TriMeshSubstructureTopologyPreservingInvariant.cpp

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#include "TriMeshSubstructureTopologyPreservingInvariant.hpp"
#include <wmtk/Mesh.hpp>
 
#include <wmtk/simplex/RawSimplexCollection.hpp>
#include <wmtk/simplex/cofaces_single_dimension.hpp>
#include <wmtk/simplex/faces_single_dimension.hpp>
#include <wmtk/simplex/link.hpp>
#include <wmtk/simplex/open_star.hpp>
 
namespace wmtk::invariants {
TriMeshSubstructureTopologyPreservingInvariant::TriMeshSubstructureTopologyPreservingInvariant(
    const Mesh& m,
    const TypedAttributeHandle<int64_t>& substructure_edge_tag_handle,
    const int64_t substructure_tag_value)
    : Invariant(m, true, false, false)
    , m_substructure_edge_tag_handle(substructure_edge_tag_handle)
    , m_substructure_tag_value(substructure_tag_value)
{}
 
bool TriMeshSubstructureTopologyPreservingInvariant::before(
    const simplex::Simplex& input_simplex) const
{
    assert(input_simplex.primitive_type() == PrimitiveType::Edge);
 
    using namespace simplex;
 
    const auto edge_tag_acc = mesh().create_const_accessor(m_substructure_edge_tag_handle);
 
    // edge e = (u,v)
 
    const simplex::Simplex edge_e = input_simplex;
    const simplex::Simplex vertex_u(mesh(), PrimitiveType::Vertex, input_simplex.tuple());
    const simplex::Simplex vertex_v(
        mesh(),
        PrimitiveType::Vertex,
        mesh().switch_tuple(input_simplex.tuple(), PrimitiveType::Vertex));
 
    RawSimplexCollection lk_u_0(link(mesh(), vertex_u));
    RawSimplexCollection lk_u_1;
    RawSimplexCollection lk_u_2;
 
    int64_t u_incident_subset_edges = 0;
 
    for (const simplex::Simplex& e_u :
         cofaces_single_dimension_simplices(mesh(), vertex_u, PrimitiveType::Edge)) {
        if (edge_tag_acc.const_scalar_attribute(e_u.tuple()) == m_substructure_tag_value) {
            ++u_incident_subset_edges;
 
            std::vector<Tuple> vertices_dummy_tri =
                faces_single_dimension_tuples(mesh(), e_u, PrimitiveType::Vertex);
            vertices_dummy_tri.emplace_back(Tuple()); // add dummy vertex
 
            RawSimplex dummy_tri(mesh(), vertices_dummy_tri);
            RawSimplex opp_dummy_edge = dummy_tri.opposite_face(mesh(), vertex_u.tuple());
            lk_u_0.add(opp_dummy_edge);
            lk_u_0.add(opp_dummy_edge.faces());
 
            lk_u_1.add(opp_dummy_edge);
            lk_u_1.add(opp_dummy_edge.faces());
 
            RawSimplex raw_e_u(mesh(), e_u);
            lk_u_2.add(raw_e_u.opposite_face(mesh(), vertex_u.tuple()));
        }
    }
 
    // if u is an order 2 vertex
    if (u_incident_subset_edges != 0 && u_incident_subset_edges != 2) {
        lk_u_2.add(RawSimplex({-1})); // add dummy vertex
    }
 
    lk_u_0.sort_and_clean();
    lk_u_1.sort_and_clean();
    lk_u_2.sort_and_clean();
 
    // same code for vertex v
 
    RawSimplexCollection lk_v_0(link(mesh(), vertex_v));
    RawSimplexCollection lk_v_1;
    RawSimplexCollection lk_v_2;
 
    int64_t v_incident_subset_edges = 0;
 
    for (const simplex::Simplex& e_v :
         cofaces_single_dimension_simplices(mesh(), vertex_v, PrimitiveType::Edge)) {
        if (edge_tag_acc.const_scalar_attribute(e_v.tuple()) == m_substructure_tag_value) {
            ++v_incident_subset_edges;
 
            std::vector<Tuple> vertices_dummy_tri =
                faces_single_dimension_tuples(mesh(), e_v, PrimitiveType::Vertex);
            vertices_dummy_tri.emplace_back(Tuple()); // add dummy vertex
 
            RawSimplex dummy_tri(mesh(), vertices_dummy_tri);
            RawSimplex opp_dummy_edge = dummy_tri.opposite_face(mesh(), vertex_v.tuple());
            lk_v_0.add(opp_dummy_edge);
            lk_v_0.add(opp_dummy_edge.faces());
 
            lk_v_1.add(opp_dummy_edge);
            lk_v_1.add(opp_dummy_edge.faces());
 
            RawSimplex raw_e_v(mesh(), e_v);
            lk_v_2.add(raw_e_v.opposite_face(mesh(), vertex_v.tuple()));
        }
    }
 
    // if v is an order 2 vertex
    if (v_incident_subset_edges != 0 && v_incident_subset_edges != 2) {
        lk_v_2.add(RawSimplex({-1})); // add dummy vertex
    }
 
    lk_v_0.sort_and_clean();
    lk_v_1.sort_and_clean();
    lk_v_2.sort_and_clean();
 
    if (!RawSimplexCollection::get_intersection(lk_u_2, lk_v_2).simplex_vector().empty()) {
        return false;
    }
 
    // lk_e
    RawSimplexCollection lk_e_0(link(mesh(), edge_e));
    RawSimplexCollection lk_e_1;
 
    RawSimplex raw_edge_e(mesh(), edge_e);
 
    if (edge_tag_acc.const_scalar_attribute(edge_e.tuple()) == m_substructure_tag_value) {
        RawSimplex dummy_vertex({-1});
        lk_e_0.add(dummy_vertex);
        lk_e_1.add(dummy_vertex);
    }
 
    lk_e_0.sort_and_clean();
    lk_e_1.sort_and_clean();
 
    RawSimplexCollection intersection_u_v_0 =
        RawSimplexCollection::get_intersection(lk_u_0, lk_v_0);
    if (!RawSimplexCollection::are_simplex_collections_equal(intersection_u_v_0, lk_e_0)) {
        return false;
    }
    RawSimplexCollection intersection_u_v_1 =
        RawSimplexCollection::get_intersection(lk_u_1, lk_v_1);
    if (!RawSimplexCollection::are_simplex_collections_equal(intersection_u_v_1, lk_e_1)) {
        return false;
    }
 
    return true;
}
 
} // namespace wmtk::invariants