SG User's Guide

Version 0.1

Table of Contents
  1. Overview
  2. Information and Resources
  3. Obtaining SG
  4. Frequently Asked Questions
  5. Installation Instructions
  6. Author Information
  7. Copyright and Terms of Use
  8. GNU GPL
NOTE: This documentation provides information about installation, configuration, and general usage of the SG libraries. Information about the programming interface provided by the SG software can be found in the Programmer's Guide.


SG is an unstructured simplex mesh OpenGL display and manipulation tool for use with the finite element research codes MC and PLTMG. SG provides OpenGL-based graphics over UNIX and INET sockets on UNIX/X-based systems, Win32-based systems, and other systems. It can also be used with MCLite as a replacement for MATLAB's builtin graphics for polygons. SG can read Geomview OFF files and OpenInventor files for polygonal surface descriptions, and it can also read PDB files for molecule descriptions. SG looks and acts somewhat like Geomview, and it mimics most of the basic features and controls of Geomview for displaying polygonal 2-manifolds.

Figure SG is designed to mimic the well-known Geomview program from the University of Minnesota's geometry center, and it uses one of Geomview's input file formats (the "OFF" format). Although SG it is quite a bit simpler than Geomview, it has three advantages when compared to Geomview. First, it can take input directly from files, UNIX pipes, UNIX domain sockets, and INET sockets (Geomview cannot take input from INET sockets). Second, it can produce provably correct PostScript renderings of meshes (Geomview uses a baricenter-based front-to-back ordering for the Painter's algorithm, which often fails for complex meshes; SG uses a linear programming approach which is mathematically guaranteed to work if the picture is paintable with the Painter's algorithm). Third, it will build and run on Win32 platforms such as Windows 2000, Windows NT, and Windows 98. (Some may actually view this as a disadvantage.) In the case of Win32, SG uses the WINSOCK API for INET socket access. The window-system specific connection to X11 or Win32 is made through "WGL" extensions to Win32 under NT, or using the SGI "GLw" widget set on X11 platforms. The graphics in SG is done in an entirely platform-independent manner using OpenGL. This portability is due to SG having been built on top of a portable low-level abstraction library called MALOC (Minimal Abstraction Layer for Object-oriented C). MALOC was written primarily to support the development of MC, but is now also used for SG. Both MALOC and SG are now both used by Randy Bank in the development of his software package PLTMG.

Quaternion-based Trackball Rotator

Figure SG is a polygonal manifold display and manipulation tool. It can also display PDB (Protein DataBase) data as a collection of intersecting triangulated spheres of appropriate color and radii. It is basically a trackball rotator, although one can also scale and translate the object being displayed. The manipulation is done with a combination of the mouse and the keyboard. The rotator is quaternion-based, following the trackball example in Mark Kilgard's OpenGL programming book. The rotator avoids gimbal lock, rotation instability, and other degeneracies through the use of a projection ball and quaternions. The hysteresis problem usually present in rotators is removed by employing Ken Shoemake's non-accumulation trick from his famous Arcball example in one of the Graphics Gems. (I.e., when you move the mouse back to the starting point in a rotation, the object resumes its original position.)

OpenGL-to-Postscript Generation

Figure SG can generate a very high-quality Postscript rendering of any displayed scene, with (provably) correct logical rendering order of the polygon primitives, through the use of builtin routine called SGps. SGps generates Postscript output from an arbitrary OpenGL scene, by using the feedback buffer mechanism in OpenGL. SGps is similar to Seth Teller's PSGL, and to Gary Wu's PSOGL, but it does not use the same baricentric depth quicksorting of the polygons, which is prone to incorrect rendering orders for complex scenes. Instead, SGps is based on a linear programming approach developed jointly with R. Bank. If a scene can be rendered by the Painter's Algorithm, then SGps is guaranteed to find a logically correct painting order, and it will then use the Painter's Algorithm to render the scene correctly in Postscript.

Input Format

Here are some examples illustrating the Geomview-compatible OFF input format tha t SG employs: tri, tet. The portability of SG is attained by the use of a low-level abstraction library called MALOC. The MALOC library must be installed before installing SG. Similar to MALOC, SG is easily buildable from source on any UNIX-like system, and uses a GNU autoconf build environment.

Information and Resources

Detailed information about SG can be found in the User's Guide and Programmers's Guide.

While SG is itself a self-contained software package, it is one of several components of FETK (the Finite Element ToolKit). FETK consists of the following components written in Clean OO C:
  • MALOC - Minimal Abstraction Layer for Object-oriented C programs.
  • PUNC - Portable Understructure for Numerical Computing.
  • GAMer - Geometry-preserving Adaptive MeshER (uses MALOC).
  • SG - Socket Graphics mesh display tool (uses MALOC).
  • MC - Manifold Code finite element package (uses MALOC and PUNC).
  • MCX - MC eXtension libraries (uses MALOC, PUNC, and MC).

MALOC is self-contained, and requires only an ANSI-C compiler on a UNIX or Win32 platform. PUNC, GAMer, SG, and MC are also self-contained, but rely on MALOC having been previously installed on the platform. Additional features of MC are enabled if PUNC is available, but PUNC is not required to build MC. The MC eXtension libraries MCX are constructed on top of MALOC and MC, and in order install and use MCX one must first correctly configure and install both MALOC and MC. MCX is made up of a number of individual libraries developed by members of our group, or contributed by one of a number of colleagues. More information about FETK can be found on the FETK website:

Obtaining SG

SG is copyrighted, but is redistributable in source and binary form under the following license. The SG source can be downloaded from the FETK Download Page.

In case you are having trouble with X11 on your MacOSX Leopard machine, here are some precompiled binaries: Some older pre-compiled SG and related binaries for Win32 platforms can be found below: SG uses the low-level FETK abstraction library MALOC, which must be installed before installing SG.

Frequently Asked Questions

What is SG and what does SG stand for?

See the Overview.

How to I obtain a copy of the SG source code?

See the Obtaining SG section.

I managed to get a copy of "sg-VERSION.[i386|src|tar].[rpm|gz]"; how do I now install SG?

See the Installation Instructions.

You gave me a "patch.gz" file to fix a bug in SG; how do I apply the patch?

To apply patches to upgrade SG to a new version, you first obtain the patch from me or my webpage as a single file with a name like "patch.gz". You apply the patch after you have unpacked the sg.tgz file as described above. To apply the patch, cd into the directory containing the root SG directory (called "sg" after unpacking sg.tgz) and execute the "patch" program as follows (the patch program exists on most UNIX machines):
  • gzip -cd patch.gz | patch -p0

Patch files are simply the output from a recursive "diff" that are used to represent all differences between two directory trees. For example, to create a patch representing the changes from version 1.0 of SG (in directory sg_1.0 for example) to version 1.1 of SG (e.g. in directory sg_1.1), I would normally type the following:
  • diff -r -u -N sg_1.0 sg_1.1 > patch1
  • gzip -v patch1
which would produce the gzipped patch file "patch1.gz". If you had previously installed version 1.0 of SG but would like to upgrade to version 1.1 of SG, you could just download the file "patch1.gz" and apply the changes using the program "patch" as above, rather than downloading and reinstalling the entire version 1.1 of SG.

I really don't know what I'm doing; how to I get more documentation for SG?

The User's Guide and the Programmers's Guide contain all of the SG documentation.

Why did you develop SG? There are many other mesh viewer packages, right?

Yes, there are. Geomview is awesome. However, we often want to display the mesh in a calculation on a local workstation, while running the calculation on a larger remote (possibly parallel) machine. For large complex meshes, opening up a remote X display is extremely slow (the X libraries may not even exist on the large number crucher). By running SG on the local machine, our numerical codes on the remote machine can send polygons in binary XDR format directly to an INET socket on the local machine. This is extremely fast, even for very large datasets. Finally, we often need to run visualization tools natively on Win32 platforms.

There are a couple of things we didn't like about Geomview, which we made different in SG. For example, the rotator in Geomview exhibits hysteresis in the sense that if you return the mouse to its original location when rotating, the object doesn't actually return to its original position. SG on the other hand uses a quaternion-based trackball rotator, and uses a rotation non-accumulation trick due to Ken Shoemake to avoid this type of hysteresis (the particular trick can be found in one of the Graphics Gems volumes). The PostScript generation mentioned above was another reason for writing SG.

What is in all of these subdirectories? Where exactly is "SG"?

SG consists of several (class) libraries from which you will call routines to handle your application. You will need to write a main driver program (and any supporting routines you need) and then link to the libraries. Alternatively, you can build the SG tools "sg" and "mcsg" by doing a "./configure ; make ; make install" in the tools subdirectory. These two tools process and display polygon data, and have functionality and behavior similar to Geomview. If you are simply after these two tools, then you don't need to actually use the libraries and headers that get installed when you configure/make/make install the SG libraries. However, the in order to successfully configure/make/make install the tools sg and mcsg, you must first succesfully configure/make/make install the SG libraries.

As described in the file "INSTALL", you will build all of the libraries in one shot for your particular architecture, along with various test programs to verify that the various pieces are functioning correctly. The libraries end up in "sg/lib", and the header files are in subdirectories in "sg/inc".

The following directory tree is created when you unpack the SG "sg.tgz" distribution file by following the instructions in the INSTALL document:
                        /      |    |       |    \
                       config doc examples src tools

The src directory has the additional subdirectory structure:
                     /    |      |    |  |   |   |  \
                aaa_inc aaa_lib base gl glu glw ogl vgl

Within each library source directory is an additional subdirectory, "sg". The "sg" subdirectory contains public headers for the library, representing the library API; these headers will be installed in the specified header install directory during the install procedure after building SG. (The OpenGL library subdirectories gl, glu, and glw contain additional OpenGL-specific API files in additional subdirectories.)

The following is a brief description of each subdirectory of the package.
    sg             - The entire SG package
    sg/config      - GNU Autoconf scripts and non-unix config files
    sg/doc         - SG documentation
    sg/examples    - Complex examples and data files for using SG
    sg/src         - SG source code (all source and headers)
    sg/src/aaa_inc - Header installation tools
    sg/src/aaa_lib - Library installation tools
    sg/src/*/sg    - The SG headers (API)
    sg/src/base    - Source for M. Holst's BASE  (SG foundation headers)
    sg/src/ogl     - Source for M. Holst's OGL   (OpenGL rotator kernel)
    sg/src/vgl     - Source for M. Holst's VGL   (Virtual openGL)
    sg/src/gl      - Source files for dubset of B. Paul's MesaGL
    sg/src/glu     - Source files for dubset of B. Paul's MesaGLU
    sg/src/glw     - Source files for dubset of B. Paul's MesaGLw
    sg/tools       - Some binary tools for use with SG

Okay, I seem to have installed SG correctly; how do I actually use it now?

Using the SG code is very simple; just type "./mcsg" without arguments and you get a list of all of the options. The socket bridging tool functions similarly; typing "./mcbridge" without arguments gives you a list of all of the possible options. The remaining tool "sg" is a motif version of "mcsg" with similar functionality, but with a more sophisticated button layout.

What is the class hierarchy? How are the various libraries related?

Detailed information on the class relationships can be found in the Programmers's Guide. The following directed graph shows the class library dependencies. (This tends to evolve as MC is developed.)
   MALOC ==> base ==> ogl ==> vgl ==> sg
                      /\      /\
                      ||      ||
   OpenGL ===> gl => glu      ||
   Window System =========> wgl/glw

Wait! I have a bunch of other questions, such as:
  • What in tarnation is "Clean OO C"?
  • Why is SG written in Clean OO C rather than C++ or Objective-C?
  • Why is SG written on top of this other package with a weird name (MALOC)?
  • I want to extend SG and/or MALOC in some way; what is the "Coding Style"?
  • I wrote a cool extension; how do I get it included in SG and/or MALOC?
These and other related questions are addressed in the MALOC FAQ, which is distributed as the README file in the MALOC source distribution.

Installation Instructions

Available distribution formats

SG is distributed in both binary format (as a binary RPM file sg-VERSION.i386.rpm for i386-based versions of Linux) and in source format (as a source RPM file sg-VERSION.src.rpm and as a gzipped tar file "sg-VERSION.tar.gz").

Installation using the binary RPM file

The following rpm command will install all of the SG headers and libraries into /usr/local/include and /usr/local/lib, and will install the SG documentation into /usr/share/doc/packages/sg:
    rpm -Uvh sg-VERSION.i386.rpm

Installation and rebuilding from sources using the source RPM file

The following rpm command will unpack the source rpm file "sg-VERSON.src.rpm" into the SG gzipped tar file containing the sources called "sg-VERSION.tar.tar.gz" and into a small RPM spec file called "sg-VERSON.spec":
    rpm -Uvh sg-VERSION.src.rpm
The sources can then be unpacked and built using the directions for the gzipped tar file below. Alternatively, the following rpm command will do these steps for you:
    rpm -bp sg-VERSION.spec

Rebuilding binary and source RPM files from the gzipped tar file

The SG sources contain the RPM spec file "sg-VERSON.spec" in the root source directory; as a result, rebuilding the RPM files from sources can be done using the rpm command:
    rpm -ta sg-VERSION.tar.gz
The result will be the corresponding source and binary rpm files, named "sg-VERSON.src.rpm" and "sg-VERSION.i386.rpm". Normally, these files are written to /usr/src/redhat/SRPMS and /usr/src/redhat/RPMS respectively, but you must be logged in as root for these to work. The destination directories can be overriden using arguments to the rpm program (see the rpm manpage).

Installation and building from sources using the gzipped tar file

The following command will unpack SG into a number of subdirectories and files on any UNIX machine (and on any WinNT machine with the GNU-Win32 tools gzip and tar).
    gzip -dc sg.tgz | tar xvf -

Building the package using the GNU "configure" shell script and "make"

The "configure" shell script in the "sg" directory (the toplevel directory created when you unpacked the SG tgz file) will build the entire package. This is a standard GNU autoconf-generated configuration script. For a list of the possible configuration options, type:
    ./configure --help

You should be able to build SG by simply typing:
    make install

However, it is often advantageous to keep the original source directory pristine; the configure script can actually be run outside the source tree, which will keep all files created by the build outside the source tree. (This idea is related to the section below describing how to build binaries for multiple architectures at the same time using the same source tree, and requires that your version of make has the VPATH facility, such as GNU make.) For example, I build SG in a separate directory from the source tree as follows:
    gzip -dc sg.tgz | tar xvf -
    mkdir sg_build
    cd sg_build
    make install

Building binaries for multiple architectures in the same source directory

If you have a version of "make" that supports the VPATH facility (such as any recent version of GNU make), then you can build the package for multiple architectures in the same source directory (in fact, you can do the compiles at the same time without collisions). This is very useful if you have your home directory on an NFS volume that you share among multiple architectures, such as SGI, Linux, etc. To build SG for all the systems at the same time, you simply make an additional subdirectory in the main SG directory for each architecture, copy "configure" into it, "cd" into the subdirectory, and then install as above. For example, on a linux machine you would do the following:
    mkdir linux
    cp configure linux/.
    cd linux
    make install

If you mount the same NFS home directory on for example an OpenStep box, you could at the same time do the following:
    mkdir next
    cp configure next/.
    cd next
    make install

Again, both builds can actually be done outside the source tree rather than in a subdirectory of the source tree, as described in the previous section.

Building shared libraries rather than static libraries

(MIKE: give an overview of libtool.)

Rebuilding the configure script and the files

If for some reason you actually need to rebuild the configure script or the files using the GNU autoconf suite, you should read the block of documentation at the top of the file. The commentary I put there explains exactly how the GNU autoconf suite must be used and in what order, and exactly what files are produced at each step of the process. A script called "bootstrap" which automates this process is located in the config subdirectory of the SG source tree.

Platform-specific information

Below is some platform-specific build/usage information for SG.
  • Linux (Source: M. Holst, UCSD)

    Things should work as described above.

  • FreeBSD/NetBSD/OpenBSD (Source: M. Holst, UCSD)

    Things should work as described above.

  • OpenStep (Source: M. Holst, UCSD)

    Things should just work, but you may have to set the CC environment variable as follows before typing ./configure:
        export CC="/bin/cc"
    or you might need to use:
        export CC="/bin/cc -ObjC"

  • IRIX (Source: M. Holst, UCSD)

    If you are on a 64-bit IRIX box such as an Onyx, Octane, or Origin, set the CC environment variable as follows before typing ./configure:
        export CC="/bin/cc -64"
    If you are on a 32-bit IRIX box such as an O2 or Indy, set the CC environment variable as follows before typing ./configure:
        export CC="/bin/cc -32"

  • Win32 (Source: M. Holst, UCSD)

    Unless you have the Cygwin environment, you need to use one of the included project file collections for one of the commercially available ANSI C or C++ compilers for the Win32 environment.

What you end up with

Once the build completes via the "configure;make;make install" procedure above with no errors, the SG library (libsg.a and/or is installed into the specified installation directory. You can also build some useful tools that employ the SG library by cd-ing into the "tools" subdirectory and repeating the "configure;make;make install" procedure. Once the tools build completes, you will end up with:
    mcsg     - Core socket OpenGL tool ([GLw | WGL] + [X | Win32] + OpenGL)
    mcbridge - A socket bridging tool (FILE/PIPE/UNIX/INET)
    sg       - A Motif version of mcsg (Motif + X + OpenGL)

If the SG tools work like they were designed, you won't need any more information to use the tools. If you want to know more about the details of the algorithms in SG, or about the implementation details such as the socket graphics, have a look at the Programmer's Guide.

Getting SG to find your installation of GL/GLU/GLw/Motif/Etc

If your installation of OpenGL (libGL, libGLU, libGLw and headers) and/or Motif is located in an unusual directory, then the configuration script may have trouble finding the libraries or the headers. The configure script prints out the state of affairs quite clearly as to whether it found the libraries and the headers. If you have the libraries and configure is not finding them, then here are several possible solutions, each of which usually works. They are listed in preferred order (i.e. you should try Solution 1 first, and if that doesn't work try Solution 2, and so on).

Note that you DO NOT need Motif in order to build SG; if you DO have Motif, then the additional Motif-based tool "sg" is built. Without Motif libraries on your system, you still get the base socket graphics tool "mcsg" and the socket bridging tool "mcbridge". ("sg" is somewhat fancier than "mcsg", but "mcsg" has all of the core functionality of the Motif tool.) On a Win32 machine such as Windows NT, you will also end up with both "mcsg" and "mcbridge".
  • Solution 1:

    Have your system administrator install MPI in a proper system directory so that MALOC (and other AUTOCONF-based codes) can find it!

  • Solution 2:
    1. Find the location of the OpenGL libraries and headers and the Motif libraries and headers on your system, either by asking your sysadmin, poking around yourself, or (if you have it) using the "locate" utility:
          locate libGL.a
          locate libGLU.a
          locate libGLw.a
          locate gl.h
          locate glu.h
          locate GLwDrawA.h
          locate libXm.a
          locate Xm.h
      On my Redhat6.2 Linux box with LessTif supplying Motif, XiGraphics' supplying two of the OpenGL libraries (libGL and libGLU), and Mesa supplying the third (libGLw), the following output is produced:
          mc:~% locate libGL.a
          mc:~% locate libGLU.a
          mc:~% locate libGLw.a
          mc:~% locate gl.h
          mc:~% locate glu.h
          mc:~% locate GLwDrawA.h
          mc:~% locate libXm.a
          mc:~% locate Xm.h
      Therefore, my OpenGL libraries are installed as:
      and the associated OpenGL headers are installed as:
      My Motif library is installed as:
      and the associated Motif headers are installed as:
    2. Before running the configure script, preset the environment variables:
      to point to the directories containing:
          libGL.a,  gl.h,
          libGLU.a, glu.h,
          libGLw.a, GLwDrawA.h,
          libXm.a,  Xm.h,
      respectively. Under bash, using the results from the example above, I would do this as follows:
          export FETK_GL_LIBRARY=/usr/lib
          export FETK_GL_INCLUDE=/usr/include
          export FETK_GLU_LIBRARY=/usr/lib
          export FETK_GLU_INCLUDE=/usr/include
          export FETK_GLW_LIBRARY=/usr/local/lib
          export FETK_GLW_INCLUDE=/usr/local/include
          export FETK_MOTIF_LIBRARY=/usr/X11R6/lib
          export FETK_MOTIF_INCLUDE=/usr/X11R6/include
      The configure script should now report that it successfully found the libraries and headers, and then SG should compile without error.

Author Information

SG (Socket Graphics) was conceived, designed, and implemented over several years by Michael Holst, beginning with an initial implementation in 1994. Various colleagues have contributed ideas and/or code to SG (see the credits list below).
    SG (Socket Graphics)
    Copyright (C) 1994-2010

    Michael Holst               TELE:  (858) 534-4899
    Department of Mathematics   FAX:   (858) 534-5273
    UC San Diego, AP&M 5739     EMAIL:
    La Jolla, CA 92093 USA      WEB:
SG was designed to be a portable networked visualization tool for use in the development of MC (Manifold Code), an adaptive multilevel finite element package also developed by Michael Holst. It is also used by Randy Bank as the primary visualization tool for PLTMG. Both SG and MC are written on top of a low-level abstraction layer called MALOC (Minimal Abstraction Layer for Object-oriented C), also developed by Michael Holst. SG was developed almost entirely on a home-grown 90Mhz Pentium PC running various flavors of Linux and [Free|Net|Open]BSD, using primarily GNU, BSD, and other free software development tools. Most of the development occurred during the hours of 10pm to 2am on a daily basis for several years, under heavy influence of Starbuck's coffee, with helpful advice provided by Mac and Mochi (two cats knowledgable in socket programming and numerical analysis).

SG was released under the GNU GPL (GNU General Public License) beginning with the initial implementation in 1994, and continues to be released under this license. What this means is that like all GNU software, SG is freely redistributable in source code form following the rules outlined in the text of the GNU GPL. You should have received a copy of the GNU GPL with this distribution of SG; a copy can be found here. If you did not receive a copy of the GNU GPL, please write to me and also write to: The Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

Software included in the SG source code package

A complete roadmap to the source code forming the SG package can be found above. While the core SG classes were developed primarily by Michael Holst, some additional software is currently included with SG:
    sg/src/vgl/vglm.c    - Motif Variant of vgl (joint Bank/Holst effort)
    sg/src/vgl/oglps.c   - Perfect PS generation (joint Bank/Holst effort)
    sg/src/gl/*          - B. Paul's MesaGL (the GL library)
    sg/src/glu/*         - B. Paul's MesaGLU (the GLU library)
    sg/src/glw/*         - SGI's OpenGL widgets (the GLw library)
The extra conditionally-build libraries provide the complete OpenGL capability that SG requires in order to function, if these libraries are not available on the particular platform. Under normal circumstances, these three libraries will not have to be built; the OpenGL API they provide is completely software-based, and will be slower than native hardware-accelerated OpenGL which is normally available on modern PCs, Macs, and SGI platforms.


Below is a credits list for the people that have contributed to SG in one way or another. The fields below follow the credits file format used in the Linux kernel CREDITS file to allow for easy manipulation via shell scripts. The fields are as follows:
          N: name of contributor
          E: email address
          W: web address
          P: PGP key ID and fingerprint
          D: description of primary contributions
          S: snail-mail address

N: Michael Holst
P: 1024/0xB5212DCD
D: sg/*                      -- The package structure
D: sg/acconfig.h             -- The platform abstraction information
D: sg/           -- The GNU autoconf/automake structure
D: sg/config/*               -- The GNU autoconf/automake shell scripts
D: sg/doc/*                  -- The package documentation
D: sg/examples/*             -- The package examples
D: sg/src/aaa_inc/*          -- Library header build structure
D: sg/src/aaa_lib/*          -- Static and shared library build structure
D: sg/src/base/*             -- M. Holst's SG Foundation headers
D: sg/src/ogl/*              -- M. Holst's OpenGL-based trackball rotator
D: sg/src/vgl/*              -- M. Holst's window system abstraction layer
D: sg/src/gl/*               -- The libGL wrapper
D: sg/src/glu/*              -- The libGLU wrapper
D: sg/src/glw/*              -- The libGLw wrapper
D: sg/tools/*                -- Tools built on the libraries
S: Department of Mathematics
S: UC San Diego, AP&M 5739
S: La Jolla, CA 92093 USA

N: Randolph E. Bank
D: sg/src/vgl/vglm.c         -- Vglm Class (Motif variant; joint w/ Holst)
D: sg/src/ogl/oglps.c        -- OglPS Class (Perfect PS; joint w/ Holst)
S: Department of Mathematics
S: UC San Diego
S: La Jolla, CA 92093 USA

N: Steve Bond
D: sg/sg.spec                -- RPM support (for building src/binary RPMs)
S: Department of Mathematics
S: UC San Diego
S: La Jolla, CA 92093 USA

Contacting the Author

If you have questions or comments about SG, please feel free to contact me at

Copyright and Terms of Use Please acknowledge your use of SG and FETK by citing:
  • M. Holst, Adaptive numerical treatment of elliptic systems on manifolds. Advances in Computational Mathematics, 15 (2001), pp. 139-191.

This version of SG is distributed under the following guidelines:
  • SG (Socket Graphics)
    Copyright (C) 1994-2010 Michael Holst

    This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

    You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.


The GPL (GNU General Public License) below is copyrighted by the Free Software Foundation. However, the instance of software that it refers to, my package in this case, is copyrighted by myself as the author of the package. Any additional software that I distribute with my software is copyrighted by the authors of those pieces of software (see the individual source files for author information). ---Michael Holst
		       Version 2, June 1991

 Copyright (C) 1989, 1991 Free Software Foundation, Inc.
 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 Everyone is permitted to copy and distribute verbatim copies
 of this license document, but changing it is not allowed.


  The licenses for most software are designed to take away your
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gratis or for a fee, you must give the recipients all the rights that
you have.  You must make sure that they, too, receive or can get the
source code.  And you must show them these terms so they know their

  We protect your rights with two steps: (1) copyright the software, and
(2) offer you this license which gives you legal permission to copy,
distribute and/or modify the software.

  Also, for each author's protection and ours, we want to make certain
that everyone understands that there is no warranty for this free
software.  If the software is modified by someone else and passed on, we
want its recipients to know that what they have is not the original, so
that any problems introduced by others will not reflect on the original
authors' reputations.

  Finally, any free program is threatened constantly by software
patents.  We wish to avoid the danger that redistributors of a free
program will individually obtain patent licenses, in effect making the
program proprietary.  To prevent this, we have made it clear that any
patent must be licensed for everyone's free use or not licensed at all.

  The precise terms and conditions for copying, distribution and
modification follow.


  0. This License applies to any program or other work which contains
a notice placed by the copyright holder saying it may be distributed
under the terms of this General Public License.  The "Program", below,
refers to any such program or work, and a "work based on the Program"
means either the Program or any derivative work under copyright law:
that is to say, a work containing the Program or a portion of it,
either verbatim or with modifications and/or translated into another
language.  (Hereinafter, translation is included without limitation in
the term "modification".)  Each licensee is addressed as "you".

Activities other than copying, distribution and modification are not
covered by this License; they are outside its scope.  The act of
running the Program is not restricted, and the output from the Program
is covered only if its contents constitute a work based on the
Program (independent of having been made by running the Program).
Whether that is true depends on what the Program does.

  1. You may copy and distribute verbatim copies of the Program's
source code as you receive it, in any medium, provided that you
conspicuously and appropriately publish on each copy an appropriate
copyright notice and disclaimer of warranty; keep intact all the
notices that refer to this License and to the absence of any warranty;
and give any other recipients of the Program a copy of this License
along with the Program.

You may charge a fee for the physical act of transferring a copy, and
you may at your option offer warranty protection in exchange for a fee.

  2. You may modify your copy or copies of the Program or any portion
of it, thus forming a work based on the Program, and copy and
distribute such modifications or work under the terms of Section 1
above, provided that you also meet all of these conditions:

    a) You must cause the modified files to carry prominent notices
    stating that you changed the files and the date of any change.

    b) You must cause any work that you distribute or publish, that in
    whole or in part contains or is derived from the Program or any
    part thereof, to be licensed as a whole at no charge to all third
    parties under the terms of this License.

    c) If the modified program normally reads commands interactively
    when run, you must cause it, when started running for such
    interactive use in the most ordinary way, to print or display an
    announcement including an appropriate copyright notice and a
    notice that there is no warranty (or else, saying that you provide
    a warranty) and that users may redistribute the program under
    these conditions, and telling the user how to view a copy of this
    License.  (Exception: if the Program itself is interactive but
    does not normally print such an announcement, your work based on
    the Program is not required to print an announcement.)

These requirements apply to the modified work as a whole.  If
identifiable sections of that work are not derived from the Program,
and can be reasonably considered independent and separate works in
themselves, then this License, and its terms, do not apply to those
sections when you distribute them as separate works.  But when you
distribute the same sections as part of a whole which is a work based
on the Program, the distribution of the whole must be on the terms of
this License, whose permissions for other licensees extend to the
entire whole, and thus to each and every part regardless of who wrote it.

Thus, it is not the intent of this section to claim rights or contest
your rights to work written entirely by you; rather, the intent is to
exercise the right to control the distribution of derivative or
collective works based on the Program.

In addition, mere aggregation of another work not based on the Program
with the Program (or with a work based on the Program) on a volume of
a storage or distribution medium does not bring the other work under
the scope of this License.

  3. You may copy and distribute the Program (or a work based on it,
under Section 2) in object code or executable form under the terms of
Sections 1 and 2 above provided that you also do one of the following:

    a) Accompany it with the complete corresponding machine-readable
    source code, which must be distributed under the terms of Sections
    1 and 2 above on a medium customarily used for software interchange; or,

    b) Accompany it with a written offer, valid for at least three
    years, to give any third party, for a charge no more than your
    cost of physically performing source distribution, a complete
    machine-readable copy of the corresponding source code, to be
    distributed under the terms of Sections 1 and 2 above on a medium
    customarily used for software interchange; or,

    c) Accompany it with the information you received as to the offer
    to distribute corresponding source code.  (This alternative is
    allowed only for noncommercial distribution and only if you
    received the program in object code or executable form with such
    an offer, in accord with Subsection b above.)

The source code for a work means the preferred form of the work for
making modifications to it.  For an executable work, complete source
code means all the source code for all modules it contains, plus any
associated interface definition files, plus the scripts used to
control compilation and installation of the executable.  However, as a
special exception, the source code distributed need not include
anything that is normally distributed (in either source or binary
form) with the major components (compiler, kernel, and so on) of the
operating system on which the executable runs, unless that component
itself accompanies the executable.

If distribution of executable or object code is made by offering
access to copy from a designated place, then offering equivalent
access to copy the source code from the same place counts as
distribution of the source code, even though third parties are not
compelled to copy the source along with the object code.

  4. You may not copy, modify, sublicense, or distribute the Program
except as expressly provided under this License.  Any attempt
otherwise to copy, modify, sublicense or distribute the Program is
void, and will automatically terminate your rights under this License.
However, parties who have received copies, or rights, from you under
this License will not have their licenses terminated so long as such
parties remain in full compliance.

  5. You are not required to accept this License, since you have not
signed it.  However, nothing else grants you permission to modify or
distribute the Program or its derivative works.  These actions are
prohibited by law if you do not accept this License.  Therefore, by
modifying or distributing the Program (or any work based on the
Program), you indicate your acceptance of this License to do so, and
all its terms and conditions for copying, distributing or modifying
the Program or works based on it.

  6. Each time you redistribute the Program (or any work based on the
Program), the recipient automatically receives a license from the
original licensor to copy, distribute or modify the Program subject to
these terms and conditions.  You may not impose any further
restrictions on the recipients' exercise of the rights granted herein.
You are not responsible for enforcing compliance by third parties to
this License.

  7. If, as a consequence of a court judgment or allegation of patent
infringement or for any other reason (not limited to patent issues),
conditions are imposed on you (whether by court order, agreement or
otherwise) that contradict the conditions of this License, they do not
excuse you from the conditions of this License.  If you cannot
distribute so as to satisfy simultaneously your obligations under this
License and any other pertinent obligations, then as a consequence you
may not distribute the Program at all.  For example, if a patent
license would not permit royalty-free redistribution of the Program by
all those who receive copies directly or indirectly through you, then
the only way you could satisfy both it and this License would be to
refrain entirely from distribution of the Program.

If any portion of this section is held invalid or unenforceable under
any particular circumstance, the balance of the section is intended to
apply and the section as a whole is intended to apply in other

It is not the purpose of this section to induce you to infringe any
patents or other property right claims or to contest validity of any
such claims; this section has the sole purpose of protecting the
integrity of the free software distribution system, which is
implemented by public license practices.  Many people have made
generous contributions to the wide range of software distributed
through that system in reliance on consistent application of that
system; it is up to the author/donor to decide if he or she is willing
to distribute software through any other system and a licensee cannot
impose that choice.

This section is intended to make thoroughly clear what is believed to
be a consequence of the rest of this License.

  8. If the distribution and/or use of the Program is restricted in
certain countries either by patents or by copyrighted interfaces, the
original copyright holder who places the Program under this License
may add an explicit geographical distribution limitation excluding
those countries, so that distribution is permitted only in or among
countries not thus excluded.  In such case, this License incorporates
the limitation as if written in the body of this License.

  9. The Free Software Foundation may publish revised and/or new versions
of the General Public License from time to time.  Such new versions will
be similar in spirit to the present version, but may differ in detail to
address new problems or concerns.

Each version is given a distinguishing version number.  If the Program
specifies a version number of this License which applies to it and "any
later version", you have the option of following the terms and conditions
either of that version or of any later version published by the Free
Software Foundation.  If the Program does not specify a version number of
this License, you may choose any version ever published by the Free Software

  10. If you wish to incorporate parts of the Program into other free
programs whose distribution conditions are different, write to the author
to ask for permission.  For software which is copyrighted by the Free
Software Foundation, write to the Free Software Foundation; we sometimes
make exceptions for this.  Our decision will be guided by the two goals
of preserving the free status of all derivatives of our free software and
of promoting the sharing and reuse of software generally.





	    How to Apply These Terms to Your New Programs

  If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these terms.

  To do so, attach the following notices to the program.  It is safest
to attach them to the start of each source file to most effectively
convey the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.

    (one line to give the program's name and a brief idea of what it does.)
    Copyright (C) 19yy  < name of author >

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

Also add information on how to contact you by electronic and paper mail.

If the program is interactive, make it output a short notice like this
when it starts in an interactive mode:

    Gnomovision version 69, Copyright (C) 19yy name of author
    Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
    This is free software, and you are welcome to redistribute it
    under certain conditions; type `show c' for details.

The hypothetical commands `show w' and `show c' should show the appropriate
parts of the General Public License.  Of course, the commands you use may
be called something other than `show w' and `show c'; they could even be
mouse-clicks or menu items--whatever suits your program.

You should also get your employer (if you work as a programmer) or your
school, if any, to sign a "copyright disclaimer" for the program, if
necessary.  Here is a sample; alter the names:

  Yoyodyne, Inc., hereby disclaims all copyright interest in the program
  `Gnomovision' (which makes passes at compilers) written by James Hacker.

  < signature of Ty Coon >, 1 April 1989
  Ty Coon, President of Vice

This General Public License does not permit incorporating your program into
proprietary programs.  If your program is a subroutine library, you may
consider it more useful to permit linking proprietary applications with the
library.  If this is what you want to do, use the GNU Library General
Public License instead of this License.