Surface Evolver Newsletter no. 13

                    Surface Evolver Newsletter Number 13
                              April 30, 1996

                   Editor: Ken Brakke, brakke@geom.umn.edu

Contents
  Version 2.00 released
  New Features
  Minor backward compatibilities
  Request for web links
  Bibliography

Version 2.00 released

  Version 2.00 is now available from geom.umn.edu by ftp, or from
  http://www.geom.umn.edu/software/download/evolver/evolver.html, or from 
  my own home page, http://www.susqu.edu/facstaff/b/brakke/evolver/evolver.htm.
  The version number is 2.00 mostly because the last version was 1.99.
  No big rewrite, but there are some major new features.

  Anybody who happened to get a pre-release version 2.00, dated before
  April 30, should get the official release, as there have been a few
  bug fixes.

New features

  There are now versions for Windows-95 and Windows-NT.

  Much of the manual has been translated into HTML form, which
  can be browsed with standard Web browsers.  I've only tested
  it with Netscape, and I don't make any guarantees about how
  other browsers will do. But it's mostly just basic text.  No
  pictures or fancy graphics yet.

  The Evolver has a "help" command which will print extracts
  from the HTML files, based on keyword.

  Error and warning messages are numbered.  Someday there may be
  helpful documentation of all the error messages, but for now the
  numbers are useful to me to pinpoint the exact error.
  
  For precision freaks, higher-order Lagrange elements have been
  added (LINEAR is Lagrange order 1, QUADRATIC is Lagrange order 2).

  Also for precision freaks, if you compile with -DLONGDOUBLE then
  all floating point calculations will be in your system's
  long double type, which may provide up to 30 significant digits.

  There is a "postscript" command that prints postscript files 
  without asking you any questions.  Various toggles control the
  options.

  The distribution has a bunch of sample command files.  One is
  "vrml.cmd", which writes a VRML file suitable for your web site.

  The "interp_bdry_param" toggle causes boundary parameters to be
  interpolated rather than extrapolated when refining an edge.

  The 'X' command shows the dictionary of extra attributes, including
  those used internally.

  There is a "return" command for exiting the current command, or causing
  a subcommand to return to its parent command.

  When using the -q option (which converts everything to named quantities),
  only the user's explicitly defined quantities are shown by the 'A' and
  'v' commands.  The "show_all_quantities" toggle will cause those commands
  to list all quantities.
  
Minor backward compatibilities

  Fixed facets, edges, and vertices are now included when calculating 
  energies and areas.

  Evolver now enforces in the datafile the rule that all variable names 
  must be at least two characters.

  The term "variable_parameter", introduced in version 1.99, has been
  replaced by the more descriptive term "optimizing_parameter".

  There have been some changes in the internal workings of the 'g'
  command that might cause slightly different numerical values. 

Request for web links

  If you have web pages relevant to the Surface Evolver, please let
  me know.  One site with several Evolver examples involving liquid
  solder is http://www.ctcms.nist.gov/programs/solder/.

Bibliography

  Xavier Michalet and David Bensimon, "Observation of stable
  shapes and conformal diffusion in genus 2 vesicles",
  Science, vol. 269 (4 Aug 1995), 666-668.
  Tests hypothesis that some cell membranes are shaped by
  an elastic bending energy (i.e. squared mean curvature)
  by comparing Evolver surfaces to actual vesicles.

  R. Phelan, D. Weaire, and K. Brakke, "Computation of equilibrium
  foam structures using the Surface Evolver", Experimental Mathematics,
  vol. 4 no. 3 (1995), 181-192.  Discusses foam structures that beat
  Kelvin's tetrakaidecahedral foam, including the now-famous
  Weaire-Phelan structure.  Also describes the stability of the 
  structures as liquid is added to form Plateau borders.  Color pictures.