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Merge pull request #13192 from drwells/fix-manifold-id-simplex-copy
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Fix manifold copying on lines when converting hexes to tets.
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@bangerth
bangerth committed Jan 10, 2022
2 parents ebc79f7 + bdf23d6 commit 33ecb3f
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4 changes: 4 additions & 0 deletions doc/news/changes/minor/20220107DavidWells
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
Fixed: GridGenerator::convert_hypercube_to_simplex_mesh() now correctly copies
line manifold ids in 3D.
<br>
(David Wells, 2022/01/07)
102 changes: 44 additions & 58 deletions source/grid/grid_generator.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -7716,58 +7716,21 @@ namespace GridGenerator
/* Boundary-edges 3D:
* For each of the 6 boundary-faces of the hexahedron, there are 8 edges (of
* different tetrahedrons) that coincide with the boundary, i.e.
* boundary-edges. Each boundary-edge is defined by 2 vertices.
* boundary-edges. Each boundary-edge is defined by 2 vertices. 4 of these
* edges are new (they are placed in the middle of a presently existing
* face); the other 4 coincide with edges present in the hexahedral
* triangulation. The new 4 edges inherit the manifold id of the relevant
* face, but the other 4 need to be copied from the input and thus do not
* require a lookup table.
*/
static const ndarray<unsigned int, 6, 8, 2>
vertex_ids_for_boundary_edges_3d = {{{{{{4, 6}},
{{4, 8}},
{{6, 8}},
{{4, 0}},
{{6, 2}},
{{0, 8}},
{{2, 8}},
{{0, 2}}}},
{{{{5, 7}},
{{5, 9}},
{{7, 9}},
{{5, 1}},
{{7, 3}},
{{1, 9}},
{{3, 9}},
{{1, 3}}}},
{{{{4, 5}},
{{4, 10}},
{{5, 10}},
{{4, 0}},
{{5, 1}},
{{0, 10}},
{{1, 10}},
{{0, 1}}}},
{{{{6, 7}},
{{6, 11}},
{{7, 11}},
{{6, 2}},
{{7, 3}},
{{2, 11}},
{{3, 11}},
{{2, 3}}}},
{{{{2, 3}},
{{2, 12}},
{{3, 12}},
{{2, 0}},
{{3, 1}},
{{0, 12}},
{{1, 12}},
{{0, 1}}}},
{{{{6, 7}},
{{6, 13}},
{{7, 13}},
{{6, 4}},
{{7, 5}},
{{4, 13}},
{{5, 13}},
{{4, 5}}}}}};

static const ndarray<unsigned int, 6, 4, 2>
vertex_ids_for_new_boundary_edges_3d = {
{{{{{4, 8}}, {{6, 8}}, {{0, 8}}, {{2, 8}}}},
{{{{5, 9}}, {{7, 9}}, {{1, 9}}, {{3, 9}}}},
{{{{4, 10}}, {{5, 10}}, {{0, 10}}, {{1, 10}}}},
{{{{6, 11}}, {{7, 11}}, {{2, 11}}, {{3, 11}}}},
{{{{2, 12}}, {{3, 12}}, {{0, 12}}, {{1, 12}}}},
{{{{6, 13}}, {{7, 13}}, {{4, 13}}, {{5, 13}}}}}};

std::vector<Point<spacedim>> vertices;
std::vector<CellData<dim>> cells;
Expand Down Expand Up @@ -7981,26 +7944,49 @@ namespace GridGenerator

// process boundary-faces: set boundary and manifold ids
if (dim == 2) // 2D boundary-faces
for (const auto &face_vertices :
vertex_ids_for_boundary_faces_2d[f])
add_cell(1, face_vertices, bid, mid);

{
for (const auto &face_vertices :
vertex_ids_for_boundary_faces_2d[f])
add_cell(1, face_vertices, bid, mid);
}
else if (dim == 3) // 3D boundary-faces
{
// set manifold id of tet-boundary-faces according to
// set manifold ids of tet-boundary-faces according to
// hex-boundary-faces
for (const auto &face_vertices :
vertex_ids_for_boundary_faces_3d[f])
add_cell(2, face_vertices, bid, mid);
// set manifold id of tet-boundary-edges according to
// set manifold ids of new tet-boundary-edges according to
// hex-boundary-faces
for (const auto &edge_vertices :
vertex_ids_for_boundary_edges_3d[f])
vertex_ids_for_new_boundary_edges_3d[f])
add_cell(1, edge_vertices, bid, mid);
}
else
Assert(false, ExcNotImplemented());
}

// set manifold ids of edges that were already present in the
// triangulation.
if (dim == 3)
{
for (const auto e : cell.line_indices())
{
auto edge = cell.line(e);
// Rather than use add_cell(), which does additional index
// translation, just add edges directly into subcell_data since
// we already know the correct global vertex indices.
CellData<1> edge_data;
edge_data.vertices[0] =
old_to_new_vertex_indices[edge->vertex_index(0)];
edge_data.vertices[1] =
old_to_new_vertex_indices[edge->vertex_index(1)];
edge_data.boundary_id = edge->boundary_id();
edge_data.manifold_id = edge->manifold_id();

subcell_data.boundary_lines.push_back(std::move(edge_data));
}
}
}

out_tria.create_triangulation(vertices, cells, subcell_data);
Expand Down
15 changes: 13 additions & 2 deletions tests/simplex/conv_hex_to_simplex.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -50,7 +50,7 @@ create_triangulation(Triangulation<dim, dim> &triangulation)

template <int dim, int spacedim>
void
check_file() // for dim = spaceim
check_file(unsigned int n_refinements = 0) // for dim = spaceim
{
Triangulation<dim, spacedim> in_tria, out_tria;
create_triangulation(in_tria);
Expand Down Expand Up @@ -83,7 +83,7 @@ check_file() // for dim = spaceim
if (i != numbers::flat_manifold_id)
out_tria.set_manifold(i, in_tria.get_manifold(i));

// out_tria.refine_global(2);
out_tria.refine_global(n_refinements);

// write 2 outputs (total mesh and only surface mesh)
const auto grid_out = [](const auto &tria,
Expand All @@ -98,6 +98,10 @@ check_file() // for dim = spaceim
flags.output_only_relevant = false;
}

// Demonstrate a bug with copying manifold ids more clearly:
if (dim == 3)
flags.output_only_relevant = false;

GridOut grid_out;
grid_out.set_flags(flags);

Expand Down Expand Up @@ -135,4 +139,11 @@ main()
"3D: conversion triangulation with tet elements to hex elements: ");
check_file<3, 3>();
deallog.pop();

// TETRAHEDRAL ELEMENTS
// dim = spacedim = 3
deallog.push(
"3D: conversion triangulation with tet elements to hex elements + refinement: ");
check_file<3, 3>(1);
deallog.pop();
}

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