Dear Luca I need a Manifold<2,3> object but I could not succeed in composing SphericalManifold with a rotation. There were many dimensions involved in the composition which I have not understood.
But I think I understood what it is supposed to do, so I modified Spherical Manifold by adding in a 90 deg rotation. I use RotatedSphericalManifold for north/south faces and SphericalManifold for the other faces. When I run my code with this, I find large errors arising in the region where north/south faces meet the other faces. Is there some incompatibility in my mapping ? Will the face normal vectors (which lie in tangent plane) be correct at the junction of the two manifolds ? The RotatedSphericalManifold is attached. Thanks praveen On Mon, May 16, 2016 at 4:20 PM, luca.heltai <luca.hel...@gmail.com> wrote: > > > On 16 May 2016, at 12:37, Praveen C <cprav...@gmail.com> wrote: > > > > Dear Luca > > > > Thanks for clarifying this issue. I need tangent vector in my code. > > > > So I first define a ChartManifold which rotates by 90 deg about x-axis, > say RotateX. Then I compose it with SphericalManifold and use > > > > SphericalManifold * RotateX > > > > Is this what you meant ? > > > > We have the constructor > > > > CompositionManifold(F, G) > > > > Does this do F*G or G*F ? The description given in words is a bit > ambiguous. > > > y = G(F(x)) > > "ChartManifold going from the chart of the firstChartManifold to the > embedding space of the second ChartManifold" > > In your case, F is your spherical manifold, while your G is the rotation > manifold (to preserve periodicity of the spherical manifold). > > Best, > > Luca. > > > > > Thanks > > praveen > > > > On Mon, May 16, 2016 at 2:29 PM, luca.heltai <luca.hel...@gmail.com> > wrote: > > Dear Praveen, > > > > there is a bug in SphericalManifold for dimension 3, which makes it > unusable so far with MappingManifold. > > > > The issue is with the computation of the tangent vector across the north > and south poles. > > > > At the moment MappingManifold is the only class using this computation, > so if you don’t use MappingManifold, you don’t see this issue. > > > > You can solve it by writing a rotated SphericalManifold descriptor (one > where the poles are east and west respectively), and associating this > Manifold to the north and south faces of the sphere. You could use, for > example, CompositionManifold to compose a rotation of 90 degree along the x > or y axis with SphericalManifold, and attach the resulting manifold to the > north and south faces. > > > > This is related to some of the issues here: > https://github.com/dealii/dealii/issues/2530 > > > > What you are hitting is a problem with the geometry, not with > MappingManifold in itself. It is not possible to describe the surface of a > sphere with a single chart without introducing at least one singularity. We > have implemented the standard polar coordinate mapping, which has two > singularities (north and south poles respectively), and these are the ones > introducing nans in your computation. > > > > Everything works fine when computing intermediate points, but not when > computing tangents. I’m still thinking of a way to fix this. The easiest > fix is to implement the SphericalManifold without charts, but I haven’t had > much time to sit down and do some fun stuff lately… > > > > Though, I can help you with implementing fixes, if you are willing to > help… :) > > > > L. > > > > > On 16 May 2016, at 10:35, Praveen C <cprav...@gmail.com> wrote: > > > > > > Dear all > > > I am solving pde on sphere and want to use MappingManifold > > > > > > My mesh is generated like this. > > > > > > Point<spacedim> center(0.0, 0.0, 0.0); > > > GridGenerator::hyper_sphere(triangulation, center, Radius); > > > static SphericalManifold<dim,spacedim> surface_description; > > > triangulation.set_all_manifold_ids(0); > > > triangulation.set_manifold (0, surface_description); > > > triangulation.refine_global(n_refine); > > > > > > Changing from MappingQ to MappingManifold leads to blow up, with nan. > > > > > > Before I debug, is there an example I can see of MappingManifold usage > ? > > > > > > Thanks > > > praveen > > > > > > -- > > > The deal.II project is located at http://www.dealii.org/ > > > For mailing list/forum options, see > https://groups.google.com/d/forum/dealii?hl=en > > > --- > > > You received this message because you are subscribed to the Google > Groups "deal.II User Group" group. > > > To unsubscribe from this group and stop receiving emails from it, send > an email to dealii+unsubscr...@googlegroups.com. > > > For more options, visit https://groups.google.com/d/optout. > > > > -- > > The deal.II project is located at http://www.dealii.org/ > > For mailing list/forum options, see > https://groups.google.com/d/forum/dealii?hl=en > > --- > > You received this message because you are subscribed to the Google > Groups "deal.II User Group" group. > > To unsubscribe from this group and stop receiving emails from it, send > an email to dealii+unsubscr...@googlegroups.com. > > For more options, visit https://groups.google.com/d/optout. > > > > > > -- > > The deal.II project is located at http://www.dealii.org/ > > For mailing list/forum options, see > https://groups.google.com/d/forum/dealii?hl=en > > --- > > You received this message because you are subscribed to the Google > Groups "deal.II User Group" group. > > To unsubscribe from this group and stop receiving emails from it, send > an email to dealii+unsubscr...@googlegroups.com. > > For more options, visit https://groups.google.com/d/optout. > > -- > The deal.II project is located at http://www.dealii.org/ > For mailing list/forum options, see > https://groups.google.com/d/forum/dealii?hl=en > --- > You received this message because you are subscribed to the Google Groups > "deal.II User Group" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to dealii+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. 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