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gerrit-public.fairphone.software / platform / external / mesa3d / ae4b1fc095abb086a50c10ec7849645f571e5b81 / . / docs / faq.html
blob: 2d0f22ffd89c4437e1b20778601fcacfdab2bff6 [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">
Erik Faye-Lundecdab0d2019-05-06 13:26:47 +0200[diff] [blame]11 The Mesa 3D Graphics Library
Andreas Bollb5da52a2012-09-18 18:57:02 +0200[diff] [blame]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
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]20<h2>Index</h2>
Erik Faye-Lundda4994f2019-04-18 13:44:10 +0200[diff] [blame]21<ol>
22 <li><a href="#part1">High-level Questions and Answers</a></li>
23 <li><a href="#part2">Compilation and Installation Problems</a></li>
24 <li><a href="#part3">Runtime / Rendering Problems</a></li>
25 <li><a href="#part4">Developer Questions</a></li>
26</ol>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]27
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame]28<h2 id="part1">1. High-level Questions and Answers</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]29
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame]30<h3>1.1 What is Mesa?</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]31<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]32Mesa is an open-source implementation of the OpenGL specification.
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]33OpenGL is a programming library for writing interactive 3D applications.
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]34See the <a href="https://www.opengl.org/">OpenGL website</a> for more
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]35information.
36</p>
37<p>
Andreas Boll5abb1f82012-09-19 18:22:37 +0200[diff] [blame]38Mesa 9.x supports the OpenGL 3.1 specification.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]39</p>
40
41
42<h2>1.2 Does Mesa support/use graphics hardware?</h2>
43<p>
Brian Paul7e4cc1c2005-10-24 23:33:27 +0000[diff] [blame]44Yes. Specifically, Mesa serves as the OpenGL core for the open-source DRI
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]45drivers for X.org.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]46</p>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]47<ul>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]48 <li>See the <a href="https://dri.freedesktop.org/">DRI website</a>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]49 for more information.</li>
Eric Engestrom771f6db2016-07-06 17:09:15 +0100[diff] [blame]50 <li>See <a href="https://01.org/linuxgraphics">01.org</a>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]51 for more information about Intel drivers.</li>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]52 <li>See <a href="https://nouveau.freedesktop.org">nouveau.freedesktop.org</a>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]53 for more information about Nouveau drivers.</li>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]54 <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]55 for more information about Radeon drivers.</li>
56</ul>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]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>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]65<li>Mesa is used as the core of the open-source X.org DRI
Brian Paul7e4cc1c2005-10-24 23:33:27 +0000[diff] [blame]66 hardware drivers.
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]67</li>
68<li>Mesa is quite portable and allows OpenGL to be used on systems
69 that have no other OpenGL solution.
70</li>
71<li>Software rendering with Mesa serves as a reference for validating the
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]72 hardware drivers.
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]73</li>
74<li>A software implementation of OpenGL is useful for experimentation,
75 such as testing new rendering techniques.
76</li>
77<li>Mesa can render images with deep color channels: 16-bit integer
78 and 32-bit floating point color channels are supported.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]79 This capability is only now appearing in hardware.
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]80</li>
81<li>Mesa's internal limits (max lights, clip planes, texture size, etc) can be
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]82 changed for special needs (hardware limits are hard to overcome).
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]83</li>
84</ul>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]85
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]86
Andreas Boll5abb1f82012-09-19 18:22:37 +0200[diff] [blame]87<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]88<p>
89<em>Stand-alone Mesa</em> is the original incarnation of Mesa.
Brian Paul7e4cc1c2005-10-24 23:33:27 +0000[diff] [blame]90On systems running the X Window System it does all its rendering through
91the Xlib API:
Andreas Bolldf2be222012-06-12 09:05:22 +0200[diff] [blame]92</p>
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]93<ul>
94<li>The GLX API is supported, but it's really just an emulation of the
95 real thing.
96<li>The GLX wire protocol is not supported and there's no OpenGL extension
97 loaded by the X server.
98<li>There is no hardware acceleration.
Erik Faye-Lund205f9602019-06-06 10:16:36 +0200[diff] [blame]99<li>The OpenGL library, <code>libGL.so</code>, contains everything (the
100 programming API, the GLX functions and all the rendering code).
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]101</ul>
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]102<p>
103Alternately, Mesa acts as the core for a number of OpenGL hardware drivers
104within the DRI (Direct Rendering Infrastructure):
105<ul>
Erik Faye-Lund205f9602019-06-06 10:16:36 +0200[diff] [blame]106<li>The <code>libGL.so</code> library provides the GL and GLX API functions,
107 a GLX protocol encoder, and a device driver loader.
108<li>The device driver modules (such as <code>r200_dri.so</code>) contain
109 a built-in copy of the core Mesa code.
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]110<li>The X server loads the GLX module.
111 The GLX module decodes incoming GLX protocol and dispatches the commands
112 to a rendering module.
113 For the DRI, this module is basically a software Mesa renderer.
114</ul>
115
116
117
118<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]119<p>
Brian Paul7e4cc1c2005-10-24 23:33:27 +0000[diff] [blame]120This wasn't easy in the past.
121Now, the DRI drivers are included in the Mesa tree and can be compiled
122separately from the X server.
123Just follow the Mesa <a href="install.html">compilation instructions</a>.
Brian Paul824a4fc2003-08-06 19:05:26 +0000[diff] [blame]124</p>
125
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]126
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]127<h2>1.6 Are there other open-source implementations of OpenGL?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]128<p>
Erik Faye-Lundb16e77e2019-06-11 10:05:51 +0200[diff] [blame]129Yes, SGI's <a href="http://web.archive.org/web/20171010115110_/http://oss.sgi.com/projects/ogl-sample/index.html">
Nathan Kidd0691b372014-01-03 16:44:00 -0700[diff] [blame]130OpenGL Sample Implementation (SI)</a> is available.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]131The SI was written during the time that OpenGL was originally designed.
132Unfortunately, development of the SI has stagnated.
133Mesa is much more up to date with modern features and extensions.
134</p>
Brian Paul186d4d82004-04-27 12:55:08 +0000[diff] [blame]135
136<p>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]137<a href="https://sourceforge.net/projects/ogl-es/">Vincent</a> is
Brian Paul186d4d82004-04-27 12:55:08 +0000[diff] [blame]138an open-source implementation of OpenGL ES for mobile devices.
139
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]140<p>
Erik Faye-Lund795b5d92019-06-11 10:11:31 +0200[diff] [blame]141<a href="http://web.archive.org/web/20130830162848/http://www.dsbox.com/minigl.html">miniGL</a>
142is a subset of OpenGL for PalmOS devices. The website is gone, but the source
143code can still be found on <a href="https://sourceforge.net/projects/minigl/">sourceforge.net</a>.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]144
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]145<p>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]146<a href="http://bellard.org/TinyGL/">TinyGL</a>
Andreas Bolla73c59b2012-09-18 19:31:28 +0200[diff] [blame]147is a subset of OpenGL.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]148</p>
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]149
150<p>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]151<a href="https://sourceforge.net/projects/softgl/">SoftGL</a>
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]152is an OpenGL subset for mobile devices.
153</p>
154
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]155<p>
Andreas Bolla73c59b2012-09-18 19:31:28 +0200[diff] [blame]156<a href="http://chromium.sourceforge.net/">Chromium</a>
Brian Paulacbc1e02003-11-26 18:10:31 +0000[diff] [blame]157isn't a conventional OpenGL implementation (it's layered upon OpenGL),
158but it does export the OpenGL API. It allows tiled rendering, sort-last
159rendering, etc.
160</p>
161
Brian Paulacbc1e02003-11-26 18:10:31 +0000[diff] [blame]162<p>
Andreas Bolla73c59b2012-09-18 19:31:28 +0200[diff] [blame]163<a href="http://www.ticalc.org/archives/files/fileinfo/361/36173.html">ClosedGL</a>
164is an OpenGL subset library for TI graphing calculators.
Brian Paul0c656042006-06-08 19:59:41 +0000[diff] [blame]165</p>
166
167<p>
Brian Paulacbc1e02003-11-26 18:10:31 +0000[diff] [blame]168There may be other open OpenGL implementations, but Mesa is the most
169popular and feature-complete.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]170</p>
171
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]172
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame]173<h2 id="part2">2. Compilation and Installation Problems</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]174
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame]175<h3>2.1 What's the easiest way to install Mesa?</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]176<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]177If you're using a Linux-based system, your distro CD most likely already
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]178has Mesa packages (like RPM or DEB) which you can easily install.
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]179</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]180
181
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame]182<h3>2.2 I get undefined symbols such as bgnpolygon, v3f, etc...</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]183<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]184You're application is written in IRIS GL, not OpenGL.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]185IRIS GL was the predecessor to OpenGL and is a different thing (almost)
186entirely.
187Mesa's not the solution.
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>2.3 Where is the GLUT library?</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]192<p>
Erik Faye-Lund205f9602019-06-06 10:16:36 +0200[diff] [blame]193GLUT (OpenGL Utility Toolkit) is no longer in the separate
194<code>MesaGLUT-x.y.z.tar.gz</code> file.
José Fonseca9a7f84d2011-07-14 17:28:52 +0100[diff] [blame]195If you don't already have GLUT installed, you should grab
196<a href="http://freeglut.sourceforge.net/">freeglut</a>.
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>2.4 Where is the GLw library?</h3>
Kenneth Graunkec5481922011-08-05 16:59:04 -0700[diff] [blame]201<p>
Erik Faye-Lunde19448c2019-06-11 10:16:32 +0200[diff] [blame]202GLw (OpenGL widget library) is now available from a separate <a href="https://gitlab.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]203</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]204
Kenneth Graunkec5481922011-08-05 16:59:04 -0700[diff] [blame]205
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]206<h2>2.5 What's the proper place for the libraries and headers?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]207<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]208On Linux-based systems you'll want to follow the
Erik Faye-Lund12f4cd62019-06-11 10:18:39 +0200[diff] [blame]209<a href="https://www.khronos.org/registry/OpenGL/ABI/">Linux ABI</a> standard.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]210Basically you'll want the following:
211</p>
Erik Faye-Lundb16e5932019-06-04 15:42:46 +0200[diff] [blame]212<dl>
213<dt><code>/usr/include/GL/gl.h</code></dt>
214<dd>the main OpenGL header</dd>
215<dt><code>/usr/include/GL/glu.h</code></dt>
216<dd>the OpenGL GLU (utility) header</dd>
217<dt><code>/usr/include/GL/glx.h</code></dt>
218<dd>the OpenGL GLX header</dd>
219<dt><code>/usr/include/GL/glext.h</code></dt>
220<dd>the OpenGL extensions header</dd>
221<dt><code>/usr/include/GL/glxext.h</code></dt>
222<dd>the OpenGL GLX extensions header</dd>
223<dt><code>/usr/include/GL/osmesa.h</code></dt>
224<dd>the Mesa off-screen rendering header</dd>
225<dt><code>/usr/lib/libGL.so</code></dt>
226<dd>a symlink to <code>libGL.so.1</code></dd>
227<dt><code>/usr/lib/libGL.so.1</code></dt>
228<dd>a symlink to <code>libGL.so.1.xyz</code></dd>
229<dt><code>/usr/lib/libGL.so.xyz</code></dt>
230<dd>the actual OpenGL/Mesa library. xyz denotes the
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]231Mesa version number.
Erik Faye-Lundb16e5932019-06-04 15:42:46 +0200[diff] [blame]232</dd>
233</dl>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]234<p>
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]235When configuring Mesa, there are three meson options that affect the install
Andreas Bollb534c392012-10-05 23:14:10 +0200[diff] [blame]236location that you should take care with: <code>--prefix</code>,
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]237<code>--libdir</code>, and <code>-D dri-drivers-path</code>. To install Mesa
Andreas Bollb534c392012-10-05 23:14:10 +0200[diff] [blame]238into the system location where it will be available for all programs to use, set
239<code>--prefix=/usr</code>. Set <code>--libdir</code> to where your Linux
240distribution installs system libraries, usually either <code>/usr/lib</code> or
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]241<code>/usr/lib64</code>. Set <code>-D dri-drivers-path</code> to the directory
Andreas Bollb534c392012-10-05 23:14:10 +0200[diff] [blame]242where your Linux distribution installs DRI drivers. To find your system's DRI
243driver directory, try executing <code>find /usr -type d -name dri</code>. For
244example, if the <code>find</code> command listed <code>/usr/lib64/dri</code>,
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]245then set <code>-D dri-drivers-path=/usr/lib64/dri</code>.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]246</p>
247<p>
Andreas Bollb534c392012-10-05 23:14:10 +0200[diff] [blame]248After determining the correct values for the install location, configure Mesa
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]249with <code>meson configure --prefix=/usr --libdir=xxx -D dri-drivers-path=xxx</code>
250and then install with <code>sudo ninja install</code>.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]251</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]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
Erik Faye-Lunda9956ed2019-06-11 10:20:12 +0200[diff] [blame]281<a href="https://www.opengl.org/archives/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
Erik Faye-Lundb2ac7582019-05-28 13:53:03 +0200[diff] [blame]288<code>glXChooseVisual</code> in your code.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]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>
Erik Faye-Lund392c0832019-05-28 13:14:03 +0200[diff] [blame]294Be sure you're requesting a depth buffered-visual. If you set the
295<code>MESA_DEBUG</code> environment variable it will warn you about trying
296to enable depth testing when you don't have a depth buffer.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]297</p>
298<p>Specifically, make sure <code>glutInitDisplayMode</code> is being called
299with <code>GLUT_DEPTH</code> or <code>glXChooseVisual</code> is being
Erik Faye-Lund392c0832019-05-28 13:14:03 +0200[diff] [blame]300called with a non-zero value for <code>GLX_DEPTH_SIZE</code>.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]301</p>
302<p>This discussion applies to stencil buffers, accumulation buffers and
303alpha channels too.
304</p>
305
306
Erik Faye-Lund392c0832019-05-28 13:14:03 +0200[diff] [blame]307<h3>3.4 Why does <code>glGetString()</code> always return <code>NULL</code>?</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]308<p>
309Be sure you have an active/current OpenGL rendering context before
Erik Faye-Lund392c0832019-05-28 13:14:03 +0200[diff] [blame]310calling <code>glGetString</code>.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]311</p>
312
313
Erik Faye-Lund392c0832019-05-28 13:14:03 +0200[diff] [blame]314<h3>3.5 <code>GL_POINTS</code> and <code>GL_LINES</code> don't touch the
315right pixels</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]316<p>
Erik Faye-Lund392c0832019-05-28 13:14:03 +0200[diff] [blame]317If you're trying to draw a filled region by using <code>GL_POINTS</code> or
318<code>GL_LINES</code> and seeing holes or gaps it's because of a float-to-int
319rounding problem. But this is not a bug. See Appendix H of the OpenGL
320Programming Guide - "OpenGL Correctness Tips". Basically, applying a
321translation of (0.375, 0.375, 0.0) to your coordinates will fix the problem.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]322</p>
323
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]324
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame]325<h2 id="part4">4. Developer Questions</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]326
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame]327<h3>4.1 How can I contribute?</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]328<p>
Andreas Boll5abb1f82012-09-19 18:22:37 +0200[diff] [blame]329First, join the <a href="lists.html">mesa-dev mailing list</a>.
Brian Pauld5299bf2006-08-21 14:26:06 +0000[diff] [blame]330That's where Mesa development is discussed.
Dan Nicholsonf71032b2007-12-14 09:59:16 -0800[diff] [blame]331</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]332<p>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]333The <a href="https://www.opengl.org/documentation">
Nathan Kidd0691b372014-01-03 16:44:00 -0700[diff] [blame]334OpenGL Specification</a> is the bible for OpenGL implementation work.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]335You should read it.
336</p>
337<p>Most of the Mesa development work involves implementing new OpenGL
338extensions, writing hardware drivers (for the DRI), and code optimization.
339</p>
340
Erik Faye-Lund269474b2019-05-06 12:57:15 +0200[diff] [blame]341<h3>4.2 How do I write a new device driver?</h3>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]342<p>
343Unfortunately, writing a device driver isn't easy.
344It requires detailed understanding of OpenGL, the Mesa code, and your
345target hardware/operating system.
3463D graphics are not simple.
347</p>
348<p>
349The best way to get started is to use an existing driver as your starting
350point.
Andreas Bollb534c392012-10-05 23:14:10 +0200[diff] [blame]351For a classic hardware driver, the i965 driver is a good example.
352For a Gallium3D hardware driver, the r300g, r600g and the i915g are good examples.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]353</p>
354<p>The DRI website has more information about writing hardware drivers.
355The process isn't well document because the Mesa driver interface changes
Nathan Kidd0691b372014-01-03 16:44:00 -0700[diff] [blame]356over time, and we seldom have spare time for writing documentation.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]357That being said, many people have managed to figure out the process.
358</p>
359<p>
360Joining the appropriate mailing lists and asking questions (and searching
361the archives) is a good way to get information.
362</p>
363
364
Erik Faye-Lund392c0832019-05-28 13:14:03 +0200[diff] [blame]365<h3>4.3 Why isn't <code>GL_EXT_texture_compression_s3tc</code> implemented in
366Mesa?</h3>
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]367<p>
Stuart Youngc95dd962018-09-20 17:12:43 +1000[diff] [blame]368Oh but it is! Prior to 2nd October 2017, the Mesa project did not include s3tc
369support due to intellectual property (IP) and/or patent issues around the s3tc
370algorithm.
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]371</p>
372<p>
Stuart Youngc95dd962018-09-20 17:12:43 +1000[diff] [blame]373As of Mesa 17.3.0, Mesa now officially supports s3tc, as the patent has expired.
374</p>
375<p>
376In versions prior to this, a 3rd party <a href="https://dri.freedesktop.org/wiki/S3TC">
377plug-in library</a> was required.
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]378</p>
379
Andreas Bollb5da52a2012-09-18 18:57:02 +0200[diff] [blame]380</div>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]381</body>
382</html>