overlapping_faces.h

/********************************************************************
 * Copyright (C) 2015 Liangliang Nan <liangliang.nan@gmail.com>
 * https://3d.bk.tudelft.nl/liangliang/
 *
 * This file is part of Easy3D. If it is useful in your research/work,
 * I would be grateful if you show your appreciation by citing it:
 * ------------------------------------------------------------------
 *      Liangliang Nan.
 *      Easy3D: a lightweight, easy-to-use, and efficient C++ library
 *      for processing and rendering 3D data.
 *      Journal of Open Source Software, 6(64), 3255, 2021.
 * ------------------------------------------------------------------
 *
 * Easy3D is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License Version 3
 * as published by the Free Software Foundation.
 *
 * Easy3D is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 ********************************************************************/
 
#ifndef EASY_ALGO_EXT_OVERLAPPING_FACES_H
#define EASY_ALGO_EXT_OVERLAPPING_FACES_H
 
 
#include <vector>
 
// Use this instead to mute errors resulting from bad CGAL assertions
//#define CGAL_KERNEL_NO_ASSERTIONS
 
#include <CGAL/Simple_cartesian.h>
#include <CGAL/intersections.h> // Triangle-triangle intersection
#include <CGAL/box_intersection_d.h>
 
#include <easy3d/core/surface_mesh.h>
 
 
namespace easy3d {

    class OverlappingFaces
    {
    public:
        OverlappingFaces() = default;
        ~OverlappingFaces() = default;

        void detect(
                SurfaceMesh *mesh,
                std::vector<std::pair<SurfaceMesh::Face, SurfaceMesh::Face > > &duplicate_faces,
                std::vector<std::pair<SurfaceMesh::Face, SurfaceMesh::Face > > &folding_faces,
                double dist_threshold = 1e-6
        );

        unsigned int remove(
                SurfaceMesh *mesh,
                bool folding_faces = false,
                double dist_threshold = 1e-6
        );
 
    private:
        typedef CGAL::Simple_cartesian<double>  Kernel;
 
        typedef CGAL::Point_3<Kernel>       Point_3;
        typedef CGAL::Vector_3<Kernel>      Vector_3;
        typedef CGAL::Triangle_3<Kernel>    Triangle_3;
 
        struct Triangle {
            Triangle(const Point_3& a, const Point_3& b, const Point_3& c, SurfaceMesh::Face f) : triangle(a, b, c), face(f) {}
            Triangle_3 triangle;
            SurfaceMesh::Face face;
            std::vector<SurfaceMesh::Vertex> vertices;
        };
 
        // Axis-align boxes for all-pairs self-intersection detection
        typedef std::vector<Triangle>               Triangles;
        typedef Triangles::iterator                 TrianglesIterator;
        typedef CGAL::Box_intersection_d::Box_with_handle_d<double, 3, TrianglesIterator>   Box;
 
    private:
        Triangles mesh_to_cgal_triangle_list(SurfaceMesh* esh);
 
        // test if two triangles duplicate
        enum OverlapType {OT_NONE, OT_SAME, OT_FOLDING};
        OverlapType do_overlap(const Triangle& A, const Triangle& B, double sqr_eps);
 
        Triangles triangle_faces_;
    };
 
}   // namespace easy3d
 
#endif  // EASY_ALGO_EXT_OVERLAPPING_FACES_H