tutorial

$Id: README,v 1.8 2001-03-01 08:04:15 geuzaine Exp $

Here are the examples in the Gmsh tutorial. These examples are
commented (both C and C++-style comments can be used in Gmsh input
files) and should introduce new features gradually, starting with
t1.geo.

(The tutorial does not explain the mesh and post-processing file
formats. See the FORMATS file for this.)

There are two ways to actually run these examples with Gmsh. (The
operations to run Gmsh may vary according to your operating system. In
the folowing examples, we will assume that you're working with a
UNIX-like shell.) The first working mode of Gmsh is the interactive
graphical mode. To launch Gmsh in interactive mode, just type

> gmsh

at the prompt on the command line. This will open two windows: the
graphic window (with a status bar at the bottom) and the menu window
(with a menu bar and some context dependent buttons). To open the
first tutorial file, select the 'File->Open' menu, and choose 't1.geo'
in the input field. To perform the mesh generation, go to the mesh
module (by selecting 'Mesh' in the module menu) and choose the
required dimension in the context-dependent buttons ('1D' will mesh
all the curves; '2D' will mesh all the surfaces ---as well as all the
curves if '1D' was not called before; '3D' will mesh all the volumes
---and all the surfaces if '2D' was not called before). To save the
resulting mesh, select 'File->Save_Mesh' in the menu bar. The default
mesh file name is based on the name of the first input file on the
command line (or 'unnamed' if there wasn't any input file given), with
an appended extension depending on the mesh format.

Note: nearly all the interactive commands have shortcuts. Select
'Help->Shortcuts' in the menu bar to learn about these shortcuts.

Instead of opening the tutorial with the 'File->Open' menu, it is
often more convenient to put the file name on the command line, for
example with:

> gmsh t1.geo

(The '.geo' extension can also be omitted.)

Note: Even if it is often handy to define the variables and the points
directly in the input files (you may use any text editor for this
purpose, e.g. Wordpad on Windows, or Emacs on Unix), it is almost
always more simple to define the curves, the surfaces and the volumes
interactively. To do so, just follow the context dependent buttons in
the Geometry module. For example, to create a line, select 'Geometry'
in the module menu, and then select 'Elementary, Add, Create,
Line'. You will then be asked (in the status bar of the graphic
window) to select a list of points, and to click 'e' to finish the
selection (or 'q' to abort it). Once the interactive command is
completed, a string is automatically added at the end of the currently
opened project file.


The second operating mode for Gmsh is the non-interactive mode. In
this mode, there is no graphical user interface, and all operations
are performed without any interaction. To mesh the first tutorial in
non-interactive mode, just type:

> gmsh t1.geo -2

Several files can be loaded simultaneously in Gmsh. The first one
defines the project, while the others are appended ("merged") to this
project. You can merge such files with the 'File->Merge' menu, or by
directly specifying the names of the files on the command line. This
is most useful for post-processing purposes. For example, to merge the
post-processing views contained in the files 'view1.pos' and
'view2.pos' together with the first tutorial 't1.geo', you can type
the following line on the command line:

> gmsh t1.geo view1.pos view2.pos

In the Post-Processing module (select 'Post_Processing' in the module
menu), two view buttons will appear, respectively labeled "a scalar
map" and "a vector map". A left mouse click toggles the visibility of
the selected view. A right mouse click provides access to the view's
options. If you want the modifications made to one view to affect also
all the other views, select the 'Link all views' option in the
'Options->Post-Processing' menu.

Note: all the options specified interactively can also be directly
specified in the ascii input files. All available options, with their
current values, can be saved into a file by selecting
'File->Save_as->GEO complete options', or simply viewed by pressing
the '?' button in the status bar. To save the current options as the
default options for all future Gmsh sessions, use the
'File->Save_Options' menu.


OK, that's all, folks. Enjoy the tutorial.