120 lines
4.5 KiB
C++
Executable File
120 lines
4.5 KiB
C++
Executable File
// ----------------------------------------------------------------------------
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// - Open3D: www.open3d.org -
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// ----------------------------------------------------------------------------
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// Copyright (c) 2018-2023 www.open3d.org
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// SPDX-License-Identifier: MIT
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// ----------------------------------------------------------------------------
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#pragma once
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#include <Eigen/Core>
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#include <unordered_map>
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#include "open3d/geometry/Geometry3D.h"
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#include "open3d/geometry/MeshBase.h"
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namespace open3d {
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namespace geometry {
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/// \class HalfEdgeTriangleMesh
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///
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/// \brief HalfEdgeTriangleMesh inherits TriangleMesh class with the addition of
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/// HalfEdge data structure for each half edge in the mesh as well as related
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/// functions.
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class HalfEdgeTriangleMesh : public MeshBase {
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public:
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/// \class HalfEdge
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///
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/// \brief HalfEdge class contains vertex, triangle info about a half edge,
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/// as well as relations of next and twin half edge.
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class HalfEdge {
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public:
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/// \brief Default Constructor.
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///
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/// Initializes all members of the instance with invalid values.
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HalfEdge()
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: next_(-1),
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twin_(-1),
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vertex_indices_(-1, -1),
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triangle_index_(-1) {}
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HalfEdge(const Eigen::Vector2i &vertex_indices,
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int triangle_index,
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int next,
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int twin);
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/// Returns `true` iff the half edge is the boundary (has not twin, i.e.
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/// twin index == -1).
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bool IsBoundary() const { return twin_ == -1; }
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public:
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/// Index of the next HalfEdge in the same triangle.
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int next_;
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/// Index of the twin HalfEdge.
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int twin_;
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/// Index of the ordered vertices forming this half edge.
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Eigen::Vector2i vertex_indices_;
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/// Index of the triangle containing this half edge.
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int triangle_index_;
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};
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public:
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/// \brief Default Constructor.
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///
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/// Creates an empty instance with GeometryType of HalfEdgeTriangleMesh.
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HalfEdgeTriangleMesh()
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: MeshBase(Geometry::GeometryType::HalfEdgeTriangleMesh) {}
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virtual HalfEdgeTriangleMesh &Clear() override;
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/// Returns `true` if half-edges have already been computed.
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bool HasHalfEdges() const;
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/// Query manifold boundary half edges from a starting vertex
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/// If query vertex is not on boundary, empty vector will be returned.
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std::vector<int> BoundaryHalfEdgesFromVertex(int vertex_index) const;
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/// Query manifold boundary vertices from a starting vertex
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/// If query vertex is not on boundary, empty vector will be returned.
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std::vector<int> BoundaryVerticesFromVertex(int vertex_index) const;
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/// Returns a vector of boundaries. A boundary is a vector of vertices.
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std::vector<std::vector<int>> GetBoundaries() const;
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HalfEdgeTriangleMesh &operator+=(const HalfEdgeTriangleMesh &mesh);
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HalfEdgeTriangleMesh operator+(const HalfEdgeTriangleMesh &mesh) const;
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/// Convert HalfEdgeTriangleMesh from TriangleMesh. Throws exception if the
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/// input mesh is not manifold.
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static std::shared_ptr<HalfEdgeTriangleMesh> CreateFromTriangleMesh(
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const TriangleMesh &mesh);
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protected:
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/// \brief Parameterized Constructor.
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///
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/// Creates an empty instance with GeometryType of specified type.
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///
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/// \param type Specifies GeometryType for the HalfEdgeTriangleMesh.
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HalfEdgeTriangleMesh(Geometry::GeometryType type) : MeshBase(type) {}
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/// Returns the next half edge from starting vertex of the input half edge,
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/// in a counterclock wise manner. Returns -1 if when hitting a boundary.
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/// This is done by traversing to the next, next and twin half edge.
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int NextHalfEdgeFromVertex(int init_half_edge_index) const;
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int NextHalfEdgeOnBoundary(int curr_half_edge_index) const;
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public:
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/// List of triangles in the mesh.
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std::vector<Eigen::Vector3i> triangles_;
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/// List of triangle normals in the mesh.
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std::vector<Eigen::Vector3d> triangle_normals_;
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/// List of HalfEdge in the mesh.
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std::vector<HalfEdge> half_edges_;
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/// Counter-clockwise ordered half-edges started from each vertex.
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/// If the vertex is on boundary, the starting edge must be on boundary too.
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std::vector<std::vector<int>> ordered_half_edge_from_vertex_;
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};
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} // namespace geometry
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} // namespace open3d
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