From 8667d4d97a3e958a7f63c18c34a62469ba5d2079 Mon Sep 17 00:00:00 2001 From: ftrapero Date: Thu, 15 Jun 2017 14:15:08 +0200 Subject: Squashed 'nx-X11/extras/Mesa_6.4.1/' content from commit 53d1bc0 git-subtree-dir: nx-X11/extras/Mesa_6.4.1 git-subtree-split: 53d1bc081eb633aecbd5ab0bf3981f734a2102f2 --- docs/faq.html | 394 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 394 insertions(+) create mode 100644 docs/faq.html (limited to 'docs/faq.html') diff --git a/docs/faq.html b/docs/faq.html new file mode 100644 index 000000000..b93d5007d --- /dev/null +++ b/docs/faq.html @@ -0,0 +1,394 @@ + + +Mesa FAQ + + + + + + + +

Mesa Frequently Asked Questions

+Last updated: 21 October 2004 + + +
+
+

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: +

Mesa is used as the core of the open-source XFree86/X.org DRI + hardware drivers. +
Mesa is quite portable and allows OpenGL to be used on systems + that have no other OpenGL solution. +
Software rendering with Mesa serves as a reference for validating the + hardware drivers. +
A software implementation of OpenGL is useful for experimentation, + such as testing new rendering techniques. +
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. +
Mesa's internal limits (max lights, clip planes, texture size, etc) can be + changed for special needs (hardware limits are hard to overcome). +

+ + +

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: +

The GLX API is supported, but it's really just an emulation of the + real thing. +
The GLX wire protocol is not supported and there's no OpenGL extension + loaded by the X server. +
There is no hardware acceleration. +
The OpenGL library, libGL.so, contains everything (the programming API, + the GLX functions and all the rendering code). +

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

The libGL.so library provides the GL and GLX API functions, a GLX + protocol encoder, and a device driver loader. +
The device driver modules (such as r200_dri.so) contain a built-in + copy of the core Mesa code. +
The X server loads the GLX module. + The GLX module decodes incoming GLX protocol and dispatches the commands + to a rendering module. + For the DRI, this module is basically a software Mesa renderer. +

+ + + +

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. +

+ +

+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 Running `configure; make` doesn't Work

+Mesa no longer supports GNU autoconf/automake. Why? +

It seemed to seldom work on anything but Linux +
The config files were hard to maintain and hard to understand +
libtool caused a lot of grief +

+ +

+Now Mesa again uses a conventional Makefile system (as it did originally). +Basically, each Makefile in the tree includes one of the configuration +files from the config/ directory. +The config files specify all the variables for a variety of popular systems. +

+ + +

2.3 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. +

+ + +

2.4 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. +

+ + + +

2.5 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: +

/usr/include/GL/gl.h - the main OpenGL header +
/usr/include/GL/glu.h - the OpenGL GLU (utility) header +
/usr/include/GL/glx.h - the OpenGL GLX header +
/usr/include/GL/glext.h - the OpenGL extensions header +
/usr/include/GL/glxext.h - the OpenGL GLX extensions header +
/usr/include/GL/osmesa.h - the Mesa off-screen rendering header +
/usr/lib/libGL.so - a symlink to libGL.so.1 +
/usr/lib/libGL.so.1 - a symlink to libGL.so.1.xyz +
/usr/lib/libGL.so.xyz - the actual OpenGL/Mesa library. xyz denotes the +Mesa version number. +
/usr/lib/libGLU.so - a symlink to libGLU.so.1 +
/usr/lib/libGLU.so.1 - a symlink to libGLU.so.1.3.xyz +
/usr/lib/libGLU.so.xyz - the OpenGL Utility library. xyz denotes the Mesa +version number. +

+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. +

+ +
+
+ + + +

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 and/or the DRI drivers?

+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). +

+Until we can get official permission to do so, this extension will not +be implemented in Mesa. +

+ + + + -- cgit v1.2.3