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NAME

geo - plot a finite element mesh (rheolef-7.2)

EXAMPLES

Plot a mesh:

geo square.geo
geo box.geo
geo box.geo -full

Plot a mesh into a file:

geo square.geo -image-format png

Convert from a old geo file format to the new one:

geo -upgrade - < square-old.geo > square.geo

See below for the geo file format specification. The old file format does not contains edges and faces connectivity in 3d geometries, or edges connectivity in 2d geometries. The converter add it automatically into the upgraded file format. Conversely, the old file format is useful when combined with a translator from another file format that do not provides edges and faces connectivity.

INPUT FILE SPECIFICATION

filename

Specifies the name of the file containing the input mesh. The ’.geo’ suffix extension is assumed.

-

Read mesh on standard input instead on a file.

-name string

When mesh comes from standard input, the mesh name is not known and is set to ’output’ by default. This option allows one to change this default. This option is useful when dealing with output formats (graphic, format conversion) that creates auxiliary files, based on this name.

-Idir -I dir

Add dir to the Rheolef file search path. This mechanism initializes a search path given by the environment variable RHEOPATH. If the environment variable RHEOPATH is not set, the default value is the current directory.

-check

Check the mesh file: numbering, bounds and that for all element, its orientation is positive.

INPUT FORMAT OPTIONS

-if format -input-format format

Load mesh in a given file format. Supported input formats are: geo, bamg, vtk.

RENDER SPECIFICATION

-gnuplot

Use the gnuplot tool. This is the default for 1D geometry.

-paraview

Use the paraview tool. This is the default for 2D and 3D geometries.

RENDER OPTIONS

-[no]lattice

When using a high order geometry, the lattice inside any element appears. Default is on.

-[no]full

All internal edges appears, for 3d meshes. Default is off.

-[no]fill

Fill mesh faces using light effects, when available.

-[no]stereo

Rendering mode suitable for red-blue anaglyph 3D stereoscopic glasses. Option only available with paraview.

-[no]shrink

shrink elements (with paraview only).

-[no]cut

cut by plane and clip (with paraview only).

-[no]showlabel

Show or hide labels, boundary domains and various annotations. By default, domains are showed with a specific color.

-round [*float*]

Round the input up to the specified precision. This option, combined with -geo, leads to a round filter. Useful for non-regression test purpose, in order to compare numerical results between files with a limited precision, since the full double precision is machine-dependent.

OUTPUT FORMAT OPTIONS

-geo

output mesh on standard output stream in geo text file format, instead of plotting it.

-upgrade

Convert from a old geo file format to the new one.

-gmsh

Output mesh on standard output stream in gmsh text file format, instead of plotting it.

-image-format string

The argument is any valid image format, such as bitmap png, jpg, gif, tif, ppm, bmp or vectorial pdf, eps, ps, svg image file formats. this option can be used with the paraview and the gnuplot renders. The output file is e.g. basename.png when basename is the name of the mesh, or can be set with the -name option.

-resolution int int

The two arguments represent a couple of sizes, for the image resolution, e.g. 1024 and 768 for a 1024x768 image size. This option can be used together with the -image-format for any of the bitmap image formats. This option requires the paraview render.

OTHERS OPTIONS

-subdivide int

Subdivide each edge in k parts, where k is the prescribed argument. The new vertices are numbered so that they coincide with the Pk Lagrange nodes. It can be combined with the -geo option to get the subdivided mesh. In that case, default value is 1, i.e. no subdividing. It can also be combined with a graphic option, such that -gnuplot or paraview: When dealing with a curved high order geometry, k corresponds to the number of points per edge used to draw a curved element. In that case, this option is activated by default and value is the curved mesh order.

-add-boundary

Check for a domain named ’boundary’. If this domain does not exists, extract the boundary of the geometry and append it to the domain list. This command is useful for mesh converted from generators, as bamg, that cannot have more than one domain specification per boundary edge.

-rz -zr

Specifies the coordinate system. Useful when converting from bamg or gmsh format, that do not have any coordinate system specification.

-[no]verbose

Print messages related to graphic files created and command system calls (this is the default).

’-[no]clean

Clear temporary graphic files (this is the default).

-[no]execute

Execute graphic command (this is the default). The -noexecute variant is useful in conjunction with the -verbose and -noclean options in order to modify some render options by hand.

-dump

Used for debug purpose.

INQUIRE OPTIONS

-size -n-element

Print the mesh size, i.e. the number of elements and then exit.

-n-vertex

Print the number of elements and then exit.

-sys-coord

Print the coordinate system and then exit.

-hmin -hmax

Print the smallest (resp. largest) edge length and then exit.

-xmin -xmax

Print the bounding box lower-left (resp. top-right) corner and exit.

-min-element-measure -max-element-measure

Print the smallest (resp. largest) element measure and then exit.

FILE FORMAT CONVERSION

For the gmsh and bamg mesh generators, automatic file conversion is provided by the msh2geo and bamg2geo commands (see bamg2geo_1 and msh2geo_1 ).

For conversion from the .vtk legacy ascii file format to the .geo one, simply writes:

geo -if vtk -geo - < input.vtk > output.geo

THE GEO FILE FORMAT

This is the default mesh file format. It contains two entities, namely a mesh and a list of domains. The mesh entity starts with the mesh keyword, that should be at the beginning of a line. It is followed by the geo format version number: the current mesh format version number is 4. Next comes the header, containing global information: the space dimension (e.g. 1, 2 or 3), the number of nodes and the number of elements, for each type of element (tetrahedron, etc). When dimension is three, the number of faces (triangles, quadrangles) is specified, and then, when dimension is two or three, the number of edges is also specified. Follows the node coordinates list and the elements connectivity list. Each element starts with a letter indicating the element type:

letter | element type
-------|-------------
p | point
e | edge
t | triangle
q | quadrangle
T | tetrahedron
P | prism
H | hexahedron

Then, for each element, comes the vertex indexes. A vertex index is numbered in the C-style, i.e. the first index started at 0 and the larger one is the number of vertices minus one. A sample mesh writes:

mesh
4
header
dimension 2
nodes 4
triangles 2
edges 5
end header
0 0
1 0
1 1
0 1
t 0 1 3
t 1 2 3
e 0 1
e 1 2
e 2 3
e 3 0
e 1 3

Note that information about edges for 2d meshes and faces for 3d one are required for maintaining P2 and higher order approximation fields in a consistent way: degrees of freedom associated to sides requires that sides are well defined.

The second entity is a list of domains, that finishes with the end of file. A domain starts with the domain keyword, that should be at the beginning of a line. It is followed by the domain name, a simple string. Then, comes the domain format version: the current domain version number is 2. Next, the domain dimension and its number of elements. Finally, the list of elements: they are specified by the element index in the mesh, preceded by its orientation. A minus sign specifies that the element (generally a side) has the opposite orientation, while the plus sign is omitted. A sample domain list writes:

domain
bottom
2 1 1
0

domain
top
2 1 1
2

Copy and paste the previous sample mesh data in a file, e.g. ’square.geo’. Be carreful for the ’mesh’ and ’domain’ to be at the beginning of a line. Then enter:

geo square.geo

and the mesh is displayed.

THE SIMPLIFIED GEO FILE FORMAT

Information about edges for 2d meshes and faces for 3d one is not provided by most mesh generators (e.g. gmsh or bamg). It could be complex to build this list, so a simplified file format is also supported, without faces and/or edges connectivity, and the geo command proposes to build it automatically and save it in a more complete, upgraded geo file.

The simplified version of the previous mesh is:

mesh
4
header
dimension 2
nodes 4
triangles 2
end header
0 0
1 0
1 1
0 1
t 0 1 3
t 1 2 3

The domain list is no more able to refer to existing sides: edges are simply listed by their complete connectivity, thanks to the domain format version number 1. For the previous example, we have:

domain
bottom
1 1 1
e 0 1

domain
top
1 1 1
e 2 3

Copy and paste the previous simplified sample mesh data in a file, e.g. square0.geo. Be carreful for the mesh and domain keywords to be at the beginning of a line. Then enter:

geo -upgrade -geo square0.geo

and the previous mesh with its complete connectivity is displayed: edges has been automatically identified and numbered, and domains now refers to edge indexes.

Copyright (C) 2000-2018 Pierre Saramito <Pierre.Saramito [AT] imag.fr> GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>;. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.

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