From: wolf Date: Fri, 6 Jun 2003 20:18:35 +0000 (+0000) Subject: Add warning about reading in grids that have hanging nodes. X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ff89fdb9001ed6e4e53f3ded65b13d897a793d2d;p=dealii-svn.git Add warning about reading in grids that have hanging nodes. git-svn-id: https://svn.dealii.org/trunk@7762 0785d39b-7218-0410-832d-ea1e28bc413d --- diff --git a/deal.II/deal.II/include/grid/grid_in.h b/deal.II/deal.II/include/grid/grid_in.h index 4e2efeefa6..6461cb6ee4 100644 --- a/deal.II/deal.II/include/grid/grid_in.h +++ b/deal.II/deal.II/include/grid/grid_in.h @@ -34,6 +34,20 @@ class SubCellData; * format for grid data. Any numerical data after the block of * topological information is ignored. * + * Since the coarse mesh fed into a @p{Triangulation} object cannot + * have hanging nodes, strange things will happen if the input file + * has them. This is due to the fact that most mesh description + * formats do not store neighborship information between cells, so the + * grid reading functions have to regenerate it. They do so by + * checking whether two cells have a common face. If there are hanging + * nodes in a triangulation, adjacent cells have no common face, so + * the grid reader concludes that the adjacent cells have no neighbors + * along these faces and must therefore be at the boundary. In effect, + * an internal crack of the domain is introduced this way. Since such + * cases are very hard to detect, the library does not make any + * attempt to abort on such situations, and you will get a + * triangulation that probably does not do what you want. + * * Note: if you experience unexpected problems with the use of this * class, be sure to read the documentation right until the end, and * also read the documentation of the @ref{GridReordering} class.