mesh_halfedges.h

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#ifndef GEOGRAM_MESH_MESH_HALFEDGES
#define GEOGRAM_MESH_MESH_HALFEDGES
 
#include <geogram/basic/common.h>
#include <geogram/mesh/mesh.h>
#include <geogram/mesh/mesh_geometry.h>
#include <iostream>
 
namespace GEO {
 
    class GEOGRAM_API MeshHalfedges {
    public:
    struct Halfedge {
 
        static constexpr index_t NO_FACET  = index_t(-1);
        static constexpr index_t NO_CORNER = index_t(-1);
 
        Halfedge() :
            facet(NO_FACET),
            corner(NO_CORNER) {
        }
 
        Halfedge(index_t f, index_t c) :
            facet(f),
            corner(c) {
        }
 
        void clear() {
            facet = NO_FACET;
            corner = NO_CORNER;
        }
 
        bool is_nil() const {
            return (facet == NO_FACET) && (corner == NO_CORNER);
        }
 
        bool operator== (const Halfedge& rhs) const {
            return facet == rhs.facet && corner == rhs.corner;
        }
 
        bool operator!= (const Halfedge& rhs) const {
            return !(rhs == *this);
        }
 
        index_t facet;
        index_t corner;
 
    };
 
    MeshHalfedges(Mesh& mesh) : mesh_(mesh) {
    }
 
    Mesh& mesh() {
        return mesh_;
    }
 
    const Mesh& mesh() const {
        return mesh_;
    }
 
    void set_use_facet_region(bool x) {
        if(x) {
            if(!facet_region_.is_bound()) {
                facet_region_.bind(mesh_.facets.attributes(),"region");
            }
        } else {
            if(facet_region_.is_bound()) {
                facet_region_.unbind();
            }
        }
    }
 
    void set_use_facet_region(const std::string& attribute_name) {
        if(facet_region_.is_bound()) {
            facet_region_.unbind();
        }
        facet_region_.bind(mesh_.facets.attributes(),attribute_name);
    }
 
    void set_use_facet_region(const char* attribute_name) {
        set_use_facet_region(std::string(attribute_name));
    }
 
 
    bool halfedge_is_valid(const Halfedge& H) const {
        return
            H.facet != Halfedge::NO_FACET &&
            H.corner != Halfedge::NO_CORNER &&
            H.facet < mesh_.facets.nb() &&
            H.corner < mesh_.facet_corners.nb()
            ;
    }
 
    bool halfedge_is_border(const Halfedge& H) const {
        geo_debug_assert(halfedge_is_valid(H));
        if(facet_region_.is_bound()) {
            index_t f = H.facet;
            index_t adj_f =
                mesh_.facet_corners.adjacent_facet(H.corner);
            return
                adj_f == NO_FACET ||
                facet_region_[f] != facet_region_[adj_f]
                ;
        }
        return mesh_.facet_corners.adjacent_facet(H.corner) == NO_FACET;
    }
 
    void move_to_next_around_facet(Halfedge& H) const {
        geo_debug_assert(halfedge_is_valid(H));
        H.corner = mesh_.facets.next_corner_around_facet(H.facet, H.corner);
    }
 
    void move_to_prev_around_facet(Halfedge& H) const {
        geo_debug_assert(halfedge_is_valid(H));
        H.corner = mesh_.facets.prev_corner_around_facet(H.facet, H.corner);
    }
 
    bool move_to_next_around_vertex(Halfedge& H) const;
 
    bool move_to_prev_around_vertex(Halfedge& H) const;
 
    void move_to_next_around_border(Halfedge& H) const;
 
    void move_to_prev_around_border(Halfedge& H) const;
 
    void move_to_opposite(Halfedge& H) const;
 
    private:
    Mesh& mesh_;
    Attribute<index_t> facet_region_;
    };
 
    inline std::ostream& operator<< (
        std::ostream& out, const MeshHalfedges::Halfedge& H
    ) {
        return out << '(' << H.facet << ',' << H.corner << ')';
    }
 
    namespace Geom {
 
        inline const vec3& halfedge_vertex_from(
            const Mesh& M, const MeshHalfedges::Halfedge& H
        ) {
            return mesh_vertex(M, M.facet_corners.vertex(H.corner));
        }
 
        inline const vec3& halfedge_vertex_to(
            const Mesh& M, const MeshHalfedges::Halfedge& H
        ) {
            index_t c = M.facets.next_corner_around_facet(H.facet, H.corner);
            return mesh_vertex(M, M.facet_corners.vertex(c));
        }
 
        inline vec3 halfedge_vector(
            const Mesh& M, const MeshHalfedges::Halfedge& H
        ) {
            return halfedge_vertex_to(M, H) - halfedge_vertex_from(M, H);
        }
 
        inline double edge_length(
            const Mesh& M, const MeshHalfedges::Halfedge& H
        ) {
            return length(halfedge_vector(M, H));
        }
    }
}
 
#endif