Surface Evolver Newsletter no. 15

                    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 here.

Evolver web page
  My Evolver home page
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 for more.