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\input texinfo.tex @c -*-texinfo-*-
@c Gmsh - Copyright (C) 1997-2009 C. Geuzaine, J.-F. Remacle
@c
@c See the LICENSE.txt file for license information. Please report all
@c bugs and problems to <gmsh@geuz.org>.
@c
@c =========================================================================
@c
@c This is the Gmsh documentation texinfo source file
@c
@c Things to do -> "Ctrl+s todo:"
@c
@c Indexing:
@c
@c * @cindex = concept index, e.g. "File formats"
@c * @tindex + @findex = type + function index, e.g. "Sqrt(expression)"
@c
@c Before release, run C-u C-c C-u C-a in GNU Emacs. This updates all node
@c pointers and menus.
@c
@c =========================================================================
@c %**start of header
@setfilename gmsh.info
@set GMSH-VERSION 2.3
@set COPYRIGHT @copyright{} 1997-2009 Christophe Geuzaine, Jean-Fran@,{c}ois Remacle
@c
@settitle Gmsh @value{GMSH-VERSION}
@footnotestyle separate
@setchapternewpage odd
@paragraphindent 0
@finalout
@c %**end of header
@c merge function index into type index
@syncodeindex fn tp
@c =========================================================================
@c Info directives
@c =========================================================================
@ifinfo
@dircategory Math
@direntry
* Gmsh: (gmsh). 3D finite element mesh generator with built-in pre- and
post-processing facilities
@end direntry
@noindent
This is the @cite{Gmsh Reference Manual} for Gmsh @value{GMSH-VERSION}
(@today{}).
@noindent
Copyright @value{COPYRIGHT}
@end ifinfo
@c =========================================================================
@c Title page
@c =========================================================================
@shorttitlepage Gmsh
@titlepage
@title Gmsh Reference Manual
@subtitle The documentation for Gmsh @value{GMSH-VERSION}
@subtitle A finite element mesh generator with built-in pre- and post-processing facilities
@subtitle
@subtitle @today{}
@author Christophe Geuzaine
@author Jean-Fran@,{c}ois Remacle
@page
@vskip 0pt plus 1filll
Copyright @value{COPYRIGHT}
@sp 1
Permission is granted to make and distribute verbatim copies of this manual
provided the copyright notice and this permission notice are preserved on
all copies.
@end titlepage
@c =========================================================================
@c Table of contents
@c =========================================================================
@summarycontents
@contents
@c =========================================================================
@c Top node (for all output, except TeX)
@c =========================================================================
@ifnottex
@node Top, Copying conditions, (dir), (dir)
@top Gmsh
Christophe Geuzaine and Jean-Fran@,{c}ois Remacle
Gmsh is an automatic 3D finite element mesh generator with build-in pre-
and post-processing facilities. This is the @cite{Gmsh Reference Manual}
for Gmsh @value{GMSH-VERSION} (@today{}).
@end ifnottex
@c =========================================================================
@c Master menu
@c =========================================================================
@menu
* Copying conditions:: Terms and conditions of use.
* Overview:: What is Gmsh?
* How to read this manual?:: Which parts of this manual should you read (if any)?
* General tools:: Description of general commands and options.
* Geometry module:: Description of all Geometry commands.
* Mesh module:: Description of all Mesh commands.
* Solver module:: Description of all Solver commands.
* Post-processing module:: Description of all Post-Processing commands.
* Tutorial:: A step-by-step tutorial.
* Running Gmsh:: How to run Gmsh on your operating system.
* File formats:: Input and output file formats.
* Programming notes:: Random notes for developers.
* Bugs and versions:: Contact information and ChangeLog
* Tips and tricks:: Some tips to make your life easier with Gmsh.
* Frequently asked questions:: The Gmsh FAQ
* License:: Complete copy of the license.
* Concept index:: Index of concepts.
* Syntax index:: Index of reserved keywords in the Gmsh language.
@detailmenu
--- The Detailed Node Listing ---
Overview
* Geometry::
* Mesh::
* Solver::
* Post-processing::
* What Gmsh is pretty good at::
* and what Gmsh is not so good at::
How to read this reference manual?
* Syntactic rules::
General tools
* Comments::
* Expressions::
* Operators::
* Built-in functions::
* User-defined functions::
* Loops and conditionals::
* General commands::
* General options::
Expressions
* Floating point expressions::
* Character expressions::
* Color expressions::
Geometry module
* Geometry commands::
* Geometry options::
Geometry commands
* Points::
* Lines::
* Surfaces::
* Volumes::
* Extrusions::
* Transformations::
* Miscellaneous geometry commands::
Mesh module
* Elementary vs physical entities::
* Mesh commands::
* Mesh options::
Mesh commands
* Characteristic lengths::
* Structured grids::
* Miscellaneous mesh commands::
Solver module
* Solver options::
* Solver example::
Post-processing module
* Post-processing commands::
* Post-processing plugins::
* Post-processing options::
Tutorial
* t1.geo::
* t2.geo::
* t3.geo::
* t4.geo::
* t5.geo::
* t6.geo::
* t7.geo::
* t8.geo::
* t9.geo::
Running Gmsh
* Interactive mode::
* Non-interactive mode::
* Command-line options::
* Mouse actions::
* Keyboard shortcuts::
File formats
* MSH ASCII file format::
* MSH binary file format::
* Node ordering::
* Legacy formats::
Legacy formats
* MSH file format version 1.0::
* POS ASCII file format::
* POS binary file format::
Programming notes
* Main code structure::
* Coding style::
* Option handling::
Bugs, versions and credits
* Bugs::
* Versions::
* Credits::
@end detailmenu
@end menu
@c =========================================================================
@c Copying Conditions
@c =========================================================================
@node Copying conditions, Overview, Top, Top
@unnumbered Copying conditions
@cindex Copyright
@cindex License
@include copying.texi
@c =========================================================================
@c Overview
@c =========================================================================
@node Overview, How to read this manual?, Copying conditions, Top
@chapter Overview
@cindex Introduction
@cindex Overview
Gmsh is an automatic three-dimensional finite element mesh generator
with built-in pre- and post-processing facilities. Its design goal is to
provide a simple meshing tool for academic problems with parametric
input and advanced visualization capabilities.
Gmsh is built around four modules: geometry, mesh, solver and
post-processing. All geometrical, mesh, solver and post-processing
instructions are prescribed either interactively using the graphical
user interface (GUI) or in text files using Gmsh's own scripting
language. Interactive actions generate language bits in the input
files, and vice versa. This makes it possible to automate all
treatments, using loops, conditionals and external system calls. A briefdescription of the four modules is given hereafter.
@menu
* Geometry::
* Mesh::
* Solver::
* Post-processing::
* What Gmsh is pretty good at::
* and what Gmsh is not so good at::
@end menu
@c -------------------------------------------------------------------------
@c Geometry: geometrical entity definition
@c -------------------------------------------------------------------------
@node Geometry, Mesh, Overview, Overview
@section Geometry: geometrical entity definition
Gmsh uses a boundary representation (``b-rep'') to describe geometries.
Models are created in a bottom-up flow by successively defining points,
oriented lines (line segments, circles, ellipses, splines, @dots{}),
oriented surfaces (plane surfaces, ruled surfaces, triangulated
surfaces, @dots{}) and volumes. Compound groups of geometrical entities
(called ``physical groups'') can also be defined, based on these
elementary geometric entities. Gmsh's scripting language allows all
geometrical entities to be fully parametrized.
@c -------------------------------------------------------------------------
@c Mesh: finite element mesh generation
@c -------------------------------------------------------------------------
@node Mesh, Solver, Geometry, Overview
@section Mesh: finite element mesh generation
A finite element mesh is a tessellation of a given subset of the
three-dimensional space by elementary geometrical elements of various
shapes (in Gmsh's case: lines, triangles, quadrangles, tetrahedra,
prisms, hexahedra and pyramids), arranged in such a way that if two of
them intersect, they do so along a face, an edge or a node, and never
otherwise. All the finite element meshes produced by Gmsh are considered
as ``unstructured'', even if they were generated in a ``structured'' way
(e.g., by extrusion). This implies that the elementary geometrical
elements are defined only by an ordered list of their nodes but that no
predefined order relation is assumed between any two elements.
The mesh generation is performed in the same bottom-up flow as the
geometry creation: lines are discretized first; the mesh of the lines is
then used to mesh the surfaces; then the mesh of the surfaces is used to
mesh the volumes. In this process, the mesh of an entity is only
constrained by the mesh of its boundary@footnote{For example, in three
dimensions:
@itemize @bullet
@item
the triangles discretizing a surface will be forced to be faces of
tetrahedra in the final 3D mesh only if the surface is part of the
boundary of a volume;
@item
the line elements discretizing a curve will be forced to be edges of
tetrahedra in the final 3D mesh only if the curve is part of the
boundary of a surface, itself part of the boundary of a volume;
@item
a single node discretizing a point in the middle of a volume will be
forced to be a vertex of one of the tetrahedra in the final 3D mesh only
if this point is connected to a curve, itself part of the boundary of a
surface, itself part of the boundary of a volume...
@end itemize
}. This automatically assures the conformity of the mesh when, for
example, two surfaces share a common line. But this also implies that
the discretization of an ``isolated'' (@var{n}-1)-th dimensional entityinside an @var{n}-th dimensional entity does @emph{not} constrain the
@var{n}-th dimensional mesh. Every meshing step is constrained by the
characteristic length field, which can be uniform, specified by
characteristic lengths associated with points in the geometry, or
defined by general ``fields'' (a scalar field defined on another mesh
using post-processing view, threshold fields associated with point or
line ``attractors'', etc.).
For each meshing step, all structured mesh directives are executed
first, and serve as additional constraints for the unstructured parts
@footnote{Note that mixing structured volume grids with unstructured
volume grids generated with the default 3D isotropic Delaunay algorithm
can result, in certain cases, to non-conform surface meshes on their
shared boundary. If this happens, you may consider using the Netgen
algorithm for the unstructured part.}.
@c -------------------------------------------------------------------------
@c Solver: external solver interface
@c -------------------------------------------------------------------------
@node Solver, Post-processing, Mesh, Overview
@section Solver: external solver interface
External solvers can be interfaced with Gmsh through Unix or TCP/IP
sockets, which permits to launch external computations and to collect
and process the results directly from within Gmsh's post-processing
module. The default solver interfaced with Gmsh is GetDP
(@uref{http://www.geuz.org/getdp/}). Examples on how to interface
solvers written in C, C++, Perl and Python are available in the source
distribution (in the @file{utils/solvers/} directory).
@c -------------------------------------------------------------------------
@c Post-processing: scalar, vector and tensor field visualization
@c -------------------------------------------------------------------------
@node Post-processing, What Gmsh is pretty good at, Solver, Overview
@section Post-processing: scalar, vector and tensor field visualization
Gmsh can load and manipulate multiple post-processing scalar, vector or
tensor maps along with the geometry and the mesh. Scalar fields are
represented by iso-value lines/surfaces or color maps, while vector
fields are represented by three-dimensional arrows or displacement
maps. Post-processing functions include section computation, offset,
elevation, boundary and component extraction, color map and range
modification, animation, vector graphic output, etc. All the
post-processing options can be accessed either interactively or through
the input script files. Scripting permits to automate all
post-processing operations, as for example to create
animations. User-defined operations can also be performed on
post-processing views through dynamically loadable plugins.
@c -------------------------------------------------------------------------
@c What Gmsh is pretty good at...
@c -------------------------------------------------------------------------
@node What Gmsh is pretty good at, and what Gmsh is not so good at, Post-processing, Overview
@section What Gmsh is pretty good at @dots{}
Gmsh is a (relatively) small program, and was principally developed ``in
academia, to solve academic problems''@dots{} Nevertheless, over the
years, many people outside universities have found Gmsh useful in their
day-to-day jobs. Here is a tentative list of what Gmsh does best:
@itemize @bullet
@item
quickly describe simple and/or ``repetitive'' geometries, thanks to
user-defined functions, loops, conditionals and includes (see
@ref{User-defined functions}, @ref{Loops and conditionals}, and @ref{General
commands});
@itemparametrize these geometries. Gmsh's scripting language enables all
commands and command arguments to depend on previous calculations (see
@ref{Expressions}, and @ref{Geometry commands});
@item
import complex models in industry-standard formats like STEP or IGES
(when Gmsh is built with OpenCascade support);
@item
generate 1D, 2D and 3D simplicial (i.e., using line segments, triangles
and tetrahedra) finite element meshes (see @ref{Mesh module}, and
@ref{Tutorial});
@item
specify target element sizes accurately. Gmsh provides several
mechanisms to control the size of the elements in the final mesh:
through interpolation from sizes specified at geometry points or using
flexible mesh size fields (@pxref{Mesh commands});
@item
create simple extruded geometries and meshes (see @ref{Geometry commands},
and @ref{Mesh commands});
@item
interact with external solvers. Gmsh provides C, C++, Perl and Python
interfaces, and others can be easily added (@pxref{Solver module});
@item
visualize computational results in a great variety of ways. Gmsh can display
scalar, vector and tensor datasets, and can perform various operations on
the resulting post-processing views (@pxref{Post-processing module});
@item
export plots in many different formats: vector PostScript or encapsulated
PostScript, LaTeX, PNG, JPEG, @dots{} (@pxref{General options});
@item
generate complex animations (see @ref{General tools}, and @ref{t8.geo});
@item
run on low end machines and/or machines with no graphical
interface. Gmsh can be compiled with or without the GUI, and all
versions can be used either interactively or directly from the command
line (@pxref{Running Gmsh});
@item
configure your preferred options. Gmsh has a large number of configuration
options that can be set interactively using the GUI, scattered inside
command files, changed on the fly in scripts, set in per-user configuration
files, or specified on the command-line (see @ref{General options},
@ref{Geometry options}, @ref{Mesh options}, @ref{Post-processing options},
and @ref{Running Gmsh});
@item
and do all the above on various platforms (Windows, Mac and Unix), for
free (@pxref{Copying conditions}), using simple script files and/or a
small but powerful GUI.
@end itemize
@c -------------------------------------------------------------------------
@c ... and what Gmsh is not so good at
@c -------------------------------------------------------------------------
@node and what Gmsh is not so good at, , What Gmsh is pretty good at, Overview
@section @dots{} and what Gmsh is not so good at
Due to its historical background and limited developer manpower, Gmsh has
also some (a lot of?) weaknesses:
@itemize @bullet
@item
the b-rep approach for describing geometries can become inconvenient for
complex models;
@item
there is no support for Nurbs and only very limited support for trimmed
surfaces in Gmsh's scripting language (however you can import STEP or
IGES models with such features when Gmsh is built with OpenCascade
support);
@item
Gmsh is not primarily a structured mesh generator: no automatic
quadrilateral or hexahedral meshing algorithm is provided. If you wantquadrangles, you have to use transfinite or extruded meshes or recombine
unstructured triangular meshes. For hexahedra, your only choice is
transfinite or extruded meshes;
@item
Gmsh is not a multi-bloc generator: all meshes produced by Gmsh are
conforming in the sense of finite element meshes;
@item
Gmsh was designed to solve academic ``test cases'', not industrial-size
problems. You may find that Gmsh is too slow for large problems (with
thousands of geometric primitives, or millions of mesh/post-processing
elements).
@end itemize
If you have the skills and some free time, feel free to join the project! We
gladly accept any code contributions (@pxref{Programming notes}) to remedy
the aforementioned (and all other) shortcomings...
@c =========================================================================
@c How to read this manual?
@c =========================================================================
@node How to read this manual?, General tools, Overview, Top
@chapter How to read this reference manual?
Gmsh can be used at three levels:
@enumerate
@item
as a stand-alone graphical program, driven by an interactive graphical
user interface (GUI);
@item
as a stand-alone script-driven program;
@item
as a library.
@end enumerate
You don't need to read the rest of this reference manual in order to use
Gmsh at the first level (i.e., interactively with the GUI). Just skip
the next chapters and have a quick look at @ref{Running Gmsh}, then go
play with the GUI and run the tutorials files (@pxref{Tutorial}) bundled
in the distribution. Screencasts that show how to use the GUI are
available here: @uref{http://www.geuz.org/gmsh/screencasts/}.
The aim of the reference manual is to explain everything you need to use
Gmsh at the second level, i.e., using the built-in scripting language.
A Gmsh script file is an ASCII text file that contains instructions in
Gmsh's built-in scripting language. Such a file is interpreted by Gmsh's
parser, and can be given any extension (or no extension at all). By
convention, Gmsh uses the @file{.geo} extension for geometry scripts,
and the @file{.pos} extension for parsed post-processing datasets. Once
you master the tutorial (read the source files: they are heavily
commented!), start reading chapter @ref{General tools}, then proceed
with the next four chapters, which detail the syntax of the geometry,
mesh, solver and post-processing scripting commands. You will see that
most of the interactive actions in the GUI have a direct equivalent in
the scripting language. If you want to use Gmsh as a pre- or
post-processor for your own software, you will also want to learn about
the non-scripting input/output files that Gmsh can read/write. In
addition to Gmsh's native ``MSH'' file format (@pxref{File formats}),
Gmsh can read/write many standard mesh files, depending on how it was
built: check the `File->Save As' menu for a list of available formats.
Finally, to use Gmsh at the third level (i.e., to link the Gmsh library
with your own code), you will need to learn the internal Gmsh
Application Programming Interface (API). No complete documentation of
this API is available yet; a good starting point is @ref{Programming
notes}, which gives a short introduction to Gmsh's internal source code
structure. Then have a look e.g. at @file{utils/misc/driver.cpp} in the
source code.
@c -------------------------------------------------------------------------
@c Syntactic rules used in the reference manual
@c -------------------------------------------------------------------------
@menu
* Syntactic rules::
@end menu
@node Syntactic rules, , How to read this manual?, How to read this manual?
@section Syntactic rules used in the manual
@cindex Syntax, rules
@cindex Rules, syntactic
@cindex Document syntax
Here are the rules we tried to follow when writing this reference
manual. Note that metasyntactic variable definitions stay valid
throughout the manual (and not only in the sections where the
definitions appear).
@enumerate
@item
Keywords and literal symbols are printed like @code{this}.
@item
Metasyntactic variables (i.e., text bits that are not part of the syntax,
but stand for other text bits) are printed like @var{this}.
@item
A colon (@code{:}) after a metasyntactic variable separates the variable
from its definition.
@item
Optional rules are enclosed in @code{<} @code{>} pairs.
@item
Multiple choices are separated by @code{|}.
@item
Three dots (@dots{}) indicate a possible (multiple) repetition of the
preceding rule.
@end enumerate
@c =========================================================================
@c General tools
@c =========================================================================
@node General tools, Geometry module, How to read this manual?, Top
@chapter General tools
This chapter describes the general commands and options that can be used
in Gmsh's script files. By ``general'', we mean ``not specifically
related to one of the geometry, mesh, solver or post-processing
modules''. Commands peculiar to these modules will be introduced in
@ref{Geometry module}, @ref{Mesh module}, @ref{Solver module}, and
@ref{Post-processing module}, respectively.
Note that, if you are just beginning to use Gmsh, or just want to see
what Gmsh is all about, you really don't need to read this chapter and
the four next ones. Just have a quick look at @ref{Running Gmsh}, and go
play with the GUI, running the tutorials and demonstration files bundled
in the distribution (@pxref{Tutorial}). Screencasts that show how to use
the GUI are available here: @uref{http://www.geuz.org/gmsh/screencasts/}.
@menu
* Comments::
* Expressions::
* Operators::
* Built-in functions::
* User-defined functions::
* Loops and conditionals::
* General commands::
* General options::
@end menu
@c -------------------------------------------------------------------------
@c Comments
@c -------------------------------------------------------------------------
@node Comments, Expressions, General tools, General tools
@section Comments
@cindex Comments
@cindex File, comments
@findex /*, */
@findex //
Gmsh script files support both C and C++ style comments:
@enumerate
@item
any text comprised between @code{/*} and @code{*/} pairs is ignored;
@item
the rest of a line after a double slash @code{//} is ignored.
@end enumerate
These commands won't have the described effects inside double quotes or
inside keywords. Also note that `white space' (spaces, tabs, new line
characters) is ignored inside all expressions.
@c -------------------------------------------------------------------------
@c Expressions
@c -------------------------------------------------------------------------
@node Expressions, Operators, Comments, General tools
@section Expressions
@cindex Expressions, definition
@cindex Constants
The two constant types used in Gmsh scripts are @var{real} and
@var{string} (there is no integer type). These types have the same
meaning and syntax as in the C or C++ programming languages.
@menu
* Floating point expressions::
* Character expressions::
* Color expressions::
@end menu
@c .........................................................................
@c Floating point expressions
@c .........................................................................
@node Floating point expressions, Character expressions, Expressions, Expressions
@subsection Floating point expressions
@cindex Expressions, floating point
@cindex Real numbers
@cindex Numbers, real
@cindex Floating point numbers
Floating point expressions (or, more simply, ``expressions'') are denoted by
the metasyntactic variable @var{expression} (remember the definition of the
syntactic rules in @ref{Syntactic rules}), and are evaluated during the
parsing of the data file:
@example
@var{expression}:
@var{real} |
@var{string} |
@var{string} [ @var{expression} ] |
# @var{string} [ ] |
( @var{expression} ) | @var{operator-unary-left} @var{expression} |
@var{expression} @var{operator-unary-right} |
@var{expression} @var{operator-binary} @var{expression} |
@var{expression} @var{operator-ternary-left} @var{expression} @var{operator-ternary-right} @var{expression} |
@var{built-in-function} |
@var{real-option} |
GetValue("@var{string}", @var{expression})
@end example
Such @w{@var{expression}s} are used in most of Gmsh's scripting
commands. The third and fourth cases in this definition permit to
extract one item from a list (see below) and get the size of a list,
respectively. The operators @var{operator-unary-left},
@var{operator-unary-right}, @var{operator-binary},
@var{operator-ternary-left} and @var{operator-ternary-right} are defined
in @ref{Operators}. For the definition of @w{@var{built-in-function}s},
see @ref{Built-in functions}. The various @w{@var{real-option}s} are
listed in @ref{General options}, @ref{Geometry options}, @ref{Mesh
options}, @ref{Solver options}, and @ref{Post-processing options}.
The last case in the definition allows to ask the user for a value
interactively. For example, inserting @code{GetValue("Value of parameter
alpha?", 5.76)} in an input file will query the user for the value of a
certain parameter alpha, assuming the default value is 5.76. If the option
@code{General.NoPopup} is set (@pxref{General options}), no question is
asked and the default value is automatically used.
@cindex Expressions, lists
List of expressions are also widely used, and are defined as:
@example
@var{expression-list}:
@var{expression-list-item} <, @var{expression-list-item}> @dots{}
@end example
@noindent with
@example
@var{expression-list-item}:
@var{expression} |
@var{expression} : @var{expression} |
@var{expression} : @var{expression} : @var{expression} |
@var{string} [ ] |
@var{string} [ @{ @var{expression-list} @} ] |
Point @{ @var{expression} @} |
@var{transform} |
@var{extrude}
@c @var{duplicata} - already implemented: should we explain this?
@end example
The second case in this last definition permits to create a list containing
the range of numbers comprised between two @w{@var{expression}s}, with a
unit incrementation step. The third case also permits to create a list
containing the range of numbers comprised between two @w{@var{expression}s},
but with a positive or negative incrementation step equal to the third
@var{expression}. The fourth case permits to reference an expression list.
The fifth case permits to reference an expression sublist (whose elements
are those corresponding to the indices provided by the
@var{expression-list}). The sixth case permits to retrieve the coordinates
of a given geometry point (@pxref{Points}). The last two cases permit to
retrieve the indices of entities created through geometrical transformations
and extrusions (see @ref{Transformations}, and @ref{Extrusions}).
@c todo: explain in detail what numbers are returned once we decide what to
@c do (chapeau et body pour extrude, etc.)...
To see the practical use of such expressions, have a look at the first
couple of examples in @ref{Tutorial}. Note that, in order to lighten the
syntax, you can always omit the braces @code{@{@}} enclosing an@var{expression-list} if this @var{expression-list} only contains a single
item. Also note that a braced @var{expression-list} can be preceded by a
minus sign in order to change the sign of all the
@w{@var{expression-list-item}s}.
@c .........................................................................
@c Character expressions
@c .........................................................................
@node Character expressions, Color expressions, Floating point expressions, Expressions
@subsection Character expressions
@cindex Expressions, character
@cindex Strings
Character expressions are defined as:
@example
@var{char-expression}:
"@var{string}" |
Today |
StrPrefix ( @var{char-expression} ) |
StrRelative ( @var{char-expression} ) |
StrCat ( @var{char-expression} , @var{char-expression} ) |
Sprintf ( @var{char-expression} , @var{expression-list} ) |
Sprintf ( @var{char-expression} )
Sprintf ( @var{char-option} )
@end example
@noindent The third and fourth cases in this definition permit to take the
prefix (e.g. to remove the extension) or the relative path of a string. The
fifth case permits to concatenate two character expressions, and the sixth
and seventh are equivalent to the @code{sprintf} C function (where
@var{char-expression} is a format string that can contain floating point
formatting characters: @code{%e}, @code{%g}, etc.). The last case permits to
use the value of a @var{char-option} as a @var{char-expression}. The
various @w{@var{char-option}s} are listed in @ref{General options},
@ref{Geometry options}, @ref{Mesh options}, @ref{Solver options}, and
@ref{Post-processing options}.
Character expressions are mostly used to specify non-numeric options and
input/output file names. See @ref{t8.geo}, for an interesting usage of
@w{@var{char-expression}s} in an animation script.
@c .........................................................................
@c Color expressions
@c .........................................................................
@node Color expressions, , Character expressions, Expressions
@subsection Color expressions
@cindex Expressions, color
@cindex Colors
Colors expressions are hybrids between fixed-length braced
@w{@var{expression-list}s} and @w{@var{string}s}:
@example
@var{color-expression}:
@var{string} |
@{ @var{expression}, @var{expression}, @var{expression} @} |
@{ @var{expression}, @var{expression}, @var{expression}, @var{expression} @} |
@var{color-option}
@end example
@noindent The first case permits to use the X Windows names to refer to colors,
e.g., @code{Red}, @code{SpringGreen}, @code{LavenderBlush3}, @dots{}
(see @file{Common/Colors.h} in Gmsh's source tree for a complete list). The
second case permits to define colors by using three expressions to specify
their red, green and blue components (with values comprised between 0 and255). The third case permits to define colors by using their red, green and
blue color components as well as their alpha channel. The last case permits
to use the value of a @var{color-option} as a @var{color-expression}. The
various @w{@var{color-option}s} are listed in @ref{General options},
@ref{Geometry options}, @ref{Mesh options}, @ref{Solver options}, and
@ref{Post-processing options}.
See @ref{t3.geo}, for an example of the use of color expressions.
@c -------------------------------------------------------------------------
@c Operators
@c -------------------------------------------------------------------------
@node Operators, Built-in functions, Expressions, General tools
@section Operators
@cindex Operators, definition
@cindex Unary operators
@cindex Binary operators
@cindex Ternary operators
@findex @var{operator-unary-left}
@findex @var{operator-unary-right}
@findex @var{operator-binary}
@findex @var{operator-unary-left}
@findex @var{operator-ternary-left}
@findex @var{operator-ternary-right}
Gmsh's operators are similar to the corresponding operators in C and
C++. Here is the list of the unary, binary and ternary operators currently
implemented.
@noindent
@var{operator-unary-left}:
@ftable @code
@item -
Unary minus.
@item !
Logical not.
@end ftable
@noindent
@var{operator-unary-right}:
@ftable @code
@item ++
Post-incrementation.
@item --
Post-decrementation.
@end ftable
@noindent
@var{operator-binary}:
@ftable @code
@item ^
Exponentiation.
@item *
Multiplication.
@item /
Division.
@item %
Modulo.
@item +
Addition.
@item -
Subtraction.
@item ==
Equality.
@item !=
Inequality.
@item >
Greater.@item >=
Greater or equality.
@item <
Less.
@item <=
Less or equality.
@item &&
Logical `and'.
@item ||
Logical `or'. (Warning: the logical `or' always implies the evaluation of
both arguments. That is, unlike in C or C++, the second operand of
@code{||} is evaluated even if the first one is true).
@end ftable
@noindent
@var{operator-ternary-left}:
@ftable @code
@item ?
@end ftable
@var{operator-ternary-right}:
@ftable @code
@item :
The only ternary operator, formed by @var{operator-ternary-left} and
@var{operator-ternary-right}, returns the value of its second argument if
the first argument is non-zero; otherwise it returns the value of its third
argument.
@end ftable
@cindex Evaluation order
@cindex Order, evaluation
@cindex Operator precedence
@cindex Precedence, operators
@findex ()
The evaluation priorities are summarized below@footnote{The affectation
operators are introduced in @ref{General commands}.} (from stronger to
weaker, i.e., @code{*} has a highest evaluation priority than @code{+}).
Parentheses @code{()} may be used anywhere to change the order of
evaluation:
@enumerate
@item @code{()}, @code{[]}, @code{.}, @code{#}
@item @code{^}
@item @code{!}, @code{++}, @code{--}, @code{-} (unary)
@item @code{*}, @code{/}, @code{%}
@item @code{+}, @code{-}
@item @code{<}, @code{>}, @code{<=}, @code{>=}
@item @code{==}, @code{!=}
@item @code{&&}
@item @code{||}
@item @code{?:}
@item @code{=}, @code{+=}, @code{-=}, @code{*=}, @code{/=}
@end enumerate
@c -------------------------------------------------------------------------
@c Built-in functions
@c -------------------------------------------------------------------------
@node Built-in functions, User-defined functions, Operators, General tools
@section Built-in functions
@cindex Functions, built-in
@findex @var{build-in-function}
A built-in function is composed of an identifier followed by a pair of
parentheses containing an @var{expression-list} (the list of its
arguments)@footnote{For compatibility with GetDP
(@uref{http://www.geuz.org/getdp/}), parentheses can be replaced by brackets@code{[]}.}. Here is the list of the built-in functions currently
implemented:
@noindent
@var{build-in-function}:
@ftable @code
@item Acos ( @var{expression} )
Arc cosine (inverse cosine) of an @var{expression} in [-1,1]. Returns a value
in [0,Pi].
@item Asin ( @var{expression} )
Arc sine (inverse sine) of an @var{expression} in [-1,1]. Returns a value in
[-Pi/2,Pi/2].
@item Atan ( @var{expression} )
Arc tangent (inverse tangent) of @var{expression}. Returns a value in
[-Pi/2,Pi/2].
@item Atan2 ( @var{expression}, @var{expression} )
Arc tangent (inverse tangent) of the first @var{expression} divided by the
second. Returns a value in [-Pi,Pi].
@item Ceil ( @var{expression} )
Rounds @var{expression} up to the nearest integer.
@item Cos ( @var{expression} )
Cosine of @var{expression}.
@item Cosh ( @var{expression} )
Hyperbolic cosine of @var{expression}.
@item Exp ( @var{expression} )
Returns the value of e (the base of natural logarithms) raised to the power
of @var{expression}.
@item Fabs ( @var{expression} )
Absolute value of @var{expression}.
@item Fmod ( @var{expression}, @var{expression} )
Remainder of the division of the first @var{expression} by the second, with
the sign of the first.
@item Floor ( @var{expression} )
Rounds @var{expression} down to the nearest integer.
@item Hypot ( @var{expression}, @var{expression} )
Returns the square root of the sum of the square of its two arguments.
@item Log ( @var{expression} )
Natural logarithm of @var{expression} (@var{expression} > 0).
@item Log10 ( @var{expression} )
Base 10 logarithm of @var{expression} (@var{expression} > 0).
@item Modulo ( @var{expression}, @var{expression} )
see @code{Fmod( @var{expression}, @var{expression} )}.
@item Rand ( @var{expression} )
Random number between zero and @var{expression}.
@item Sqrt ( @var{expression} )
Square root of @var{expression} (@var{expression} >= 0).
@item Sin ( @var{expression} )
Sine of @var{expression}.
@item Sinh ( @var{expression} )
Hyperbolic sine of @var{expression}.
@item Tan ( @var{expression} )
Tangent of @var{expression}.
@item Tanh ( @var{expression} )
Hyperbolic tangent of @var{expression}.
@end ftable
@c -------------------------------------------------------------------------
@c User-defined functions
@c -------------------------------------------------------------------------
@node User-defined functions, Loops and conditionals, Built-in functions, General tools
@section User-defined functions
@cindex Functions, user-defined
User-defined functions take no arguments, and are evaluated as if a file
containing the function body was included at the location of the @code{Call}
statement.
@ftable @code
@item Function @var{string}
Begins the declaration of a user-defined function named @var{string}. The
body of the function starts on the line after `@code{Function
@var{string}}', and can contain any Gmsh command.
@item Return
Ends the body of the current user-defined function. Function declarations
cannot be imbricated.
@item Call @var{string};
Executes the body of a (previously defined) function named @var{string}.
@end ftable
See @ref{t5.geo}, for an example of a user-defined function. A
shortcoming of Gmsh's scripting language is that all variables are
``public''. Variables defined inside the body of a function will thus be
available outside, too!
@c -------------------------------------------------------------------------
@c Loops and conditionals
@c -------------------------------------------------------------------------
@node Loops and conditionals, General commands, User-defined functions, General tools
@section Loops and conditionals
@cindex Loops
@cindex Conditionals
Loops and conditionals are defined as follows, and can be imbricated:
@ftable @code
@item For ( @var{expression} : @var{expression} )
Iterates from the value of the first @var{expression} to the value of the
second @var{expression}, with a unit incrementation step. At each iteration,
the commands comprised between `@code{For ( @var{expression} :
@var{expression} )}' and the matching @code{EndFor} are executed.
@item For ( @var{expression} : @var{expression} : @var{expression} )
Iterates from the value of the first @var{expression} to the value of the
second @var{expression}, with a positive or negative incrementation step
equal to the third @var{expression}. At each iteration, the commands
comprised between `@code{For ( @var{expression} : @var{expression} :
@var{expression} )}' and the matching @code{EndFor} are executed.
@item For @var{string} In @{ @var{expression} : @var{expression} @}
Iterates from the value of the first @var{expression} to the value of the
second @var{expression}, with a unit incrementation step. At each iteration,
the value of the iterate is affected to an expression named @var{string},
and the commands comprised between `@code{For @var{string} In @{@var{expression} : @var{expression} @}}' and the matching @code{EndFor} are
executed.
@item For @var{string} In @{ @var{expression} : @var{expression} : @var{expression} @}
Iterates from the value of the first @var{expression} to the value of the
second @var{expression}, with a positive or negative incrementation step
equal to the third @var{expression}. At each iteration, the value of the
iterate is affected to an expression named @var{string}, and the commands
comprised between `@code{For @var{string} In @{ @var{expression} :
@var{expression} : @var{expression} @}}' and the matching @code{EndFor} are
executed.
@item EndFor
Ends a matching @code{For} command.
@item If ( @var{expression} )
The body enclosed between `@code{If ( @var{expression} )}' and the matching
@code{Endif} is evaluated if @var{expression} is non-zero.
@item EndIf
Ends a matching @code{If} command.
@end ftable
See @ref{t5.geo}, for an example of @code{For} and @code{If} commands. Gmsh
does not provide any @code{Else} (or similar) command at the time of this
writing.
@c -------------------------------------------------------------------------
@c General commands
@c -------------------------------------------------------------------------
@node General commands, General options, Loops and conditionals, General tools
@section General commands
@cindex General commands
@cindex Commands, general
@cindex Expressions, affectation
@cindex Expressions, identifiers
@findex =
@findex +=
@findex -=
@findex *=
@findex /=
The following commands can be used anywhere in a Gmsh script:
@ftable @code
@item @var{string} = @var{expression};
Creates a new expression identifier @var{string}, or affects
@var{expression} to an existing expression identifier. Eleven expression
identifiers are predefined (hardcoded in Gmsh's parser):
@ftable @code
@item Pi
Returns 3.1415926535897932.
@item GMSH_MAJOR_VERSION
Returns Gmsh's major version number.
@item GMSH_MINOR_VERSION
Returns Gmsh's minor version number.
@item GMSH_PATCH_VERSION
Returns Gmsh's patch version number.
@item MPI_Size
Returns the number of processors on which Gmsh is running (always 1, except
if you compiled Gmsh's parallel extensions).
@item MPI_Rank
Returns the rank of the current processor.
@item newp
Returns the next available point number. As explained in @ref{Geometry
module}, a unique number must be associated with every geometrical point:
@code{newp} permits to know the highest number already attributed (plus
one). This is mostly useful when writing user-defined functions
(@pxref{User-defined functions}) or general geometric primitives, when one
does not know @emph{a priori} which numbers are already attributed, and
which ones are still available.
@item newl
Returns the next available line number.
@item news
Returns the next available surface number.
@item newv
Returns the next available volume number.
@item newll
Returns the next available line loop number.
@item newsl
Returns the next available surface loop number.
@item newreg
Returns the next available region number. That is, @code{newreg} returns the
maximum of @code{newp}, @code{newl}, @code{news}, @code{newv} and all
physical entity numbers@footnote{For compatibility purposes, the behavior
of @code{newl}, @code{news}, @code{newv} and @code{newreg} can be modified
with the @code{Geometry.OldNewReg} option (@pxref{Geometry options}).}.
@end ftable
@item @var{string} [ ] = @{ @};
Creates a new expression list identifier @code{@var{string}[]} with an
empty list.
@item @var{string} [ ] = @{ @var{expression-list} @};
Creates a new expression list identifier @code{@var{string}[]} with the
list @var{expression-list}, or affects @var{expression-list} to an
existing expression list identifier. (Remember the remark we made when
we defined @w{@var{expression-list}s}: the braces enclosing an
@var{expression-list} are optional if the list only contains a single
item.)
@item @var{string} [ @{ @var{expression-list} @} ] = @{ @var{expression-list} @};
Affects each item in the right hand side @var{expression-list} to the
elements (indexed by the left hand side @var{expression-list}) of an
existing expression list identifier. The two @w{@var{expression-list}s} must
contain the same number of items.
@item @var{real-option} = @var{expression};
Affects @var{expression} to a real option.
@item @var{char-option} = @var{char-expression};
Affects @var{char-expression} to a character option.
@item @var{color-option} = @var{color-expression};
Affects @var{color-expression} to a color option.
@item @var{string} | @var{real-option} += @var{expression};
Adds and affects @var{expression} to an existing expression identifier or to
a real option.
@item @var{string} | @var{real-option} -= @var{expression};
Subtracts and affects @var{expression} to an existing expression identifier
or to a real option.
@item @var{string} | @var{real-option} *= @var{expression};
Multiplies and affects @var{expression} to an existing expression identifier
or to a real option.
@item @var{string} | @var{real-option} /= @var{expression};
Divides and affects @var{expression} to an existing expression identifier
or to a real option.
@item @var{string} [ ] += @{ @var{expression-list} @};
Appends @var{expression-list} to an existing expression list or creates
a new expression list with @var{expression-list}).
@item @var{string} [ @{ @var{expression-list} @} ] += @{ @var{expression-list} @};
Adds and affects, item per item, the right hand side @var{expression-list}
to an existing expression list identifier.
@item @var{string} [ @{ @var{expression-list} @} ] -= @{ @var{expression-list} @};
Subtracts and affects, item per item, the right hand side
@var{expression-list} to an existing expression list identifier.
@item @var{string} [ @{ @var{expression-list} @} ] *= @{ @var{expression-list} @};
Multiplies and affects, item per item, the right hand side
@var{expression-list} to an existing expression list identifier.
@item @var{string} [ @{ @var{expression-list} @} ] /= @{ @var{expression-list} @};
Divides and affects, item per item, the right hand side
@var{expression-list} to an existing expression list identifier.
@item Exit;
Aborts the current script.
@item Printf ( @var{char-expression} , @var{expression-list} );
Prints a character expression in the information window and/or on the
terminal. @code{Printf} is equivalent to the @code{printf} C function:
@var{char-expression} is a format string that can contain formatting
characters (@code{%f}, @code{%e}, etc.). Note that all @w{@var{expression}s}
are evaluated as floating point values in Gmsh (@pxref{Expressions}), so
that only valid floating point formatting characters make sense in
@var{char-expression}. See @ref{t5.geo}, for an example of the use of
@code{Printf}.
@item Printf ( @var{char-expression} , @var{expression-list} ) > @var{char-expression};
Same as @code{Printf} above, but output the expression in a file.
@item Printf ( @var{char-expression} , @var{expression-list} ) >> @var{char-expression};
Same as @code{Printf} above, but appends the expression at the end of
the file.
@item Merge @var{char-expression};
Merges a file named @var{char-expression}. This command is equivalent to
the `File->Merge' menu in the GUI. If the path in @var{char-expression}
is not absolute, @var{char-expression} is appended to the path of the
current file.
@item Draw;
Redraws the scene.
@item BoundingBox;
Recomputes the bounding box of the scene (which is normally computed only
after new geometrical entities are added or after files are included or
merged). The bounding box is computed as follows:
@enumerate
@item
If there is a mesh (i.e., at least one mesh vertex), the bounding
box is taken as the box enclosing all the mesh vertices;
@item
If there is no mesh but there is a geometry (i.e., at least one geometrical
point), the bounding box is taken as the box enclosing all the geometrical
points;@item
If there is no mesh and no geometry, but there are some post-processing
views, the bounding box is taken as the box enclosing all the primitives in
the views.
@end enumerate
@item BoundingBox @{ @var{expression}, @var{expression}, @var{expression}, @var{expression}, @var{expression}, @var{expression} @};
Forces the bounding box of the scene to the given @w{@var{expression}s} (X
min, X max, Y min, Y max, Z min, Z max).
@item Delete Model;
Deletes the current model (all geometrical entities and their associated
meshes).
@item Delete Physicals;
Deletes all physical groups.
@item Delete Variables;
Deletes all the expressions.
@item Delete @var{string};
Deletes the expression @var{string}.
@item Mesh @var{expression};
Generate @var{expression}-D mesh.
@item Print @var{char-expression};
Prints the graphic window in a file named @var{char-expression}, using the
current @code{Print.Format} (@pxref{General options}). If the path in
@var{char-expression} is not absolute, @var{char-expression} is appended to
the path of the current file.
@item Sleep @var{expression};
Suspends the execution of Gmsh during @var{expression} seconds.
@item System @var{char-expression};
Executes a system call.
@item Include @var{char-expression};
Includes the file named @var{char-expression} at the current position in the
input file. The include command should be given on a line of its own. If
the path in @var{char-expression} is not absolute, @var{char-expression} is
appended to the path of the current file.
@end ftable
@c -------------------------------------------------------------------------
@c General options
@c -------------------------------------------------------------------------
@node General options, , General commands, General tools
@section General options
Here is the list of the general @w{@var{char-option}s},
@w{@var{real-option}s} and @w{@var{color-option}s} (in that
order---check the default values to see the actual types). Most of these
options are accessible in the GUI, but not all of them. When running
Gmsh interactively, changing an option in the script file will modify
the option in the GUI in real time. This permits for example to resize
the graphical window in a script, or to interact with animations in the
script and in the GUI at the same time.
Gmsh's default behavior is to save some of these options in a per-user
``session resource'' file (@code{General.SessionFileName}) every time Gmsh
is shut down. This permits for example to automatically remember the size
and location of the windows or which fonts to use. Other options can be
saved in a per-user ``option'' file (@code{General.OptionsFileName}),
automatically loaded by Gmsh every time it starts up, by using the
`Tools->Options->Save as defaults' menu.
@c All the opt_XXX.texi files are generated automatically with `gmsh -doc'
@include opt_general.texi
@include opt_print.texi
@c =========================================================================
@c Geometry module
@c =========================================================================
@node Geometry module, Mesh module, General tools, Top
@chapter Geometry module
@cindex Geometry, module
@cindex Module, geometry
Gmsh's geometry module provides a simple CAD engine, using a bottom-up
(boundary representation) approach: you need to first define points (using
the @code{Point} command: see below), then lines (using @code{Line},
@code{Circle}, @code{Spline}, @dots{}, commands or by extruding points),
then surfaces (using for example the @code{Plane Surface} or @code{Ruled
Surface} commands, or by extruding lines), and finally volumes (using the
@code{Volume} command or by extruding surfaces).
These geometrical entities are called ``elementary'' in Gmsh's jargon, and
are assigned identification numbers when they are created:
@enumerate
@item each elementary point must possess a unique identification number;
@item each elementary line must possess a unique identification number;
@item each elementary surface must possess a unique identification number;
@item each elementary volume must possess a unique identification number.
@end enumerate
@noindent Elementary geometrical entities can then be manipulated in various
ways, for example using the @code{Translate}, @code{Rotate}, @code{Scale} or
@code{Symmetry} commands.
Compound groups of elementary geometrical entities can also be defined and
are called ``physical'' entities. These physical entities cannot be modified
by geometry commands: their only purpose is to assemble elementary entities
into larger groups, possibly modifying their orientation, so that they can
be referred to by the mesh module as single entities. As is the case with
elementary entities, each physical point, physical line, physical surface or
physical volume must be assigned a unique identification number. See
@ref{Mesh module}, for more information about how physical entities affect
the way meshes are saved.
@menu
* Geometry commands::
* Geometry options::
@end menu
@c -------------------------------------------------------------------------
@c Geometry commands
@c -------------------------------------------------------------------------
@node Geometry commands, Geometry options, Geometry module, Geometry module
@section Geometry commands
@cindex Geometry commands
@cindex Commands, geometry
The next subsections describe all the available geometry commands. These
commands can be used anywhere in a Gmsh script file. Note that the
following general syntax rule is followed for the definition of
geometrical entities: ``If an @var{expression} defines a new entity, it
is enclosed between parentheses. If an @var{expression} refers to a
previously defined entity, it is enclosed between braces.''
@menu* Points::
* Lines::
* Surfaces::
* Volumes::
* Extrusions::
* Transformations::
* Miscellaneous geometry commands::
@end menu
@c .........................................................................
@c Points
@c .........................................................................
@node Points, Lines, Geometry commands, Geometry commands
@subsection Points
@cindex Elementary points
@cindex Points, elementary
@cindex Physical points
@cindex Points, physical
@ftable @code
@item Point ( @var{expression} ) = @{ @var{expression}, @var{expression}, @var{expression}, @var{expression} @};
Creates an elementary point. The @var{expression} inside the parentheses is
the point's identification number; the three first @w{@var{expression}s}
inside the braces on the right hand side give the three X, Y and Z
coordinates of the point in the three-dimensional Euclidean space; the last
@var{expression} sets the characteristic mesh length at that point. See
@ref{Characteristic lengths}, for more information about how this
characteristic length information is used in the meshing process.
@item Physical Point ( @var{expression} | @var{char-expression} ) = @{ @var{expression-list} @};
Creates a physical point. The @var{expression} inside the parentheses is
the physical point's identification number (if a @var{char-expression}
is given instead, a unique identification number is automatically
created); the @var{expression-list} on the right hand side should
contain the identification numbers of all the elementary points that
need to be grouped inside the physical point.
@end ftable
@c .........................................................................
@c Lines
@c .........................................................................
@node Lines, Surfaces, Points, Geometry commands
@subsection Lines
@cindex Elementary lines
@cindex Lines, elementary
@cindex Physical lines
@cindex Lines, physical
@ftable @code
@c @item Bezier ( @var{expression} ) = @{ @var{expression-list} @};
@c Creates a Bezier curve. The @var{expression} inside the parentheses is the
@c Bezier curve's identification number; the @var{expression-list} on the right
@c hand side should contain the identification numbers of all the curve's
@c control points.
@item BSpline ( @var{expression} ) = @{ @var{expression-list} @};
Creates a B-spline curve. The @var{expression} inside the parentheses is the
B-spline curve's identification number; the @var{expression-list} on the
right hand side should contain the identification numbers of all the
B-spline's control points. Repeating control points has the expected effect.
@item Circle ( @var{expression} ) = @{ @var{expression}, @var{expression}, @var{expression} @};
Creates a circle arc (strictly) smaller than Pi. The @var{expression} inside
the parentheses is the circle arc's identification number; the first
@var{expression} inside the braces on the right hand side gives the
identification number of the start point of the arc; the second@var{expression} gives the identification number of the center of the
circle; the last @var{expression} gives the identification number of the end
point of the arc.
@c todo:
@c @item Circle ( @var{expression} ) = @{ @var{expression}, @var{expression}, @var{expression} @} Plane @{ @var{expression}, @var{expression}, @var{expression} @};
@item CatmullRom ( @var{expression} ) = @{ @var{expression-list} @};
@code{CatmullRom} is a synonym for @code{Spline}.
@item Ellipse ( @var{expression} ) = @{ @var{expression}, @var{expression}, @var{expression}, @var{expression} @};
Creates an ellipse arc. The @var{expression} inside the parentheses is the
ellipse arc's identification number; the first @var{expression} inside the
braces on the right hand side gives the identification number of the start
point of the arc; the second @var{expression} gives the identification
number of the center of the ellipse; the third @var{expression} gives the
identification number of any point located on the major axis of the ellipse;
the last @var{expression} gives the identification number of the end point
of the arc.
(A deprecated synonym for @code{Ellipse} is @code{Ellipsis}.)
@item Line ( @var{expression} ) = @{ @var{expression}, @var{expression} @};
Creates a straight line segment. The @var{expression} inside the parentheses
is the line segment's identification number; the two @w{@var{expression}s}
inside the braces on the right hand side give identification numbers of the
start and end points of the segment.
@c todo: multi-lines not authorized yet
@c todo:
@c @item Nurbs ( @var{expression} ) = @{ @var{expression-list} @};
@c todo:
@c @item Parametric ( @var{expression} ) = @{ @var{expression}, @var{expression}, "@var{string}", "@var{string}", "@var{string}" @};
@item Spline ( @var{expression} ) = @{ @var{expression-list} @};
Creates a spline curve. The @var{expression} inside the parentheses is the
spline's identification number; the @var{expression-list} on the right hand
side should contain the identification numbers of all the spline's control
points.
@item Line Loop ( @var{expression} ) = @{ @var{expression-list} @};
Creates an oriented line loop. The @var{expression} inside the parentheses
is the line loop's identification number; the @var{expression-list} on the
right hand side should contain the identification numbers of all the
elementary lines that constitute the line loop. A line loop must be a closed
loop, and the elementary lines should be ordered and oriented (using
negative identification numbers to specify reverse orientation). If the
orientation is correct, but the ordering is wrong, Gmsh will actually
reorder the list internally to create a consistent loop. Although Gmsh
supports it, it is not recommended to specify multiple line loops (or
subloops) in a single @code{Line Loop} command. (Line loops are used to
create surfaces: see @ref{Surfaces}.)
@item Physical Line ( @var{expression} | @var{char-expression} ) = @{ @var{expression-list} @};
Creates a physical line. The @var{expression} inside the parentheses is
the physical line's identification number (if a @var{char-expression} is
given instead, a unique identification number is automatically
created); the @var{expression-list} on the right hand side should
contain the identification numbers of all the elementary lines that need
to be grouped inside the physical line. Specifying negative
identification numbers in the @var{expression-list} will reverse the
orientation of the mesh elements belonging to the corresponding
elementary lines in the saved mesh.
@end ftable
@c .........................................................................
@c Surfaces
@c .........................................................................
@node Surfaces, Volumes, Lines, Geometry commands
@subsection Surfaces
@cindex Elementary surfaces
@cindex Surfaces, elementary
@cindex Physical surfaces
@cindex Surfaces, physical
@ftable @code
@item Plane Surface ( @var{expression} ) = @{ @var{expression-list} @};
Creates a plane surface. The @var{expression} inside the parentheses is the
plane surface's identification number; the @var{expression-list} on the
right hand side should contain the identification numbers of all the line
loops defining the surface. The first line loop defines the exterior
boundary of the surface; all other line loops define holes in the surface.
A line loop defining a hole should not have any lines in common with the
exterior line loop (in which case it is not a hole, and the two surfaces
should be defined separately). Likewise, a line loop defining a hole should
not have any lines in common with another line loop defining a hole in the
same surface (in which case the two line loops should be combined).
@item Ruled Surface ( @var{expression} ) = @{ @var{expression-list} @} < In Sphere @{ @var{expression} @} >;
Creates a ruled surface, i.e., a surface that can be interpolated using
transfinite interpolation. The @var{expression} inside the parentheses
is the ruled surface's identification number; the first
@var{expression-list} on the right hand side should the identification
number of a line loop composed of either three or four elementary
lines. The optional @code{In Sphere} argument forces the surface to be a
spherical patch (the extra parameter gives the identification number of
the center of the sphere).
@item Surface Loop ( @var{expression} ) = @{ @var{expression-list} @};
Creates a surface loop (a shell). The @var{expression} inside the
parentheses is the surface loop's identification number; the
@var{expression-list} on the right hand side should contain the
identification numbers of all the elementary surfaces that constitute the
surface loop. A surface loop must always represent a closed shell, and the
elementary surfaces should be oriented consistently (using negative
identification numbers to specify reverse orientation). (Surface loops are
used to create volumes: see @ref{Volumes}.)
@item Physical Surface ( @var{expression} | @var{char-expression} ) = @{ @var{expression-list} @};
Creates a physical surface. The @var{expression} inside the parentheses
is the physical surface's identification number (if a
@var{char-expression} is given instead, a unique identification number
is automatically created); the @var{expression-list} on the right hand
side should contain the identification numbers of all the elementary
surfaces that need to be grouped inside the physical surface. Specifying
negative identification numbers in the @var{expression-list} will
reverse the orientation of the mesh elements belonging to the
corresponding elementary surfaces in the saved mesh.
@end ftable
@c .........................................................................
@c Volumes
@c .........................................................................
@node Volumes, Extrusions, Surfaces, Geometry commands
@subsection Volumes
@cindex Elementary volumes
@cindex Volumes, elementary
@cindex Physical volumes
@cindex Volumes, physical
@ftable @code
@item Volume ( @var{expression} ) = @{ @var{expression-list} @};
Creates a volume. The @var{expression} inside the parentheses is the
volume's identification number; the @var{expression-list} on the right hand
side should contain the identification numbers of all the surface loopsdefining the volume. The first surface loop defines the exterior boundary of
the volume; all other surface loops define holes in the volume. A surface
loop defining a hole should not have any surfaces in common with the
exterior surface loop (in which case it is not a hole, and the two volumes
should be defined separately). Likewise, a surface loop defining a hole
should not have any surfaces in common with another surface loop defining a
hole in the same volume (in which case the two surface loops should be
combined).
(A deprecated synonym for @code{Volume} is @code{Complex Volume}.)
@item Physical Volume ( @var{expression} | @var{char-expression} ) = @{ @var{expression-list} @};
Creates a physical volume. The @var{expression} inside the parentheses
is the physical volume's identification number (if a
@var{char-expression} is given instead, a unique identification number
is automatically created); the @var{expression-list} on the right hand
side should contain the identification numbers of all the elementary
volumes that need to be grouped inside the physical volume.
@end ftable
@c .........................................................................
@c Extrusions
@c .........................................................................
@node Extrusions, Transformations, Volumes, Geometry commands
@subsection Extrusions
@cindex Extrusion, geometry
@cindex Geometry, extrusion
@findex @var{extrude}
Lines, surfaces and volumes can also be created through extrusion of points,
lines and surfaces, respectively. Here is the syntax of the geometrical
extrusion commands (go to @ref{Structured grids}, to see how these commands
can be extended in order to also extrude the mesh):
@var{extrude}:
@ftable @code
@item Extrude @{ @var{expression-list} @} @{ @var{extrude-list} @}
Extrudes all elementary entities (points, lines or surfaces) in
@var{extrude-list} using a translation. The @var{expression-list} should
contain three @w{@var{expression}s} giving the X, Y and Z components of
the translation vector.
@item Extrude @{ @{ @var{expression-list} @}, @{ @var{expression-list} @}, @var{expression} @} @{ @var{extrude-list} @}
Extrudes all elementary entities (points, lines or surfaces) in
@var{extrude-list} using a rotation. The first @var{expression-list}
should contain three @w{@var{expression}s} giving the X, Y and Z
direction of the rotation axis; the second @var{expression-list} should
contain three @w{@var{expression}s} giving the X, Y and Z components of
any point on this axis; the last @var{expression} should contain the
rotation angle (in radians).
@item Extrude @{ @{ @var{expression-list} @}, @{ @var{expression-list} @}, @{ @var{expression-list} @}, @var{expression} @} @{ @var{extrude-list} @}
Extrudes all elementary entities (points, lines or surfaces) in
@var{extrude-list} using a translation combined with a rotation. The
first @var{expression-list} should contain three @w{@var{expression}s}
giving the X, Y and Z components of the translation vector; the second
@var{expression-list} should contain three @w{@var{expression}s} giving
the X, Y and Z direction of the rotation axis; the third
@var{expression-list} should contain three @w{@var{expression}s} giving
the X, Y and Z components of any point on this axis; the last
@var{expression} should contain the rotation angle (in radians).
@end ftable
@noindent with
@example
@var{extrude-list}:
Point | Line | Surface @{ @var{expression-list} @}; @dots{}@end example
@c .........................................................................
@c Transformations
@c .........................................................................
@node Transformations, Miscellaneous geometry commands, Extrusions, Geometry commands
@subsection Transformations
@cindex Transformations, geometry
@cindex Geometry, transformations
@cindex Rotation
@cindex Scale
@cindex Symmetry
@cindex Translation
@findex @var{transform}
Geometrical transformations can be applied to elementary entities, or to
copies of elementary entities (using the @code{Duplicata} command: see
below). The syntax of the transformation commands is:
@var{transform}:
@ftable @code
@item Dilate @{ @{ @var{expression-list} @}, @var{expression} @} @{ @var{transform-list} @}
Scales all elementary entities in @var{transform-list} by a factor
@var{expression}. The @var{expression-list} should contain three
@w{@var{expression}s} giving the X, Y and Z direction of the homothetic
transformation.
@item Rotate @{ @{ @var{expression-list} @}, @{ @var{expression-list} @}, @var{expression} @} @{ @var{transform-list} @}
Rotates all elementary entities in @var{transform-list} by an angle of
@var{expression} radians. The first @var{expression-list} should contain
three @w{@var{expression}s} giving the X, Y and Z direction of the
rotation axis; the second @var{expression-list} should contain three
@w{@var{expression}s} giving the X, Y and Z components of any point on
this axis.
@item Symmetry @{ @var{expression-list} @} @{ @var{transform-list} @}
Transforms all elementary entities symmetrically to a plane. The
@var{expression-list} should contain four @w{@var{expression}s} giving
the coefficients of the plane's equation.
@item Translate @{ @var{expression-list} @} @{ @var{transform-list} @}
Translates all elementary entities in @var{transform-list}. The
@var{expression-list} should contain three @w{@var{expression}s} giving
the X, Y and Z components of the translation vector.
@item Boundary @{ @var{transform-list} @}
(Not a transformation per-se.) Returns the boundary of the elementary
entities in @var{transform-list}.
@c @item Intersect Line @{ @var{expression-list} @} Surface @{ @var{expression} @}
@c (Not a transformation per-se.) Returns the intersections of the lines
@c given in @var{expression-list} with the specified surface.
@end ftable
@noindent with
@example
@var{transform-list}:
Point | Line | Surface | Volume @{ @var{expression-list} @}; @dots{} |
Duplicata @{ Point | Line | Surface | Volume @{ @var{expression-list} @}; @dots{} @} |
@var{transform}
@end example
@c .........................................................................
@c Miscellaneous
@c .........................................................................
@node Miscellaneous geometry commands, , Transformations, Geometry commands@subsection Miscellaneous
Here is a list of all other geometry commands currently available:
@ftable @code
@item Coherence;
Removes all duplicate elementary geometrical entities (e.g., points having
identical coordinates). Note that Gmsh executes the @code{Coherence} command
automatically after each geometrical transformation, unless
@code{Geometry.AutoCoherence} is set to zero (@pxref{Geometry options}).
@item Delete @{ Point | Line | Surface | Volume @{ @var{expression-list} @}; @dots{} @}
Deletes all elementary entities whose identification numbers are given
in @var{expression-list}.
@item Hide @{ Point | Line | Surface | Volume @{ @var{expression-list} @}; @dots{} @}
Hide the entities listed in @var{expression-list}, if
@code{General.VisibilityMode} is set to @code{0} or @code{1}.
@item Hide @var{char-expression};
Hide the entity @var{char-expression}, if @code{General.VisibilityMode} is
set to @code{0} or @code{1} (@var{char-expression} can for example be
@code{"*"}).
@item Show @{ Point | Line | Surface | Volume @{ @var{expression-list} @}; @dots{} @}
Show the entities listed in @var{expression-list}, if
@code{General.VisibilityMode} is set to @code{0} or @code{1}.
@item Show @var{char-expression};
Show the entity @var{char-expression}, if @code{General.VisibilityMode} is
set to @code{0} or @code{1} (@var{char-expression} can for example be
@code{"*"}).
@end ftable
@c -------------------------------------------------------------------------
@c Geometry options
@c -------------------------------------------------------------------------
@node Geometry options, , Geometry commands, Geometry module
@section Geometry options
@cindex Options, geometry
@cindex Geometry, options
Geometry options control the behavior of geometry commands, as well as
the way geometrical entities are handled in the GUI. For the
signification of the `Saved in:' field in the following list, see
@ref{General options}.
@include opt_geometry.texi
@c =========================================================================
@c Mesh module
@c =========================================================================
@node Mesh module, Solver module, Geometry module, Top
@chapter Mesh module
@cindex Mesh, module
@cindex Module, Mesh
Gmsh's mesh module regroups several 1D, 2D and 3D mesh algorithms, all
producing grids conforming in the sense of finite elements (@pxref{Mesh}).
The 2D @emph{unstructured} algorithms generate triangles or both triangles
and quadrangles (when @code{Recombine Surface} is used: see
@ref{Miscellaneous mesh commands}). The 3D unstructured algorithms only
generate tetrahedra.
The 2D @emph{structured} algorithms (transfinite and extrusion) generatetriangles by default, but quadrangles can be obtained by using the
@code{Recombine} commands (see @ref{Structured grids}, and
@ref{Miscellaneous mesh commands}). The 3D structured algorithms
generate tetrahedra, hexahedra, prisms and pyramids, depending on the
type of the surface meshes they are based on.
@c todo: explain what happens if we have a degenerate geometry (incorrect
@c holes with surfaces in contact with the exterior shell, intersecting
@c primitives, etc.)
@menu
* Elementary vs physical entities::
* Mesh commands::
* Mesh options::
@end menu
@c -------------------------------------------------------------------------
@c Elementary vs. physical entities
@c -------------------------------------------------------------------------
@node Elementary vs physical entities, Mesh commands, Mesh module, Mesh module
@section Elementary vs. physical entities
If only elementary geometrical entities are defined (or if the
@code{Mesh.SaveAll} option is set; see @ref{Mesh options}), the grid
produced by the mesh module will be saved ``as is''. That is, all the
elements in the grid will be saved to disk using the identification
number of the elementary entities they discretize as their elementary
region number (and 0 as their physical region number@footnote{This
behaviour was introduced in Gmsh 2.0. In older versions, both the
elementary and the physical region numbers would be set to the
identification number of the elementary region.}; @ref{File
formats}). This can sometimes be inconvenient:
@itemize @bullet
@item
mesh elements cannot be duplicated;
@item
the orientation of the mesh elements (the ordering of their nodes) is
determined entirely by the orientation of their ``parent'' elementary
entities, and cannot be modified;
@item
elements belonging to different elementary entities cannot be linked as
being part of a larger group having a physical or mathematical meaning (like
`Left wing', `Metallic part', `Dirichlet boundary condition', @dots{}).
@end itemize
To remedy these problems, the geometry module (@pxref{Geometry module})
introduces the notion of ``physical'' entities (also called ``physical
groups''). The purpose of physical entities is to assemble elementary
entities into larger, possibly overlapping groups, and to control the
orientation of the elements in these groups. The introduction of
physical entities in large models usually greatly facilitates the
manipulation of the model (e.g., using `Tools->Visibility' in the GUI)
and the interfacing with external solvers.
In the MSH file format (@pxref{File formats}), if physical entities are
defined, the output mesh only contains those elements that belong to
physical entities. Other file formats each treat physical entities in
slightly different ways, depending on their capability to define groups.
@c -------------------------------------------------------------------------
@c Mesh commands
@c -------------------------------------------------------------------------
@node Mesh commands, Mesh options, Elementary vs physical entities, Mesh module
@section Mesh commands
@cindex Mesh commands
@cindex Commands, mesh
The mesh module commands mostly permit to modify the characteristic
lengths and specify structured grid parameters. The actual mesh
``actions'' (i.e., ``mesh the lines'', ``mesh the surfaces'' and ``mesh
the volumes'') cannot be specified in the script files. They have to be
given either in the GUI or on the command line (see @ref{Running Gmsh},
and @ref{Command-line options}).
@menu
* Characteristic lengths::
* Structured grids::
* Miscellaneous mesh commands::
@end menu
@c .........................................................................
@c Characteristic lengths
@c .........................................................................
@node Characteristic lengths, Structured grids, Mesh commands, Mesh commands
@subsection Characteristic lengths
@cindex Characteristic lengths
@cindex Mesh, element size
@cindex Size, elements
@cindex Mesh, background
@cindex Background mesh
There are three ways to specify the size of the mesh elements for a
given geometry:
@enumerate
@item
First, if @code{Mesh.CharacteristicLengthFromPoints} is set (it is by
default), you can simply specify characteristic lengths at the
geometrical points of the model (with the @code{Point} command: see
@ref{Points}). The size of the mesh elements will then be computed by
linearly interpolating these characteristic lengths on the initial mesh
(see @ref{Mesh}). This might sometimes lead to over-refinement in some
areas, so that you may have to add ``dummy'' geometrical entities in the
model in order to get the desired element sizes.
This method works with all the algorithms implemented in the mesh
module. The final element sizes are of course constrained by the structured
algorithms for which the element sizes are explicitly specified (e.g.,
transfinite and extruded grids: see @ref{Structured grids}).
@item
Second, if @code{Mesh.CharacteristicLengthFromCurvature} is set (it is
not by default), the mesh will be adapted with respect to the curvature
of the geometrical entities.
@item
Finally, you can specify general characteristic lengths using mesh size
``fields''. Various fields exist:
@itemize @bullet
@item
A @code{PostView} field specifies an explicit background mesh in the
form of a scalar post-processing view (see @ref{Post-processing
commands}, and @ref{File formats}) in which the nodal values are the
target element sizes. This method is very general but it requires a
first (usually rough) mesh and a way to compute the target sizes on this
mesh (usually through an error estimation procedure, in an iterative
process of mesh adaptation).
(Note that you can also load a background mesh directly from the command
line using the @code{-bgm} option (@pxref{Command-line options}), or in
the GUI by selecting `Apply as background mesh' in the post-processing
view option menu.)
@item
A @code{Box} field specifies the size of the elements inside and outside
of a parallelipipedic region.
@item A @code{Threshold} field specifies the size of the mesh according to the
distance to some geometrical entities. These entities can for example be
geometry points and lines specified by an @code{Attractor} field.
@item
A @code{MathEval} field specifies the size of the mesh using an explicit
mathematical function.
@item
A @code{Min} field specifies the size as the minimum of the sizes
computed using other fields
@item
@dots{}
@end itemize
Fields are supported by all the algorithms except those based on
Netgen. The list of available fields with their options is given below.
@end enumerate
The three aforementioned methods can be used simultaneously, in which
case the smallest element size is selected at any given point.
All element sizes are further constrained by the
@code{Mesh.CharacteristicLengthMin}, @code{Mesh.CharacteristicLengthMax}
and @code{Mesh.CharacteristicLengthFactor} options (@pxref{Mesh
options})
Here are the mesh commands that are related to the specification of
characteristic lengths:
@ftable @code
@item Characteristic Length @{ @var{expression-list} @} = @var{expression};
Modify the characteristic length of the points whose identification
numbers are listed in @var{expression-list}. The new value is given by
@var{expression}.
@item Field[@var{expression}] = @var{string};
Create a new field (with id number @var{expression}), of type
@var{string}.
@item Field[@var{expression}].@var{string} = @var{char-expression} | @var{expression} | @var{expression-list};
Set the option @var{string} of the @var{expression}-th field.
@item Background Field = @var{expression};
Select the @var{expression}-th field as the one used to compute element
sizes. Only one background field can be given; if you want to combine
several field, use the @code{Min} or @code{Max} field (see below).
@end ftable
Here is the list of all available fields with their associated options:
@include opt_fields.texi
@c .........................................................................
@c Structured grids
@c .........................................................................
@node Structured grids, Miscellaneous mesh commands, Characteristic lengths, Mesh commands
@subsection Structured grids
@cindex Extrusion, mesh
@cindex Mesh, extrusion
@cindex Transfinite, mesh
@cindex Mesh, transfinite
@ftable @code
@item Extrude @{ @var{expression-list} @} @{ @var{extrude-list} @var{layers} @}
Extrudes both the geometry and the mesh using a translation
(@pxref{Extrusions}). The @var{layers} option determines how the mesh is
extruded and has the following syntax:
@example
@var{layers}:
@group
Layers @{ @var{expression} @} | Layers @{ @{ @var{expression-list} @}, @{ @var{expression-list} @} @} |
Recombine; @dots{}
@end group
@end example
In the first @code{Layers} form, @var{expression} gives the number of
elements to be created in the (single) layer. In the second form, the
first @var{expression-list} defines how many elements should be created
in each extruded layer, and the second @var{expression-list} gives the
normalized height of each layer (the list should contain a sequence of
@var{n} numbers 0 < @var{h1} < @var{h2} < @dots{} < @var{hn} <= 1). See
@ref{t3.geo}, for an example.
For line extrusions, the @code{Recombine} option will recombine triangles
into quadrangles when possible. For surface extrusions, the
@code{Recombine} option will recombine tetrahedra into prisms, hexahedra or
pyramids.
Please note that, starting with Gmsh 2.0, region numbers cannot be
specified explicitly anymore in @code{Layers} commands. Instead, as with
all other geometry commands, you must use the automatically created
entity identifier created by the extrusion command. For example, the
following extrusion command will return the id of the new ``top''
surface in @code{num[0]} and the id of the new volume in @code{num[1]}:
@example
num[] = Extrude @{0,0,1@} @{ Surface@{1@}; Layers@{10@}; @};
@end example
@item Extrude @{ @{ @var{expression-list} @}, @{ @var{expression-list} @}, @var{expression} @} @{ @var{extrude-list} @var{layers} @}
Extrudes both the geometry and the mesh using a rotation
(@pxref{Extrusions}). The @var{layers} option is defined as above.
@item Extrude @{ @{ @var{expression-list} @}, @{ @var{expression-list} @}, @{ @var{expression-list} @}, @var{expression} @} @{ @var{extrude-list} @var{layers} @}
Extrudes both the geometry and the mesh using a combined translation and
rotation (@pxref{Extrusions}). The @var{layers} option is defined as
above.
@item Extrude @{ Surface @{ @var{expression-list} @}; @var{layers} @}
Extrudes a boundary layer along the normals of the specified surfaces.
@item Transfinite Line @{ @var{expression-list} @} | "*" = @var{expression} < Using Progression | Bump @var{expression} >;
Selects the lines in @var{expression-list} to be meshed with the 1D
transfinite algorithm. The @var{expression} on the right hand side gives the
number of nodes that will be created on the line (this overrides any
characteristic length prescription---see @ref{Characteristic lengths}). The
optional argument `@code{Using Progression @var{expression}}' instructs the
transfinite algorithm to distribute the nodes following a geometric
progression (@code{Progression 2} meaning for example that each line element
in the series will be twice as long as the preceding one). The optional
argument `@code{Using Bump @var{expression}}' instructs the transfinite
algorithm to distribute the nodes with a refinement at both ends of the
line.
(A deprecated synonym for @code{Progression} is @code{Power}.)
@item Transfinite Surface @{ @var{expression-list} @} | "*" < = @{ @var{expression-list} @} > < Left | Right | Alternate > ;
Selects surfaces to be meshed with the 2D transfinite algorithm. The
@var{expression-list} on the right-hand-side should contain the
identification numbers of three or four points on the boundary of the
surface that define the corners of the transfinite interpolation. If no
identfication numbers are given, the transfinite algorithm will try to
find the corners automatically. The optional argument specifies the way
the triangles are oriented when the mesh is not recombined.
@item Transfinite Volume @{ @var{expression-list} @} | "*" < = @{ @var{expression-list} @} > ;
Selects five- or six-face volumes to be meshed with the 3D transfinite
algorithm. The @var{expression-list} on the right-hand-side should
contain the identification numbers of the six or eight points on the
boundary of the volume that define the corners of the transfinite
interpolation. If no identfication numbers are given, the transfinitealgorithm will try to find the corners automatically.
@end ftable
@c .........................................................................
@c Miscellaneous
@c .........................................................................
@node Miscellaneous mesh commands, , Structured grids, Mesh commands
@subsection Miscellaneous
Here is a list of all other mesh commands currently available:
@ftable @code
@item Coherence Mesh;
Removes all duplicate mesh vertices.
@item Color @var{color-expression} @{ Point | Line | Surface | Volume @{ @var{expression-list} @}; @dots{} @}
Sets the mesh color of the entities in @var{expression-list} to @var{color-expression}.
@item Hide @{ Point | Line | Surface | Volume @{ @var{expression-list} @}; @dots{} @}
Hides the mesh of the entities in @var{expression-list}, if
@code{General.VisibilityMode} is set to @code{0} or @code{2}.
@item Hide @var{char-expression};
Hides the mesh of the entity @var{char-expression}, if
@code{General.VisibilityMode} is set to @code{0} or @code{2}
(@var{char-expression} can for example be @code{"*"}).
@item Recombine Surface @{ @var{expression-list} @} | "*" < = @var{expression} >;
Recombines the triangular meshes of the surfaces listed in
@var{expression-list} into mixed triangular/quadrangular meshes. The
optional @var{expression} on the right hand side specifies the maximum
difference (in degrees) allowed between the largest angle of a
quadrangle and a right angle (a value of 0 would only accept quadrangles
with right angles; a value of 90 would allow degenerate quadrangles;
default value is 45).
@item Save @var{char-expression};
Saves the mesh in a file named @var{char-expression}, using the current
@code{Mesh.Format} (@pxref{Mesh options}). If the path in
@var{char-expression} is not absolute, @var{char-expression} is appended to
the path of the current file.
@item Show @{ Point | Line | Surface | Volume @{ @var{expression-list} @}; @dots{} @}
Shows the mesh of the entities in @var{expression-list}, if
@code{General.VisibilityMode} is set to @code{0} or @code{2}.
@item Show @var{char-expression};
Shows the mesh of the entity @var{char-expression}, if
@code{General.VisibilityMode} is set to @code{0} or @code{2}
(@var{char-expression} can for example be @code{"*"}).
@item Smoother Surface @{ @var{expression-list} @} = @var{expression};
Sets number of elliptic smoothing steps for the surfaces listed in
@var{expression-list} (smothing only applies to transfinite meshes at
the moment).
@end ftable
@c -------------------------------------------------------------------------
@c Mesh options
@c -------------------------------------------------------------------------
@node Mesh options, , Mesh commands, Mesh module
@section Mesh options
@cindex Options, mesh
@cindex Mesh, options
Mesh options control the behavior of mesh commands, as well as the waymeshes are displayed in the GUI. For the signification of the `Saved
in:' field in the following list, see @ref{General options}.
@include opt_mesh.texi
@c =========================================================================
@c Solver module
@c =========================================================================
@node Solver module, Post-processing module, Mesh module, Top
@chapter Solver module
@cindex Solver, module
@cindex Module, Solver
Five external solvers can be interfaced simultaneously with Gmsh.
If you just want to start a solver from the solver module, with no further
interactions between the solver and Gmsh, just edit the options relative to
one of the five available solvers (e.g., @code{Solver.Name0},
@code{Solver.Executable0}, @dots{}; see @ref{Solver options}), and set the
corresponding ``client-server'' option to zero
(e.g., @code{Solver.ClientServer0 = 0}). This doesn't require any
modification to be made to the solver.
If you want the solver to interact with Gmsh (for error messages, option
definitions, post-processing, etc.), you need to link your solver with the
@file{GmshClient.c} file and add the appropriate function calls inside your
program. You can then proceed as in the previous case, but this time you
should set the client-server option to 1 (e.g., @code{Solver.ClientServer0 =
1}), so that Gmsh and the solver can communicate through a Unix socket. See
@ref{Solver example}, for an example of how to interface a C++
solver. Bindings for solvers written in other languages (C, Perl and Python)
are available in the source distribution.
@menu
* Solver options::
* Solver example::
@end menu
@c -------------------------------------------------------------------------
@c Solver options
@c -------------------------------------------------------------------------
@node Solver options, Solver example, Solver module, Solver module
@section Solver options
@cindex Solver commands
@cindex Options, geometry
@include opt_solver.texi
@c -------------------------------------------------------------------------
@c Solver example
@c -------------------------------------------------------------------------
@node Solver example, , Solver options, Solver module
@section Solver example
@cindex Solver example
@cindex Example, solver
Here is a small example of how to interface a C++ solver with Gmsh. The
following listing reproduces the @file{utils/solvers/c++/solver.cpp} file
from the Gmsh source distribution (C, Perl and Python examples are also
available).
@sp 1
@verbatiminclude ../../utils/solvers/c++/solver.cpp
@sp 1
To define the above solver as the second external solver in Gmsh, you then
need to define the following options (either merge them in your Gmsh option
file, or use the @code{-option} command-line option---see @ref{Command-line
options}):
@sp 1
@verbatiminclude ../../utils/solvers/c++/solver.opt
@c =========================================================================
@c Post-processing module
@c =========================================================================
@node Post-processing module, Tutorial, Solver module, Top
@chapter Post-processing module
@cindex Post-processing, module
@cindex Module, Post-processing
@cindex 2D plots
@cindex 3D plots
@cindex Plots
@cindex Graphs
@cindex Views
Gmsh's post-processing module can handle multiple scalar, vector or
tensor datasets along with the geometry and the mesh. The datasets can
be given in several formats: in human-readable ``parsed'' format (these
are just part of a standard input script, but are usually put in
separate files with a @file{.pos} extension), in native MSH files (ASCII
or binary files with @file{.msh} extensions: see @ref{File formats}), or
in standard third-party formats (like MED:
@uref{http://www.code-aster.org/outils/med/}).
Once loaded into Gmsh, scalar fields can be displayed as iso-value lines
and surfaces or color maps, whereas vector fields can be represented
either by three-dimensional arrows or by displacement maps. (Tensor
fields are currently displayed as Von-Mises effective stresses. To
display other (combinations of) components, use @code{Plugin(Extract)}:
see @ref{Post-processing plugins}.)
In Gmsh's jargon, each dataset is called a ``view''. Each view is given
a name, and can be manipulated either individually (each view has its
own button in the GUI and can be referred to by its index in a script)
or globally (see the @code{PostProcessing.Link} option in
@ref{Post-processing options}).
By default, Gmsh treats all post-processing views as three-dimensional
plots, i.e., draws the scalar, vector and tensor primitives (points, lines,
triangles, tetrahedra, etc.) in 3D space. But Gmsh can also represent each
post-processing view containing @emph{scalar points} as two-dimensional
(``X-Y'') plots, either space- or time-oriented:
@itemize @bullet
@item
in a `2D space' plot, the scalar points are taken in the same order as they
are defined in the post-processing view: the abscissa of the 2D graph is
the curvilinear abscissa of the curve defined by the point series, and only
one curve is drawn using the values associated with the points. If several
time steps are available, each time step generates a new curve;
@item
in a `2D time' plot, one curve is drawn for each scalar point in the view
and the abscissa is the time step.
@end itemize
Although visualization is usually mostly an interactive task, Gmsh exposes
all the post-processing commands and options to the user in its scripting
language to permit a complete automation of the post-processing process (seee.g., @ref{t8.geo}, and @ref{t9.geo}).
The two following sections summarize all available post-processing commands
and options. Most options apply to both 2D and 3D plots (colormaps,
point/line sizes, interval types, time step selection, etc.), but some are
peculiar to 3D (lightning, element selection, etc.) or 2D plots (abscissa
labels, etc.). Note that 2D plots can be positioned explicitly inside the
graphical window, or be automatically positioned in order to avoid overlaps.
Sample post-processing files in human-readable ``parsed'' format and in
the native MSH file format are available in the @file{tutorial}
directory of Gmsh's distribution (@file{.pos} and @file{.msh}
files). The ``parsed'' format is defined in the next section (cf. the
@code{View} command); the MSH format is defined in @ref{File formats}.
@menu
* Post-processing commands::
* Post-processing plugins::
* Post-processing options::
@end menu
@c -------------------------------------------------------------------------
@c Post-processing commands
@c -------------------------------------------------------------------------
@node Post-processing commands, Post-processing plugins, Post-processing module, Post-processing module
@section Post-processing commands
@cindex Post-processing commands
@cindex Commands, post-processing
@ftable @code
@item Alias View[@var{expression}];
Creates an alias of the @var{expression}-th post-processing view.
Note that @code{Alias} creates a logical duplicate of the view without
actually duplicating the data in memory. This is very useful when you want
multiple simultaneous renderings of the same large dataset (usually with
different display options), but you cannot afford to store all copies in
memory. If what you really want is multiple physical copies of the data,
just merge the file containing the post-processing view multiple times.
@item AliasWithOptions View[@var{expression}];
Creates an alias of the @var{expression}-th post-processing view and copies
all the options of the @var{expression}-th view to the new aliased view.
@item Combine ElementsByViewName;
Combines all the post-processing views having the same name into new views.
The combination is done ``spatially'', i.e., simply by appending the
elements at the end of the new views.
@item Combine ElementsFromAllViews | Combine Views;
Combines all the post-processing views into a single new view. The
combination is done ``spatially'', i.e., simply by appending the elements at
the end of the new view.
@item Combine ElementsFromVisibleViews;
Combines all the visible post-processing views into a single new view. The
combination is done ``spatially'', i.e., simply by appending the elements at
the end of the new view.
@item Combine TimeStepsByViewName | Combine TimeSteps;
Combines the data from all the post-processing views having the same name
into new multi-time-step views. The combination is done ``temporally'',
i.e., as if the data in each view corresponds to a different time
instant. The combination will fail if the meshes in all the views are not
identical.
@item Combine TimeStepsFromAllViews;
Combines the data from all the post-processing views into a newmulti-time-step view. The combination is done ``temporally'', i.e., as if
the data in each view corresponds to a different time instant. The
combination will fail if the meshes in all the views are not identical.
@item Combine TimeStepsFromVisibleViews;
Combines the data from all the visible post-processing views into a new
multi-time-step view. The combination is done ``temporally'', i.e., as if
the data in each view corresponds to a different time instant. The
combination will fail if the meshes in all the views are not identical.
@item Delete View[@var{expression}];
Deletes (removes) the @var{expression}-th post-processing view. Note that
post-processing view numbers start at 0.
@item Delete Empty Views;
Deletes (removes) all the empty post-processing views.
@item Background Mesh View[@var{expression}];
Applies the @var{expression}-th post-processing view as the current
background mesh. Note that post-processing view numbers start at 0.
@item Plugin (@var{string}) . Run;
Executes the plugin @var{string}. The list of default plugins is given in
@ref{Post-processing plugins}.
@item Plugin (@var{string}) . @var{string} = @var{expression} | @var{char-expression};
Sets an option for a given plugin. See @ref{Post-processing plugins}, for a
list of default plugins and @ref{t9.geo}, for some examples.
@item Save View[@var{expression}] @var{char-expression};
Saves the the @var{expression}-th post-processing view in a file named
@var{char-expression}. If the path in @var{char-expression} is not absolute,
@var{char-expression} is appended to the path of the current file.
@item View "@var{string}" @{ @var{string} < ( @var{expression-list} ) > @{ @var{expression-list} @}; @dots{} @};
Creates a new post-processing view, named @code{"@var{string}"}. This
is an easy and quite powerful way to import post-processing data: all
the values are @var{expressions}, you can embed datasets directly into
your geometrical descriptions (see, e.g., @ref{t4.geo}), the data can be
easily generated ``on-the-fly'' (there is no header containing @emph{a
priori} information on the size of the dataset). The syntax is also very
permissive, which makes it ideal for testing purposes.
However this ``parsed format'' is read by Gmsh's script parser, which
makes it inefficient if there are many elements in the dataset. Also,
there is no connectivity information in parsed views and all the
elements are independent (all fields can be discontinuous), so a lot of
information can be duplicated. For large datasets, you should thus use
the mesh-based post-processing file format described in @ref{File
formats}, or use one of the standard formats like MED.
More explicitly, the syntax for a parsed @code{View} is the following
@example
@group
View "@var{string}" @{
< TIME @{ @var{expression-list} @}; >
@var{type} ( @var{list-of-coords} ) @{ @var{list-of-values} @};
@dots{}
@};
@end group
@end example
where the 47 object @w{@var{type}s} that can be displayed are:
@smallexample
@var{type} #@var{list-of-coords} #@var{list-of-values}
--------------------------------------------------------------------
Scalar point SP 3 1 * @var{nb-time-steps}
Vector point VP 3 3 * @var{nb-time-steps}Tensor point TP 3 9 * @var{nb-time-steps}
Scalar line SL 6 2 * @var{nb-time-steps}
Vector line VL 6 6 * @var{nb-time-steps}
Tensor line TL 6 18 * @var{nb-time-steps}
Scalar triangle ST 9 3 * @var{nb-time-steps}
Vector triangle VT 9 9 * @var{nb-time-steps}
Tensor triangle TT 9 27 * @var{nb-time-steps}
Scalar quadrangle SQ 12 4 * @var{nb-time-steps}
Vector quadrangle VQ 12 12 * @var{nb-time-steps}
Tensor quadrangle TQ 12 36 * @var{nb-time-steps}
Scalar tetrahedron SS 12 4 * @var{nb-time-steps}
Vector tetrahedron VS 12 12 * @var{nb-time-steps}
Tensor tetrahedron TS 12 36 * @var{nb-time-steps}
Scalar hexahedron SH 24 8 * @var{nb-time-steps}
Vector hexahedron VH 24 24 * @var{nb-time-steps}
Tensor hexahedron TH 24 72 * @var{nb-time-steps}
Scalar prism SI 18 6 * @var{nb-time-steps}
Vector prism VI 18 18 * @var{nb-time-steps}
Tensor prism TI 18 54 * @var{nb-time-steps}
Scalar pyramid SY 15 5 * @var{nb-time-steps}
Vector pyramid VY 15 15 * @var{nb-time-steps}
Tensor pyramid TY 15 45 * @var{nb-time-steps}
2nd order scalar line SL2 9 3 * @var{nb-time-steps}
2nd order vector line VL2 9 9 * @var{nb-time-steps}
2nd order tensor line TL2 9 27 * @var{nb-time-steps}
2nd order scalar triangle ST2 18 6 * @var{nb-time-steps}
2nd order vector triangle VT2 18 18 * @var{nb-time-steps}
2nd order tensor triangle TT2 18 54 * @var{nb-time-steps}
2nd order scalar quadrangle SQ2 27 9 * @var{nb-time-steps}
2nd order vector quadrangle VQ2 27 27 * @var{nb-time-steps}
2nd order tensor quadrangle TQ2 27 81 * @var{nb-time-steps}
2nd order scalar tetrahedron SS2 30 10 * @var{nb-time-steps}
2nd order vector tetrahedron VS2 30 30 * @var{nb-time-steps}
2nd order tensor tetrahedron TS2 30 90 * @var{nb-time-steps}
2nd order scalar hexahedron SH2 81 27 * @var{nb-time-steps}
2nd order vector hexahedron VH2 81 81 * @var{nb-time-steps}
2nd order tensor hexahedron TH2 81 243* @var{nb-time-steps}
2nd order scalar prism SI2 54 18 * @var{nb-time-steps}
2nd order vector prism VI2 54 54 * @var{nb-time-steps}
2nd order tensor prism TI2 54 162* @var{nb-time-steps}
2nd order scalar pyramid SY2 42 14 * @var{nb-time-steps}
2nd order vector pyramid VY2 42 42 * @var{nb-time-steps}
2nd order tensor pyramid TY2 42 126* @var{nb-time-steps}
2D text T2 3 arbitrary
3D text T3 4 arbitrary
@end smallexample
The coordinates are given `by node', i.e.,
@itemize @bullet
@item
@code{(@var{coord1}, @var{coord2}, @var{coord3})} for a point,
@item
@code{(@var{coord1-node1}, @var{coord2-node1}, @var{coord3-node1},}@*
@code{ @var{coord1-node2}, @var{coord2-node2}, @var{coord3-node2})} for a line,
@item
@code{(@var{coord1-node1}, @var{coord2-node1}, @var{coord3-node1},}@*
@code{ @var{coord1-node2}, @var{coord2-node2}, @var{coord3-node2},}@*
@code{ @var{coord1-node3}, @var{coord2-node3}, @var{coord3-node3})} for a triangle,
@item
etc.
@end itemize
The ordering of the nodes is given in @ref{Node ordering}.
The values are given by time step, by node and by component, i.e.:
@example
@var{comp1-node1-time1}, @var{comp2-node1-time1}, @var{comp3-node1-time1},
@var{comp1-node2-time1}, @var{comp2-node2-time1}, @var{comp3-node2-time1},
@var{comp1-node3-time1}, @var{comp2-node3-time1}, @var{comp3-node3-time1},@var{comp1-node1-time2}, @var{comp2-node1-time2}, @var{comp3-node1-time2},
@var{comp1-node2-time2}, @var{comp2-node2-time2}, @var{comp3-node2-time2},
@var{comp1-node3-time2}, @var{comp2-node3-time2}, @var{comp3-node3-time2},
@dots{}
@end example
For the 2D text objects, the two first @w{@var{expression}s} in
@var{list-of-coords} give the X-Y position of the string in screen
coordinates, measured from the top-left corner of the window. If the first
(respectively second) @var{expression} is negative, the position is measured
from the right (respectively bottom) edge of the window. If the value of the
first (respectively second) @var{expression} is larger than 99999, the
string is centered horizontally (respectively vertically). If the third
@var{expression} is equal to zero, the text is aligned bottom-left and
displayed using the default font and size. Otherwise, the third
@var{expression} is converted into an integer whose eight lower bits give
the font size, whose eight next bits select the font (the index corresponds
to the position in the font menu in the GUI), and whose eight next bits
define the text alignment (0=bottom-left, 1=bottom-center, 2=bottom-right,
3=top-left, 4=top-center, 5=top-right, 6=center-left, 7=center-center,
8=center-right).
For the 3D text objects, the three first @w{@var{expression}s} in
@var{list-of-coords} give the XYZ position of the string in model (real
world) coordinates. The fourth @var{expression} has the same meaning as the
third @var{expression} in 2D text objects.
For both 2D and 3D text objects, the @var{list-of-values} can contain an
arbitrary number of @w{@var{char-expression}s}.
The optional @code{TIME} list can contain a list of expressions giving the
value of the time (or any other variable) for which an evolution was saved.
@end ftable
@c -------------------------------------------------------------------------
@c Post-processing plugins
@c -------------------------------------------------------------------------
@node Post-processing plugins, Post-processing options, Post-processing commands, Post-processing module
@section Post-processing plugins
@cindex Post-processing plugins
@cindex Plugins, post-processing
Post-processing plugins permit to extend the functionality of Gmsh's
post-processing module. The difference between regular post-processing
options (@pxref{Post-processing options}) and post-processing plugins is
that regular post-processing options only change the way the data is
displayed, while post-processing plugins either create new post-processing
views, or modify the data stored in a view (in a destructive, non-reversible
way).
Plugins are available in the GUI by right-clicking on a view button (or
by clicking on the black arrow next to the view button) and then
selecting the `Plugin' submenu.
Here is the list of the plugins that are shipped by default with Gmsh:
@include opt_plugin.texi
@c -------------------------------------------------------------------------
@c Post-processing options
@c -------------------------------------------------------------------------
@node Post-processing options, , Post-processing plugins, Post-processing module
@section Post-processing options
@cindex Post-processing, options
@cindex Options, post-processing
General post-processing option names have the form
`@code{PostProcessing.@var{string}}'. Options peculiar to post-processing
views take two forms:
@enumerate
@item options that should apply to all views can be set through
`@code{View.@var{string}}', @emph{before any view is loaded};
@item options that should apply only to the @var{n}-th
view take the form `@code{View[@var{n}].@var{string}}' (@var{n} = 0, 1, 2,
@dots{}), @emph{after the @var{n}-th view is loaded}.
@end enumerate
See @ref{t8.geo}, and @ref{t9.geo}, for some examples.
@include opt_post.texi
@include opt_view.texi
@c todo:
@c @sp 1
@c The @code{ColorTable} is defined as a list...
@c =========================================================================
@c Tutorial
@c =========================================================================
@node Tutorial, Running Gmsh, Post-processing module, Top
@chapter Tutorial
@cindex Examples
@cindex Tutorial
The nine following examples introduce new features gradually, starting with
@file{t1.geo}. The files corresponding to these examples are available in
the @file{tutorial} directory of the Gmsh distribution.
To learn how to run Gmsh on your computer, see @ref{Running
Gmsh}. Screencasts that show how to use the GUI are available on
@uref{http://www.geuz.org/gmsh/screencasts/}.
@menu
* t1.geo::
* t2.geo::
* t3.geo::
* t4.geo::
* t5.geo::
* t6.geo::
* t7.geo::
* t8.geo::
* t9.geo::
@end menu
@c -------------------------------------------------------------------------
@c t1.geo
@c -------------------------------------------------------------------------
@node t1.geo, t2.geo, Tutorial, Tutorial
@section @file{t1.geo}
@verbatiminclude ../../tutorial/t1.geo
@c -------------------------------------------------------------------------
@c t2.geo
@c -------------------------------------------------------------------------
@node t2.geo, t3.geo, t1.geo, Tutorial
@section @file{t2.geo}
@verbatiminclude ../../tutorial/t2.geo
@c -------------------------------------------------------------------------
@c t3.geo
@c -------------------------------------------------------------------------
@node t3.geo, t4.geo, t2.geo, Tutorial
@section @file{t3.geo}
@verbatiminclude ../../tutorial/t3.geo
@c -------------------------------------------------------------------------
@c t4.geo
@c -------------------------------------------------------------------------
@node t4.geo, t5.geo, t3.geo, Tutorial
@section @file{t4.geo}
@verbatiminclude ../../tutorial/t4.geo
@c -------------------------------------------------------------------------
@c t5.geo
@c -------------------------------------------------------------------------
@node t5.geo, t6.geo, t4.geo, Tutorial
@section @file{t5.geo}
@verbatiminclude ../../tutorial/t5.geo
@c -------------------------------------------------------------------------
@c t6.geo
@c -------------------------------------------------------------------------
@node t6.geo, t7.geo, t5.geo, Tutorial
@section @file{t6.geo}
@verbatiminclude ../../tutorial/t6.geo
@c -------------------------------------------------------------------------
@c t7.geo
@c -------------------------------------------------------------------------
@node t7.geo, t8.geo, t6.geo, Tutorial
@section @file{t7.geo}
@verbatiminclude ../../tutorial/t7.geo
@c -------------------------------------------------------------------------
@c t8.geo
@c -------------------------------------------------------------------------
@node t8.geo, t9.geo, t7.geo, Tutorial
@section @file{t8.geo}
@verbatiminclude ../../tutorial/t8.geo
@c -------------------------------------------------------------------------
@c t9.geo
@c -------------------------------------------------------------------------
@node t9.geo, , t8.geo, Tutorial
@section @file{t9.geo}
@verbatiminclude ../../tutorial/t9.geo
@c =========================================================================
@c Running Gmsh
@c =========================================================================
@node Running Gmsh, File formats, Tutorial, Top
@chapter Running Gmsh
@cindex Operating system
@cindex Running Gmsh
@menu
* Interactive mode::
* Non-interactive mode::
* Command-line options::
* Mouse actions::
* Keyboard shortcuts::
@end menu
@c -------------------------------------------------------------------------
@c Interactive mode
@c -------------------------------------------------------------------------
@node Interactive mode, Non-interactive mode, Running Gmsh, Running Gmsh
@section Interactive mode
@cindex Interactive mode
Gmsh's first operating mode is the `interactive graphical mode'. To launch
Gmsh in interactive mode, just click or double-click on the Gmsh icon
(Windows and Mac), or type
@example
> gmsh
@end example
@noindent at your shell prompt in a terminal (Unix). 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 (@pxref{Tutorial}), select the `File->Open'
menu, and choose @file{t1.geo} in the input field. When using a terminal,
you can also specify the file name directly on the command line, i.e.:
@example
> gmsh t1.geo
@end example
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 lines; `2D' will mesh all
the surfaces---as well as all the lines 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 in the current mesh format, choose
`Save' in the context-dependent buttons, or select the appropriate format
with the `File->Save As' menu. The default mesh file name is based on the
name of the first input file on the command line (or @file{untitled} if
there wasn't any input file given), with an appended extension depending on
the mesh format@footnote{Nearly all the interactive commands have shortcuts:
see @ref{Keyboard shortcuts}, or select `Help->Keyboard Shortcuts' in the
menu.}.
To create a new geometry or to modify an existing geometry, select
'Geometry' in the module menu, and follow the context-dependent buttons.
For example, to create a spline, select `Elementary', `Add', `New' and
`Spline'. You will then be asked to select a list of points, and to type
@kbd{e} to finish the selection (or @kbd{q} to abort it). Once the
interactive command is completed, a text string is automatically added
at the end of the current project file. You can edit this project file
by hand at any time by pressing the `Edit' button in the `Geometry' menu
and then reloading the project by pressing `Reload'. For example, it is
often faster to define variables and points directly in the project
file, and then use the GUI to define the lines, the surfaces and the
volumes interactively.
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 bydirectly specifying the names of the files on the command line. For
example, to merge the post-processing views contained in the files
@file{view1.pos} and @file{view5.msh} together with the geometry of the
first tutorial @file{t1.geo}, you can type the following command:
@example
> gmsh t1.geo view1.pos view5.msh
@end example
In the Post-Processing module (select `Post-Processing' in the module
menu), three view buttons will appear, respectively labeled `A scalar
map', `Nodal scalar map' and `Element 1 vector'. These views contain
several time steps: you can loop through them with the small
``remote-control'' icons at the bottom of the graphic window. A mouse
click on the name will toggle the visibility of the selected view, while
a click on the arrow button on the right will provide access to the
view's options. If you want the modifications made to one view to affect
also all the other views, select the `Apply next changes to all views'
or `Force same options for all views' option in the
`Tools->Options->Post-processing' menu.
Note that all the options specified interactively can also be directly
specified in the script files. All available options, with their current
values, can be saved into a file by selecting `File->Save As->Gmsh
options', or simply viewed by pressing the `?' button in the status
bar. To save the current options as your default preferences for all
future Gmsh sessions, use the `Tools->Options->Save as defaults' button.
@c -------------------------------------------------------------------------
@c Non-interactive mode
@c -------------------------------------------------------------------------
@node Non-interactive mode, Command-line options, Interactive mode, Running Gmsh
@section Non-interactive mode
@cindex Non-interactive mode
Gmsh's second operating mode is the non-interactive (or `batch')
mode. In this mode, there is no GUI, and all operations are performed
without any user interaction@footnote{If you compile Gmsh without the
GUI, i.e., with @code{./configure --disable-gui}, this is the only mode
you have access to.}. For example, to mesh the first tutorial in
non-interactive mode, just type:
@example
> gmsh t1.geo -2
@end example
To mesh the same example, but with the background mesh available in the file
@file{bgmesh.pos}, type:
@example
> gmsh t1.geo -2 -bgm bgmesh.pos
@end example
For the list of all command-line options, see @ref{Command-line options}.
@c -------------------------------------------------------------------------
@c Command-line options
@c -------------------------------------------------------------------------
@node Command-line options, Mouse actions, Non-interactive mode, Running Gmsh
@section Command-line options
@cindex Command-line options
@cindex Options, command-line
@include command_line.texi
@c -------------------------------------------------------------------------@c Mouse actions
@c -------------------------------------------------------------------------
@node Mouse actions, Keyboard shortcuts, Command-line options, Running Gmsh
@section Mouse actions
@cindex Mouse, actions
@cindex Bindings, mouse
In the following, for a 2 button mouse, @kbd{Middle button} =
@kbd{Shift+Left button}. For a 1 button mouse, @kbd{Middle button} =
@kbd{Shift+Left button} and @kbd{Right button} = @kbd{Alt+Left button}.
@kbd{Move the mouse}:
@itemize @bullet
@item
Highlight the entity under the mouse pointer and display its properties
in the status bar
@item
Resize a lasso zoom or a lasso selection/unselection started with
@kbd{Ctrl+Left button}
@end itemize
@kbd{Left button}:
@itemize @bullet
@item
Rotate
@item
Select an entity
@item
Accept a lasso zoom or a lasso selection started with @kbd{Ctrl+Left
button}
@end itemize
@kbd{Ctrl+Left button}: Start a lasso zoom or a lasso selection/unselection
@kbd{Middle button}:
@itemize @bullet
@item
Zoom
@item
Unselect an entity
@item
Accept a lasso zoom or a lasso unselection
@end itemize
@kbd{Ctrl+Middle button}: Orthogonalize display
@kbd{Right button}:
@itemize @bullet
@item
Pan
@item
Cancel a lasso zoom or a lasso selection/unselection
@item
Pop-up menu on post-processing view button
@end itemize
@kbd{Ctrl+Right button}: Reset to default viewpoint
@c -------------------------------------------------------------------------
@c Keyboard shortcuts
@c -------------------------------------------------------------------------
@node Keyboard shortcuts, , Mouse actions, Running Gmsh
@section Keyboard shortcuts
@cindex Keyboard, shortcuts
@cindex Shortcuts, keyboard
@cindex Bindings, keyboard
(On Mac Ctrl is replaced by Cmd (the `Apple key') in the shortcuts
below.)
@include shortcuts.texi
@c =========================================================================
@c File Formats
@c =========================================================================
@node File formats, Programming notes, Running Gmsh, Top
@chapter File formats
@cindex File formats
This chapter describes Gmsh's native ``MSH'' file format, used to store
meshes and associated post-processing datasets. The MSH format exists in
two flavors: ASCII and binary. The format has a version number
(currently: 2.0) that is independent of Gmsh's main version number.
(Remember that for small post-processing datasets you can also use
human-readable ``parsed'' post-processing views, as described in
@ref{Post-processing commands}. Such ``parsed'' views do not require an
underlying mesh, and can therefore be easier easier to use in some
cases.)
@menu
* MSH ASCII file format::
* MSH binary file format::
* Node ordering::
* Legacy formats::
@end menu
@c -------------------------------------------------------------------------
@c MSH ASCII file format
@c -------------------------------------------------------------------------
@node MSH ASCII file format, MSH binary file format, File formats, File formats
@section MSH ASCII file format
@cindex Mesh, file format
@cindex File format, mesh
@cindex MSH file
The MSH ASCII file format contains one mandatory section giving
information about the file (@code{$MeshFormat}), followed by several
optional sections defining the nodes (@code{$Nodes}), elements
(@code{$Elements}), region names (@code{$PhysicalName}) and
post-processing datasets (@code{$NodeData}, @code{$ElementData},
@code{$ElementNodeData}).
Any section with an unrecognized header is simply ignored: you can thus
add comments in a @file{.msh} file by putting them e.g. inside a
@code{$Comments}/@code{$EndComments}) section.
Sections can be repeated in the same file, and post-processing sections
can be put into separate files (e.g. one file per time step).
The format is defined as follows:
@example
$MeshFormat
@var{version-number} @var{file-type} @var{data-size}
$EndMeshFormat
$Nodes
@var{number-of-nodes}
@var{node-number} @var{x-coord} @var{y-coord} @var{z-coord}
@dots{}
$EndNodes
$Elements@var{number-of-elements}
@var{elm-number} @var{elm-type} @var{number-of-tags} < @var{tag} > @dots{} @var{node-number-list}
@dots{}
$EndElements
$PhysicalNames
@var{number-of-names}
@var{phyical-number} "@var{physical-name}"
@dots{}
$EndPhysicalNames
$NodeData
@var{number-of-string-tags}
< "@var{string-tag}" >
@dots{}
@var{number-of-real-tags}
< @var{real-tag} >
@dots{}
@var{number-of-integer-tags}
< @var{integer-tag} >
@dots{}
@var{node-number} @var{value} @dots{}
@dots{}
$EndNodeData
$ElementData
@var{number-of-string-tags}
< "@var{string-tag}" >
@dots{}
@var{number-of-real-tags}
< @var{real-tag} >
@dots{}
@var{number-of-integer-tags}
< @var{integer-tag} >
@dots{}
@var{elm-number} @var{value} @dots{}
@dots{}
$EndElementData
$ElementNodeData
@var{number-of-string-tags}
< "@var{string-tag}" >
@dots{}
@var{number-of-real-tags}
< @var{real-tag} >
@dots{}
@var{number-of-integer-tags}
< @var{integer-tag} >
@dots{}
@var{elm-number} @var{number-of-nodes-per-element} @var{value} @dots{}
@dots{}
$ElementEndNodeData
@end example
@noindent
where
@table @code
@item @var{version-number}
is a real number equal to 2.0
@item @var{file-type}
is an integer equal to 0 in the ASCII file format.
@item @var{data-size}
is an integer equal to the size of the floating point numbers used in the
file (currently only @var{data-size} = sizeof(double) is supported).
@item @var{number-of-nodes}
is the number of nodes in the mesh.
@item @var{node-number}
is the number (index) of the @var{n}-th node in the mesh;
@var{node-number} must be a postive (non-zero) integer. Note that the
@w{@var{node-number}s} do not necessarily have to form a dense nor anordered sequence.
@item @var{x-coord} @var{y-coord} @var{z-coord}
are the floating point values giving the X, Y and Z coordinates of the
@var{n}-th node.
@item @var{number-of-elements}
is the number of elements in the mesh.
@item @var{elm-number}
is the number (index) of the @var{n}-th element in the mesh;
@var{elm-number} must be a postive (non-zero) integer. Note that the
@w{@var{elm-number}s} do not necessarily have to form a dense nor an
ordered sequence.
@item @var{elm-type}
defines the geometrical type of the @var{n}-th element:
@table @code
@item 1
2-node line.
@item 2
3-node triangle.
@item 3
4-node quadrangle.
@item 4
4-node tetrahedron.
@item 5
8-node hexahedron.
@item 6
6-node prism.
@item 7
5-node pyramid.
@item 8
3-node second order line (2 nodes associated with the vertices and 1
with the edge).
@item 9
6-node second order triangle (3 nodes associated with the vertices and 3
with the edges).
@item 10
9-node second order quadrangle (4 nodes associated with the vertices, 4
with the edges and 1 with the face).
@item 11
10-node second order tetrahedron (4 nodes associated with the vertices
and 6 with the edges).
@item 12
27-node second order hexahedron (8 nodes associated with the vertices,
12 with the edges, 6 with the faces and 1 with the volume).
@item 13
18-node second order prism (6 nodes associated with the vertices, 9 with
the edges and 3 with the quadrangular faces).
@item 14
14-node second order pyramid (5 nodes associated with the vertices, 8
with the edges and 1 with the quadrangular face).
@item 15
1-node point.
@item 16
8-node second order quadrangle (4 nodes associated with the vertices and
4 with the edges).
@item 17
20-node second order hexahedron (8 nodes associated with the vertices
and 12 with the edges).
@item 18
15-node second order prism (6 nodes associated with the vertices and 9
with the edges).
@item 19
13-node second order pyramid (5 nodes associated with the vertices and 8
with the edges).
@item 20
9-node third order incomplete triangle (3 nodes associated with the vertices, 6
with the edges)@item 21
10-node third order triangle (3 nodes associated with the vertices, 6
with the edges, 1 with the face)
@item 22
12-node fourth order incomplete triangle (3 nodes associated with the vertices, 9
with the edges)
@item 23
15-node fourth order triangle (3 nodes associated with the vertices, 9
with the edges, 3 with the face)
@item 24
15-node fifth order incomplete triangle (3 nodes associated with the vertices, 12
with the edges)
@item 25
21-node fifth order complete triangle (3 nodes associated with the vertices, 12
with the edges, 6 with the face)
@item 26
4-node third order edge (2 nodes associated with the vertices, 2
internal to the edge)
@item 27
5-node fourth order edge (2 nodes associated with the vertices, 3
internal to the edge)
@item 28
6-node fifth order edge (2 nodes associated with the vertices, 4
internal to the edge)
@item 29
20-node third order tetrahedron (4 nodes associated with the vertices,
12 with the edges, 4 with the faces)
@item 30
35-node fourth order tetrahedron (4 nodes associated with the vertices,
18 with the edges, 12 with the faces, 1 in the volume)
@item 31
56-node fifth order tetrahedron (4 nodes associated with the vertices,
24 with the edges, 24 with the faces, 4 in the volume)
@end table
See below for the ordering of the nodes.
@item @var{number-of-tags}
gives the number of integer tags that follow for the @var{n}-th
element. By default, the first @var{tag} is the number of the physical
entity to which the element belongs; the second is the number of the
elementary geometrical entity to which the element belongs; the third is
the number of a mesh partition to which the element belongs. All tags
must be postive integers, or zero. A zero tag is equivalent to no tag.
@item @var{node-number-list}
is the list of the node numbers of the @var{n}-th element. The ordering of
the nodes is given in @ref{Node ordering}.
@item @var{number-of-string-tags}
gives the number of string tags that follow. By default the first
@var{string-tag} is interpreted as the name of the post-processing view.
@c FIXME and the second as the name of the interpolation scheme.
@item @var{number-of-real-tags}
gives the number of real number tags that follow. By default the first
@var{real-tag} is interpreted as a time value associated with the
dataset.
@item @var{number-of-integer-tags}
gives the number of integer tags that follow. By default the first
@var{integer-tag} is interpreted as a time step index (starting at 0),
the second as the number of field components of the data in the view (1,
3 or 9), the third as the number of entities (nodes or elements) in the
view, and the fourth as the partition index for the view data (0 for no
partition).
@item @var{number-of-nodes-per-elements}
gives the number of node values for an element in an element-based view.
@item @var{value}is a real number giving the value associated with a node or an
element. For @code{NodeData} (respectively @code{ElementData}) views,
there are @var{ncomp} values per node (resp. per element), where
@var{ncomp} is the number of field components. For
@code{ElementNodeData} views, there are @var{ncomp} times
@var{number-of-nodes-per-elements} values per element.
@end table
Below is a small example (a mesh consisting of two quadrangles with an
associated nodal scalar dataset; the comments are not part of the actual
file!):
@smallexample
$MeshFormat
2.0 0 8
$EndMeshFormat
$Nodes
6 @emph{six mesh nodes:}
1 0.0 0.0 0.0 @emph{ node #1: coordinates (0.0, 0.0, 0.0)}
2 1.0 0.0 0.0 @emph{ node #2: coordinates (1.0, 0.0, 0.0)}
3 1.0 1.0 0.0 @emph{ etc.}
4 0.0 1.0 0.0
5 2.0 0.0 0.0
6 2.0 1.0 0.0
$EndNodes
$Elements
2 @emph{two elements:}
1 3 2 99 2 1 2 3 4 @emph{ quad #1: type 3, physical 99, elementary 2, nodes 1 2 3 4}
2 3 2 99 2 2 5 6 3 @emph{ quad #2: type 3, physical 99, elementary 2, nodes 2 5 6 3}
$EndElements
$NodeData
1 @emph{one string tag:}
"A scalar view" @emph{ the name of the view ("A scalar view")}
1 @emph{one real tag:}
0.0 @emph{ the time value (0.0)}
3 @emph{three integer tags:}
0 @emph{ the time step (0; time steps always start at 0)}
1 @emph{ 1-component (scalar) field}
6 @emph{ six associated nodal values}
1 0.0 @emph{value associated with node #1 (0.0)}
2 0.1 @emph{value associated with node #2 (0.1)}
3 0.2 @emph{etc.}
4 0.0
5 0.2
6 0.4
$EndNodeData
@end smallexample
@c -------------------------------------------------------------------------
@c MSH binary file format
@c -------------------------------------------------------------------------
@node MSH binary file format, Node ordering, MSH ASCII file format, File formats
@section MSH binary file format
The binary file format is similar to the ASCII format described above:
@example
$MeshFormat
@var{version-number} @var{file-type} @var{data-size}
@var{one-binary}
$EndMeshFormat
$Nodes
@var{number-of-nodes}
@var{nodes-binary}
$EndNodes
$Elements
@var{number-of-elements}
@var{element-header-binary}
@var{elements-binary}@var{element-header-binary}
@var{elements-binary}
@dots{}
$EndElements
[ all other sections are identical to ASCII, except that @var{node-number},
@var{elm-number}, @var{number-of-nodes-per-element} and @var{values} are written in
binary format ]
@end example
@noindent
where
@table @code
@item @var{version-number}
is a real number equal to 2.0.
@item @var{file-type}
is an integer equal to 1.
@item @var{data-size}
has the same meaning as in the ASCII file format. Currently only
@var{data-size} = sizeof(double) is supported.
@item @var{one-binary}
is an integer of value 1 written in binary form. This integer is used
for detecting if the computer on which the binary file was written and
the computer on which the file is read are of the same type (little or
big endian).
Here is a pseudo C code to write @var{one-binary}:
@example
int one = 1;
fwrite(&one, sizeof(int), 1, file);
@end example
@item @var{number-of-nodes}
has the same meaning as in the ASCII file format.
@item @var{nodes-binary}
is the list of nodes in binary form, i.e., a array of
@var{number-of-nodes} * (4 + 3 * @var{data-size}) bytes. For each node,
the first 4 bytes contain the node number and the next (3 *
@var{data-size}) bytes contain the three floating point coordinates.
Here is a pseudo C code to write @var{nodes-binary}:
@example
for(i = 0; i < number_of_nodes; i++)@{
fwrite(&num_i, sizeof(int), 1, file);
double xyz[3] = @{node_i_x, node_i_y, node_i_z@};
fwrite(&xyz, sizeof(double), 3, file);
@}
@end example
@item @var{number-of-elements}
has the same meaning as in the ASCII file format.
@item @var{element-header-binary}
is a list of 3 integers in binary form, i.e., an array of (3 * 4) bytes:
the first four bytes contain the type of the elements that follow (same
as @var{elm-type} in the ASCII format), the next four contain the number
of elements that follow, and the last four contain the number of tags
per element (same as @var{number-of-tags} in the ASCII format).
Here is a pseudo C code to write @var{element-header-binary}:
@example
int header[3] = @{elm_type, num_elm_follow, num_tags@};
fwrite(&header, sizeof(int), 3, file);
@end example
@item @var{elements-binary}is a list of elements in binary form, i.e., an array of ``number of
elements that follow'' * (4 + @var{number-of-tags} * 4 +
#@var{node-number-list} * 4) bytes. For each element, the first four
bytes contain the element number, the next (@var{number-of-tags} * 4)
contain the tags, and the last (#@var{node-number-list} * 4) contain the
node indices.
Here is a pseudo C code to write @var{elements-binary} for triangles
with the 3 standard tags (the physical and elementary regions, and the
mesh partition):
@example
for(i = 0; i < number_of_triangles; i++)@{
int data[7] = @{num_i, physical, elementary, partition,
node_i_1, node_i_2, node_i_3@};
fwrite(data, sizeof(int), 7, file);
@}
@end example
@end table
@c -------------------------------------------------------------------------
@c Node ordering
@c -------------------------------------------------------------------------
@node Node ordering, Legacy formats, MSH binary file format, File formats
@section Node ordering
@cindex Nodes, ordering
For all mesh and post-processing file formats, the reference elements
are defined as follows.
@smallexample
@group
Line: Line3: Line4:
0----------1 --> u 0-----2----1 0----2----3----1
@end group
@end smallexample
@smallexample
@group
Triangle: Triangle6: Triangle9/10: Triangle12/15:
v
^ 2
| | \
2 2 2 9 8
|`\ |`\ | \ | \
| `\ | `\ 7 6 10 (14) 7
| `\ 5 `4 | \ | \
| `\ | `\ 8 (9) 5 11 (12) (13) 6
| `\ | `\ | \ | \
0----------1 --> u 0-----3----1 0---3---4---1 0---3---4---5---1
@end group
@end smallexample
@smallexample
@group
Quadrangle: Quadrangle8: Quadrangle9:
v
^
|
3-----------2 3-----6-----2 3-----6-----2
| | | | | | |
| | | | | | |
| +---- | --> u 7 5 7 8 5
| | | | | | | | | | | |
0-----------1 0-----4-----1 0-----4-----1
@end group
@end smallexample
@smallexample
@group
Tetrahedron: Tetrahedron10:
v
.
,/
/
2 2
,/|`\ ,/|`\
,/ | `\ ,/ | `\
,/ '. `\ ,6 '. `5
,/ | `\ ,/ 8 `\
,/ | `\ ,/ | `\
0-----------'.--------1 --> u 0--------4--'.--------1
`\. | ,/ `\. | ,/
`\. | ,/ `\. | ,9
`\. '. ,/ `7. '. ,/
`\. |/ `\. |/
`3 `3
`\.
` w
@end group
@end smallexample
@smallexample
@group
Hexahedron: Hexahedron20: Hexahedron27:
v
3----------2 3----13----2 3----13----2
|\ ^ |\ |\ |\ |\ |\
| \ | | \ | 15 | 14 |15 24 | 14
| \ | | \ 9 \ 11 \ 9 \ 20 11 \
| 7------+---6 | 7----19+---6 | 7----19+---6
| | +-- |-- | -> u | | | | |22 | 26 | 23|
0---+---\--1 | 0---+-8----1 | 0---+-8----1 |
\ | \ \ | \ 17 \ 18 \ 17 25 \ 18
\ | \ \ | 10 | 12| 10 | 21 12|
\| w \| \| \| \| \|
4----------5 4----16----5 4----16----5
@end group
@end smallexample
@smallexample
@group
Prism: Prism15: Prism18:
w
^
|
3 3 3
,/|`\ ,/|`\ ,/|`\
,/ | `\ 12 | 13 12 | 13
,/ | `\ ,/ | `\ ,/ | `\
4------+------5 4------14-----5 4------14-----5
| | | | 8 | | 8 |
| ,/|`\ | | | | | ,/|`\ |
| ,/ | `\ | | | | | 15 | 16 |
|,/ | `\| | | | |,/ | `\|
,| | `\ 10 | 11 10-----17-----11
,/ | 0 | `\ | 0 | | 0 |
u | ,/ `\ | v | ,/ `\ | | ,/ `\ | | ,/ `\ | | ,6 `7 | | ,6 `7 |
|,/ `\| |,/ `\| |,/ `\|
1-------------2 1------9------2 1------9------2
@end group
@end smallexample
@smallexample
@group
Pyramid: Pyramid13: Pyramid14:
4 4 4
,/|\ ,/|\ ,/|\
,/ .'|\ ,/ .'|\ ,/ .'|\
,/ | | \ ,/ | | \ ,/ | | \
,/ .' | `. ,/ .' | `. ,/ .' | `.
,/ | '. \ ,7 | 12 \ ,7 | 12 \
,/ .' w | \ ,/ .' | \ ,/ .' | \
,/ | ^ | \ ,/ 9 | 11 ,/ 9 | 11
0----------.'--|-3 `. 0--------6-.'----3 `. 0--------6-.'----3 `.
`\ | | `\ \ `\ | `\ \ `\ | `\ \
`\ .' +----`\ - \ -> v `5 .' 10 \ `5 .' 13 10 \
`\ | `\ `\ \ `\ | `\ \ `\ | `\ \
`\.' `\ `\` `\.' `\` `\.' `\`
1----------------2 1--------8-------2 1--------8-------2
`\
u
@end group
@end smallexample
The nodes of a curved element are numbered in the following order:
@itemize --
@item the element principal vertices;
@item the internal nodes for each edge;
@item the internal nodes for each face;
@item the volume internal nodes.
@end itemize
The numbering for face and volume internal nodes is recursive, ie. the
numbering follows that of the nodes of an embedded face / volume. The
higher order nodes are assumed to be equispaced on the element.
@c -------------------------------------------------------------------------
@c Legacy formats
@c -------------------------------------------------------------------------
@node Legacy formats, , Node ordering, File formats
@section Legacy formats
This section describes Gmsh's older native file formats. Future versions
of Gmsh will continue to support these formats, but we recommend that
you do not use them in new aplications.
@c .........................................................................
@c MSH file format version 1.0
@c .........................................................................
@menu
* MSH file format version 1.0::
* POS ASCII file format::
* POS binary file format::
@end menu
@node MSH file format version 1.0, POS ASCII file format, Legacy formats, Legacy formats
@subsection MSH file format version 1.0
The MSH file format version 1.0 is Gmsh's old native mesh file format,
now superseded by the format described in @ref{MSH ASCII file
format}. It is defined as follows:
@example
$NOD
@var{number-of-nodes}
@var{node-number} @var{x-coord} @var{y-coord} @var{z-coord}
@dots{}
$ENDNOD
$ELM
@var{number-of-elements}
@var{elm-number} @var{elm-type} @var{reg-phys} @var{reg-elem} @var{number-of-nodes} @var{node-number-list}
@dots{}
$ENDELM
@end example
@noindent
where
@table @code
@item @var{number-of-nodes}
is the number of nodes in the mesh.
@item @var{node-number}
is the number (index) of the @var{n}-th node in the mesh;
@var{node-number} must be a postive (non-zero) integer. Note that the
@w{@var{node-number}s} do not necessarily have to form a dense nor an
ordered sequence.
@item @var{x-coord} @var{y-coord} @var{z-coord}
are the floating point values giving the X, Y and Z coordinates of the
@var{n}-th node.
@item @var{number-of-elements}
is the number of elements in the mesh.
@item @var{elm-number}
is the number (index) of the @var{n}-th element in the mesh;
@var{elm-number} must be a postive (non-zero) integer. Note that the
@w{@var{elm-number}s} do not necessarily have to form a dense nor an
ordered sequence.
@item @var{elm-type}
defines the geometrical type of the @var{n}-th element:
@table @code
@item 1
2-node line.
@item 2
3-node triangle.
@item 3
4-node quadrangle.
@item 4
4-node tetrahedron.
@item 5
8-node hexahedron.
@item 6
6-node prism.
@item 7
5-node pyramid.
@item 8
3-node second order line (2 nodes associated with the vertices and 1
with the edge).
@item 9
6-node second order triangle (3 nodes associated with the vertices and 3
with the edges).
@item 10
9-node second order quadrangle (4 nodes associated with the vertices, 4
with the edges and 1 with the face).
@item 11
10-node second order tetrahedron (4 nodes associated with the vertices
and 6 with the edges).
@item 12
27-node second order hexahedron (8 nodes associated with the vertices,
12 with the edges, 6 with the faces and 1 with the volume).@item 13
18-node second order prism (6 nodes associated with the vertices, 9 with
the edges and 3 with the quadrangular faces).
@item 14
14-node second order pyramid (5 nodes associated with the vertices, 8
with the edges and 1 with the quadrangular face).
@item 15
1-node point.
@item 16
8-node second order quadrangle (4 nodes associated with the vertices and
4 with the edges).
@item 17
20-node second order hexahedron (8 nodes associated with the vertices
and 12 with the edges).
@item 18
15-node second order prism (6 nodes associated with the vertices and 9
with the edges).
@item 19
13-node second order pyramid (5 nodes associated with the vertices and 8
with the edges).
@end table
See below for the ordering of the nodes.
@item @var{reg-phys}
is the number of the physical entity to which the element belongs;
@var{reg-phys} must be a postive integer, or zero. If @var{reg-phys} is
equal to zero, the element is considered not to belong to any physical
entity.
@item @var{reg-elem}
is the number of the elementary entity to which the element belongs;
@var{reg-elem} must be a postive (non-zero) integer.
@item @var{number-of-nodes}
is the number of nodes for the @var{n}-th element. This is redundant, but
kept for backward compatibility.
@item @var{node-number-list}
is the list of the @var{number-of-nodes} node numbers of the @var{n}-th
element. The ordering of the nodes is given in @ref{Node ordering}.
@end table
@c .........................................................................
@c POS ASCII file format
@c .........................................................................
@node POS ASCII file format, POS binary file format, MSH file format version 1.0, Legacy formats
@subsection POS ASCII file format
The POS ASCII file is Gmsh's old native post-processing format, now
superseded by the format described in @ref{MSH ASCII file format}. It is
defined as follows:
@example
$PostFormat
1.4 @var{file-type} @var{data-size}
$EndPostFormat
$View
@var{view-name} @var{nb-time-steps}
@var{nb-scalar-points} @var{nb-vector-points} @var{nb-tensor-points}
@var{nb-scalar-lines} @var{nb-vector-lines} @var{nb-tensor-lines}
@var{nb-scalar-triangles} @var{nb-vector-triangles} @var{nb-tensor-triangles}
@var{nb-scalar-quadrangles} @var{nb-vector-quadrangles} @var{nb-tensor-quadrangles}
@var{nb-scalar-tetrahedra} @var{nb-vector-tetrahedra} @var{nb-tensor-tetrahedra}
@var{nb-scalar-hexahedra} @var{nb-vector-hexahedra} @var{nb-tensor-hexahedra}
@var{nb-scalar-prisms} @var{nb-vector-prisms} @var{nb-tensor-prisms}
@var{nb-scalar-pyramids} @var{nb-vector-pyramids} @var{nb-tensor-pyramids}
@var{nb-scalar-lines2} @var{nb-vector-lines2} @var{nb-tensor-lines2}
@var{nb-scalar-triangles2} @var{nb-vector-triangles2} @var{nb-tensor-triangles2}
@var{nb-scalar-quadrangles2} @var{nb-vector-quadrangles2} @var{nb-tensor-quadrangles2}@var{nb-scalar-tetrahedra2} @var{nb-vector-tetrahedra2} @var{nb-tensor-tetrahedra2}
@var{nb-scalar-hexahedra2} @var{nb-vector-hexahedra2} @var{nb-tensor-hexahedra2}
@var{nb-scalar-prisms2} @var{nb-vector-prisms2} @var{nb-tensor-prisms2}
@var{nb-scalar-pyramids2} @var{nb-vector-pyramids2} @var{nb-tensor-pyramids2}
@var{nb-text2d} @var{nb-text2d-chars} @var{nb-text3d} @var{nb-text3d-chars}
@var{time-step-values}
< @var{scalar-point-value} > @dots{} < @var{vector-point-value} > @dots{}
< @var{tensor-point-value} > @dots{}
< @var{scalar-line-value} > @dots{} < @var{vector-line-value} > @dots{}
< @var{tensor-line-value} > @dots{}
< @var{scalar-triangle-value} > @dots{} < @var{vector-triangle-value} > @dots{}
< @var{tensor-triangle-value} > @dots{}
< @var{scalar-quadrangle-value} > @dots{} < @var{vector-quadrangle-value} > @dots{}
< @var{tensor-quadrangle-value} > @dots{}
< @var{scalar-tetrahedron-value} > @dots{} < @var{vector-tetrahedron-value} > @dots{}
< @var{tensor-tetrahedron-value} > @dots{}
< @var{scalar-hexahedron-value} > @dots{} < @var{vector-hexahedron-value} > @dots{}
< @var{tensor-hexahedron-value} > @dots{}
< @var{scalar-prism-value} > @dots{} < @var{vector-prism-value} > @dots{}
< @var{tensor-prism-value} > @dots{}
< @var{scalar-pyramid-value} > @dots{} < @var{vector-pyramid-value} > @dots{}
< @var{tensor-pyramid-value} > @dots{}
< @var{scalar-line2-value} > @dots{} < @var{vector-line2-value} > @dots{}
< @var{tensor-line2-value} > @dots{}
< @var{scalar-triangle2-value} > @dots{} < @var{vector-triangle2-value} > @dots{}
< @var{tensor-triangle2-value} > @dots{}
< @var{scalar-quadrangle2-value} > @dots{} < @var{vector-quadrangle2-value} > @dots{}
< @var{tensor-quadrangle2-value} > @dots{}
< @var{scalar-tetrahedron2-value} > @dots{} < @var{vector-tetrahedron2-value} > @dots{}
< @var{tensor-tetrahedron2-value} > @dots{}
< @var{scalar-hexahedron2-value} > @dots{} < @var{vector-hexahedron2-value} > @dots{}
< @var{tensor-hexahedron2-value} > @dots{}
< @var{scalar-prism2-value} > @dots{} < @var{vector-prism2-value} > @dots{}
< @var{tensor-prism2-value} > @dots{}
< @var{scalar-pyramid2-value} > @dots{} < @var{vector-pyramid2-value} > @dots{}
< @var{tensor-pyramid2-value} > @dots{}
< @var{text2d} > @dots{} < @var{text2d-chars} > @dots{}
< @var{text3d} > @dots{} < @var{text3d-chars} > @dots{}
$EndView
@end example
@noindent
where
@table @code
@item @var{file-type}
is an integer equal to 0 in the ASCII file format.
@item @var{data-size}
is an integer equal to the size of the floating point numbers used in the
file (usually, @var{data-size} = sizeof(double)).
@item @var{view-name}
is a string containing the name of the view (max. 256 characters).
@item @var{nb-time-steps}
is an integer giving the number of time steps in the view.
@item @var{nb-scalar-points}
@item @var{nb-vector-points}
@item @dots{}
are integers giving the number of scalar points, vector points, @dots{}, in
the view.
@item @var{nb-text2d}
@item @var{nb-text3d}
are integers giving the number of 2D and 3D text strings in the
view.
@item @var{nb-text2d-chars}
@item @var{nb-text3d-chars}are integers giving the total number of characters in the 2D and 3D strings.
@item @var{time-step-values}
is a list of @var{nb-time-steps} double precision numbers giving the value
of the time (or any other variable) for which an evolution was saved.
@item @var{scalar-point-value}
@item @var{vector-point-value}
@item @dots{}
are lists of double precision numbers giving the node coordinates and the
values associated with the nodes of the @var{nb-scalar-points} scalar
points, @var{nb-vector-points} vector points, @dots{}, for each of the
@var{time-step-values}.
For example, @var{vector-triangle-value} is defined as:
@example
@var{coord1-node1} @var{coord1-node2} @var{coord1-node3}
@var{coord2-node1} @var{coord2-node2} @var{coord2-node3}
@var{coord3-node1} @var{coord3-node2} @var{coord3-node3}
@var{comp1-node1-time1} @var{comp2-node1-time1} @var{comp3-node1-time1}
@var{comp1-node2-time1} @var{comp2-node2-time1} @var{comp3-node2-time1}
@var{comp1-node3-time1} @var{comp2-node3-time1} @var{comp3-node3-time1}
@var{comp1-node1-time2} @var{comp2-node1-time2} @var{comp3-node1-time2}
@var{comp1-node2-time2} @var{comp2-node2-time2} @var{comp3-node2-time2}
@var{comp1-node3-time2} @var{comp2-node3-time2} @var{comp3-node3-time2}
@dots{}
@end example
The ordering of the nodes is given in @ref{Node ordering}.
@item @var{text2d}
is a list of 4 double precision numbers:
@example
@var{coord1} @var{coord2} @var{style} @var{index}
@end example
where @var{coord1} and @var{coord2} give the X-Y position of the 2D string
in screen coordinates (measured from the top-left corner of the window) and
where @var{index} gives the starting index of the string in
@var{text2d-chars}. If @var{coord1} (respectively @var{coord2}) is negative,
the position is measured from the right (respectively bottom) edge of the
window. If @var{coord1} (respectively @var{coord2}) is larger than 99999,
the string is centered horizontally (respectively vertically). If
@var{style} is equal to zero, the text is aligned bottom-left and displayed
using the default font and size. Otherwise, @var{style} is converted into an
integer whose eight lower bits give the font size, whose eight next bits
select the font (the index corresponds to the position in the font menu in
the GUI), and whose eight next bits define the text alignment
(0=bottom-left, 1=bottom-center, 2=bottom-right, 3=top-left, 4=top-center,
5=top-right, 6=center-left, 7=center-center, 8=center-right).
@item @var{text2d-chars}
is a list of @var{nb-text2d-chars} characters. Substrings are separated with
the null `@code{\0}' character.
@item @var{text3d}
is a list of 5 double precision numbers
@example
@var{coord1} @var{coord2} @var{coord3} @var{style} @var{index}
@end example
where @var{coord1}, @var{coord2} and @var{coord3} give the XYZ coordinates
of the string in model (real world) coordinates, @var{index} gives the
starting index of the string in @var{text3d-chars}, and @var{style} has the
same meaning as in @var{text2d}.
@item @var{text3d-chars}
is a list of @var{nb-text3d-chars} chars. Substrings are separated with the
null `@code{\0}' character.
@end table
@c .........................................................................@c POS binary file format
@c .........................................................................
@node POS binary file format, , POS ASCII file format, Legacy formats
@subsection POS binary file format
The POS binary file format is the same as the POS ASCII file format
described in @ref{POS ASCII file format}, except that:
@enumerate
@item
@var{file-type} equals 1.
@item
all lists of floating point numbers and characters are written in binary
format
@item
there is an additional integer, of value 1, written before
@var{time-step-values}. This integer is used for detecting if the computer
on which the binary file was written and the computer on which the file is
read are of the same type (little or big endian).
@end enumerate
Here is a pseudo C code to write a post-processing file in binary format:
@example
int one = 1;
fprintf(file, "$PostFormat\n");
fprintf(file, "%g %d %d\n", 1.4, 1, sizeof(double));
fprintf(file, "$EndPostFormat\n");
fprintf(file, "$View\n");
fprintf(file, "%s %d "
"%d %d %d %d %d %d %d %d %d "
"%d %d %d %d %d %d %d %d %d "
"%d %d %d %d %d %d %d %d %d "
"%d %d %d %d %d %d %d %d %d "
"%d %d %d %d %d %d %d %d %d "
"%d %d %d %d\n",
view-name, nb-time-steps,
nb-scalar-points, nb-vector-points, nb-tensor-points,
nb-scalar-lines, nb-vector-lines, nb-tensor-lines,
nb-scalar-triangles, nb-vector-triangles, nb-tensor-triangles,
nb-scalar-quadrangles, nb-vector-quadrangles, nb-tensor-quadrangles,
nb-scalar-tetrahedra, nb-vector-tetrahedra, nb-tensor-tetrahedra,
nb-scalar-hexahedra, nb-vector-hexahedra, nb-tensor-hexahedra,
nb-scalar-prisms, nb-vector-prisms, nb-tensor-prisms,
nb-scalar-pyramids, nb-vector-pyramids, nb-tensor-pyramids,
nb-scalar-lines2, nb-vector-lines2, nb-tensor-lines2,
nb-scalar-triangles2, nb-vector-triangles2, nb-tensor-triangles2,
nb-scalar-quadrangles2, nb-vector-quadrangles2, nb-tensor-quadrangles2,
nb-scalar-tetrahedra2, nb-vector-tetrahedra2, nb-tensor-tetrahedra2,
nb-scalar-hexahedra2, nb-vector-hexahedra2, nb-tensor-hexahedra2,
nb-scalar-prisms2, nb-vector-prisms2, nb-tensor-prisms2,
nb-scalar-pyramids2, nb-vector-pyramids2, nb-tensor-pyramids2,
nb-text2d, nb-text2d-chars, nb-text3d, nb-text3d-chars);
fwrite(&one, sizeof(int), 1, file);
fwrite(time-step-values, sizeof(double), nb-time-steps, file);
fwrite(all-scalar-point-values, sizeof(double), ..., file);
...
fprintf(file, "\n$EndView\n");
@end example
In this pseudo-code, @var{all-scalar-point-values} is the array of double
precision numbers containing all the @var{scalar-point-value} lists, put one
after each other in order to form a long array of doubles. The principle is
the same for all other kinds of values.
@c =========================================================================
@c Programming notes
@c =========================================================================
@node Programming notes, Bugs and versions, File formats, Top
@chapter Programming notes
@cindex Programming, notes
Gmsh is written in C++, the scripting language is parsed using Lex and
Yacc (actually, Flex and Bison), and the GUI relies on OpenGL for the 3D
graphics and FLTK (@uref{http://www.fltk.org}) for the widget
set. Gmsh's build system is based on autoconf. Practical notes on how to
compile Gmsh's source code are included in the distribution. See
@ref{Frequently asked questions}, for more information.
@menu
* Main code structure::
* Coding style::
* Option handling::
@end menu
@c -------------------------------------------------------------------------
@c Main code structure
@c -------------------------------------------------------------------------
@node Main code structure, Coding style, Programming notes, Programming notes
@section Main code structure
Gmsh's code is structured in several libraries, roughly separated
between the three main core modules (Geo, Mesh, Post) and associated
utility libraries (Common, Numeric) on one hand, and graphics (Graphics)
and interface (Fltk, Parser) libraries on the other.
The geometry and mesh modules are based on an object-oriented model
class (Geo/GModel.h), built upon abstract geometrical entity classes
(Geo/GVertex.h, Geo/Gedge.h, Geo/GFace.h and Geo/GRegion.h). The
post-processing module is based on the concept of views (Post/PView.h)
and abstract data containers (derived from Post/PViewData.h).
@c -------------------------------------------------------------------------
@c Coding style
@c -------------------------------------------------------------------------
@node Coding style, Option handling, Main code structure, Programming notes
@section Coding style
If you plan to contribute code to the Gmsh project, here are some easy rules
to make the code easy to read/debug/maintain:
@enumerate
@item
please enable full warnings for your compiler (e.g., add @code{-Wall} to
@code{FLAGS} in the @file{variables} file);
@item
always use the @code{Msg::} class to print information, errors, @dots{};
@item
indent your files using @file{utils/misc/indent.sh};
@item
convert all tabs to spaces.
@end enumerate
@c -------------------------------------------------------------------------
@c Option handling
@c -------------------------------------------------------------------------
@node Option handling, , Coding style, Programming notes
@section Option handling
To add a new option in Gmsh:
@enumerate
@item
create the option in the @code{Context_T} class(@file{Common/Context.h}) if it's a classical option, or in the
@code{PViewOptions} class (@file{Post/PViewOptions.h}) if it's a
post-processing view-dependent option;
@item
in @file{Common/DefaultOptions.h}, give a name (for the parser to be able to
access it), a reference to a handling routine (i.e. @code{opt_XXX}) and a
default value for this option;
@item
create the handling routine @code{opt_XXX} in @file{Common/Options.cpp} (and
add the prototype in @file{Common/Options.h});
@item
optional: create the associated widget in @file{Fltk/optionWindow.cpp};
@end enumerate
@c todo:
@c Tools to check memory leaks
@c * on mac: use GMALLOC
@c (gdb) set env DYLD_INSERT_LIBRARIES /usr/lib/libgmalloc.dylib
@c * LIBNJAMD
@c export LD_PRELOAD=libnjamd.so
@c kill -USR1
@c * valgrind --leak-check=yes --show-reachable=yes gmsh file.geo -3
@c * purify
@c * memprof
@c =========================================================================
@c Bugs, versions and credits
@c =========================================================================
@node Bugs and versions, Tips and tricks, Programming notes, Top
@chapter Bugs, versions and credits
@menu
* Bugs::
* Versions::
* Credits::
@end menu
@c -------------------------------------------------------------------------
@c Bugs
@c -------------------------------------------------------------------------
@node Bugs, Versions, Bugs and versions, Bugs and versions
@section Bugs
@cindex Bugs, reporting
@cindex Reporting bugs
@cindex Contact information
@cindex Mailing list
@cindex Authors, e-mail
@cindex E-mail, authors
If you think you have found a bug in Gmsh, you can report it by electronic
mail to the Gmsh mailing list at @email{gmsh@@geuz.org}. Please send as
precise a description of the problem as you can, including sample input
files that produce the bug. Don't forget to mention both the version of Gmsh
and the version of your operation system (@pxref{Command-line options} to
see how to get this information).
See @ref{Frequently asked questions}, and the @file{TODO.txt} file in
the distribution to see which problems we already know about.
@c -------------------------------------------------------------------------
@c Versions
@c -------------------------------------------------------------------------
@node Versions, Credits, Bugs, Bugs and versions
@section Versions
@cindex Versions@cindex History, versions
@cindex Changelog
@verbatiminclude ../VERSIONS.txt
@c -------------------------------------------------------------------------
@c Credits
@c -------------------------------------------------------------------------
@node Credits, , Versions, Bugs and versions
@section Credits
@cindex Acknowledgments
@cindex Contributors, list
@cindex Credits
@verbatiminclude ../CREDITS.txt
@c =========================================================================
@c Tips ans Tricks
@c =========================================================================
@node Tips and tricks, Frequently asked questions, Bugs and versions, Top
@appendix Tips and tricks
@cindex Tips
@cindex Tricks
@cindex Efficiency, tips
@itemize @bullet
@item
Install the `info' version of this reference manual! On your (Unix)
system, this can be achieved by
@enumerate
@item
copying all @file{gmsh.info*} files to the place where your info files live
(usually @file{/usr/info}), and
@item
issuing the command @code{install-info /usr/info/gmsh.info /usr/info/dir}.
@end enumerate
You will then be able to access the documentation with the command
@code{info gmsh}. Note that particular sections (`nodes') can be accessed
directly. For example, @code{info gmsh surfaces} or @code{info gmsh surf}
will take you directly to @ref{Surfaces}.
@item
Use emacs to edit your files, and load the C++ mode. This permits automatic
syntax highlighting and easy indentation. Automatic loading of the C++ mode
for @file{.geo} files can be achieved by adding the following command in
your @code{.emacs} file: @code{(setq auto-mode-alist (append '(("\\.geo$"
. c++-mode)) auto-mode-alist))}.
@item
Define common geometrical objects and options in separate files, reusable in
all your problem definition structures.
@item
Save your preferred options with `Tools->Options->Save as defaults'. To
reset the default options, erase the @code{General.OptionsFileName}
(usually @file{.gmsh-options} in your home directory) or use the
`Restore default options' button in `Tools->Options->General->Output'.
@item
In the GUI:
@itemize --
@item
dragging the mouse in a numeric input field slides the value. The left
button moves one step per pixel, the middle by 10 * step, and the right
button by 100 * step;
@item
selecting the content of an input field, or lines in the message console(`Tools->Message Console'), copies the selected text to the clipboard;
@end itemize
@item
Read @ref{Frequently asked questions}...
@end itemize
@c =========================================================================
@c Frequently asked questions
@c =========================================================================
@node Frequently asked questions, License, Tips and tricks, Top
@appendix Frequently asked questions
@cindex Frequently asked questions
@cindex Questions, frequently asked
@cindex FAQ
@verbatiminclude ../FAQ.txt
@c =========================================================================
@c License
@c =========================================================================
@node License, Concept index, Frequently asked questions, Top
@appendix License
@cindex License
@include license.texi
@c =========================================================================
@c Concept Index (cindex)
@c =========================================================================
@node Concept index, Syntax index, License, Top
@unnumbered Concept index
@cindex Index, concepts
@cindex Concepts, index
@printindex cp
@c =========================================================================
@c Syntax Index (tindex+findex)
@c =========================================================================
@node Syntax index, , Concept index, Top
@unnumbered Syntax index
@cindex Index, syntax
@cindex Syntax, index
@cindex Keywords, index
@printindex tp
@bye