[Gmsh] List of Questions

[Joe Koski]

Many thanks. Everything works as advertised in your message, so I'm ready to
write a simple translator and try to make a 2D finite element run.

Apparently the Version 2 data output format includes only those elements
that are from geometric entities that are also listed as physical entities.
Correct?  

I never could get "Recombine" to work the way I thought it should, and make
some mesh triangles into quads. That isn't critical to this test. I'll
resubmit that question at a later date when I have a bit more experience.

Joe Koski

on 6/1/04 12:42 PM, Christophe Geuzaine at geuzaine at acm.caltech.edu wrote:

> Joe Koski wrote:
> 
>> I've been trying to create meshes with some success, but some questions have
>> regarding the proper use of GMSH have arisen. I'm using GMSH 1.52.1 on a
>> Macintosh with OS X 10.3.4.
>> 
>> Here are the questions, in no particular order:
>> 
>> 1) My .msh files follow the Version 1 format, not Version 2. For example,
>> the node section starts with $NOD, not $Nodes. Is this correct? When will
>> Version 2 be used?
> 
> Yes, the default is still version 1. You can save your mesh in the new
> format with File->Save as->Gmsh v2.0. To make version 2.0 the default
> format, just add "Mesh.MshFileVersion = 2;" in your option file
> ($HOME/.gmsh-options).
> 
>> 
>> 2) For Diriclet type boundary conditions, is it possible to associate a
>> unique value or a flag with a geometric line or surface (other than line or
>> surface number) that can be used later to trigger a translator to recognize
>> that particular boundary? For example, if the temperature at a boundary is
>> to be 293 K, is it possible to enter the value 293 somewhere during the
>> geometry construction? Should I use physical entities for this or is there
>> another mechanism?
> 
> Physical entities are exactly what you need. Look for example at
> tutorial/t1.geo to see how they work.
> 
>> 
>> 3) If I zoom and pan to a particular view on the screen, is it possible to
>> interactively write a .jpg of that view? I know how to do a screen capture,
>> but resolution can be lost that way.
> 
> Sure: File->Save as (or Ctrl+Shift+s) and enter "file.jpg" in the input
> field. By default, Gmsh tries to recognize the format by looking at the
> extension you provide. If you don't like that, just select the
> appropriate format from the drop-down list in the dialog.
> 
>> 
>> 4) So far I have been unsuccessful in recombining a simple 1 x 1 square mesh
>> of triangles to obtain some quadrilaterals. First, when I try to create a
>> Plane Surface, I am told to "Select Exterior Boundary" and I successfully
>> pick a line loop. Then I am asked to "Select Hole Boundary," but there is no
>> hole. What to do?
> 
> Press 'q'.
> 
> Note that the geometrical selection interface will be greatly improved
> in version 1.53 (which should be released really soon now).
> 
>> I've tried selecting the exterior boundary again, without
>> success. When I do fiddle somehow and successfully get a mesh, I do
>> "Define," "Recombine," and "Select Surface" then 'e' for end, and nothing
>> happens to the mesh. Any suggestions? My .geo file keeps changing, or I
>> would include it.
>> 
>> 5) I have Gmsh.app in my /Applications folder. Is there a way of running
>> gmsh from the terminal command line on a Mac? Otherwise, how do you access
>> the command line options?
> 
> If you want to use Gmsh in batch mode, you can simply call, e.g.,
> 
> /Applications/Gmsh.app/Contents/MacOS/Gmsh file.geo -3
> 
> Launching the GUI version will not work well, as I cannot include the
> resource forks in the binary in a tar.gz archive (I use the much nicer
> OS X XML scheme for that). If you really need to launch the GUI version
> from the command line, you will have to recompile Gmsh from the sources.
> 
> Best,
> 
> Christophe