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9<h1>Mesa Frequently Asked Questions</h1>
Brian Paul824a4fc2003-08-06 19:05:26 +0000[diff] [blame^]10Last updated: 6 August 2003
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 Paula376e332003-03-30 16:54:36 +0000[diff] [blame]56<h2>1.3 What purpose does Mesa (software-based rendering) 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
83<h2>1.4 How do I upgrade my DRI installation to use a new Mesa release?</h2>
84<p>
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]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.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]87If you try to install Mesa over an XFree86/DRI installation, you'll lose
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]88hardware rendering (because stand-alone Mesa's libGL.so is different than
89the XFree86 libGL.so).
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]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>
Brian Paul824a4fc2003-08-06 19:05:26 +0000[diff] [blame^]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
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]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">
106OpenGL Sample Implemenation (SI)</a> is available.
107The SI was written during the time that OpenGL was originally designed.
108Unfortunately, development of the SI has stagnated.
109Mesa is much more up to date with modern features and extensions.
110</p>
111<p>
112<a href="http://www.dsbox.com/minigl.html">miniGL</a> is a subset of OpenGL
113for PalmOS devices.
114
115<a href="http://fabrice.bellard.free.fr/TinyGL/">TinyGL</a> is another
116subset of OpenGL.
117</p>
118<p>
119There may be others but Mesa is the most popular and feature-complete.
120</p>
121
122<br>
123<br>
124
125
126<a name="part2">
127</a><h1><a name="part2">2. Compilation and Installation Problems</a></h1>
128
129
130<h2><a name="part2">2.1 What's the easiest way to install Mesa?</a></h2>
131<p>
132<a name="part2">If you're using a Linux-based system, your distro CD most likely already
133has Mesa packages (like RPM or DEB) which you can easily install.
134</a></p>
135
136
137<h2><a name="part2">2.2 Running <code>configure; make</code> Doesn't Work</a></h2>
138<p>
139<a name="part2">Unfortunately, the GNU autoconf/automake/libtool system doesn't seem to work
140too well on non GNU/Linux systems, even after installing gmake, gcc, etc.
141For that reason, Mesa's <b>old-style</b> makefile system is still included.
142The old-style system uses good old traditional Makefiles. Try the following:
143</a></p><pre><a name="part2"> cd Mesa-x.y.z
144 cp Makefile.X11 Makefile
145 make
146</a></pre>
147<a name="part2">You'll see a list of system configurations from which to choose.
148For example:
149</a><pre><a name="part2"> make linux-x86
150</a></pre>
151<p>
152<a name="part2">If you're experienced with GNU autoconf/automake/libtool and think you can help
153with maintence, contact the Mesa developers.
154FYI, the Mesa developers generally don't use the autoconf/automake system.
155We're especially annoyed with the fact that a +5000-line script (libtool)
156is needed to make shared libraries (ugh).
157</a></p>
158
159<h2><a name="part2">2.3 Mesa still doesn't compile</a></h2>
160<p>
161<a name="part2">If the old-style Makefile system doesn't work either, make sure you have
162the most recent version of Mesa.
163Otherwise, file a bug report or post to the Mesa3d-users mailing list.
164Give as much info as possible when describing your problem.
165</a></p>
166
167
168<h2><a name="part2">2.4 I get undefined symbols such as bgnpolygon, v3f, etc...</a></h2>
169<p>
170<a name="part2">You're application is written in IRIS GL, not OpenGL.
171IRIS GL was the predecessor to OpenGL and is a different thing (almost)
172entirely.
173Mesa's not the solution.
174</a></p>
175
176
177<h2><a name="part2">2.5 Where is the GLUT library?</a></h2>
178<p>
179<a name="part2">GLUT (OpenGL Utility Toolkit) is in the separate MesaDemos-x.y.z.tar.gz file.
180If you don't already have GLUT installed, you should grab the MesaDemos
181package and unpack it before compiling Mesa.
182</a></p>
183
184
185
186<h2><a name="part2">2.6 What's the proper place for the libraries and headers?</a></h2>
187<p>
188<a name="part2">On Linux-based systems you'll want to follow the
189</a><a href="http://oss.sgi.com/projects/ogl-sample/ABI/index.html">Linux ABI</a>
190standard.
191Basically you'll want the following:
192</p>
193<ul>
194<li>/usr/include/GL/gl.h - the main OpenGL header
195</li><li>/usr/include/GL/glu.h - the OpenGL GLU (utility) header
196</li><li>/usr/include/GL/glx.h - the OpenGL GLX header
197</li><li>/usr/include/GL/glext.h - the OpenGL extensions header
198</li><li>/usr/include/GL/glxext.h - the OpenGL GLX extensions header
199</li><li>/usr/include/GL/osmesa.h - the Mesa off-screen rendering header
200</li><li>/usr/lib/libGL.so - a symlink to libGL.so.1
201</li><li>/usr/lib/libGL.so.1 - a symlink to libGL.so.1.xyz
202</li><li>/usr/lib/libGL.so.xyz - the actual OpenGL/Mesa library. xyz denotes the
203Mesa version number.
204</li><li>/usr/lib/libGLU.so - a symlink to libGLU.so.1
205</li><li>/usr/lib/libGLU.so.1 - a symlink to libGLU.so.1.3.xyz
206</li><li>/usr/lib/libGLU.so.xyz - the OpenGL Utility library. xyz denotes the Mesa
207version number.
208</li></ul>
209<p>
210After installing XFree86 and the DRI drivers, some of these files
211may be symlinks into the /usr/X11R6/ tree.
212</p>
213<p>
214The old-style Makefile system doesn't install the Mesa libraries; it's
215up to you to copy them (and the headers) to the right place.
216</p>
217<p>
218The GLUT header and library should go in the same directories.
219</p>
220<br>
221<br>
222
223
224<a name="part3">
225</a><h1><a name="part3">3. Runtime / Rendering Problems</a></h1>
226
227<h2><a name="part3">3.1 Rendering is slow / why isn't my graphics hardware being used?</a></h2>
228<p>
229<a name="part3">Stand-alone Mesa (downloaded as MesaLib-x.y.z.tar.gz) doesn't have any
230support for hardware acceleration (with the exception of the 3DFX Voodoo
231driver).
232</a></p>
233<p>
234<a name="part3">What you really want is a DRI or NVIDIA (or another vendor's OpenGL) driver
235for your particular hardware.
236</a></p>
237<p>
238<a name="part3">You can run the <code>glxinfo</code> program to learn about your OpenGL
239library.
240Look for the GL_VENDOR and GL_RENDERER values.
241That will identify who's OpenGL library you're using and what sort of
242hardware it has detected.
243</a></p>
244<p>
245<a name="part3">If your DRI-based driver isn't working, go to the
246</a><a href="http://dri.sf.net/">DRI website</a> for trouble-shooting information.
247</p>
248
249
250<h2>3.2 I'm seeing errors in depth (Z) buffering. Why?</h2>
251<p>
252Make sure the ratio of the far to near clipping planes isn't too great.
253Look
254<a href="http://www.sgi.com/software/opengl/advanced97/notes/node18.html">
255here</a> for details.
256</p>
257<p>
258Mesa uses a 16-bit depth buffer by default which is smaller and faster
259to clear than a 32-bit buffer but not as accurate.
260If you need a deeper you can modify the parameters to
261<code> glXChooseVisual</code> in your code.
262</p>
263
264
265<h2>3.3 Why Isn't depth buffering working at all?</h2>
266<p>
267Be sure you're requesting a depth buffered-visual. If you set the MESA_DEBUG
268environment variable it will warn you about trying to enable depth testing
269when you don't have a depth buffer.
270</p>
271<p>Specifically, make sure <code>glutInitDisplayMode</code> is being called
272with <code>GLUT_DEPTH</code> or <code>glXChooseVisual</code> is being
273called with a non-zero value for GLX_DEPTH_SIZE.
274</p>
275<p>This discussion applies to stencil buffers, accumulation buffers and
276alpha channels too.
277</p>
278
279
280<h2>3.4 Why does glGetString() always return NULL?</h2>
281<p>
282Be sure you have an active/current OpenGL rendering context before
283calling glGetString.
284</p>
285
286
287<h2>3.5 GL_POINTS and GL_LINES don't touch the right pixels</h2>
288<p>
289If you're trying to draw a filled region by using GL_POINTS or GL_LINES
290and seeing holes or gaps it's because of a float-to-int rounding problem.
291But this is not a bug.
292See Appendix H of the OpenGL Programming Guide - "OpenGL Correctness Tips".
293Basically, applying a translation of (0.375, 0.375, 0.0) to your coordinates
294will fix the problem.
295</p>
296
297<br>
298<br>
299
300
301<a name="part4">
302</a><h1><a name="part4">4. Developer Questions</a></h1>
303
304<h2><a name="part4">4.1 How can I contribute?</a></h2>
305<p>
306<a name="part4">First, join the Mesa3d-dev mailing list. That's where Mesa development
307is discussed.
308</a></p>
309<p>
310<a name="part4">The </a><a href="http://www.opengl.org/developers/documentation/specs.html">
311OpenGL Specification</a> is the bible for OpenGL implemention work.
312You should read it.
313</p>
314<p>Most of the Mesa development work involves implementing new OpenGL
315extensions, writing hardware drivers (for the DRI), and code optimization.
316</p>
317
318<h2>4.2 How do I write a new device driver?</h2>
319<p>
320Unfortunately, writing a device driver isn't easy.
321It requires detailed understanding of OpenGL, the Mesa code, and your
322target hardware/operating system.
3233D graphics are not simple.
324</p>
325<p>
326The best way to get started is to use an existing driver as your starting
327point.
328For a software driver, the X11 and OSMesa drivers are good examples.
329For a hardware driver, the Radeon and R200 DRI drivers are good examples.
330</p>
331<p>The DRI website has more information about writing hardware drivers.
332The process isn't well document because the Mesa driver interface changes
333over time, and we seldome have spare time for writing documentation.
334That being said, many people have managed to figure out the process.
335</p>
336<p>
337Joining the appropriate mailing lists and asking questions (and searching
338the archives) is a good way to get information.
339</p>
340
341
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343</html>