Meshing problem with CSG

[Stefan Jakobsson]

The following code meshes a union of a cylinder and a box.

from dolfin import *
R =1.0
H=0.5
fragments=51
cyl = Cylinder(Point(0.0,0.0,H),Point(0.0,0.0,0.0),R,fragments)
box = Box(-R,-R,0,R,0,H)
geom = cyl+box
mesh = Mesh(geom,20)
plot(mesh)
interactive()

The dimensions are chosen so the geometries match. However, since fragments is not an even number the polygonial representations do not match. This results in a bad mesh as can be seen in the figure. In more complicated cases the meshing just goes on forever.

What would be desirable is to have some tolerance to fix the polygonial representations before meshing. Maybe the Triangulated Surface Mesh Simplification tools in CGAL can be helpful for this.

[Prof Garth Wells]

CGAL-based mesh generation is being moved out of DOLFIN and into mshr:

https://bitbucket.org/benjamik/mshr

Try out mshr, and add any feedback on the mshr Bitbucket page. Feedback, like you've provided, will be much appreciated.