$Id: README,v 1.2 2000-12-10 14:16:34 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 depending on your operating system. In
the following, 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, you have to select the 'File->Open' menu, and
choose 't1.geo' in the input field. To perform the mesh generation,
you have to go to the mesh module (by selecting 'Module->Mesh' in the
menu bar) 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
'?->Short_Help' 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, here
for example with:

> gmsh t1.geo

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

Note: to define new geometries, if it is often handy to define the
variables and the points directly in the input files, it is almost
always simpler 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
'Module->Geometry' in the menu bar, 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' when
you're done. 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 user 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 'Module->Post_Processing'), two
view buttons will appear, respectively labeled "a scalar map" and "a
vector map". A left mouse click will toggle the visibility of the
selected view. A right mouse click provides access to the view's
options:
- Reload: reloads the file from which the view was loaded 
- Remove: removes the view 
- Duplicate: makes a copy of the view (without duplicating the data) 
- Lighting: activates/deactivates lighting for the view 
- Scale: gives access to the scale menu (range definition, iso-value
  choice, ...)
- Color: defines the color map for the view
- Offset: permits to move the view around, and to make elevation 
  maps
- Vector display: changes vector attributes
- Time step: selects the displayed time step
- Export as background mesh: exports the map, considered as an
  error map, as a background mesh, i.e. as a characteristic length map
- Apply as current bg mesh: applies the view as the current background 
  mesh.  
If you want the modifications made to one view to affect also all 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. The current options can be saved
into a file by selecting 'File->Save_Options_as'. For UNIX versions,
all user interface options can be changed in a standard X resource file
('.gmshrc' in your home directory or app-defaults directory, or
'.Xdefaults'). Use 'editres' to get the full widget tree and
associated resources.



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