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9<h1>Mesa Frequently Asked Questions</h1>
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame^]10Last updated: 17 November 2004
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]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.
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]35OpenGL is a programming library for writing interactive 3D applications.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]36See the </a><a href="http://www.opengl.org/">OpenGL website</a> for more
37information.
38</p>
39<p>
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]40Mesa 5.x supports the OpenGL 1.4 specification.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]41</p>
42
43
44<h2>1.2 Does Mesa support/use graphics hardware?</h2>
45<p>
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]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.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]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
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame^]56<h2>1.3 What purpose does Mesa serve today?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]57<p>
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]58Hardware-accelerated OpenGL implementations are available for most popular
59operating systems today.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]60Still, Mesa serves at least these purposes:
61</p>
62<ul>
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]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
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]69 hardware drivers.
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]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.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]76 This capability is only now appearing in hardware.
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]77</li>
78<li>Mesa's internal limits (max lights, clip planes, texture size, etc) can be
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]79 changed for special needs (hardware limits are hard to overcome).
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]80</li>
81</ul>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]82
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame^]83
84<h2>1.4 What's the difference between"Stand-Alone" Mesa and the DRI drivers?</h2>
85<p>
86<em>Stand-alone Mesa</em> is the original incarnation of Mesa.
87On systems running the X Window System, it does all its rendering through
88the Xlib API.
89<ul>
90<li>The GLX API is supported, but it's really just an emulation of the
91 real thing.
92<li>The GLX wire protocol is not supported and there's no OpenGL extension
93 loaded by the X server.
94<li>There is no hardware acceleration.
95<li>The OpenGL library, libGL.so, contains everything (the programming API,
96 the GLX functions and all the rendering code).
97</ul>
98</p>
99<p>
100Alternately, Mesa acts as the core for a number of OpenGL hardware drivers
101within the DRI (Direct Rendering Infrastructure):
102<ul>
103<li>The libGL.so library provides the GL and GLX API functions, a GLX
104 protocol encoder, and a device driver loader.
105<li>The device driver modules (such as r200_dri.so) contain a built-in
106 copy of the core Mesa code.
107<li>The X server loads the GLX module.
108 The GLX module decodes incoming GLX protocol and dispatches the commands
109 to a rendering module.
110 For the DRI, this module is basically a software Mesa renderer.
111</ul>
112
113
114
115<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]116<p>
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]117You don't! A copy of the Mesa source code lives inside the XFree86/DRI source
118tree and gets compiled into the individual DRI driver modules.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]119If you try to install Mesa over an XFree86/DRI installation, you'll lose
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]120hardware rendering (because stand-alone Mesa's libGL.so is different than
121the XFree86 libGL.so).
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]122</p>
123<p>
124The DRI developers will incorporate the latest release of Mesa into the
125DRI drivers when the time is right.
126</p>
Brian Paul824a4fc2003-08-06 19:05:26 +0000[diff] [blame]127<p>
128To upgrade, either look for a new release of <a href="http://www.xfree86.org"
129target="_parent">XFree86</a> or visit the
130<a href="http://dri.sf.net" target="_parent">DRI website</a> to see
131if there's newer drivers.
132</p>
133
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]134
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame^]135<h2>1.6 Are there other open-source implementations of OpenGL?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]136<p>
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]137Yes, SGI's <a href="http://oss.sgi.com/projects/ogl-sample/index.html"
138target="_parent">
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]139OpenGL Sample Implemenation (SI)</a> is available.
140The SI was written during the time that OpenGL was originally designed.
141Unfortunately, development of the SI has stagnated.
142Mesa is much more up to date with modern features and extensions.
143</p>
Brian Paul186d4d82004-04-27 12:55:08 +0000[diff] [blame]144
145<p>
146<a href="http://ogl-es.sourceforge.net" target="_parent">Vincent</a> is
147an open-source implementation of OpenGL ES for mobile devices.
148
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]149<p>
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]150<a href="http://www.dsbox.com/minigl.html" target="_parent">miniGL</a>
151is a subset of OpenGL for PalmOS devices.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]152
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]153<p>
154<a href="http://fabrice.bellard.free.fr/TinyGL/"
155target="_parent">TinyGL</a> is a subset of OpenGL.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]156</p>
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]157
158<p>
159<a href="http://softgl.studierstube.org/" target="_parent">SoftGL</a>
160is an OpenGL subset for mobile devices.
161</p>
162
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]163<p>
Brian Paulacbc1e02003-11-26 18:10:31 +0000[diff] [blame]164<a href="http://chromium.sourceforge.net/" target="_parent">Chromium</a>
165isn't a conventional OpenGL implementation (it's layered upon OpenGL),
166but it does export the OpenGL API. It allows tiled rendering, sort-last
167rendering, etc.
168</p>
169
Brian Paulacbc1e02003-11-26 18:10:31 +0000[diff] [blame]170<p>
171There may be other open OpenGL implementations, but Mesa is the most
172popular and feature-complete.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]173</p>
174
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame^]175
176
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]177<br>
178<br>
179
180
181<a name="part2">
182</a><h1><a name="part2">2. Compilation and Installation Problems</a></h1>
183
184
185<h2><a name="part2">2.1 What's the easiest way to install Mesa?</a></h2>
186<p>
187<a name="part2">If you're using a Linux-based system, your distro CD most likely already
188has Mesa packages (like RPM or DEB) which you can easily install.
189</a></p>
190
191
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame^]192<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]193<p>
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame^]194Mesa no longer supports GNU autoconf/automake. Why?
195<ul>
196<li>It seemed to seldom work on anything but Linux
197<li>The config files were hard to maintain and hard to understand
198<li>libtool caused a lot of grief
199</ul>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]200
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]201<p>
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame^]202Now, Mesa again uses a conventional Makefile system (as it did originally).
203Basically, each Makefile in the tree includes one of the configuration
204files from the config/ directory.
205The config files specify all the variables for a variety of popular systems.
206</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]207
208
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame^]209<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]210<p>
211<a name="part2">You're application is written in IRIS GL, not OpenGL.
212IRIS GL was the predecessor to OpenGL and is a different thing (almost)
213entirely.
214Mesa's not the solution.
215</a></p>
216
217
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame^]218<h2><a name="part2">2.4 Where is the GLUT library?</a></h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]219<p>
220<a name="part2">GLUT (OpenGL Utility Toolkit) is in the separate MesaDemos-x.y.z.tar.gz file.
221If you don't already have GLUT installed, you should grab the MesaDemos
222package and unpack it before compiling Mesa.
223</a></p>
224
225
226
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame^]227<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]228<p>
229<a name="part2">On Linux-based systems you'll want to follow the
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]230</a><a href="http://oss.sgi.com/projects/ogl-sample/ABI/index.html"
231target="_parent">Linux ABI</a> standard.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]232Basically you'll want the following:
233</p>
234<ul>
235<li>/usr/include/GL/gl.h - the main OpenGL header
236</li><li>/usr/include/GL/glu.h - the OpenGL GLU (utility) header
237</li><li>/usr/include/GL/glx.h - the OpenGL GLX header
238</li><li>/usr/include/GL/glext.h - the OpenGL extensions header
239</li><li>/usr/include/GL/glxext.h - the OpenGL GLX extensions header
240</li><li>/usr/include/GL/osmesa.h - the Mesa off-screen rendering header
241</li><li>/usr/lib/libGL.so - a symlink to libGL.so.1
242</li><li>/usr/lib/libGL.so.1 - a symlink to libGL.so.1.xyz
243</li><li>/usr/lib/libGL.so.xyz - the actual OpenGL/Mesa library. xyz denotes the
244Mesa version number.
245</li><li>/usr/lib/libGLU.so - a symlink to libGLU.so.1
246</li><li>/usr/lib/libGLU.so.1 - a symlink to libGLU.so.1.3.xyz
247</li><li>/usr/lib/libGLU.so.xyz - the OpenGL Utility library. xyz denotes the Mesa
248version number.
249</li></ul>
250<p>
251After installing XFree86 and the DRI drivers, some of these files
252may be symlinks into the /usr/X11R6/ tree.
253</p>
254<p>
255The old-style Makefile system doesn't install the Mesa libraries; it's
256up to you to copy them (and the headers) to the right place.
257</p>
258<p>
259The GLUT header and library should go in the same directories.
260</p>
261<br>
262<br>
263
264
265<a name="part3">
266</a><h1><a name="part3">3. Runtime / Rendering Problems</a></h1>
267
268<h2><a name="part3">3.1 Rendering is slow / why isn't my graphics hardware being used?</a></h2>
269<p>
270<a name="part3">Stand-alone Mesa (downloaded as MesaLib-x.y.z.tar.gz) doesn't have any
271support for hardware acceleration (with the exception of the 3DFX Voodoo
272driver).
273</a></p>
274<p>
275<a name="part3">What you really want is a DRI or NVIDIA (or another vendor's OpenGL) driver
276for your particular hardware.
277</a></p>
278<p>
279<a name="part3">You can run the <code>glxinfo</code> program to learn about your OpenGL
280library.
281Look for the GL_VENDOR and GL_RENDERER values.
282That will identify who's OpenGL library you're using and what sort of
283hardware it has detected.
284</a></p>
285<p>
286<a name="part3">If your DRI-based driver isn't working, go to the
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]287</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]288</p>
289
290
291<h2>3.2 I'm seeing errors in depth (Z) buffering. Why?</h2>
292<p>
293Make sure the ratio of the far to near clipping planes isn't too great.
294Look
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]295<a href="http://www.sgi.com/software/opengl/advanced97/notes/node18.html"
296target="_parent">
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]297here</a> for details.
298</p>
299<p>
300Mesa uses a 16-bit depth buffer by default which is smaller and faster
301to clear than a 32-bit buffer but not as accurate.
302If you need a deeper you can modify the parameters to
303<code> glXChooseVisual</code> in your code.
304</p>
305
306
307<h2>3.3 Why Isn't depth buffering working at all?</h2>
308<p>
309Be sure you're requesting a depth buffered-visual. If you set the MESA_DEBUG
310environment variable it will warn you about trying to enable depth testing
311when you don't have a depth buffer.
312</p>
313<p>Specifically, make sure <code>glutInitDisplayMode</code> is being called
314with <code>GLUT_DEPTH</code> or <code>glXChooseVisual</code> is being
315called with a non-zero value for GLX_DEPTH_SIZE.
316</p>
317<p>This discussion applies to stencil buffers, accumulation buffers and
318alpha channels too.
319</p>
320
321
322<h2>3.4 Why does glGetString() always return NULL?</h2>
323<p>
324Be sure you have an active/current OpenGL rendering context before
325calling glGetString.
326</p>
327
328
329<h2>3.5 GL_POINTS and GL_LINES don't touch the right pixels</h2>
330<p>
331If you're trying to draw a filled region by using GL_POINTS or GL_LINES
332and seeing holes or gaps it's because of a float-to-int rounding problem.
333But this is not a bug.
334See Appendix H of the OpenGL Programming Guide - "OpenGL Correctness Tips".
335Basically, applying a translation of (0.375, 0.375, 0.0) to your coordinates
336will fix the problem.
337</p>
338
339<br>
340<br>
341
342
343<a name="part4">
344</a><h1><a name="part4">4. Developer Questions</a></h1>
345
346<h2><a name="part4">4.1 How can I contribute?</a></h2>
347<p>
348<a name="part4">First, join the Mesa3d-dev mailing list. That's where Mesa development
349is discussed.
350</a></p>
351<p>
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]352<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]353OpenGL Specification</a> is the bible for OpenGL implemention work.
354You should read it.
355</p>
356<p>Most of the Mesa development work involves implementing new OpenGL
357extensions, writing hardware drivers (for the DRI), and code optimization.
358</p>
359
360<h2>4.2 How do I write a new device driver?</h2>
361<p>
362Unfortunately, writing a device driver isn't easy.
363It requires detailed understanding of OpenGL, the Mesa code, and your
364target hardware/operating system.
3653D graphics are not simple.
366</p>
367<p>
368The best way to get started is to use an existing driver as your starting
369point.
370For a software driver, the X11 and OSMesa drivers are good examples.
371For a hardware driver, the Radeon and R200 DRI drivers are good examples.
372</p>
373<p>The DRI website has more information about writing hardware drivers.
374The process isn't well document because the Mesa driver interface changes
375over time, and we seldome have spare time for writing documentation.
376That being said, many people have managed to figure out the process.
377</p>
378<p>
379Joining the appropriate mailing lists and asking questions (and searching
380the archives) is a good way to get information.
381</p>
382
383
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]384<h2>4.3 Why isn't GL_EXT_texture_compression_s3tc implemented in Mesa and/or the DRI drivers?</h2>
385<p>
386The <a href="http://oss.sgi.com/projects/ogl-sample/registry/EXT/texture_compression_s3tc.txt" target="_parent">specification for the extension</a>
387indicates that there are intellectual property (IP) and/or patent issues
388to be dealt with.
389</p>
390<p>We've been unsucessful in getting a response from S3 (or whoever owns
391the IP nowadays) to indicate whether or not an open source project can
392implement the extension (specifically the compression/decompression
393algorithms).
394</p>
395<p>
396Until we can get official permission to do so, this extension will not
397be implemented in Mesa.
398</p>
399
400
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]401</body>
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