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doc/FAQ.txt

-$Id: FAQ.txt,v 1.4 2009-02-23 23:56:19 geuzaine Exp $
+$Id: FAQ.txt,v 1.5 2009-03-30 06:34:13 geuzaine Exp $
 
 This is the Gmsh FAQ
 
@@ -58,7 +58,7 @@ configuration options.) To compile Gmsh on Windows with Visual C++ see
 doc/README.msvc.
 
 Compiling a bare-bones non-graphical version of Gmsh does not require
-any extra packages. To get a usable version you will need the Blas and
+any extra packages. To get a usable version you will need the BLAS and
 Lapack libraries. To build the graphical version you will need FLTK >=
 1.1.7 (freely available from http://www.fltk.org), configured with
 OpenGL support.
@@ -68,7 +68,7 @@ OpenGL support.
 Section 3: General problems
 
 * 3.1 Gmsh (from a binary distribution) complains about missing
-libraries.
+  libraries.
 
 Try 'ldd gmsh' (or 'otool -L gmsh' on Mac OS X) to check if all the
 required shared libraries are installed on your system. If not,
@@ -76,7 +76,7 @@ install them. If it still doesn't work, recompile Gmsh from the
 sources.
 
 * 3.2 Gmsh keeps re-displaying its graphics when other windows
-partially hide the graphical window.
+  partially hide the graphical window.
 
 Disable opaque move in your window manager.
 
@@ -87,7 +87,7 @@ without GLX?  You should turn double buffering off (with the '-nodb'
 command line option).
 
 * 3.4 There is an ugly "ghost triangulation" in the vector
-PostScript/PDF files generated by Gmsh!
+  PostScript/PDF files generated by Gmsh!
 
 No, there isn't. This "ghost triangulation" is due to the fact that
 most PostScript previewers nowadays antialias the graphic primitives
@@ -116,7 +116,7 @@ files). Gmsh has to be compiled with OpenCascade support for this to
 work.
 
 * 4.2 Gmsh is very slow when I use many transformations (Translate,
-Rotate, Symmetry, Extrude, etc. ). What's wrong?
+  Rotate, Symmetry, Extrude, etc. ). What's wrong?
 
 The default behavior of Gmsh is to check and suppress all duplicate
 entities (points, lines and surfaces) each time a transformation
@@ -140,12 +140,13 @@ or per window).
 
 * 4.4 Can I edit STEP/IGES/BRep models?
 
-Not yet. At the moment you can only change characteristic lengths and
-define physical groups. The easiest way to do this is to merge the
-model in a .geo file using 'Merge "file.step";' and add the relevant
-scripting command after that. We plan to add more advanced editing
-features in the future (to delete entities, to create "mixed" surfaces
-and volumes, to export in .geo format, etc.).
+Not yet. At the moment you can only change characteristic lengths,
+define volumes and physical groups, or delete entities. The easiest
+way to do this is to merge the model in a .geo file using 'Merge
+"file.step";' and add the relevant scripting command after that. We
+plan to add more advanced editing features in the future (to delete
+entities, to create "mixed" surfaces and volumes, to export in .geo
+format, etc.).
 
 ********************************************************************
 
@@ -153,10 +154,9 @@ Section 5: Mesh module
 
 * 5.1 What should I do when the 2D unstructured algorithm fails?
 
-Verify that the curves in the model do not self-intersect. If the
-model has very small features (such that the smallest characteristic
-length times the random perturbation factor Mesh.RandomFactor
-approaches machine accuracy), try increasing Mesh.RandomFactor.
+Verify that the curves in the model do not self-intersect. If
+Mesh.RandomFactor * size(triangle)/size(model) approaches machine
+accuracy, increase Mesh.RandomFactor.
 
 If everything fails send us a bug report with the version of your
 operating system and the full geometry.
@@ -172,7 +172,7 @@ better matches the geometrical details of the model.
 If nothing works, send us a bug report (including your geometry).
 
 * 5.3 The quality of the elements generated by the 3D algorithm is
-very bad.
+  very bad.
 
 Use 'Optimize quality' in the mesh menu. 
 
@@ -183,7 +183,7 @@ the surface mesh a bit, or recombine your mesh to generate prisms or
 hexahedra instead of tetrahedra.
 
 * 5.5 Does Gmsh automatically couple unstructured tetrahedral meshes
-and structured hexahedral meshed using pyramids?
+  and structured hexahedral meshed using pyramids?
 
 No. We need your help to implement this.
 
@@ -206,14 +206,14 @@ elements, select 'Generate second order elements' in the mesh option
 panel. From the command line, you can also use '-order 2'.
 
 * 5.9 Can I import an existing surface mesh in Gmsh and use it to
-build a 3D mesh?
+  build a 3D mesh?
 
 Yes, you can import a surface mesh in any one of the supported mesh
 file formats, define a volume, and mesh it. For an example see
 'demos/sphere-discrete.geo'.
 
 * 5.10 How do I define boundary conditions or material properties in
-Gmsh?
+  Gmsh?
 
 By design, Gmsh does not try to incorporate every possible definition
 of boundary conditions or material properties--this is a job best left
@@ -226,12 +226,12 @@ manual as well as the tutorials (in particular 'tutorial/t1.geo') for
 a detailed description and some examples.
 
 * 5.11 How can I display only the mesh associated with selected
-geometrical entities?
+  geometrical entities?
 
 See question 4.3.
 
 * 5.12 How can I "explore" a mesh (for example, to see inside a
-complex structure)?
+  complex structure)?
 
 You can use 'Tools->Clipping Planes' to clip the region of
 interest. You can define up to 6 clipping planes in Gmsh (i.e., enough
@@ -242,8 +242,8 @@ coefficients A,B,C,D of the equation A*x+B*y+C*y+D=0, which can be
 adjusted interactively by dragging the mouse in the input
 fields.
 
-* 5.13 What is the signification of Rho, Eta and Gamma in 
-Tools->Statistics?
+* 5.13 What is the signification of Rho, Eta and Gamma in
+  Tools->Statistics?
 
 They measure the quality of the tetrahedra in a mesh:
 
@@ -254,6 +254,15 @@ Rho ~ min_edge_length / max_edge_length
 For the exact definitions, see Geo/MElement.cpp. The graphs plot the
 the number of elements vs. the quality measure.
 
+* 5.14 Why don't the vertex and/or elememt numbers on the screen match
+  the numbers in the mesh file?
+
+Gmsh reindexes the mesh vertices and elements so that they are
+numbered in a continuous sequence in the output files. The numbers
+displayed on screen after mesh generation thus usually differ from the
+ones saved in the mesh files. To check the actual numbers saved in the
+output file just load the mesh file back using File->Open.
+
 ********************************************************************
 
 Section 6: Solver module
@@ -275,14 +284,13 @@ Perl and Python solver examples are available in the source
 distribution in the 'utils/solvers' directory.
 
 * 6.2 On Windows, Gmsh does not seem to find the solver
-executable. What's wrong?
+  executable. What's wrong?
 
 The solver executable (for example, 'getdp.exe') has to be in your
-path. If it is not, simply go to the solver options (the second tab in
-the Solver dialog) and specify its location in the 'Command' field.
+path. If it is not specify its location in the 'Command' field.
 
 * 6.3 Can I launch Gmsh from my solver (instead of launching my solver
-from Gmsh) in order to monitor a solution?
+  from Gmsh) in order to monitor a solution?
 
 Sure. The simplest (but rather crude) approach if to re-launch Gmsh
 everytime you want to visualize something (a simple C program showing
@@ -357,14 +365,14 @@ the displacement map selected as the data source.
 And yet another solution is to use the Warp plugin.
 
 * 7.7 Can I color the arrows representing a vector field with data
-from a scalar field?
+  from a scalar field?
 
 Yes: load both the vector and the scalar fields (the two views must
 have the same number of elements) and, in the vector field options,
 select the scalar view in 'Data source'.
 
 * 7.8 Can I color isovalue surfaces with data from another scalar
-view?
+  view?
 
 Yes, using either the CutMap plugin (with the 'dView' option) or the
 Evaluate plugin.
@@ -375,12 +383,12 @@ Yes, using scripts. Have a look at 'tutorial/t8.geo' or
 'demos/anim.script' for some examples.
 
 * 7.10 Is there a way to visualize only certain components of
-vector/tensor fields?
+  vector/tensor fields?
 
 Yes, using 'Tools->Plugins->Extract'.
 
 * 7.11 Can I do arithmetic operations on a view? Can I perform
-operations involving different views?
+  operations involving different views?
 
 Yes, with the Evaluate plugin.
 
@@ -419,7 +427,7 @@ Yet another (destructive) option is to use the ExtractVolume option in
 the CutSphere or CutPlane plugins.
 
 * 7.14 I am loading a valid 3D scalar view but Gmsh does not display
-anything!
+  anything!
 
 If your dataset is constant per element make sure you don't use the
 'Iso-values' interval type in 'Tools->Options->View->Range'.

doc/texinfo/gmsh.texi

@@ -2198,10 +2198,10 @@ Lyon, 2000.}. New points are inserted sequentially at the circumcenter
 of the element that has the largest adimensional circumradius. The mesh
 is then reconnected using an anisotropic Delaunay criterion.
 @item
-The ``Frontal'' algorithm is based on the work of
-Rebay@footnote{S. Rebay, @emph{Efficient unstructured mesh generation by
-means of Delaunay triangulation and Bowyer-Watson algorithm}, J. Comput.
-Phys. 106, pp. 25--138, 1993.}.
+The ``Frontal'' algorithm is inspired by the work of
+S. Rebay@footnote{S. Rebay, @emph{Efficient unstructured mesh generation
+by means of Delaunay triangulation and Bowyer-Watson algorithm},
+J. Comput.  Phys. 106, pp. 25--138, 1993.}.
 @end enumerate
 
 These algorithms can be ranked as follows:
@@ -2224,12 +2224,12 @@ In 3D two unstructured algorithms are available:
 @item 
 The ``Delaunay'' algorithm is split into two separate steps. First, an
 initial mesh of the union of all the volumes in the model is performed
-using the Tetgen algorithm@footnote{H. Si, @emph{Tetgen: a quality
+using H. Si's Tetgen algorithm@footnote{H. Si, @emph{Tetgen: a quality
 tetrahedral mesh generator and three-dimensional Delaunay triangulator},
 2004.}. Then a three-dimensional version of the 2D Delaunay algorithm
 described above is applied.
 @item
-The ``Frontal'' algorithm uses J. Schoeberl's Netgen frontal
+The ``Frontal'' algorithm uses J. Schoeberl's Netgen
 algorithm@footnote{J. Schoeberl, @emph{Netgen, an advancing front
 2d/3d-mesh generator based on abstract rules}, Comput. Visual. Sci., 1,
 pp. 41--52, 1997.}.
@@ -2287,6 +2287,12 @@ 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.
 
+In all cases, Gmsh reindexes the mesh vertices and elements so that they
+are numbered in a continuous sequence in the output files. Note that the
+numbers displayed on screen after mesh generation thus usually differ
+from the ones saved in the mesh files. To check the actual numbers saved
+in the output file just load the file back using `File->Open'.
+
 @c -------------------------------------------------------------------------
 @c Mesh commands
 @c -------------------------------------------------------------------------