# Surface Evolver Newsletter no. 15

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                        Surface Evolver Newsletter Number 15
                                  August 10, 1998

                       Editor: Ken Brakke, brakke@susqu.edu

    Contents
      Version 2.10b
      New features and changes
      Geometry Center shutdown
      Evolver web page
      Geomview bug

    Version 2.10b
      Surface Evolver Version 2.10 is now available.  It's been a while
    since the last version, 2.01, so I bumped the version number up to
    2.10; actually a few more changes in the last month bring the version
    number to 2.10b.  No major changes, just bug fixes and some minor new features.
    The Windows NT/95/98 version has much improved OpenGL graphics.
    The Mac version is still 2.01, since I don't have access to a Mac
    with a compiler.

    New features and changes

       Most of the changes have been bug fixes, tweaks, and special purpse
       features for various users.  Here are general interest updates:

       In the datafile, making an edge FIXED no longer fixes its endpoints.
       This is compatible with how fixed facets and run-time fixing edges
       have always worked.  If you relied on fixed edges making their
       endpoints fixed in any datafiles, and didn't explicitly fix the
       endpoints, you should revise your datafiles.  One cheap way to
       do that is to put a command "foreach edge ee where fixed do fix
       ee.vertex" in the READ section at the end of the datafile.  Dump
       files do not need to be fixed.

       The "load" command now terminates the command containing it, since
       technically the command was wiped out along with the old surface.
       "Load" is useful as the last command in a script, or in a script
       used as stdin by redirection.

       Window NT/95/98 version using OpenGL has much better graphics.
       Can rotate, translate, or zoom with left mouse button, pick elements
       with right button, even do cross-eyed stereo.
       Type 'h' in the graphics window for a command summary.
       Also made catenoid icon for the program.

       C-style assignment operators +=, -=, *=, /= work where reasonable.

       Level set constraint formulas and parameterized boundary formulas
       may contain vertex extra attributes, which can be very useful
       in customizing formulas to vertices, for example keeping each
       vertex at its own z level.

       Parameterized boundaries can have energy and content integrals,
       in the same way level set constraints have had.

       Command output redirection to a file using >> for append, >>>
        for overwrite.

       A variable can be toggled between optimizing or non-optimizing at run
       time with "unfix varname" and "fix varname" respectively.

       "keep_macros" in datafile header keeps macros active after datafile.

       Command line option -i will keep element ids the same as in the
       datafile, rather than renumbering consecutively as is the default.

       If you want to reorder elements in the internal lists (the way
       elements are listed by, say, 'list vertices', you can define
       the extra attributes vertex_order_key, edge_order_key,
       facet_order_key, body_order_key, facetedge_order_key, give them
       all appropriate values, and then give the command reorder_storage.
       See reorder.cmd in the distribution fe directory.

       'renumber_all' renumbers elements in internal list order.

       Read-only internal variable 'random' for random numbers
       uniformly distributed between 0 and 1.

       Added warnings about using keywords as identifiers in the datafile.
       The datafile will still run, but your commands will misinterpret
       those identifiers.

       All keywords are in the on-line help.  Do 'help "keyword"' if you
       want to check on a potential keyword.  'help' also recognizes
       identifiers defined by the user in the current surface.  For
       testing in scripts, there is a function is_defined(stringexpr)
       that returns 1 if a name is already in use, 0 if not.

       In the datafile, making an edge FIXED no longer fixes its endpoints.
       This is compatible with how fixed facets and fixing edges at run
       time have always worked.

       For named methods that logically depend on the orientation of the
       element (i.e. facet_vector_integral, etc.), the relative orientation
       of the element when the method is applied is recorded. Default is
       positive in the datafile, unless a '-' is added after the name of
       a method or quantity applied to an individual element.

    Geometry Center shutdown
      The Geometry Center, which has sponsored much of my Surface Evolver
    work, will be shutting down in August.  The Geometry Center web site
    and ftp site should continue to exist for at least a year.  My email
    address brakke@geom.umn.edu should continue to work.  However, my
    preferred email address is now brakke@susqu.edu, and the home Evolver
    web site is http://www.susqu.edu/facstaff/b/brakke/evolver.

    Evolver web page
      My Evolver home page http://www.susqu.edu/facstaff/b/brakke/evolver
    has downloads, papers, and many example datafiles.  The examples have
    various degrees of commentary, but they generally have at least a
    sample evolution script.

    Geomview bug
      Geomview version 1.6 has a bug in picking that prevents it from
    reporting the correct elements to Evolver.  This bug has been
    fixed in geomview patch 1.6p7, which unfortunately hasn't been
    posted to the geomview site.  See the Evolver home page
    http://www.susqu.edu/facstaff/b/brakke/evolver for more.

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