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gerrit-public.fairphone.software / platform / external / mesa3d / 87683ba0587a0d62d0b336143344ba283316bcb0 / . / docs / faq.html
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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">
5 <title>Mesa FAQ</title>
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
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]17<h1>Mesa 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
32
33
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]34<h1 id="part1">1. High-level Questions and Answers</h1>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]35
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]36<h2>1.1 What is Mesa?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]37<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]38Mesa is an open-source implementation of the OpenGL specification.
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]39OpenGL is a programming library for writing interactive 3D applications.
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]40See the <a href="https://www.opengl.org/">OpenGL website</a> for more
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]41information.
42</p>
43<p>
Andreas Boll5abb1f82012-09-19 18:22:37 +0200[diff] [blame]44Mesa 9.x supports the OpenGL 3.1 specification.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]45</p>
46
47
48<h2>1.2 Does Mesa support/use graphics hardware?</h2>
49<p>
Brian Paul7e4cc1c2005-10-24 23:33:27 +0000[diff] [blame]50Yes. Specifically, Mesa serves as the OpenGL core for the open-source DRI
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]51drivers for X.org.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]52</p>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]53<ul>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]54 <li>See the <a href="https://dri.freedesktop.org/">DRI website</a>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]55 for more information.</li>
Eric Engestrom771f6db2016-07-06 17:09:15 +0100[diff] [blame]56 <li>See <a href="https://01.org/linuxgraphics">01.org</a>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]57 for more information about Intel drivers.</li>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]58 <li>See <a href="https://nouveau.freedesktop.org">nouveau.freedesktop.org</a>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]59 for more information about Nouveau drivers.</li>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]60 <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]61 for more information about Radeon drivers.</li>
62</ul>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]63
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]64<h2>1.3 What purpose does Mesa serve today?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]65<p>
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]66Hardware-accelerated OpenGL implementations are available for most popular
67operating systems today.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]68Still, Mesa serves at least these purposes:
69</p>
70<ul>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]71<li>Mesa is used as the core of the open-source X.org DRI
Brian Paul7e4cc1c2005-10-24 23:33:27 +0000[diff] [blame]72 hardware drivers.
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]73</li>
74<li>Mesa is quite portable and allows OpenGL to be used on systems
75 that have no other OpenGL solution.
76</li>
77<li>Software rendering with Mesa serves as a reference for validating the
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]78 hardware drivers.
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]79</li>
80<li>A software implementation of OpenGL is useful for experimentation,
81 such as testing new rendering techniques.
82</li>
83<li>Mesa can render images with deep color channels: 16-bit integer
84 and 32-bit floating point color channels are supported.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]85 This capability is only now appearing in hardware.
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]86</li>
87<li>Mesa's internal limits (max lights, clip planes, texture size, etc) can be
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]88 changed for special needs (hardware limits are hard to overcome).
Brian Paula376e332003-03-30 16:54:36 +0000[diff] [blame]89</li>
90</ul>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]91
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]92
Andreas Boll5abb1f82012-09-19 18:22:37 +0200[diff] [blame]93<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]94<p>
95<em>Stand-alone Mesa</em> is the original incarnation of Mesa.
Brian Paul7e4cc1c2005-10-24 23:33:27 +0000[diff] [blame]96On systems running the X Window System it does all its rendering through
97the Xlib API:
Andreas Bolldf2be222012-06-12 09:05:22 +0200[diff] [blame]98</p>
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]99<ul>
100<li>The GLX API is supported, but it's really just an emulation of the
101 real thing.
102<li>The GLX wire protocol is not supported and there's no OpenGL extension
103 loaded by the X server.
104<li>There is no hardware acceleration.
105<li>The OpenGL library, libGL.so, contains everything (the programming API,
106 the GLX functions and all the rendering code).
107</ul>
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]108<p>
109Alternately, Mesa acts as the core for a number of OpenGL hardware drivers
110within the DRI (Direct Rendering Infrastructure):
111<ul>
112<li>The libGL.so library provides the GL and GLX API functions, a GLX
113 protocol encoder, and a device driver loader.
114<li>The device driver modules (such as r200_dri.so) contain a built-in
115 copy of the core Mesa code.
116<li>The X server loads the GLX module.
117 The GLX module decodes incoming GLX protocol and dispatches the commands
118 to a rendering module.
119 For the DRI, this module is basically a software Mesa renderer.
120</ul>
121
122
123
124<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]125<p>
Brian Paul7e4cc1c2005-10-24 23:33:27 +0000[diff] [blame]126This wasn't easy in the past.
127Now, the DRI drivers are included in the Mesa tree and can be compiled
128separately from the X server.
129Just follow the Mesa <a href="install.html">compilation instructions</a>.
Brian Paul824a4fc2003-08-06 19:05:26 +0000[diff] [blame]130</p>
131
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]132
Brian Paul65b79052004-11-22 17:49:15 +0000[diff] [blame]133<h2>1.6 Are there other open-source implementations of OpenGL?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]134<p>
Andreas Bolla73c59b2012-09-18 19:31:28 +0200[diff] [blame]135Yes, SGI's <a href="http://oss.sgi.com/projects/ogl-sample/index.html">
Nathan Kidd0691b372014-01-03 16:44:00 -0700[diff] [blame]136OpenGL Sample Implementation (SI)</a> is available.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]137The SI was written during the time that OpenGL was originally designed.
138Unfortunately, development of the SI has stagnated.
139Mesa is much more up to date with modern features and extensions.
140</p>
Brian Paul186d4d82004-04-27 12:55:08 +0000[diff] [blame]141
142<p>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]143<a href="https://sourceforge.net/projects/ogl-es/">Vincent</a> is
Brian Paul186d4d82004-04-27 12:55:08 +0000[diff] [blame]144an open-source implementation of OpenGL ES for mobile devices.
145
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]146<p>
Andreas Bolla73c59b2012-09-18 19:31:28 +0200[diff] [blame]147<a href="http://www.dsbox.com/minigl.html">miniGL</a>
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]148is a subset of OpenGL for PalmOS devices.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]149
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]150<p>
Andreas Boll8504f182012-09-20 16:23:15 +0200[diff] [blame]151<a href="http://bellard.org/TinyGL/">TinyGL</a>
Andreas Bolla73c59b2012-09-18 19:31:28 +0200[diff] [blame]152is a subset of OpenGL.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]153</p>
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]154
155<p>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]156<a href="https://sourceforge.net/projects/softgl/">SoftGL</a>
Brian Paul7df4f952003-11-25 21:13:26 +0000[diff] [blame]157is an OpenGL subset for mobile devices.
158</p>
159
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]160<p>
Andreas Bolla73c59b2012-09-18 19:31:28 +0200[diff] [blame]161<a href="http://chromium.sourceforge.net/">Chromium</a>
Brian Paulacbc1e02003-11-26 18:10:31 +0000[diff] [blame]162isn't a conventional OpenGL implementation (it's layered upon OpenGL),
163but it does export the OpenGL API. It allows tiled rendering, sort-last
164rendering, etc.
165</p>
166
Brian Paulacbc1e02003-11-26 18:10:31 +0000[diff] [blame]167<p>
Andreas Bolla73c59b2012-09-18 19:31:28 +0200[diff] [blame]168<a href="http://www.ticalc.org/archives/files/fileinfo/361/36173.html">ClosedGL</a>
169is an OpenGL subset library for TI graphing calculators.
Brian Paul0c656042006-06-08 19:59:41 +0000[diff] [blame]170</p>
171
172<p>
Brian Paulacbc1e02003-11-26 18:10:31 +0000[diff] [blame]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
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]183<h1 id="part2">2. Compilation and Installation Problems</h1>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]184
185
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]186<h2>2.1 What's the easiest way to install Mesa?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]187<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]188If you're using a Linux-based system, your distro CD most likely already
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]189has Mesa packages (like RPM or DEB) which you can easily install.
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]190</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]191
192
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]193<h2>2.2 I get undefined symbols such as bgnpolygon, v3f, etc...</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]194<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]195You're application is written in IRIS GL, not OpenGL.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]196IRIS GL was the predecessor to OpenGL and is a different thing (almost)
197entirely.
198Mesa's not the solution.
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]199</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]200
201
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]202<h2>2.3 Where is the GLUT library?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]203<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]204GLUT (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]205If you don't already have GLUT installed, you should grab
206<a href="http://freeglut.sourceforge.net/">freeglut</a>.
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]207</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]208
209
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]210<h2>2.4 Where is the GLw library?</h2>
Kenneth Graunkec5481922011-08-05 16:59:04 -0700[diff] [blame]211<p>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]212GLw (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]213</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]214
Kenneth Graunkec5481922011-08-05 16:59:04 -0700[diff] [blame]215
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]216<h2>2.5 What's the proper place for the libraries and headers?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]217<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]218On Linux-based systems you'll want to follow the
Andreas Bolla73c59b2012-09-18 19:31:28 +0200[diff] [blame]219<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]220Basically you'll want the following:
221</p>
222<ul>
223<li>/usr/include/GL/gl.h - the main OpenGL header
224</li><li>/usr/include/GL/glu.h - the OpenGL GLU (utility) header
225</li><li>/usr/include/GL/glx.h - the OpenGL GLX header
226</li><li>/usr/include/GL/glext.h - the OpenGL extensions header
227</li><li>/usr/include/GL/glxext.h - the OpenGL GLX extensions header
228</li><li>/usr/include/GL/osmesa.h - the Mesa off-screen rendering header
229</li><li>/usr/lib/libGL.so - a symlink to libGL.so.1
230</li><li>/usr/lib/libGL.so.1 - a symlink to libGL.so.1.xyz
231</li><li>/usr/lib/libGL.so.xyz - the actual OpenGL/Mesa library. xyz denotes the
232Mesa version number.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]233</li></ul>
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>
252<br>
253<br>
254
255
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]256<h1 id="part3">3. Runtime / Rendering Problems</h1>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]257
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]258<h2>3.1 Rendering is slow / why isn't my graphics hardware being used?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]259<p>
Andreas Bollb534c392012-10-05 23:14:10 +0200[diff] [blame]260If Mesa can't use its hardware accelerated drivers it falls back on one of its software renderers.
261(eg. classic swrast, softpipe or llvmpipe)
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]262</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]263<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]264You can run the <code>glxinfo</code> program to learn about your OpenGL
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]265library.
Andreas Bollb534c392012-10-05 23:14:10 +0200[diff] [blame]266Look for the <code>OpenGL vendor</code> and <code>OpenGL renderer</code> values.
267That 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]268hardware it has detected.
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]269</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]270<p>
Andreas Bollb534c392012-10-05 23:14:10 +0200[diff] [blame]271If you're using a hardware accelerated driver you want <code>direct rendering: Yes</code>.
272</p>
273<p>
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]274If your DRI-based driver isn't working, go to the
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]275<a href="https://dri.freedesktop.org/">DRI website</a> for trouble-shooting information.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]276</p>
277
278
279<h2>3.2 I'm seeing errors in depth (Z) buffering. Why?</h2>
280<p>
281Make sure the ratio of the far to near clipping planes isn't too great.
282Look
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]283<a href="https://www.opengl.org/resources/faq/technical/depthbuffer.htm#0040">here</a>
Andreas Bolla73c59b2012-09-18 19:31:28 +0200[diff] [blame]284for details.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]285</p>
286<p>
287Mesa uses a 16-bit depth buffer by default which is smaller and faster
288to clear than a 32-bit buffer but not as accurate.
289If you need a deeper you can modify the parameters to
290<code> glXChooseVisual</code> in your code.
291</p>
292
293
294<h2>3.3 Why Isn't depth buffering working at all?</h2>
295<p>
296Be sure you're requesting a depth buffered-visual. If you set the MESA_DEBUG
297environment variable it will warn you about trying to enable depth testing
298when you don't have a depth buffer.
299</p>
300<p>Specifically, make sure <code>glutInitDisplayMode</code> is being called
301with <code>GLUT_DEPTH</code> or <code>glXChooseVisual</code> is being
302called with a non-zero value for GLX_DEPTH_SIZE.
303</p>
304<p>This discussion applies to stencil buffers, accumulation buffers and
305alpha channels too.
306</p>
307
308
309<h2>3.4 Why does glGetString() always return NULL?</h2>
310<p>
311Be sure you have an active/current OpenGL rendering context before
312calling glGetString.
313</p>
314
315
316<h2>3.5 GL_POINTS and GL_LINES don't touch the right pixels</h2>
317<p>
318If you're trying to draw a filled region by using GL_POINTS or GL_LINES
319and seeing holes or gaps it's because of a float-to-int rounding problem.
320But this is not a bug.
321See Appendix H of the OpenGL Programming Guide - "OpenGL Correctness Tips".
322Basically, applying a translation of (0.375, 0.375, 0.0) to your coordinates
323will fix the problem.
324</p>
325
326<br>
327<br>
328
329
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]330<h1 id="part4">4. Developer Questions</h1>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]331
Andreas Bollcc418882012-06-12 09:05:33 +0200[diff] [blame]332<h2>4.1 How can I contribute?</h2>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]333<p>
Andreas Boll5abb1f82012-09-19 18:22:37 +0200[diff] [blame]334First, join the <a href="lists.html">mesa-dev mailing list</a>.
Brian Pauld5299bf2006-08-21 14:26:06 +0000[diff] [blame]335That's where Mesa development is discussed.
Dan Nicholsonf71032b2007-12-14 09:59:16 -0800[diff] [blame]336</p>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]337<p>
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]338The <a href="https://www.opengl.org/documentation">
Nathan Kidd0691b372014-01-03 16:44:00 -0700[diff] [blame]339OpenGL Specification</a> is the bible for OpenGL implementation work.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]340You should read it.
341</p>
342<p>Most of the Mesa development work involves implementing new OpenGL
343extensions, writing hardware drivers (for the DRI), and code optimization.
344</p>
345
346<h2>4.2 How do I write a new device driver?</h2>
347<p>
348Unfortunately, writing a device driver isn't easy.
349It requires detailed understanding of OpenGL, the Mesa code, and your
350target hardware/operating system.
3513D graphics are not simple.
352</p>
353<p>
354The best way to get started is to use an existing driver as your starting
355point.
Andreas Bollb534c392012-10-05 23:14:10 +0200[diff] [blame]356For a classic hardware driver, the i965 driver is a good example.
357For a Gallium3D hardware driver, the r300g, r600g and the i915g are good examples.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]358</p>
359<p>The DRI website has more information about writing hardware drivers.
360The process isn't well document because the Mesa driver interface changes
Nathan Kidd0691b372014-01-03 16:44:00 -0700[diff] [blame]361over time, and we seldom have spare time for writing documentation.
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]362That being said, many people have managed to figure out the process.
363</p>
364<p>
365Joining the appropriate mailing lists and asking questions (and searching
366the archives) is a good way to get information.
367</p>
368
369
Brian Paul0c656042006-06-08 19:59:41 +0000[diff] [blame]370<h2>4.3 Why isn't GL_EXT_texture_compression_s3tc implemented in Mesa?</h2>
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]371<p>
Stuart Youngc95dd962018-09-20 17:12:43 +1000[diff] [blame]372Oh but it is! Prior to 2nd October 2017, the Mesa project did not include s3tc
373support due to intellectual property (IP) and/or patent issues around the s3tc
374algorithm.
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]375</p>
376<p>
Stuart Youngc95dd962018-09-20 17:12:43 +1000[diff] [blame]377As of Mesa 17.3.0, Mesa now officially supports s3tc, as the patent has expired.
378</p>
379<p>
380In versions prior to this, a 3rd party <a href="https://dri.freedesktop.org/wiki/S3TC">
381plug-in library</a> was required.
Brian Paulfc528e22003-12-31 20:59:51 +0000[diff] [blame]382</p>
383
Andreas Bollb5da52a2012-09-18 18:57:02 +0200[diff] [blame]384</div>
Brian Paul0b27ace2003-03-08 17:38:57 +0000[diff] [blame]385</body>
386</html>