[Gmsh] Area/Volume of physical groups

[Johannes]

Hello,

thanks! I use the plugin in my script, but unfortunately I encounter a problem:
I build various parametric meshes in a row, e.g. in the function `build_model` (see following source code). The second function call fails in the gmsh.view.getListData function with a non-zero return code.



import gmsh

def build_model():
    gmsh.initialize()

    gmsh.option.setNumber("General.Terminal", 1)

    s = gmsh.model.occ.addRectangle(0,0,0, 3,2)
    gmsh.model.occ.synchronize()
    p = gmsh.model.addPhysicalGroup(2, [s])
    gmsh.model.mesh.generate(2)

    gmsh.plugin.setNumber("MeshVolume", "Dimension", 2)
    gmsh.plugin.setNumber("MeshVolume", "Physical", p)
    gmsh.plugin.run("MeshVolume")

    _, _, data = gmsh.view.getListData(0)
    volume = data[0][-1]

    gmsh.finalize()

    return volume


vol1 = build_model()
vol2 = build_model()



Is there a way to fix this?

Kind regards,
Johannes




> > On 8 Mar 2019, at 17:19, Johannes joey5938 at protonmail.com wrote:
> > Hello,
> > thank you very much for your help!
> > The plugin works great, but I still have a question regarding its implementation: What's the idea behind pushing the coordinates of the models bounding box center also into the vector `data2->SP`?
>
> Just so that when execute the plugin interactively, you'll see the value in the middle of the volume.
>
> Christophe
>
> > Kind regards,
> > Johannes
> >
> > > > On 6 Mar 2019, at 17:46, Max Orok morok at mevex.com wrote:
> > > > Hello Johannes,
> > > > Volume case:
> > > > I think you can use the Plugin "MeshVolume" for this, calling it through the plugin API interface.
> > > > Here is a link to the implementation:
> > > > https://gitlab.onelab.info/gmsh/gmsh/blob/master/Plugin/MeshVolume.cpp
> > >
> > > Indeed; I've just modified the implementation a little bit so that it returns a post-processing view with the result (the version in Gmsh 4.2.0 only outputs a message). It will work for 1D, 2D and 3D. With the latest development snapshot, you can then just do something like this (here in Python):
> > > import gmsh
> > > gmsh.initialize()
> > > gmsh.option.setNumber("General.Terminal", 1)
> > > s = gmsh.model.occ.addRectangle(0,0,0, 3,2)
> > > gmsh.model.occ.synchronize()
> > > p = gmsh.model.addPhysicalGroup(2, [s])
> > > gmsh.model.mesh.generate(2)
> > > gmsh.plugin.setNumber("MeshVolume", "Dimension", 2)
> > > gmsh.plugin.setNumber("MeshVolume", "Physical", p)
> > > gmsh.plugin.run("MeshVolume")
> > > _, _, data = gmsh.view.getListData(0)
> > > print(data)
> > > gmsh.finalize()
> > >
> > > > Surface case:
> > > > Perhaps you could use the Integrate Plugin? I think you would have to first have to make a physical group of just the 2D boundary elements and then use the integrate plugin with a value of 1 (see discussion in link for more info)
> > > > https://gitlab.onelab.info/gmsh/gmsh/merge_requests/197
> > >
> > > Plugin(Integrate) is indeed also a possibility, that will also work in 1D, 2D and 3D. It's a bit more complicated, tough, as you need to create a post-processing view first (e.g. with "NewView"), then set the value to 1 (e.g. with "ModifyComponents"), then hide the parts of the mesh that you don't want consider, and finally call "Integrate". But it's of course more general, as you can integrate any function.
> > > Cheers,
> > > Christophe
> > >
> > > > I hope this helps!
> > > > Max
> > > > On Wed, Mar 6, 2019 at 11:23 AM Johannes joey5938 at protonmail.com wrote:
> > > >
> > > > > Hello,
> > > > > is there a way to get the surface area or volume of a physical group via the Gmsh API?
> > > > > Kind Regards
> > > > > Johannes
> > > > >
> > > > > gmsh mailing list
> > > > > gmsh at onelab.info
> > > > > http://onelab.info/mailman/listinfo/gmsh
> > > >
> > > > --
> > > > Max Orok
> > > > Contractor
> > > > www.mevex.com
> > > >
> > > > gmsh mailing list
> > > > gmsh at onelab.info
> > > > http://onelab.info/mailman/listinfo/gmsh
> > >
> > > —
> > > Prof. Christophe Geuzaine
> > > University of Liege, Electrical Engineering and Computer Science
> > > http://www.montefiore.ulg.ac.be/~geuzaine
>
> —
> Prof. Christophe Geuzaine
> University of Liege, Electrical Engineering and Computer Science
> http://www.montefiore.ulg.ac.be/~geuzaine