# Surface Evolver Newsletter no. 13

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                        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.

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