232 lines
10 KiB
C
232 lines
10 KiB
C
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// Copyright (c) 2018 Liangliang Nan. All rights reserved.
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//
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// This file is part of CGAL (www.cgal.org)
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//
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// $URL: https://github.com/CGAL/cgal/blob/v5.1/Polygonal_surface_reconstruction/include/CGAL/internal/alpha_shape_mesh.h $
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// $Id: alpha_shape_mesh.h 0779373 2020-03-26T13:31:46+01:00 Sébastien Loriot
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// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
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//
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// Author(s) : Liangliang Nan
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#ifndef CGAL_POLYGONAL_SURFACE_RECONSTRUCTION_ALPHA_SHAPE_MESH_H
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#define CGAL_POLYGONAL_SURFACE_RECONSTRUCTION_ALPHA_SHAPE_MESH_H
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#include <CGAL/license/Polygonal_surface_reconstruction.h>
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#include <CGAL/Alpha_shape_2.h>
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#include <CGAL/Delaunay_triangulation_2.h>
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#include <CGAL/Triangulation_hierarchy_2.h>
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#include <CGAL/Surface_mesh.h>
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// warn the user if he/she is using an unsupported version of CGAL
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#if CGAL_VERSION_NR < 1041100000
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#error CGAL 4.11 or above is required (due to the breaking change in CGAL 4.11). Please update your code.
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#endif
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/*!
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\file alpha_shape_mesh.h
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*/
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namespace CGAL {
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namespace internal {
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/// \cond SKIP_IN_MANUA
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template <typename Ht>
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class Alpha_shape;
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/// \endcond
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/// \cond SKIP_IN_MANUA
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/* A vertex class with an additional member representing its index */
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template < class Gt, class VB = CGAL::Triangulation_hierarchy_vertex_base_2<Gt> >
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class AS_vertex_base : public VB
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{
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public:
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typedef VB Base;
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typedef typename VB::Vertex_handle Vertex_handle;
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typedef typename VB::Face_handle Face_handle;
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typedef typename VB::Point Point;
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template < typename TDS2 >
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struct Rebind_TDS {
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typedef typename VB::template Rebind_TDS<TDS2>::Other VB2;
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typedef AS_vertex_base<Gt, VB2> Other;
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};
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public:
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AS_vertex_base() : Base(), index_(-1) {}
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AS_vertex_base(const Point & p) : Base(p), index_(-1) {}
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AS_vertex_base(const Point & p, Face_handle f) : Base(f, p), index_(-1) {}
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AS_vertex_base(Face_handle f) : Base(f), index_(-1) {}
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void set_index(int idx) { index_ = idx; }
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int index() const { return index_; }
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private:
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int index_;
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};
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template <typename Ht>
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class Alpha_shape : public Alpha_shape_2<Ht>
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{
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public:
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typedef Alpha_shape_2<Ht> Parent_class;
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typedef typename Ht::Point_2 Point2;
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typedef typename Parent_class::Vertex_handle Vertex_handle;
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public:
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// constructs alpha shapes from the input points
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template <typename InputIterator>
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Alpha_shape(InputIterator first, InputIterator beyond);
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};
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/// \endcond
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/**
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* An Alpha Shape Mesh approximates the point covered region by a mesh representation.
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*/
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template <typename Kernel>
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class Alpha_shape_mesh
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{
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typedef typename Kernel::FT FT;
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typedef typename Kernel::Point_2 Point2;
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typedef typename Kernel::Point_3 Point3;
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typedef typename Kernel::Plane_3 Plane3;
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typedef CGAL::Surface_mesh<Point3> Mesh3;
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typedef typename Mesh3::Vertex_index Vertex_descriptor;
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typedef CGAL::Alpha_shape_vertex_base_2<Kernel> Avb;
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typedef AS_vertex_base<Avb> Av;
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typedef CGAL::Triangulation_face_base_2<Kernel> Tf;
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typedef CGAL::Alpha_shape_face_base_2<Kernel, Tf> Af;
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typedef CGAL::Triangulation_default_data_structure_2<Kernel, Av, Af> Tds;
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typedef CGAL::Delaunay_triangulation_2<Kernel, Tds> Dt;
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typedef CGAL::Triangulation_hierarchy_2<Dt> Ht;
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public:
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/// Given a set of 3D points lying on 'plane', constructs alpha shapes from the
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/// the projection of the points onto 'plane'
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template <typename InputIterator>
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Alpha_shape_mesh(InputIterator first, InputIterator beyond, const Plane3& plane);
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~Alpha_shape_mesh() { delete alpha_shape_; }
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/// Extracts the 3D mesh representation of the alpha shapes
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bool extract_mesh(FT alpha_value, Mesh3& mesh);
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private:
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Alpha_shape<Ht>* alpha_shape_;
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std::vector<const Point3*> original_points_;
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};
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//////////////////////////////////////////////////////////////////////////
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// implementation
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template <typename Traits>
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template <typename InputIterator>
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Alpha_shape<Traits>::Alpha_shape(InputIterator first, InputIterator beyond) {
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InputIterator it = first;
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for (int id = 0; it != beyond; ++it, ++id) {
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const Point2& p = *it;
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Vertex_handle vh = Traits::insert(p);
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if (vh->index() == -1)
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vh->set_index(id);
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else {
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// p was not inserted (there might be a duplicated point)
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}
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}
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if (Parent_class::dimension() == 2) {
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// Computes the associated _interval_face_map
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Parent_class::initialize_interval_face_map();
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// Computes the associated _interval_edge_map
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Parent_class::initialize_interval_edge_map();
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// Computes the associated _interval_vertex_map
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Parent_class::initialize_interval_vertex_map();
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// Merges the two maps
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Parent_class::initialize_alpha_spectrum();
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}
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}
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template <typename Kernel>
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template <typename InputIterator>
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Alpha_shape_mesh<Kernel>::Alpha_shape_mesh(InputIterator first, InputIterator beyond, const Plane3& plane) {
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original_points_.clear();
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std::vector<Point2> pts;
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for (InputIterator it = first; it != beyond; ++it) {
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const Point3& p = *it;
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const Point2& q = plane.to_2d(p);
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pts.push_back(q);
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original_points_.push_back(&p);
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}
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alpha_shape_ = new Alpha_shape<Ht>(pts.begin(), pts.end());
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}
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template <typename Kernel>
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bool Alpha_shape_mesh<Kernel>::extract_mesh(FT alpha_value, Mesh3& mesh) {
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alpha_shape_->set_alpha(alpha_value);
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typedef std::vector<std::size_t> Triangle;
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std::vector<Triangle> faces;
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typedef Alpha_shape<Ht> Alpha_shape;
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typename Alpha_shape::Finite_faces_iterator fit = alpha_shape_->finite_faces_begin();
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for (; fit != alpha_shape_->finite_faces_end(); ++fit) {
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if (alpha_shape_->classify(fit) == Alpha_shape::INTERIOR) {
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Triangle tri;
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for (int i = 0; i < 3; ++i) {
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typename Alpha_shape::Vertex_handle vh = fit->vertex(i);
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int idx = vh->index();
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tri.push_back(idx);
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}
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faces.push_back(tri);
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}
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}
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if (faces.empty())
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return false;
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mesh.clear();
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std::vector<Vertex_descriptor> descriptors(original_points_.size());
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for (std::size_t i = 0; i < original_points_.size(); ++i) {
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const Point3* p = original_points_[i];
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descriptors[i] = mesh.add_vertex(*p);
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}
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for (std::size_t i = 0; i < faces.size(); ++i) {
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std::vector<Vertex_descriptor> face;
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const Triangle& tri = faces[i];
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for (std::size_t j = 0; j < tri.size(); ++j) {
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std::size_t idx = tri[j];
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face.push_back(descriptors[idx]);
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}
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mesh.add_face(face);;
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}
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return true;
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}
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} //namespace internal
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} //namespace CGAL
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#endif // CGAL_POLYGONAL_SURFACE_RECONSTRUCTION_ALPHA_SHAPE_MESH_H
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