294<p>
295Make sure the ratio of the far to near clipping planes isn't too great.
296Look
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]297<a href="http://www.sgi.com/software/opengl/advanced97/notes/node18.html"
298target="_parent">
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]299here</a> for details.
300</p>
301<p>
302Mesa uses a 16-bit depth buffer by default which is smaller and faster
303to clear than a 32-bit buffer but not as accurate.
304If you need a deeper you can modify the parameters to
305<code> glXChooseVisual</code> in your code.
306</p>
307
308
309<h2>3.3 Why Isn't depth buffering working at all?</h2>
310<p>
311Be sure you're requesting a depth buffered-visual. If you set the MESA_DEBUG
312environment variable it will warn you about trying to enable depth testing
313when you don't have a depth buffer.
314</p>
315<p>Specifically, make sure <code>glutInitDisplayMode</code> is being called
316with <code>GLUT_DEPTH</code> or <code>glXChooseVisual</code> is being
317called with a non-zero value for GLX_DEPTH_SIZE.
318</p>
319<p>This discussion applies to stencil buffers, accumulation buffers and
320alpha channels too.
321</p>
322
323
324<h2>3.4 Why does glGetString() always return NULL?</h2>
325<p>
326Be sure you have an active/current OpenGL rendering context before
327calling glGetString.
328</p>
329
330
331<h2>3.5 GL_POINTS and GL_LINES don't touch the right pixels</h2>
332<p>
333If you're trying to draw a filled region by using GL_POINTS or GL_LINES
334and seeing holes or gaps it's because of a float-to-int rounding problem.
335But this is not a bug.
336See Appendix H of the OpenGL Programming Guide - "OpenGL Correctness Tips".
337Basically, applying a translation of (0.375, 0.375, 0.0) to your coordinates
338will fix the problem.
339</p>
340
341<br>
342<br>
343
344
345<a name="part4">
346</a><h1><a name="part4">4. Developer Questions</a></h1>
347
348<h2><a name="part4">4.1 How can I contribute?</a></h2>
349<p>
350<a name="part4">First, join the Mesa3d-dev mailing list. That's where Mesa development
351is discussed.
352</a></p>
353<p>
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]354<a name="part4">The </a><a href="http://www.opengl.org/developers/documentation/specs.html" target="_parent">
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]355OpenGL Specification</a> is the bible for OpenGL implemention work.
356You should read it.
357</p>
358<p>Most of the Mesa development work involves implementing new OpenGL
359extensions, writing hardware drivers (for the DRI), and code optimization.
360</p>
361
362<h2>4.2 How do I write a new device driver?</h2>
363<p>
364Unfortunately, writing a device driver isn't easy.
365It requires detailed understanding of OpenGL, the Mesa code, and your
366target hardware/operating system.
3673D graphics are not simple.
368</p>
369<p>
370The best way to get started is to use an existing driver as your starting
371point.
372For a software driver, the X11 and OSMesa drivers are good examples.
373For a hardware driver, the Radeon and R200 DRI drivers are good examples.
374</p>
375<p>The DRI website has more information about writing hardware drivers.
376The process isn't well document because the Mesa driver interface changes
377over time, and we seldome have spare time for writing documentation.
378That being said, many people have managed to figure out the process.
379</p>
380<p>
381Joining the appropriate mailing lists and asking questions (and searching
382the archives) is a good way to get information.
383</p>
384
385
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]386<h2>4.3 Why isn't GL_EXT_texture_compression_s3tc implemented in Mesa and/or the DRI drivers?</h2>
387<p>
388The <a href="http://oss.sgi.com/projects/ogl-sample/registry/EXT/texture_compression_s3tc.txt" target="_parent">specification for the extension</a>
389indicates that there are intellectual property (IP) and/or patent issues
390to be dealt with.
391</p>
392<p>We've been unsucessful in getting a response from S3 (or whoever owns
393the IP nowadays) to indicate whether or not an open source project can
394implement the extension (specifically the compression/decompression
395algorithms).
396</p>
397<p>
398Until we can get official permission to do so, this extension will not
399be implemented in Mesa.
400</p>
401
402
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]403</body>
404</html>