On Fri, Mar 16, 2012 at 10:27:58AM +0000, Garth N. Wells wrote: > On 16 March 2012 10:11, Anders Logg <l...@simula.no> wrote: > > On Fri, Mar 16, 2012 at 09:28:41AM +0000, Garth N. Wells wrote: > >> On 16 March 2012 09:17, Johan Hake <hake....@gmail.com> wrote: > >> > Hello! > >> > > >> > I have implemented a new version of UnitSphere based on subdivision of an > >> > initial octahedral surface mesh and tetrahedralization using the CGAL > >> > framework. > >> > > >> > This is all fine, but CGAL uses alot of time tetrahedralizing the initial > >> > surface mesh. CGAL is also doing some funny things with the surface mesh. > >> > > >> > 1) It subdivide the initial surface mesh, which I want to prevent. Is > >> > that possible. > >> > 2) 1) results in small triangles on the surface, but large triangles > >> > in the interior. I set a tentative volume constraint based on the > >> > size of a triangle of the input mesh. > >> > > >> > You can try it out here: > >> > > >> > bzr branch lp:~dolfin-core/dolfin/hake-trunk > >> > > >> > from dolfin import * > >> > mesh = UnitSphereNew(4) > >> > # Do not try larger subdivisions than 4, at least for now. > >> > > >> > >> Did you look at the CGAL demo for generating a mesh or a sphere: > >> > >> > >> http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Mesh_3/Chapter_main.html#Subsection_50.3.1 > >> > >> ? It uses an implicit surface description. I has planning to add > >> support for meshing geometries from implicit descriptions. > > > > We (Johannes, Benjamin and myself) are planning to port the Netgen > > Python wrappers for CSG (Constructive Solid Geometry) to DOLFIN C++ > > based on CGAL (which will allow boolean operations). Is this the same > > thing? > > > > No - the implicit description is like a level set - the surface of an > object is described by f(x) = 0. The user needs to provide f and > sphere in which the object lies. One can also provides a tolerance > (the accepted distance from the true object edge and the mesh > boundary). This description is good for non-polyhedral domains,
ok, sounds useful. -- Anders > Garth > > > > > > >> Garth > >> > >> > > >> > Johan > >> > > >> > _______________________________________________ > >> > Mailing list: https://launchpad.net/~dolfin > >> > Post to : dolfin@lists.launchpad.net > >> > Unsubscribe : https://launchpad.net/~dolfin > >> > More help : https://help.launchpad.net/ListHelp > >> > >> _______________________________________________ > >> Mailing list: https://launchpad.net/~dolfin > >> Post to : dolfin@lists.launchpad.net > >> Unsubscribe : https://launchpad.net/~dolfin > >> More help : https://help.launchpad.net/ListHelp _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : dolfin@lists.launchpad.net Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
