From 5351aaed37d0bfef8b65a875859d282ab1cdc224 Mon Sep 17 00:00:00 2001 From: Wolfgang Bangerth Date: Sun, 22 Nov 2015 19:21:57 -0600 Subject: [PATCH] Fix an issue with GridGenerator::extract_boundary_mesh(). Order the vertices of the surface mesh in such a way that the coordinate systems of all cells that make up the surface are either right-handed or left-handed when viewed from one side of the resulting surface. --- source/grid/grid_generator.cc | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) diff --git a/source/grid/grid_generator.cc b/source/grid/grid_generator.cc index cd984b565c..57a4480fc1 100644 --- a/source/grid/grid_generator.cc +++ b/source/grid/grid_generator.cc @@ -4213,9 +4213,6 @@ namespace GridGenerator std::map map_vert_index; //volume vertex indices to surf ones - unsigned int v_index; - CellData< boundary_dim > c_data; - for (typename Container::cell_iterator cell = volume_mesh.begin(0); cell != volume_mesh.end(0); @@ -4230,10 +4227,12 @@ namespace GridGenerator (boundary_ids.empty() || ( boundary_ids.find(face->boundary_id()) != boundary_ids.end())) ) { + CellData< boundary_dim > c_data; + for (unsigned int j=0; j::vertices_per_cell; ++j) { - v_index = face->vertex_index(j); + const unsigned int v_index = face->vertex_index(j); if ( !touched[v_index] ) { @@ -4246,6 +4245,19 @@ namespace GridGenerator c_data.material_id = static_cast(face->boundary_id()); } + // if we start from a 3d mesh, then we have copied the + // vertex information in the same order in which they + // appear in the face; however, this means that we + // impart a coordinate system that is right-handed when + // looked at *from the outside* of the cell if the + // current face has index 0, 2, 4 within a 3d cell, but + // right-handed when looked at *from the inside* for the + // other faces. we fix this by flipping opposite + // vertices if we are on a face 1, 3, 5 + if (dim == 3) + if (i % 2 == 1) + std::swap (c_data.vertices[1], c_data.vertices[2]); + cells.push_back(c_data); mapping.push_back(face); } -- 2.39.5