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* 1.3 What does 'Gmsh' mean?
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Nothing... The name was derived from a previous version called "msh"
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(a shortcut for "mesh"), with the "g" prefix added to differentiate
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it. The default mesh file format used by Gmsh still uses the ".msh"
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(Note that in the US, people tend to pronounce 'Gmsh' as
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In English people tend to pronounce 'Gmsh' as "gee-mesh".
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* 1.4 Where can I find more information?
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* 2.1 Which OSes does Gmsh run on?
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Gmsh is known to run on Windows 95/98/NT/2000/XP, Linux, Mac OS X,
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Compaq Tru64 Unix (aka OSF1, aka Digital Unix), Sun OS, IBM AIX, SGI
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IRIX, FreeBSD and HP-UX. It should compile on any Unix-like operating
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system, provided that you have access to a recent C and C++ compiler.
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Gmsh is known to run on Windows 2000/XP/Vista, Mac OS X, Linux and
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* 2.2 Are there additional requirements to run Gmsh?
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the path of the library loader. A free replacement for OpenGL can be
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found at http://www.mesa3d.org.
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* 2.3 What do I need to compile Gmsh from the sources?
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You need a C and a C++ compiler (e.g. the GNU compilers gcc and g++)
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as well as the GSL (version 1.2 or higher; freely available from
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http://sources.redhat.com/gsl/) and FLTK (version 1.1.x, configured
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with OpenGL support; freely available from http://www.fltk.org).
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* 2.4 How do I compile Gmsh?
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Just type './configure; make; make install'. (Type './configure
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--help' to get the list of all configuration options.)
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* 2.3 How do I compile Gmsh from the source code?
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You need a C++ compiler. On Unix-like systems just type './configure;
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make; make install'. (Type './configure --help' to get the list of all
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configuration options.) To compile Gmsh on Windows with Visual C++ see
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Compiling a bare-bones non-graphical version of Gmsh does not require
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any extra packages. To get a usable version you will need the Blas and
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Lapack libraries. To build the graphical version you will need FLTK >=
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1.1.7 (freely available from http://www.fltk.org), configured with
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********************************************************************
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* 3.5 How can I save GIF, JPEG, ..., images?
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Just choose the appropriate format in 'File->Save As'.
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Just choose the appropriate format in 'File->Save As'. By default Gmsh
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guesses the format from the file extension, so you can just choose
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"myfile.jpg" in the dialog.
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* 3.6 How can I save MPEG, AVI, ..., animations?
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* 4.1 Does Gmsh support NURBS curves/surfaces?
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Yes, but only via STEP, IGES or BREP model import (not in .geo files).
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Yes, but only via STEP, IGES or BREP model import (not in .geo
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files). Gmsh has to be compiled with OpenCascade support for this to
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* 4.2 Gmsh is very slow when I use many transformations (Translate,
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Rotate, Symmetry, Extrude, etc. ). What's wrong?
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* 4.3 How can I display only selected parts of my model?
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Use 'Tool->Visibility'.
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There are three main modes: 'Elementary entities', in which the
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selections will apply to elementary geometrical entities; 'Physical
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groups', in which the selections will apply to physical entities; and
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'Mesh partitions', in which the selections will apply to mesh
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If the 'Recursive' option is set, selecting an entity also selects all
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its boundaries, recursively. For example, if 'Recursive' is set,
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selecting a surface will automatically select its boundary curves, as
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well as the boundaries of these curves (i.e., points).
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In the 'Browser' tab, you can select which entities to show or hide in
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a list (several entities can be selected at once by dragging the mouse
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or by holding the Ctrl or Shift keys while clicking). In the
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'Numerical input' tab, you can choose which entities to show or hide
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by explicitly specifying their identification tags. In the
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'Interactive' tab, you can hide/show entities using the mouse.
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4.4 When compiled with OpenCascade support, Gmsh crashes at startup
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Try changing these environment variables, which govern how OpenCascade
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4.5 Can I edit STEP/IGES/BRep models?
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Use 'Tools->Visibility'. This allows you to select elementary entities
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and physical groups, as well as mesh elements, in a variety of ways
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(in a list or tree browser, by identification number, interactively,
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* 4.4 Can I edit STEP/IGES/BRep models?
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Not yet. At the moment you can only change characteristic lengths and
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define physical groups. The easiest way to do this is to merge the
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* 5.1 What should I do when the 2D unstructured algorithm fails?
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Verify that the 1D mesh does not self-intersect. If it does, use a
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smaller characteristic length. If it doesn't, send us a bug report
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(including your geometry).
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Verify that the curves in the model do not self-intersect. If the
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model has very small features (such that the smallest characteristic
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length times the random perturbation factor Mesh.RandomFactor
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approaches machine accuracy), try increasing Mesh.RandomFactor.
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If everything fails send us a bug report with the version of your
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operating system and the full geometry.
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* 5.2 What should I do when the 3D unstructured algorithm fails?
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Try the other 3D algorithms (Tool->Options->Mesh->General->3D
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algorithm). If none works, try to adapt the characteristic lengths in
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your input file so that the surface mesh better matches the
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geometrical details of the model. If nothing works, send us a bug
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report (including your geometry).
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Verify that the surfaces in your model do not self-intersect or
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partially overlap. If they don't, try the other 3D algorithms
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(Tool->Options->Mesh->General->3D algorithm) or try to adapt the
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characteristic lengths in your input file so that the surface mesh
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better matches the geometrical details of the model.
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If nothing works, send us a bug report (including your geometry).
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* 5.3 The quality of the elements generated by the 3D algorithm is
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* 5.5 Does Gmsh automatically couple unstructured tetrahedral meshes
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and structured hexahedral meshed using pyramids?
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No. We need you help to implement this.
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No. We need your help to implement this.
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* 5.6 Can I explicitly assign region numbers to extruded layers?
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of the above. The clipping planes are defined using the four
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coefficients A,B,C,D of the equation A*x+B*y+C*y+D=0, which can be
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adjusted interactively by dragging the mouse in the input
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fields. There is also one additional clipping plane available for
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"cutting" only the mesh (by keeping entire elements), in
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'Tools->Options->Mesh->Cutting'.
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* 5.13 What is the signification of Rho, Eta and Gamma in
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Tools->Statistics?
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Rho ~ min_edge_length / max_edge_length
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For the exact definitions, see Geo/MElement.cpp. The graphs plot the
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the number of elements vs the quality measure.
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the number of elements vs. the quality measure.
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********************************************************************
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The solver executable (for example, 'getdp.exe') has to be in your
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path. If it is not, simply go to the solver options (the second tab in
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the Solver dialog) and specify its location in the 'Executable' field.
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the Solver dialog) and specify its location in the 'Command' field.
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* 6.3 Can I launch Gmsh from my solver (instead of launching my solver
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from Gmsh) in order to monitor a solution?
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'Displacement factor' option. (Remember that you can drag the mouse in
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all numeric input fields to slide the value!)
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Another option is to use the "general transformation expressions" (in
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Another option is to use the 'General transformation expressions' (in
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View->Options->Offset) on a scalar view, with the displacement map
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selected as the data source.
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'View->Remove->Empty Views' in the GUI, or with "Delete Empty Views;"
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* 7.13 My code generates data "time step by time step", and thus
423
cannot easily output Gmsh's multi-time-step post-processing files,
424
where the values for all the time steps are given per element. How can
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I use Gmsh's post-processor in this situation?
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Just create one view for each time step: Gmsh can handle an arbitrary
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number of views and it can deal with these separate views as
429
efficiently as with a single multi-time-step view. The only
430
disadvantage is that the total amount of disk space used is greater
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(since the node data is repeated for each time step).
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In practice, depending on the size of the data set, you may want to
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store all the views in a single file or create one separate file for
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each view, which you can then load selectively (and thus reduce the
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memory required for the analysis). In any case you can use
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'Tools->Options->Post-processing->View links' to apply options to
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multiple views at once, and the up and down arrow keys to loop through
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(animate) the views (instead of the left and right arrow keys for
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multi-time-step views).
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Also note that if all the views are based on the same grid, Gmsh can
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combine the separate views into a multi-time-step view by using the
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'View->Combine->Time Steps' menu, or by using the '-combine' command
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* 7.14 How can I see "inside" a complicated post-processing view?
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* 7.13 How can I see "inside" a complicated post-processing view?
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See question 5.12.
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Yet another (destructive) option is to use the ExtractVolume option in
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the CutSphere or CutPlane plugins.
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* 7.15 I am loading a valid 3D scalar view but Gmsh does not display
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* 7.14 I am loading a valid 3D scalar view but Gmsh does not display
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In versions < 1.61, the default drawing mode for 3D scalar views was
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to draw iso-surfaces. If your data set was constant per element, Gmsh
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would not draw anything (a fix for this would be to run
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Plugin(Smooth), which would average the data on the nodes of the
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grid)... This behavior has changed in version 1.61, and Gmsh now draws
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the solution on the boundary of the elements by default. Iso-surfaces
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are of course still available by setting 'Intervals type' to
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'Iso-values' in 'Tools->Options->View->Range'.
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Note that the most efficient way to visualize the dataset on the
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boundary of the elements is to run Plugin(Skin) on the view: this will
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extract the boundary of the dataset and only draw the data on this
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If your dataset is constant per element make sure you don't use the
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'Iso-values' interval type in 'Tools->Options->View->Range'.
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doc/FAQ.txt
