ShortestEdgeCollapse.h

#pragma once
#include <wmtk/utils/PartitionMesh.h>
#include <wmtk/utils/VectorUtils.h>
#include <wmtk/AttributeCollection.hpp>
 
// clang-format off
#include <wmtk/utils/DisableWarnings.hpp>
#include <igl/write_triangle_mesh.h>
#include <wmtk/threading/enumerable_thread_specific.hpp>
#include <fastenvelope/FastEnvelope.h>
#include <wmtk/utils/EnableWarnings.hpp>
// clang-format on
 
#include <Eigen/Core>
#include <Eigen/Geometry>
 
#include <atomic>
#include <memory>
#include <queue>
 
#include <wmtk/envelope/Envelope.hpp>
 
namespace wmtk::components::shortest_edge_collapse {
 
struct VertexAttributes
{
    Eigen::Vector3d pos;
    size_t partition_id = 0;
    bool freeze = false;
};
 
class ShortestEdgeCollapse : public wmtk::TriMesh
{
public:
    wmtk::SampleEnvelope m_envelope;
    bool m_has_envelope = false;
    wmtk::AttributeCollection<VertexAttributes> vertex_attrs;
 
    int retry_limit = 10;
    ShortestEdgeCollapse(
        std::vector<Eigen::Vector3d> _m_vertex_positions,
        int num_threads = 1,
        bool use_exact_envelope = true);
 
    void freeze_boundary();
 
    void create_mesh(
        size_t n_vertices,
        const std::vector<std::array<size_t, 3>>& tris,
        const std::vector<size_t>& frozen_verts = {},
        double eps = 0);
 
    ~ShortestEdgeCollapse() {}
 
    void partition_mesh();
 
    size_t get_partition_id(const Tuple& loc) const
    {
        return vertex_attrs[loc.vid(*this)].partition_id;
    }
 
    void write_vtu(const std::string& path);
 
public:
    bool collapse_edge_before(const Tuple& t) override;
    bool collapse_edge_after(const Tuple& t) override;
    bool collapse_shortest(int target_vertex_count);
    bool write_triangle_mesh(std::string path);
    bool invariants(const std::vector<Tuple>& new_tris) override;
 
private:
    struct PositionInfoCache
    {
        Eigen::Vector3d v1p;
        Eigen::Vector3d v2p;
        // v1 is the endpoint the collapse removes, v2 the one it keeps.
        bool v1_frozen = false;
        bool v2_frozen = false;
    };
    wmtk::threading::enumerable_thread_specific<PositionInfoCache> position_cache;
 
    std::vector<TriMesh::Tuple> new_edges_after(const std::vector<TriMesh::Tuple>& t) const;
};
 
} // namespace wmtk::components::shortest_edge_collapse