Open source sofware for creating 3D objects

Mesh generators, CAD programs, and other tools
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Captain Slow
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Open source sofware for creating 3D objects

Post by Captain Slow » 10 Nov 2009, 20:25

Hi,

I am rather new to Elmer, I understand that one must import 3D objects, then create a mesh and that you cannot create the 3D object in Elmer itself.

I do not have access to any CAD type software so was wondering if anyone could recomend a free/open source software with which to draw objects before importing to Elmer.

I am using windows XP by the way.

Cheers

hazelsct
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Re: Open source sofware for creating 3D objects

Post by hazelsct » 10 Nov 2009, 21:57

You might try FreeCAD which does very frequent Windows builds of its development repository. I'm pretty sure it can save in STEP or IGES formats, which Elmer can import and mesh. http://juergen-riegel.net/FreeCAD/Docu/ ... =Main_Page

I generally use Gmsh, which also has Windows binaries: http://www.geuz.org/gmsh/

You'll probably get about as many other answers as there are people on this forum. :-)

raback
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Re: Open source sofware for creating 3D objects

Post by raback » 10 Nov 2009, 22:27

Yes, Elmer does not include geometry definitions tools. In addition to CAD objects to be meshed with netgen/tetgen you can import meshes created with other mesh generation software. For really simple meshes (mainly in 2D) you could even use some of the provided ascii formats to define the geometry (in2d, grd). There is a large number of examples in the directories under $ELMER_HOME/samples/ElmerGUI. You can study the different formats with ElmerGUI in File -> Open. There is a minimalistic README in each directory as well.

To get to the core of your question the answer is SALOME using OpenCASCADE technology. If you can deal with relatively simple geometries try Gmsh for mesh generation. You could perhaps also try some relatively inexpensive mesh generation tools such as GiD.

-Peter

Captain Slow
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Re: Open source sofware for creating 3D objects

Post by Captain Slow » 11 Nov 2009, 18:33

Thanks for the replys,

I have decided to use gmsh, it seemed to have a little more documentation than freecad for example. However (I may be being really stupid) I'm strugling to work out what file type to save my drawing in such that elmer can open it. Should I save my file with a mesh on it? When I try to open some my drawing in elmer the window remains blank.....

raback
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Re: Open source sofware for creating 3D objects

Post by raback » 11 Nov 2009, 20:21

Save as mesh (with the default extension .msh). If you define physical entities they are used in numbering of boundaries and bodies, if you do not use them the geometric entities will be used but with a new numbering.

There are existing .msh files in $ELMER_HOME/samples/ElmerGUI/gmsh.

-Peter

Captain Slow
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Re: Open source sofware for creating 3D objects

Post by Captain Slow » 11 Nov 2009, 20:28

Excellent! it works! Thankyou very much raback (and hazelsct), now I get to fiddle with the Navier-Stokes equations!

P.S. sorry for the tediously simple questions!

saha
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Re: Open source sofware for creating 3D objects

Post by saha » 10 Apr 2010, 19:15

Dear Raback
i am new in elmer. Please see the pipe.grd file in attachment. i am trying to revolve the geometry around the lower horizontal edge to create volume mesh. please help. please suggest any easier alternative way.
saha
Attachments
pipe.grd
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raback
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Re: Open source sofware for creating 3D objects

Post by raback » 10 Apr 2010, 19:30

Hi saha

Many people choose Gmsh among the open source meshers, see http://www.geuz.org/gmsh/. It certainly is more intuitive than ElmerGrid. Unfortunately I don't have time to study your case at the moment.

-Peter

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