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+

Mesa Frequently Asked Questions

+Last updated: 21 August 2006 +
+ +
+
+

Index

+1. High-level Questions and Answers +
+2. Compilation and Installation Problems +
+3. Runtime / Rendering Problems +
+4. Developer Questions +
+
+
+ + + + +

1. High-level Questions and Answers

+ +

1.1 What is Mesa?

+

+Mesa is an open-source implementation of the OpenGL specification. +OpenGL is a programming library for writing interactive 3D applications. +See the OpenGL website for more +information. +

+

+Mesa 6.x supports the OpenGL 1.5 specification. +

+ + +

1.2 Does Mesa support/use graphics hardware?

+

+Yes. Specifically, Mesa serves as the OpenGL core for the open-source DRI +drivers for XFree86/X.org. See the DRI +website for more information. +

+

+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. +

+ +

1.3 What purpose does Mesa serve today?

+

+Hardware-accelerated OpenGL implementations are available for most popular +operating systems today. +Still, Mesa serves at least these purposes: +

+ + + +

1.4 What's the difference between"Stand-Alone" Mesa and the DRI drivers?

+

+Stand-alone Mesa is the original incarnation of Mesa. +On systems running the X Window System it does all its rendering through +the Xlib API: +

+

+

+Alternately, Mesa acts as the core for a number of OpenGL hardware drivers +within the DRI (Direct Rendering Infrastructure): +

+ + + +

1.5 How do I upgrade my DRI installation to use a new Mesa release?

+

+This wasn't easy in the past. +Now, the DRI drivers are included in the Mesa tree and can be compiled +separately from the X server. +Just follow the Mesa compilation instructions. +

+ + +

1.6 Are there other open-source implementations of OpenGL?

+

+Yes, SGI's +OpenGL Sample Implemenation (SI) 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. +

+ +

+Vincent is +an open-source implementation of OpenGL ES for mobile devices. + +

+miniGL +is a subset of OpenGL for PalmOS devices. + +

+TinyGL is a subset of OpenGL. +

+ +

+SoftGL +is an OpenGL subset for mobile devices. +

+ +

+Chromium +isn't a conventional OpenGL implementation (it's layered upon OpenGL), +but it does export the OpenGL API. It allows tiled rendering, sort-last +rendering, etc. +

+ +

+ClosedGL is an OpenGL subset library for TI +graphing calculators. +

+ +

+There may be other open OpenGL implementations, but Mesa is the most +popular and feature-complete. +

+ + + +
+
+ + + +

2. Compilation and Installation Problems

+ + +

2.1 What's the easiest way to install Mesa?

+

+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. +

+ + +

2.2 I get undefined symbols such as bgnpolygon, v3f, etc...

+

+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. +

+ + +

2.3 Where is the GLUT library?

+

+GLUT (OpenGL Utility Toolkit) is in the separate MesaGLUT-x.y.z.tar.gz file. +If you don't already have GLUT installed, you should grab the MesaGLUT +package and compile it with the rest of Mesa. +

+ + + +

2.4 What's the proper place for the libraries and headers?

+

+On Linux-based systems you'll want to follow the +Linux ABI standard. +Basically you'll want the following: +

+ +

+After installing XFree86/X.org and the DRI drivers, some of these files +may be symlinks into the /usr/X11R6/ tree. +

+

+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. +

+

+The GLUT header and library should go in the same directories. +

+
+
+ + + +

3. Runtime / Rendering Problems

+ +

3.1 Rendering is slow / why isn't my graphics hardware being used?

+

+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). +

+

+What you really want is a DRI or NVIDIA (or another vendor's OpenGL) driver +for your particular hardware. +

+

+You can run the glxinfo 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. +

+

+If your DRI-based driver isn't working, go to the +DRI website for trouble-shooting information. +

+ + +

3.2 I'm seeing errors in depth (Z) buffering. Why?

+

+Make sure the ratio of the far to near clipping planes isn't too great. +Look + here for details. +

+

+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 + glXChooseVisual in your code. +

+ + +

3.3 Why Isn't depth buffering working at all?

+

+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. +

+

Specifically, make sure glutInitDisplayMode is being called +with GLUT_DEPTH or glXChooseVisual is being +called with a non-zero value for GLX_DEPTH_SIZE. +

+

This discussion applies to stencil buffers, accumulation buffers and +alpha channels too. +

+ + +

3.4 Why does glGetString() always return NULL?

+

+Be sure you have an active/current OpenGL rendering context before +calling glGetString. +

+ + +

3.5 GL_POINTS and GL_LINES don't touch the right pixels

+

+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. +

+ +

3.6 How can I change the maximum framebuffer size in Mesa's +swrast backend?

+

+These can be overridden by using the --with-max-width and +--with-max-height options. The two need not be equal. +

+Do note that Mesa uses these values to size some internal buffers, +so increasing these sizes will cause Mesa to require additional +memory. Furthermore, increasing these limits beyond 4096 +may introduce rasterization artifacts; see the leading comments in +src/mesa/swrast/s_tritemp.h. +

+ +
+
+ + + +

4. Developer Questions

+ +

4.1 How can I contribute?

+

+First, join the Mesa3d-dev +mailing list. +That's where Mesa development is discussed. +

+

+The +OpenGL Specification is the bible for OpenGL implemention work. +You should read it. +

+

Most of the Mesa development work involves implementing new OpenGL +extensions, writing hardware drivers (for the DRI), and code optimization. +

+ +

4.2 How do I write a new device driver?

+

+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. +

+

+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. +

+

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. +

+

+Joining the appropriate mailing lists and asking questions (and searching +the archives) is a good way to get information. +

+ + +

4.3 Why isn't GL_EXT_texture_compression_s3tc implemented in Mesa?

+

+The specification for the extension +indicates that there are intellectual property (IP) and/or patent issues +to be dealt with. +

+

We've been unsucessful in getting a response from S3 (or whoever owns +the IP nowadays) to indicate whether or not an open source project can +implement the extension (specifically the compression/decompression +algorithms). +

+

+In the mean time, a 3rd party plug-in library is available. +

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