corner_vertices_are_constrained_vertex_map.h

// Copyright (c) 2018 Coronis Computing S.L. (Spain)
// All rights reserved.
//
// This file is part of EMODnet Quantized Mesh Generator for Cesium.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program 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 <https://www.gnu.org/licenses/>.
//
// Author: Ricard Campos (ricardcd@gmail.com)

#ifndef EMODNET_QMGC_CORNER_VERTICES_ARE_CONSTRAINED_VERTEX_MAP_H
#define EMODNET_QMGC_CORNER_VERTICES_ARE_CONSTRAINED_VERTEX_MAP_H

#include "tin_creation/tin_creation_cgal_types.h"
#include "cgal_utils.h"
#include <iostream>


template <class Polyhedron>
struct CornerVerticesAreConstrainedVertexMap
{
    typedef typename boost::graph_traits<Polyhedron>::vertex_descriptor key_type;
    typedef typename boost::graph_traits<Polyhedron>::halfedge_descriptor  HalfedgeDescriptor;
    typedef bool value_type;
    typedef value_type reference;
    typedef typename Polyhedron::Point_3 Point_3;

    const Polyhedron *m_pPolyPtr;

    CornerVerticesAreConstrainedVertexMap( const Polyhedron &sm ) : m_pPolyPtr(&sm) {}

    friend bool get(CornerVerticesAreConstrainedVertexMap m, const key_type &vertex)
    {
        // The vertex must be on the border
        boost::optional<HalfedgeDescriptor> he = CGAL::is_border( vertex, *m.m_pPolyPtr ) ;

        if (he) {
            // Next edge on the border (since we are in a border halfedge, the next operator should point to the next halfedge around the "hole")
            if ( (*he)->next()->is_border() ) {
                // Check the differences in X and Y to discern if this is a corner vertex

                // Relevant geometric info of the current edge
                Point_3 p0 = vertex->point() ;
                Point_3 p1 = (*he)->opposite()->vertex()->point() ; // This is the previous vertex, with which p0 forms an edge

                // Differences between the points in the edge
                double diffX = fabs( p1.x() - p0.x() ) ;
                double diffY = fabs( p1.y() - p0.y() ) ;

                Point_3 p2 = (*he)->next()->vertex()->point() ;

                double diffXNext = fabs( p2.x() - p0.x() ) ;
                double diffYNext = fabs( p2.y() - p0.y() ) ;

                return ( ( diffX < diffY ) && ( diffXNext > diffYNext ) ) ||
                       ( ( diffX > diffY ) && ( diffXNext < diffYNext ) ) ;
            }
            else {
                return false ;
            }
        }
        else {
            return false ;
        }
    }
};

#endif // EMODNET_QMGC_CORNER_VERTICES_ARE_CONSTRAINED_VERTEX_MAP_H