HalfEdgeTriangleMesh.h

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// ----------------------------------------------------------------------------
// -                        CloudViewer: www.cloudViewer.org                  -
// ----------------------------------------------------------------------------
// Copyright (c) 2018-2024 www.cloudViewer.org
// SPDX-License-Identifier: MIT
// ----------------------------------------------------------------------------
 
#pragma once
 
#include <Eigen/Core>
#include <unordered_map>
 
// LOCAL
#include "ecvMeshBase.h"
 
namespace cloudViewer {
namespace geometry {
 
class CV_DB_LIB_API HalfEdgeTriangleMesh : public ecvMeshBase {
public:
    class HalfEdge {
    public:
        HalfEdge()
            : next_(-1),
              twin_(-1),
              vertex_indices_(-1, -1),
              triangle_index_(-1) {}
        HalfEdge(const Eigen::Vector2i &vertex_indices,
                 int triangle_index,
                 int next,
                 int twin);
        bool IsBoundary() const { return twin_ == -1; }
 
    public:
        int next_;
        int twin_;
        Eigen::Vector2i vertex_indices_;
        int triangle_index_;
    };
 
public:
    HalfEdgeTriangleMesh(const char *name = "HalfEdgeTriangleMesh")
        : ecvMeshBase(name) {}
 
    ~HalfEdgeTriangleMesh() override {}
 
    // inherited methods (ccHObject)
    virtual bool isSerializable() const override { return true; }
    virtual CV_CLASS_ENUM getClassID() const override {
        return CV_TYPES::HALF_EDGE_MESH;
    }
 
public:
    virtual HalfEdgeTriangleMesh &clear() override;
 
    inline std::size_t edgeSize() const { return half_edges_.size(); }
 
    virtual bool hasTriangles() const override {
        return vertices_.size() > 0 && triangles_.size() > 0;
    }
 
    bool HasTriangleNormals() const {
        return hasTriangles() && triangles_.size() == triangle_normals_.size();
    }
 
    bool hasHalfEdges() const;
 
    std::vector<int> boundaryHalfEdgesFromVertex(int vertex_index) const;
 
    std::vector<int> boundaryVerticesFromVertex(int vertex_index) const;
 
    std::vector<std::vector<int>> getBoundaries() const;
 
    HalfEdgeTriangleMesh &operator+=(const HalfEdgeTriangleMesh &mesh);
 
    HalfEdgeTriangleMesh operator+(const HalfEdgeTriangleMesh &mesh) const;
 
    static std::shared_ptr<HalfEdgeTriangleMesh> CreateFromTriangleMesh(
            const ccMesh &mesh);
 
protected:
    int nextHalfEdgeFromVertex(int init_half_edge_index) const;
    int nextHalfEdgeOnBoundary(int curr_half_edge_index) const;
 
public:
    std::vector<Eigen::Vector3i> triangles_;
    std::vector<Eigen::Vector3d> triangle_normals_;
    std::vector<HalfEdge> half_edges_;
 
    std::vector<std::vector<int>> ordered_half_edge_from_vertex_;
};
 
}  // namespace geometry
}  // namespace cloudViewer