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| <head><title>Mesa FAQ</title></head> |
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| <h1>Mesa Frequently Asked Questions</h1> |
| Last updated: 25 November 2003 |
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| <br> |
| <br> |
| <h2>Index</h2> |
| <a href="#part1">1. High-level Questions and Answers</a> |
| <br> |
| <a href="#part2">2. Compilation and Installation Problems</a> |
| <br> |
| <a href="#part3">3. Runtime / Rendering Problems</a> |
| <br> |
| <a href="#part4">4. Developer Questions</a> |
| <br> |
| <br> |
| <br> |
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| <a name="part1"> |
| </a><h1><a name="part1">1. High-level Questions and Answers</a></h1> |
| |
| <h2><a name="part1">1.1 What is Mesa?</a></h2> |
| <p> |
| <a name="part1">Mesa is an open-source implementation of the OpenGL specification. |
| OpenGL is a programming library for writing interactive 3D applications. |
| See the </a><a href="http://www.opengl.org/">OpenGL website</a> for more |
| information. |
| </p> |
| <p> |
| Mesa 5.x supports the OpenGL 1.4 specification. |
| </p> |
| |
| |
| <h2>1.2 Does Mesa support/use graphics hardware?</h2> |
| <p> |
| Yes. Specifically, Mesa serves as the OpenGL core for the open-source |
| XFree86/DRI OpenGL drivers. See the <a href="http://dri.sf.net/">DRI |
| website</a> for more information. |
| </p> |
| <p> |
| There have been other hardware drivers for Mesa over the years (such as |
| the 3Dfx Glide/Voodoo driver, an old S3 driver, etc) but the DRI drivers |
| are the modern ones. |
| </p> |
| |
| <h2>1.3 What purpose does Mesa (software-based rendering) serve today?</h2> |
| <p> |
| Hardware-accelerated OpenGL implementations are available for most popular |
| operating systems today. |
| Still, Mesa serves at least these purposes: |
| </p> |
| <ul> |
| <li>Mesa is used as the core of the open-source XFree86/DRI hardware drivers. |
| </li> |
| <li>Mesa is quite portable and allows OpenGL to be used on systems |
| that have no other OpenGL solution. |
| </li> |
| <li>Software rendering with Mesa serves as a reference for validating the |
| hardware drivers. |
| </li> |
| <li>A software implementation of OpenGL is useful for experimentation, |
| such as testing new rendering techniques. |
| </li> |
| <li>Mesa can render images with deep color channels: 16-bit integer |
| and 32-bit floating point color channels are supported. |
| This capability is only now appearing in hardware. |
| </li> |
| <li>Mesa's internal limits (max lights, clip planes, texture size, etc) can be |
| changed for special needs (hardware limits are hard to overcome). |
| </li> |
| </ul> |
| |
| <h2>1.4 How do I upgrade my DRI installation to use a new Mesa release?</h2> |
| <p> |
| You don't! A copy of the Mesa source code lives inside the XFree86/DRI source |
| tree and gets compiled into the individual DRI driver modules. |
| If you try to install Mesa over an XFree86/DRI installation, you'll lose |
| hardware rendering (because stand-alone Mesa's libGL.so is different than |
| the XFree86 libGL.so). |
| </p> |
| <p> |
| The DRI developers will incorporate the latest release of Mesa into the |
| DRI drivers when the time is right. |
| </p> |
| <p> |
| To upgrade, either look for a new release of <a href="http://www.xfree86.org" |
| target="_parent">XFree86</a> or visit the |
| <a href="http://dri.sf.net" target="_parent">DRI website</a> to see |
| if there's newer drivers. |
| </p> |
| |
| |
| <h2>1.5 Are there other open-source implementations of OpenGL?</h2> |
| <p> |
| Yes, SGI's <a href="http://oss.sgi.com/projects/ogl-sample/index.html" |
| target="_parent"> |
| OpenGL Sample Implemenation (SI)</a> is available. |
| The SI was written during the time that OpenGL was originally designed. |
| Unfortunately, development of the SI has stagnated. |
| Mesa is much more up to date with modern features and extensions. |
| </p> |
| <p> |
| <a href="http://www.dsbox.com/minigl.html" target="_parent">miniGL</a> |
| is a subset of OpenGL for PalmOS devices. |
| |
| <p> |
| <a href="http://fabrice.bellard.free.fr/TinyGL/" |
| target="_parent">TinyGL</a> is a subset of OpenGL. |
| </p> |
| |
| <p> |
| <a href="http://softgl.studierstube.org/" target="_parent">SoftGL</a> |
| is an OpenGL subset for mobile devices. |
| </p> |
| |
| <p> |
| There may be others but Mesa is the most popular and feature-complete. |
| </p> |
| |
| <br> |
| <br> |
| |
| |
| <a name="part2"> |
| </a><h1><a name="part2">2. Compilation and Installation Problems</a></h1> |
| |
| |
| <h2><a name="part2">2.1 What's the easiest way to install Mesa?</a></h2> |
| <p> |
| <a name="part2">If you're using a Linux-based system, your distro CD most likely already |
| has Mesa packages (like RPM or DEB) which you can easily install. |
| </a></p> |
| |
| |
| <h2><a name="part2">2.2 Running <code>configure; make</code> Doesn't Work</a></h2> |
| <p> |
| <a name="part2">Unfortunately, the GNU autoconf/automake/libtool system doesn't seem to work |
| too well on non GNU/Linux systems, even after installing gmake, gcc, etc. |
| For that reason, Mesa's <b>old-style</b> makefile system is still included. |
| The old-style system uses good old traditional Makefiles. Try the following: |
| </a></p><pre><a name="part2"> cd Mesa-x.y.z |
| cp Makefile.X11 Makefile |
| make |
| </a></pre> |
| <a name="part2">You'll see a list of system configurations from which to choose. |
| For example: |
| </a><pre><a name="part2"> make linux-x86 |
| </a></pre> |
| <p> |
| <a name="part2">If you're experienced with GNU autoconf/automake/libtool and think you can help |
| with maintence, contact the Mesa developers. |
| FYI, the Mesa developers generally don't use the autoconf/automake system. |
| We're especially annoyed with the fact that a +5000-line script (libtool) |
| is needed to make shared libraries (ugh). |
| </a></p> |
| |
| <h2><a name="part2">2.3 Mesa still doesn't compile</a></h2> |
| <p> |
| <a name="part2">If the old-style Makefile system doesn't work either, make sure you have |
| the most recent version of Mesa. |
| Otherwise, file a bug report or post to the Mesa3d-users mailing list. |
| Give as much info as possible when describing your problem. |
| </a></p> |
| |
| |
| <h2><a name="part2">2.4 I get undefined symbols such as bgnpolygon, v3f, etc...</a></h2> |
| <p> |
| <a name="part2">You're application is written in IRIS GL, not OpenGL. |
| IRIS GL was the predecessor to OpenGL and is a different thing (almost) |
| entirely. |
| Mesa's not the solution. |
| </a></p> |
| |
| |
| <h2><a name="part2">2.5 Where is the GLUT library?</a></h2> |
| <p> |
| <a name="part2">GLUT (OpenGL Utility Toolkit) is in the separate MesaDemos-x.y.z.tar.gz file. |
| If you don't already have GLUT installed, you should grab the MesaDemos |
| package and unpack it before compiling Mesa. |
| </a></p> |
| |
| |
| |
| <h2><a name="part2">2.6 What's the proper place for the libraries and headers?</a></h2> |
| <p> |
| <a name="part2">On Linux-based systems you'll want to follow the |
| </a><a href="http://oss.sgi.com/projects/ogl-sample/ABI/index.html">Linux ABI</a> |
| standard. |
| Basically you'll want the following: |
| </p> |
| <ul> |
| <li>/usr/include/GL/gl.h - the main OpenGL header |
| </li><li>/usr/include/GL/glu.h - the OpenGL GLU (utility) header |
| </li><li>/usr/include/GL/glx.h - the OpenGL GLX header |
| </li><li>/usr/include/GL/glext.h - the OpenGL extensions header |
| </li><li>/usr/include/GL/glxext.h - the OpenGL GLX extensions header |
| </li><li>/usr/include/GL/osmesa.h - the Mesa off-screen rendering header |
| </li><li>/usr/lib/libGL.so - a symlink to libGL.so.1 |
| </li><li>/usr/lib/libGL.so.1 - a symlink to libGL.so.1.xyz |
| </li><li>/usr/lib/libGL.so.xyz - the actual OpenGL/Mesa library. xyz denotes the |
| Mesa version number. |
| </li><li>/usr/lib/libGLU.so - a symlink to libGLU.so.1 |
| </li><li>/usr/lib/libGLU.so.1 - a symlink to libGLU.so.1.3.xyz |
| </li><li>/usr/lib/libGLU.so.xyz - the OpenGL Utility library. xyz denotes the Mesa |
| version number. |
| </li></ul> |
| <p> |
| After installing XFree86 and the DRI drivers, some of these files |
| may be symlinks into the /usr/X11R6/ tree. |
| </p> |
| <p> |
| The old-style Makefile system doesn't install the Mesa libraries; it's |
| up to you to copy them (and the headers) to the right place. |
| </p> |
| <p> |
| The GLUT header and library should go in the same directories. |
| </p> |
| <br> |
| <br> |
| |
| |
| <a name="part3"> |
| </a><h1><a name="part3">3. Runtime / Rendering Problems</a></h1> |
| |
| <h2><a name="part3">3.1 Rendering is slow / why isn't my graphics hardware being used?</a></h2> |
| <p> |
| <a name="part3">Stand-alone Mesa (downloaded as MesaLib-x.y.z.tar.gz) doesn't have any |
| support for hardware acceleration (with the exception of the 3DFX Voodoo |
| driver). |
| </a></p> |
| <p> |
| <a name="part3">What you really want is a DRI or NVIDIA (or another vendor's OpenGL) driver |
| for your particular hardware. |
| </a></p> |
| <p> |
| <a name="part3">You can run the <code>glxinfo</code> program to learn about your OpenGL |
| library. |
| Look for the GL_VENDOR and GL_RENDERER values. |
| That will identify who's OpenGL library you're using and what sort of |
| hardware it has detected. |
| </a></p> |
| <p> |
| <a name="part3">If your DRI-based driver isn't working, go to the |
| </a><a href="http://dri.sf.net/">DRI website</a> for trouble-shooting information. |
| </p> |
| |
| |
| <h2>3.2 I'm seeing errors in depth (Z) buffering. Why?</h2> |
| <p> |
| Make sure the ratio of the far to near clipping planes isn't too great. |
| Look |
| <a href="http://www.sgi.com/software/opengl/advanced97/notes/node18.html"> |
| here</a> for details. |
| </p> |
| <p> |
| Mesa uses a 16-bit depth buffer by default which is smaller and faster |
| to clear than a 32-bit buffer but not as accurate. |
| If you need a deeper you can modify the parameters to |
| <code> glXChooseVisual</code> in your code. |
| </p> |
| |
| |
| <h2>3.3 Why Isn't depth buffering working at all?</h2> |
| <p> |
| Be sure you're requesting a depth buffered-visual. If you set the MESA_DEBUG |
| environment variable it will warn you about trying to enable depth testing |
| when you don't have a depth buffer. |
| </p> |
| <p>Specifically, make sure <code>glutInitDisplayMode</code> is being called |
| with <code>GLUT_DEPTH</code> or <code>glXChooseVisual</code> is being |
| called with a non-zero value for GLX_DEPTH_SIZE. |
| </p> |
| <p>This discussion applies to stencil buffers, accumulation buffers and |
| alpha channels too. |
| </p> |
| |
| |
| <h2>3.4 Why does glGetString() always return NULL?</h2> |
| <p> |
| Be sure you have an active/current OpenGL rendering context before |
| calling glGetString. |
| </p> |
| |
| |
| <h2>3.5 GL_POINTS and GL_LINES don't touch the right pixels</h2> |
| <p> |
| If you're trying to draw a filled region by using GL_POINTS or GL_LINES |
| and seeing holes or gaps it's because of a float-to-int rounding problem. |
| But this is not a bug. |
| See Appendix H of the OpenGL Programming Guide - "OpenGL Correctness Tips". |
| Basically, applying a translation of (0.375, 0.375, 0.0) to your coordinates |
| will fix the problem. |
| </p> |
| |
| <br> |
| <br> |
| |
| |
| <a name="part4"> |
| </a><h1><a name="part4">4. Developer Questions</a></h1> |
| |
| <h2><a name="part4">4.1 How can I contribute?</a></h2> |
| <p> |
| <a name="part4">First, join the Mesa3d-dev mailing list. That's where Mesa development |
| is discussed. |
| </a></p> |
| <p> |
| <a name="part4">The </a><a href="http://www.opengl.org/developers/documentation/specs.html"> |
| OpenGL Specification</a> is the bible for OpenGL implemention work. |
| You should read it. |
| </p> |
| <p>Most of the Mesa development work involves implementing new OpenGL |
| extensions, writing hardware drivers (for the DRI), and code optimization. |
| </p> |
| |
| <h2>4.2 How do I write a new device driver?</h2> |
| <p> |
| Unfortunately, writing a device driver isn't easy. |
| It requires detailed understanding of OpenGL, the Mesa code, and your |
| target hardware/operating system. |
| 3D graphics are not simple. |
| </p> |
| <p> |
| The best way to get started is to use an existing driver as your starting |
| point. |
| For a software driver, the X11 and OSMesa drivers are good examples. |
| For a hardware driver, the Radeon and R200 DRI drivers are good examples. |
| </p> |
| <p>The DRI website has more information about writing hardware drivers. |
| The process isn't well document because the Mesa driver interface changes |
| over time, and we seldome have spare time for writing documentation. |
| That being said, many people have managed to figure out the process. |
| </p> |
| <p> |
| Joining the appropriate mailing lists and asking questions (and searching |
| the archives) is a good way to get information. |
| </p> |
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