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gerrit-public.fairphone.software / platform / external / mesa3d / 269474b4283888c8ae13d7ed8a17359b898ff246 / . / docs / faq.html
blob: f4b511d45fddfb8f8a569301c18395deef3f8777 [file] [log] [blame]
Andreas Bollecd5c7c2012-06-12 09:05:03 +0200[diff] [blame]1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
2<html lang="en">
3<head>
4 <meta http-equiv="content-type" content="text/html; charset=utf-8">
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]5 <title>Frequently Asked Questions</title>
Andreas Bollecd5c7c2012-06-12 09:05:03 +0200[diff] [blame]6 <link rel="stylesheet" type="text/css" href="mesa.css">
7</head>
8<body>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]9
Andreas Bollb5da52a2012-09-18 18:57:02 +0200[diff] [blame]10<div class="header">
11 <h1>The Mesa 3D Graphics Library</h1>
12</div>
13
14<iframe src="contents.html"></iframe>
15<div class="content">
16
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]17<h1>Frequently Asked Questions</h1>
Stuart Youngc95dd962018-09-20 17:12:43 +1000[diff] [blame]18Last updated: 19 September 2018
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]19
20<br>
21<br>
22<h2>Index</h2>
Erik Faye-Lundda4994f2019-04-18 13:44:10 +0200[diff] [blame]23<ol>
24 <li><a href="#part1">High-level Questions and Answers</a></li>
25 <li><a href="#part2">Compilation and Installation Problems</a></li>
26 <li><a href="#part3">Runtime / Rendering Problems</a></li>
27 <li><a href="#part4">Developer Questions</a></li>
28</ol>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]29<br>
30<br>
31
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]32<h2 id="part1">1. High-level Questions and Answers</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]33
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]34<h3>1.1 What is Mesa?</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]35<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]36Mesa 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.
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]38See the <a href="https://www.opengl.org/">OpenGL website</a> for more
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]39information.
40</p>
41<p>
Andreas Boll5abb1f82012-09-19 18:22:37 +0200[diff] [blame]42Mesa 9.x supports the OpenGL 3.1 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 Paul7e4cc1c2005-10-24 23:33:27 +0000[diff] [blame]48Yes. Specifically, Mesa serves as the OpenGL core for the open-source DRI
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]49drivers for X.org.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]50</p>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]51<ul>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]52 <li>See the <a href="https://dri.freedesktop.org/">DRI website</a>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]53 for more information.</li>
Eric Engestrom771f6db2016-07-06 17:09:15 +0100[diff] [blame]54 <li>See <a href="https://01.org/linuxgraphics">01.org</a>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]55 for more information about Intel drivers.</li>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]56 <li>See <a href="https://nouveau.freedesktop.org">nouveau.freedesktop.org</a>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]57 for more information about Nouveau drivers.</li>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]58 <li>See <a href="https://www.x.org/wiki/RadeonFeature">www.x.org/wiki/RadeonFeature</a>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]59 for more information about Radeon drivers.</li>
60</ul>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]61
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]62<h2>1.3 What purpose does Mesa serve today?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]63<p>
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]64Hardware-accelerated OpenGL implementations are available for most popular
65operating systems today.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]66Still, Mesa serves at least these purposes:
67</p>
68<ul>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]69<li>Mesa is used as the core of the open-source X.org DRI
Brian Paul7e4cc1c2005-10-24 23:33:27 +0000[diff] [blame]70 hardware drivers.
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]71</li>
72<li>Mesa is quite portable and allows OpenGL to be used on systems
73 that have no other OpenGL solution.
74</li>
75<li>Software rendering with Mesa serves as a reference for validating the
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]76 hardware drivers.
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]77</li>
78<li>A software implementation of OpenGL is useful for experimentation,
79 such as testing new rendering techniques.
80</li>
81<li>Mesa can render images with deep color channels: 16-bit integer
82 and 32-bit floating point color channels are supported.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]83 This capability is only now appearing in hardware.
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]84</li>
85<li>Mesa's internal limits (max lights, clip planes, texture size, etc) can be
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]86 changed for special needs (hardware limits are hard to overcome).
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]87</li>
88</ul>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]89
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]90
Andreas Boll5abb1f82012-09-19 18:22:37 +0200[diff] [blame]91<h2>1.4 What's the difference between "Stand-Alone" Mesa and the DRI drivers?</h2>
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]92<p>
93<em>Stand-alone Mesa</em> is the original incarnation of Mesa.
Brian Paul7e4cc1c2005-10-24 23:33:27 +0000[diff] [blame]94On systems running the X Window System it does all its rendering through
95the Xlib API:
Andreas Bolldf2be222012-06-12 09:05:22 +0200[diff] [blame]96</p>
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]97<ul>
98<li>The GLX API is supported, but it's really just an emulation of the
99 real thing.
100<li>The GLX wire protocol is not supported and there's no OpenGL extension
101 loaded by the X server.
102<li>There is no hardware acceleration.
103<li>The OpenGL library, libGL.so, contains everything (the programming API,
104 the GLX functions and all the rendering code).
105</ul>
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]106<p>
107Alternately, Mesa acts as the core for a number of OpenGL hardware drivers
108within the DRI (Direct Rendering Infrastructure):
109<ul>
110<li>The libGL.so library provides the GL and GLX API functions, a GLX
111 protocol encoder, and a device driver loader.
112<li>The device driver modules (such as r200_dri.so) contain a built-in
113 copy of the core Mesa code.
114<li>The X server loads the GLX module.
115 The GLX module decodes incoming GLX protocol and dispatches the commands
116 to a rendering module.
117 For the DRI, this module is basically a software Mesa renderer.
118</ul>
119
120
121
122<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]123<p>
Brian Paul7e4cc1c2005-10-24 23:33:27 +0000[diff] [blame]124This wasn't easy in the past.
125Now, the DRI drivers are included in the Mesa tree and can be compiled
126separately from the X server.
127Just follow the Mesa <a href="install.html">compilation instructions</a>.
Brian Paul824a4fc2003-08-06 19:05:26 +0000[diff] [blame]128</p>
129
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]130
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]131<h2>1.6 Are there other open-source implementations of OpenGL?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]132<p>
Andreas Bolla73c59b2012-09-18 19:31:28 +0200[diff] [blame]133Yes, SGI's <a href="http://oss.sgi.com/projects/ogl-sample/index.html">
Nathan Kidd0691b372014-01-03 16:44:00 -0700[diff] [blame]134OpenGL Sample Implementation (SI)</a> is available.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]135The SI was written during the time that OpenGL was originally designed.
136Unfortunately, development of the SI has stagnated.
137Mesa is much more up to date with modern features and extensions.
138</p>
Brian Paul186d4d82004-04-27 12:55:08 +0000[diff] [blame]139
140<p>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]141<a href="https://sourceforge.net/projects/ogl-es/">Vincent</a> is
Brian Paul186d4d82004-04-27 12:55:08 +0000[diff] [blame]142an open-source implementation of OpenGL ES for mobile devices.
143
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]144<p>
Andreas Bolla73c59b2012-09-18 19:31:28 +0200[diff] [blame]145<a href="http://www.dsbox.com/minigl.html">miniGL</a>
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]146is a subset of OpenGL for PalmOS devices.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]147
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]148<p>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]149<a href="http://bellard.org/TinyGL/">TinyGL</a>
Andreas Bolla73c59b2012-09-18 19:31:28 +0200[diff] [blame]150is a subset of OpenGL.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]151</p>
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]152
153<p>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]154<a href="https://sourceforge.net/projects/softgl/">SoftGL</a>
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]155is an OpenGL subset for mobile devices.
156</p>
157
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]158<p>
Andreas Bolla73c59b2012-09-18 19:31:28 +0200[diff] [blame]159<a href="http://chromium.sourceforge.net/">Chromium</a>
Brian Paulacbc1e02003-11-26 18:10:31 +0000[diff] [blame]160isn't a conventional OpenGL implementation (it's layered upon OpenGL),
161but it does export the OpenGL API. It allows tiled rendering, sort-last
162rendering, etc.
163</p>
164
Brian Paulacbc1e02003-11-26 18:10:31 +0000[diff] [blame]165<p>
Andreas Bolla73c59b2012-09-18 19:31:28 +0200[diff] [blame]166<a href="http://www.ticalc.org/archives/files/fileinfo/361/36173.html">ClosedGL</a>
167is an OpenGL subset library for TI graphing calculators.
Brian Paul0c656042006-06-08 19:59:41 +0000[diff] [blame]168</p>
169
170<p>
Brian Paulacbc1e02003-11-26 18:10:31 +0000[diff] [blame]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
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]181<h2 id="part2">2. Compilation and Installation Problems</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]182
183
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]184<h3>2.1 What's the easiest way to install Mesa?</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]185<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]186If you're using a Linux-based system, your distro CD most likely already
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]187has Mesa packages (like RPM or DEB) which you can easily install.
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]188</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]189
190
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]191<h3>2.2 I get undefined symbols such as bgnpolygon, v3f, etc...</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]192<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]193You're application is written in IRIS GL, not OpenGL.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]194IRIS GL was the predecessor to OpenGL and is a different thing (almost)
195entirely.
196Mesa's not the solution.
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]197</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]198
199
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]200<h3>2.3 Where is the GLUT library?</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]201<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]202GLUT (OpenGL Utility Toolkit) is no longer in the separate MesaGLUT-x.y.z.tar.gz file.
José Fonseca9a7f84d2011-07-14 17:28:52 +0100[diff] [blame]203If you don't already have GLUT installed, you should grab
204<a href="http://freeglut.sourceforge.net/">freeglut</a>.
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]205</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]206
207
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]208<h3>2.4 Where is the GLw library?</h3>
Kenneth Graunkec5481922011-08-05 16:59:04 -0700[diff] [blame]209<p>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]210GLw (OpenGL widget library) is now available from a separate <a href="https://cgit.freedesktop.org/mesa/glw/">git repository</a>. Unless you're using very old Xt/Motif applications with OpenGL, you shouldn't need it.
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]211</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]212
Kenneth Graunkec5481922011-08-05 16:59:04 -0700[diff] [blame]213
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]214<h2>2.5 What's the proper place for the libraries and headers?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]215<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]216On Linux-based systems you'll want to follow the
Andreas Bolla73c59b2012-09-18 19:31:28 +0200[diff] [blame]217<a href="http://oss.sgi.com/projects/ogl-sample/ABI/index.html">Linux ABI</a> standard.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]218Basically you'll want the following:
219</p>
220<ul>
221<li>/usr/include/GL/gl.h - the main OpenGL header
222</li><li>/usr/include/GL/glu.h - the OpenGL GLU (utility) header
223</li><li>/usr/include/GL/glx.h - the OpenGL GLX header
224</li><li>/usr/include/GL/glext.h - the OpenGL extensions header
225</li><li>/usr/include/GL/glxext.h - the OpenGL GLX extensions header
226</li><li>/usr/include/GL/osmesa.h - the Mesa off-screen rendering header
227</li><li>/usr/lib/libGL.so - a symlink to libGL.so.1
228</li><li>/usr/lib/libGL.so.1 - a symlink to libGL.so.1.xyz
229</li><li>/usr/lib/libGL.so.xyz - the actual OpenGL/Mesa library. xyz denotes the
230Mesa version number.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]231</li></ul>
232<p>
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]233When configuring Mesa, there are three meson options that affect the install
Andreas Bollb534c392012-10-05 23:14:10 +0200[diff] [blame]234location that you should take care with: <code>--prefix</code>,
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]235<code>--libdir</code>, and <code>-D dri-drivers-path</code>. To install Mesa
Andreas Bollb534c392012-10-05 23:14:10 +0200[diff] [blame]236into the system location where it will be available for all programs to use, set
237<code>--prefix=/usr</code>. Set <code>--libdir</code> to where your Linux
238distribution installs system libraries, usually either <code>/usr/lib</code> or
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]239<code>/usr/lib64</code>. Set <code>-D dri-drivers-path</code> to the directory
Andreas Bollb534c392012-10-05 23:14:10 +0200[diff] [blame]240where your Linux distribution installs DRI drivers. To find your system's DRI
241driver directory, try executing <code>find /usr -type d -name dri</code>. For
242example, if the <code>find</code> command listed <code>/usr/lib64/dri</code>,
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]243then set <code>-D dri-drivers-path=/usr/lib64/dri</code>.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]244</p>
245<p>
Andreas Bollb534c392012-10-05 23:14:10 +0200[diff] [blame]246After determining the correct values for the install location, configure Mesa
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]247with <code>meson configure --prefix=/usr --libdir=xxx -D dri-drivers-path=xxx</code>
248and then install with <code>sudo ninja install</code>.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]249</p>
250<br>
251<br>
252
253
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]254<h2 id="part3">3. Runtime / Rendering Problems</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]255
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]256<h3>3.1 Rendering is slow / why isn't my graphics hardware being used?</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]257<p>
Andreas Bollb534c392012-10-05 23:14:10 +0200[diff] [blame]258If Mesa can't use its hardware accelerated drivers it falls back on one of its software renderers.
259(eg. classic swrast, softpipe or llvmpipe)
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]260</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]261<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]262You can run the <code>glxinfo</code> program to learn about your OpenGL
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]263library.
Andreas Bollb534c392012-10-05 23:14:10 +0200[diff] [blame]264Look for the <code>OpenGL vendor</code> and <code>OpenGL renderer</code> values.
265That will identify who's OpenGL library with which driver you're using and what sort of
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]266hardware it has detected.
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]267</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]268<p>
Andreas Bollb534c392012-10-05 23:14:10 +0200[diff] [blame]269If you're using a hardware accelerated driver you want <code>direct rendering: Yes</code>.
270</p>
271<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]272If your DRI-based driver isn't working, go to the
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]273<a href="https://dri.freedesktop.org/">DRI website</a> for trouble-shooting information.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]274</p>
275
276
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]277<h3>3.2 I'm seeing errors in depth (Z) buffering. Why?</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]278<p>
279Make sure the ratio of the far to near clipping planes isn't too great.
280Look
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]281<a href="https://www.opengl.org/resources/faq/technical/depthbuffer.htm#0040">here</a>
Andreas Bolla73c59b2012-09-18 19:31:28 +0200[diff] [blame]282for details.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]283</p>
284<p>
285Mesa uses a 16-bit depth buffer by default which is smaller and faster
286to clear than a 32-bit buffer but not as accurate.
287If you need a deeper you can modify the parameters to
288<code> glXChooseVisual</code> in your code.
289</p>
290
291
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]292<h3>3.3 Why Isn't depth buffering working at all?</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]293<p>
294Be sure you're requesting a depth buffered-visual. If you set the MESA_DEBUG
295environment variable it will warn you about trying to enable depth testing
296when you don't have a depth buffer.
297</p>
298<p>Specifically, make sure <code>glutInitDisplayMode</code> is being called
299with <code>GLUT_DEPTH</code> or <code>glXChooseVisual</code> is being
300called with a non-zero value for GLX_DEPTH_SIZE.
301</p>
302<p>This discussion applies to stencil buffers, accumulation buffers and
303alpha channels too.
304</p>
305
306
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]307<h3>3.4 Why does glGetString() always return NULL?</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]308<p>
309Be sure you have an active/current OpenGL rendering context before
310calling glGetString.
311</p>
312
313
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]314<h3>3.5 GL_POINTS and GL_LINES don't touch the right pixels</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]315<p>
316If you're trying to draw a filled region by using GL_POINTS or GL_LINES
317and seeing holes or gaps it's because of a float-to-int rounding problem.
318But this is not a bug.
319See Appendix H of the OpenGL Programming Guide - "OpenGL Correctness Tips".
320Basically, applying a translation of (0.375, 0.375, 0.0) to your coordinates
321will fix the problem.
322</p>
323
324<br>
325<br>
326
327
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]328<h2 id="part4">4. Developer Questions</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]329
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]330<h3>4.1 How can I contribute?</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]331<p>
Andreas Boll5abb1f82012-09-19 18:22:37 +0200[diff] [blame]332First, join the <a href="lists.html">mesa-dev mailing list</a>.
Brian Pauld5299bf2006-08-21 14:26:06 +0000[diff] [blame]333That's where Mesa development is discussed.
Dan Nicholsonf71032b2007-12-14 09:59:16 -0800[diff] [blame]334</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]335<p>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]336The <a href="https://www.opengl.org/documentation">
Nathan Kidd0691b372014-01-03 16:44:00 -0700[diff] [blame]337OpenGL Specification</a> is the bible for OpenGL implementation work.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]338You should read it.
339</p>
340<p>Most of the Mesa development work involves implementing new OpenGL
341extensions, writing hardware drivers (for the DRI), and code optimization.
342</p>
343
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]344<h3>4.2 How do I write a new device driver?</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]345<p>
346Unfortunately, writing a device driver isn't easy.
347It requires detailed understanding of OpenGL, the Mesa code, and your
348target hardware/operating system.
3493D graphics are not simple.
350</p>
351<p>
352The best way to get started is to use an existing driver as your starting
353point.
Andreas Bollb534c392012-10-05 23:14:10 +0200[diff] [blame]354For a classic hardware driver, the i965 driver is a good example.
355For a Gallium3D hardware driver, the r300g, r600g and the i915g are good examples.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]356</p>
357<p>The DRI website has more information about writing hardware drivers.
358The process isn't well document because the Mesa driver interface changes
Nathan Kidd0691b372014-01-03 16:44:00 -0700[diff] [blame]359over time, and we seldom have spare time for writing documentation.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]360That being said, many people have managed to figure out the process.
361</p>
362<p>
363Joining the appropriate mailing lists and asking questions (and searching
364the archives) is a good way to get information.
365</p>
366
367
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame^]368<h3>4.3 Why isn't GL_EXT_texture_compression_s3tc implemented in Mesa?</h3>
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]369<p>
Stuart Youngc95dd962018-09-20 17:12:43 +1000[diff] [blame]370Oh but it is! Prior to 2nd October 2017, the Mesa project did not include s3tc
371support due to intellectual property (IP) and/or patent issues around the s3tc
372algorithm.
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]373</p>
374<p>
Stuart Youngc95dd962018-09-20 17:12:43 +1000[diff] [blame]375As of Mesa 17.3.0, Mesa now officially supports s3tc, as the patent has expired.
376</p>
377<p>
378In versions prior to this, a 3rd party <a href="https://dri.freedesktop.org/wiki/S3TC">
379plug-in library</a> was required.
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]380</p>
381
Andreas Bollb5da52a2012-09-18 18:57:02 +0200[diff] [blame]382</div>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]383</body>
384</html>