Mesh generation with specific mesh size

On Wed, Jan 30, 2013 at 10:25:54AM -0000, corrado maurini wrote:
> New question #220533 on DOLFIN:
> https://answers.launchpad.net/dolfin/+question/220533
>
> I try to generate a mesh with a specific mesh size using the new CSG features.
>
> I followed the indication given on the doc page
>
> http://fenicsproject.org/documentation/dolfin/dev/python/programmers-reference/cpp/mesh/Mesh.html#dolfin.cpp.mesh.Mesh
>
> but I get the following error:
>
> TypeError: __init__() got an unexpected keyword argument 'meshsize'
>
> Below the code to reproduce the issue
>
> ## BEGIN ###
> from dolfin import *
> geom=Rectangle(0,0,1,2)
> mesh = Mesh(geometry, meshsize="fine")
> ## END ###
>
> If I use a integer as a parameter (as one should do looking at Mesh.ccp), Mesh accepts it, but it seems to do not affect the mesh resolution. For example
>
> mesh = Mesh(geometry, 10)
>
> gives the same result as
>
> mesh = Mesh(geometry, 1)
>
> How the integer parameter is expected to control the resolution?
>
> Is there a way to generate a unstructured mesh with given mesh size within dolfin?
>
> I use the development version of FEniCS
>
> P.S.: I currently use an external mesh generator, but the feature may be useful for test problems

Last I heard the resolution option was not implemented in 2D, only 3D.

Perhaps Benjamin or Johannes could give an updated on this?

--
Anders

Yes, the int parameter is not implemented in 2D and the keyword argument 'meshsize' does not work in either 2D or 3D.

Thanks for the information!

Note that you can use the 'cell_size' parameter in CSGCGALMeshGenerator2D to change the resolution of the mesh in 2D. I'm not sure if this is documented anywhere, but something like this should work:

from dolfin import *
geom = Rectangle(0,0,1,2)
mesh = Mesh(geom, 1)
gen = CSGCGALMeshGenerator2D(geom)
gen.parameters["cell_size"] = 0.05
gen.generate(mesh)

very nice, it works, thanks!

 11:41, Johannes Ring a écrit :

> from dolfin import *
> geom = Rectangle(0,0,1,2)
> mesh = Mesh(geom, 1)
> gen = CSGCGALMeshGenerator2D(geom)
> gen.parameters["cell_size"] = 0.05
> gen.generate(mesh)