From: David Wells Date: Fri, 20 May 2022 17:45:52 +0000 (-0400) Subject: Remove std::abs() from the tet volume calculation. X-Git-Tag: v9.4.0-rc1~184^2 X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=15f66452f4ec7b27de84693ccbc8940d7d1b69a1;p=dealii.git Remove std::abs() from the tet volume calculation. --- diff --git a/source/grid/grid_tools.cc b/source/grid/grid_tools.cc index 85ba1aa885..d15f5b4c11 100644 --- a/source/grid/grid_tools.cc +++ b/source/grid/grid_tools.cc @@ -871,16 +871,8 @@ namespace GridTools const std::vector> &all_vertices, std::vector> & cells) { - // This function only works for quads and hexes, - // and triangles. From the examples we tested, - // tetrahedron meshes loaded from Gmsh don't have - // negative measures, so we skip them for now. - - // Since we use std::abs() in GridTools::cell_measure() to - // compute the measures of tetrahdra, the measures - // are always positive. But if the orientation is wrong, - // we may get negative determinants of the Jacobians in - // MappingFE, which will triger the assert there. + // This function is presently only implemented for hypercube and simplex + // volumetric (codimension 0) elements. if (dim == 1) return 0; @@ -919,15 +911,11 @@ namespace GridTools .is_simplex()) { ++n_negative_cells; - if (dim == 2) - { - // Triangular mesh, swap any two vertices - std::swap(cell.vertices[1], cell.vertices[2]); - } - else - { - AssertThrow(false, ExcNotImplemented()); - } + // By basic rules for computing determinants we can just swap + // two vertices to fix a negative volume. Arbitrarily pick the + // last two. + std::swap(cell.vertices[n_vertices - 2], + cell.vertices[n_vertices - 1]); } else { diff --git a/source/grid/grid_tools_nontemplates.cc b/source/grid/grid_tools_nontemplates.cc index 03e867d3cc..cf2a3be76a 100644 --- a/source/grid/grid_tools_nontemplates.cc +++ b/source/grid/grid_tools_nontemplates.cc @@ -128,7 +128,7 @@ namespace GridTools const auto &c = all_vertices[vertex_indices[2]]; const auto &d = all_vertices[vertex_indices[3]]; - return (1.0 / 6.0) * std::abs((a - d) * cross_product_3d(b - d, c - d)); + return (1.0 / 6.0) * (d - a) * cross_product_3d(b - a, c - a); } else if (vertex_indices.size() == 6) // wedge { diff --git a/tests/simplex/grid_in_msh.cc b/tests/simplex/grid_in_msh.cc index 087581a009..75fc6bcf09 100644 --- a/tests/simplex/grid_in_msh.cc +++ b/tests/simplex/grid_in_msh.cc @@ -70,4 +70,9 @@ main() deallog.push("tetrahedral_elements_dim3_spacedim3: "); check_file<3, 3>(std::string(SOURCE_DIR "/grid_in_msh/tet.msh")); deallog.pop(); + + // Make sure things work when half of the tets are twisted too: + deallog.push("tetrahedral_elements_dim3_spacedim3_twisted: "); + check_file<3, 3>(std::string(SOURCE_DIR "/grid_in_msh/tet_half_twisted.msh")); + deallog.pop(); } diff --git a/tests/simplex/grid_in_msh.output b/tests/simplex/grid_in_msh.output index b1fa345b50..a76b63f017 100644 --- a/tests/simplex/grid_in_msh.output +++ b/tests/simplex/grid_in_msh.output @@ -133,3 +133,67 @@ LOOKUP_TABLE default DEAL:tetrahedral_elements_dim3_spacedim3: ::OK! +# vtk DataFile Version 3.0 +Triangulation generated with deal.II +ASCII +DATASET UNSTRUCTURED_GRID +POINTS 14 double +0.00000 0.00000 1.00000 +0.00000 0.00000 0.00000 +0.00000 1.00000 1.00000 +0.00000 1.00000 0.00000 +1.00000 0.00000 1.00000 +1.00000 0.00000 0.00000 +1.00000 1.00000 1.00000 +1.00000 1.00000 0.00000 +0.00000 0.500000 0.500000 +1.00000 0.500000 0.500000 +0.500000 0.00000 0.500000 +0.500000 1.00000 0.500000 +0.500000 0.500000 0.00000 +0.500000 0.500000 1.00000 + +CELLS 24 120 +4 13 10 11 9 +4 9 10 11 12 +4 11 8 10 13 +4 8 11 10 12 +4 4 13 6 9 +4 3 8 11 2 +4 1 8 0 10 +4 0 8 2 13 +4 4 10 0 13 +4 9 4 10 5 +4 11 2 13 6 +4 9 6 7 11 +4 1 3 8 12 +4 12 3 11 7 +4 7 12 5 9 +4 12 1 5 10 +4 13 4 10 9 +4 13 11 8 2 +4 13 6 9 11 +4 8 10 13 0 +4 10 1 8 12 +4 12 8 11 3 +4 9 7 12 11 +4 12 10 5 9 + +CELL_TYPES 24 +10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 + + + +CELL_DATA 24 +SCALARS MaterialID int 1 +LOOKUP_TABLE default +1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 + + + +SCALARS ManifoldID int 1 +LOOKUP_TABLE default +-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 + + +DEAL:tetrahedral_elements_dim3_spacedim3_twisted: ::OK! 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