Beverly, in DG elements, the degrees of freedom are associated with the interior part of the cell, in particular they cannot be associated with vertices, nor faces, because for each vertex there could be more than one degree of freedom (in FE_DGQ<2>(1) there are 4, for example).
If you are looking for support points (of which, some are physically located on the vertices, but are not directly associated with them), then you could ask for fe.get_unit_support_points(), which would give you, numbered as in local dofs, the support points in the reference cell associated with each degree of freedom. If you build a quadrature formula with those support points and feed it to fe_values, with the compute_quadrature_points flag on, for example, you would get the location in real space of the support points of your FE. That is, only if the FE you are using supports them. If, for example, you use FE_DGP, then no support points are defined... Hope this helps. Luca. -- Luca Heltai <[email protected]> http://people.sissa.it/~heltai/ Scuola Internazionale Superiore di Studi Avanzati Phone: +39 040 3787 449, Office: 732 -- There are no answers, only cross references. On 29/lug/2010, at 18.04, Beverley Grieshaber wrote: > Hi > > In a code for 3D linear elasticity, I'm using an FESystem made up of 3 FE_DGQ > elements. I'm trying to access, in a given cell, the degrees of freedom > associated with a given vertex. Is there a way of doing this, for > discontinuous elements? > > The call "cell->vertex_dof_index(vertex_no, component)" ( with, for example, > vertex_no = 1, component = 0) is giving me an error, with the following > description: > The violated condition was: local_index < > dof_handler.selected_fe->dofs_per_vertex > The name and call sequence of the exception was: > ExcIndexRange(local_index, 0, > dof_handler.selected_fe->dofs_per_vertex) > Additional Information: > Index 0 is not in [0,0[ > > (It seems that the dofs on the cell are not directly associated with > particular vertices: if I call fe.dofs_per_vertex, it's returning the value > 0, although fe.dofs_per_cell is returning the value 24.) > > Thanks, > Beverley > > ### > > UNIVERSITY OF CAPE TOWN > > > This e-mail is subject to the UCT ICT policies and e-mail disclaimer > published on our website at > http://www.uct.ac.za/about/policies/emaildisclaimer/ or obtainable from +27 > 21 650 4500. This e-mail is intended only for the person(s) to whom it is > addressed. If the e-mail has reached you in error, please notify the author. > If you are not the intended recipient of the e-mail you may not use, > disclose, copy, redirect or print the content. If this e-mail is not related > to the business of UCT it is sent by the sender in the sender's individual > capacity. > > > ### > _______________________________________________ > dealii mailing list http://poisson.dealii.org/mailman/listinfo/dealii _______________________________________________ dealii mailing list http://poisson.dealii.org/mailman/listinfo/dealii
