
		      The Mesa 3-D graphics library

			      Version 1.2.1

		      Copyright (C) 1995  Brian Paul



Introduction
============

Mesa is a 3-D graphics library with an API which is very similar to that
of OpenGL*.  To the extent that Mesa utilizes the OpenGL command syntax
or state machine, it is being used with authorization from Silicon Graphics,
Inc.  However, the author makes no claim that Mesa is in any way a
compatible replacement for OpenGL or associated with Silicon Graphics, Inc.
Those who want a licensed implementation of OpenGL should contact a licensed
vendor.  This software is distributed under the terms of the GNU Library
General Public License, see the LICENSE file for details.

* OpenGL(R) is a registered trademark of Silicon Graphics, Inc.



Author
======

Brian Paul
Space Science and Engineering Center
University of Wisconsin - Madison
1225 W. Dayton St.
Madison, WI  53706

brianp@ssec.wisc.edu



Status
======

I've been working on this library in my spare time since August, 1993.
It's currently about 90% complete.  You'll find that most programs which
use the OpenGL tk, aux or GLUT toolkits will work with Mesa without changing
the source code at all.

Features which are complete:
	all glBegin() primitives
	all model and view transformations
	clipping (against user clip planes and view volume)
	lighting
	smooth shading
	depth buffering
	accumulation buffer
	alpha testing/blending
	stencil buffer
	dithering
	logic operations
	evaluators  (curves and surfaces)
	feedback/selection
	fog (per-pixel or per-vertex)
	polygon/line stippling
	read/write/copy pixels
	tk and aux libraries for X11
	context switching (multiple windows)
	RGB mode simulated in color mapped windows
	the GLX library (as close as I can get)

Features which are mostly complete:
	display lists
	texture mapping
	the GLU library

Missing features:
	anti-aliasing
	mipmapping, non-point-sampled texture mapping
	NURBS
	glPixelZoom

The primary goal of this library has been correctness, speed was secondary
(but not neglected!).  Many optimizations can still be done.

The core library was originally written on an Amiga using the DCC compiler.
Later on it was moved to an SGI.  Current development is done on an SGI
system.

Mesa works on most Unix workstations with ANSI C and X11.  Now there's also
a Microsoft Windows driver (see windows/README.WIN).  A very outdated and
inoperative Amiga driver is also included.

While a 24-bit TrueColor display is recommended for RGB mode rendering,
the Mesa/X driver supports rendering on 8-bit and even 1-bit displays by
dithering.

Please send bug reports to the author.  Include information describing
your system, which version of Mesa you're using, and how to reproduce the
problem.  Bug fixes are especially welcome.  Note that some parts of Mesa
(widgets, GLU tesselator, GLE library, etc) were contributed by others and
any bugs in those components should be sent to the respective author.



Manifest
========

The archive file Mesa-1.2.1.tar.Z can be unpacked with:
	zcat Mesa-1.2.1.tar.Z | tar xvf -

After you unpacking you should have the following:

Mesa/README		- this file
Mesa/LICENSE		- the GNU library license
Mesa/Makefile		- top-level Makefile
Mesa/Make-config	- system configurations used by the Makefiles
Mesa/include/		- application include files
Mesa/lib/		- application libraries, directory created by make
Mesa/src/		- source code for core library
Mesa/src-glu/		- source code for utility library
Mesa/src-tk/		- source code for tk library
Mesa/src-aux/		- source code for aux library
Mesa/demos/		- demo programs
Mesa/samples/		- sample OpenGL programs from SGI
Mesa/book/		- example programs from the OpenGL Programming Guide
Mesa/GLUT/		- the home for GLUT
Mesa/widgets/		- the Mesa widgets
Mesa/contrib/		- user contributed software
Mesa/windows/		- Microsoft Windows driver stuff


Installation for Unix/X11
=========================

To compile the library, first type 'make' alone to see the list of system
configurations currently supported.  If you see your configuration on the
list, type 'make <system>'.  Most popular Unix/X workstations are currently
supported.

The top-level makefile will execute the makefiles in a number of sub-
directories.  When finished, there should be executables in the "demos/",
"samples/", and "book/" directories for you to try out.

If your system is not listed by 'make', you'll have to modify the top-level
Makefile and Make-config files.  There are instructions in each file.

If you have compilation problems you should try to fix them and return the
patches to the author.

The file src/config.h has many parameters which you can tune before building.

If you want to build the Mesa widgets read the widgets/INSTALL file.

If you want to build the GLUT library read the GLUT/README-MESA file.



Installation for Microsoft Windows
==================================

See the windows/README.WIN file for details.  Note that any problems with
the Windows driver should be addressed to Mark Peterson.  Also, be aware
that this is a preliminary release of the Windows driver; there are prob-
ably bugs.



Using the library (with Unix/X11 systems)
=========================================

To use the library with your own applications you may want to move the
files in "include/" to "/usr/local/include/" and the libraries in "lib/"
to "/usr/local/lib/".  Then compile your graphics application with
"-I/usr/local/include" and link with "-L/usr/local/lib -lMesaGL -lMesaGLU",
for example.  Look at the demos/Makefile for an example.

Since the OpenGL API is used, OpenGL documentation can serve as the
documentation for Mesa's core functions.

Initially, you may write your own Mesa programs using the aux or tk tool-
kits which are used in the OpenGL Programming Guide and in SGI's demos,
respectively.  However, these toolkits weren't meant for use in real app-
lications.  You have several alternatives:

1. Go directly to the X/Mesa interface using the functions described in
include/GL/xmesa.h.  This requires experience with X programming.

2. Use the GLX (simulated since Mesa doesn't implement the GLX extension)
functions.  These functions look like, and try to act like, the real GLX
functions used by OpenGL in conjunction with the X window system.

3. GLUT (OpenGL Utility Toolkit) was written by Mark Kilgard at SGI as
a replacement for aux and tk.  It provides a simple, portable, window-
system independent interface allowing you to write OpenGL applications
quickly and easily.  GLUT isn't included with Mesa but you'll find instruc-
tions on how to get and build GLUT in the file GLUT/README-MESA.

4. Use a Mesa widgets.  Look in the widgets/ directory for more info.


A few tips on getting the best performance from Mesa:

1. Turn off smooth shading when you don't need it (glShadeModel)
2. Turn off depth buffering when you don't need it.
3. Use double buffering as it's often faster than single buffering
4. Compile in the X Shared Memory extension option if it's supported
   on your system by adding -DSHM to CFLAGS and -lXext to XLIBS for
   your system in the Make-config file.
5. Recompile Mesa with more optimization if possible.
6. Try to maximize the amount of drawing done between glBegin/glEnd pairs.
7. Use the MESA_BACK_BUFFER variable to find best performance in double
   buffered mode.


Debugging:  normally Mesa records but does not notify the user of errors.
It is up to the application to call glGetError to check for errors.  Mesa
supports an environment variable, MESA_DEBUG, to help with debugging.  If
MESA_DEBUG is defined, a message will be printed to stdout when an error
occurs.


Display Modes:  The glXChooseVisual function tries its best to pick an
appropriate visual for the given attribute list.  However, if this doesn't
suit your needs you can force Mesa to use any X visual you want (though not
all are supported) by setting the MESA_RGB_VISUAL and MESA_CI_VISUAL envi-
ronment variables.  When an RGB visual is requested, glXChooseVisual will
first look if the MESA_RGB_VISUAL variable is defined.  If so, it will try
to use the specified visual.  Similarly, when a color index visual is re-
quested, glXChooseVisual will look for the MESA_CI_VISUAL variable.

The format of accepted values is:  <visual-class> <depth>
Here are some examples:

using the C-shell:
	% setenv MESA_RGB_VISUAL "TrueColor 8"		// 8-bit TrueColor
	% setenv MESA_CI_VISUAL "PseudoColor 12"	// 12-bit PseudoColor
	% setenv MESA_RGB_VISUAL "PseudoColor 8"	// 8-bit PseudoColor

using the KornShell:
	$ export MESA_RGB_VISUAL="TrueColor 8"
	$ export MESA_CI_VISUAL="PseudoColor 12"
	$ export MESA_RGB_VISUAL="PseudoColor 8"


Another environment variable, MESA_BACK_BUFFER, controls whether the back
buffer (for double buffering) is implemented using an X Pixmap or XImage.
A pixmap is faster when drawing simple lines and polygons while an XImage
is faster when Mesa has to do pixel-by-pixel rendering.  Using the
MESA_BACK_BUFFER variable you can experiment to see which is faster for
your application.  The valid values for MESA_BACK_BUFFER are:  Pixmap and
XImage (only the first letter is checked, case doesn't matter).


While Mesa includes its own header files GL/gl.h GL/glx.h GL/glu.h you can
optionally compile Mesa using the real OpenGL header files if you have
them.  Just remove or move the GL/gl.h GL/glx.h GL/glu.h Mesa files and
replace them with copies or links to the real OpenGL header files.  Then
recompile Mesa.



Miscellaneous
=============

See the src/NOTES file for more detailed info about the implementation
of Mesa.  See the book/NOTES and samples/NOTES files for information
about which demos work or don't work, and why.

The latest version of Mesa can be found at iris.ssec.wisc.edu in pub/misc/

There is a Mesa WWW page:  http://www.ssec.wisc.edu/~brianp/Mesa.html

There is a Mesa mailing list.  To subscribe, send the following message to
the address listserv@iqm.unicamp.br

subs mesa <your name>
set mesa mail ack

For example:

subs mesa Brian Paul
set mesa mail ack

The second line tells the list processor to send you a copy of your own
messages.

You will receive a welcome message from the list server when you have been
added to the list.  It tells you how to post messages to the list, how
to unsubscribe, etc.  Thanks to Pedro Vazquez for setting up the list.

There is a contrib/ subdirectory containing contributions from Mesa users.
See the README file in that directory for more information.



Known Bugs
==========

Polygons with two nearly-co-located vertices may be mis-rendered or acciden-
tally culled.

Perspective-corrected texture map coordinate interpolation can fail under
certain conditions due to numerical error.



Version History
===============

1.0 beta   February 1995
    Initial release

1.1 beta   March 4, 1995
    Many improvements:
	- faster point and line drawing (2x faster)
	- more systems supported, better Makefiles
	- many small bug fixes
	- pseudo-GLX functions added
	- GLUT support
	- new implementation of evaluators (eval2.c)
	- Renamed lib*.a files to avoid collisions

1.1.1 beta   March 7, 1995
    Reverted from eval2.c to eval.c due to FPE on Linux
    more speed improvements
    more Makefile changes

1.1.2 beta   March 14,1995
    Using eval2.c again
    more FPE-prevention checks (0-length normals are OK)
    a few small bug fixes
    much faster pixel logic ops!
    faster transformation arithmetic
    implementation of SGI's blending extensions
    glXUseXFont implemented
    added MESA_DEBUG environment variable support

1.1.3 beta   March 31,1995
    gluScaleImage() and gluBuild2DMipMaps() implemented
    Mesa widgets for Xt/Motif
    more bug fixes
    blendEXT demos
    added environment variables for selecting visuals
    almost all GLUT demos work correctly now
    faster X device driver functions

1.1.4 beta   April 20,1995
    Bug fixes:
	- missing #define SEEK_SET in src-tk/image.c
	- compile glShadeModel into display lists
	- fixed pow() domain error in src/light.c
	- fixed "flickering bitmaps" in double buffer mode
	- fixed tk.h and aux.h for C++
	- state of LIGHT_MODEL_LOCAL_VIEWER was inverted
    New features:
	- MUCH, MUCH nicer dithering in 8-bit RGB mode
	- updated widgets and widget demos
	- Implemented GLXPixmap functions
	- Added GLU 1.1 and GLX 1.1 functions
	- Changed the X/Mesa interface API, more versatile
	- Implemented gluPartialDisk()

1.2   May 22,1995
    Bug fixes:
	- IRIX 4.x makefile problem
	- modified tk to share root colormap as needed
	- gluLookAt normalization problem
	- suppress Expose, NoExpose events in swapbuffers
	- glBitmap() and glDrawPixels() clipping
    New features:
	- GL_BLEND, GL_MODULATE, GL_DECAL, and GL_REPLACE_EXT texture
	      modes implemented
	- texture maps stored more efficiently
	- texture maps can be compiled into display lists
	- Bogdan Sikorski's GLU polygon tesselation code
	- Linas Vepstas's sweep and extrusion library
	- glXCreateContext()'s shareList parameter works as it's supposed to.
	      XMesaCreateContext() updated to accept a shareList parameter too.
	- Mesa can be compiled with real OpenGL .h files
	- MESA_BACK_BUFFER environment variable
	- better GLX error checking

1.2.1   June 22, 1995
    Bug fixes:
	- X/Mesa double buffer window resize crash
	- widgets now pass PointerMotion events
	- X/Mesa incorrect default clear color and drawing color
	- more robust X MIT-SHM support in X/Mesa
	- glTexImage( format=GL_LUMINANCE ) didn't work
	- GL_LINE mode polygons with line width > 1.0 could cause a crash
	- numerous feedback bugs
	- glReadPixels() from depth buffer was wrong
	- error prone depth and stencil buffer allocation
    New features:
	- Preliminary Microsoft Windows driver
	- Implemented a number of missing functions: glEvalCoord[12][df]v(),
	    glGet...(), etc.
	- Added a few missing symbols to gl.h and glu.h
	- Faster rendering of smooth-shaded, RGBA, depth-buffered polygons.
	- Faster rendering of lines when width=2.0
	- Stencil-related functions now work in display lists
    Changes:
	- renamed aux.h as glaux.h (MS-DOS names can't start with aux)
	- most filenames are in 8.3 format to accomodate MS-DOS
	- use GLubytes to store arrays of colors instead of GLints

Coming up...
	All new triangle rasterization



Why is it the library called Mesa?
==================================

Why not?  More obvious names were considered but had to be rejected:
FreeGL (too similar to the trademarked name OpenGL), Free3D (too similar
to DEC's Open3D).  Also, I'm tired of acronyms.

[I've recently discovered that at least two other software products use the
name Mesa.  A name change may be necessary in the future.  Suggestions are
welcome!]



Thanks to
=========

Erich Stefan Boleyn - for the glRotate code and testing early Mesa
Joe Kiniry, Kendall Bennett - for opinions and discussion
Marc Buffat - for the gluProject and gluUnproject functions
Bernd Barsuhn, Volker Weiss - for the new implementation of evaluators
Philip Brown - for the initial GLX, GLUT implementation
Thorsten Ohl - for glXUseXFont() and glBitmap bug fixes
Thomas Malik - for new invert_matrix and other xform.c code
Michael Pichler - for X colormap code
Thorsten Ohl, Jeroen van der Zijp - for the widget set
Bob Mercier - for the new 8-bit RGB dithering code
Pedro Vazquez - for establishing the Mesa mailing list
Bogdan Sikorski - for the GLU polygon tesselation code
Linas Vepstas - for his extrusion and swept surface library
Frederic Devernay - for improved X shared memory support
Asif Khan - for bringing _many_ subtle bugs to my attention
Mark Peterson - for the MS Windows driver for Mesa


Your contributionss are greatly appreciated!



This file last revised:  22 June 1995
