CGAL users discussion list

[Iason Manolas <>]

ah! you are right, it is not valid..

So probably  there is something wrong with the way i build it?

I use the following code to build it:

using Kernel=CGAL::Exact_predicates_inexact_constructions_kernel;
using CGALPolyhedron=CGAL::Polyhedron_3<Kernel>;
using HalfedgeDS=CGALPolyhedron::HalfedgeDS;

template<class HDS>
class  PolyhedronBuilder:public CGAL::Modifier_base<HDS>
{
public:


    Mesh         M;

    PolyhedronBuilder(){}
    explicit PolyhedronBuilder(const Mesh& model):M{model}{}
    void operator()(HDS& hds)
    {
        typedef typename HDS::Vertex    Vertex;
        typedef typename Vertex::Point     Point;

        CGAL::Polyhedron_incremental_builder_3<HDS> B(hds,true);
        B.begin_surface(M.vertices.size(),M.indices.size()/3);

        //add vertices
        for(const auto& vert:M.vertices)
            B.add_vertex(Point(vert.Position.x,vert.Position.y,vert.Position.z));

        //add faces
        for(uint i=0;i<M.indices.size()/3;i+=3)
        {
            B.begin_facet();
            B.add_vertex_to_facet(M.indices[i]);
            B.add_vertex_to_facet(M.indices[i+1]);
            B.add_vertex_to_facet(M.indices[i+2]);
            B.end_facet();
        }
        B.end_surface();

    }
};

and then:

PolyhedronBuilder<HalfedgeDS> builder(mesh);

myPolyhedron.delegate(builder);

which was based on .

On 7 November 2016 at 10:24, Sebastien Loriot (GeometryFactory) <> wrote:

Could you check P.is_valid() returns true before calling compute_normals?

On 11/04/2016 03:58 PM, Iason Manolas wrote:

This
<https://github.com/IasonManolas/Thesis/blob/meshScene/mypolyhedron.h>
is my code.
Do you think there could be something wrong with my cgal distribution?

Iason


On 4 November 2016 at 16:17, Iason Manolas <
<mailto:>> wrote:

    CGAL::Polyhedron_3<CGAL::Exact_predicates_inexact_constructions_kernel>

    On 4 November 2016 at 16:10, Sebastien Loriot (GeometryFactory)

    < <mailto:>> wrote:

        What is your polyhedron type?

        Sebastien.

        On 11/04/2016 02:59 PM, Iason Manolas wrote:

            My program crashes when I call compute_vertex_normals.
            The stack calling the function that crashes is:
            4.In *compute_normal.h*at line 183: *(!is_border**(he,pmesh))*
            3.In *helpers.h* at line 45: *face(hd,g)*
            2.In *graph_traits_Polyhedron_3.h* at line: 420: *h->face();*
            1.In H*alfedgeDS_halfedge_base.h* at line 327:*face()*

            The error I get in Qt creator is SIGSEGV
            <http://stackoverflow.com/questions/2454192/whats-sigsegv-segmentation-fault-in-qt
            <http://stackoverflow.com/questions/2454192/whats-sigsegv-segmentation-fault-in-qt>>
            which after searching found out that propably means: "Trying
            to access
            pointer with invalid value."
            My guess was that I had not correctly initialized the
            Polyhedron but
            everything seems fine..

            Any idea why this happens?

            Best Regards,
            Iason Manolas

            On 1 November 2016 at 10:53, Andreas Fabri
            <
            <mailto:>

            <mailto:

            <mailto:>>> wrote:

                You must
                #include <boost/property_map/property_map.hpp>

                and write

            compute_vertex_normals(P,boost::make_assoc_property_map(normals))


                On 01/11/2016 09:45, Iason Manolas wrote:

                    Thanks for your response Sebastien.

                    After reading your code  I wrote:
                    using
            vd=boost::graph_traits<CGALPolyhedron>::vertex_descriptor;
                    std::map<vd,Kernel::Vector_3>* normals;

            CGAL::Polygon_mesh_processing::compute_vertex_normals(P,normals);
            (since
                    I want to compute vertex and not face normals)

                    But I get:


            /usr/include/CGAL/Polygon_mesh_processing/compute_normal.h:228:
                    error:
                    no matching function for call to

            ‘put(std::map<CGAL::internal::In_place_list_iterator<CGAL::HalfedgeDS_in_place_list_vertex<CGAL::I_Polyhedron_vertex<CGAL::HalfedgeDS_vertex_base<CGAL::HalfedgeDS_list_types<CGAL::Epick,

            CGAL::I_Polyhedron_derived_items_3<CGAL::Polyhedron_items_3>,
                    std::allocator<int> >, CGAL::Boolean_tag<true>,
                    CGAL::Point_3<CGAL::Epick> > > >,

            std::allocator<CGAL::HalfedgeDS_in_place_list_vertex<CGAL::I_Polyhedron_vertex<CGAL::HalfedgeDS_vertex_base<CGAL::HalfedgeDS_list_types<CGAL::Epick,

            CGAL::I_Polyhedron_derived_items_3<CGAL::Polyhedron_items_3>,
                    std::allocator<int> >, CGAL::Boolean_tag<true>,
                    CGAL::Point_3<CGAL::Epick> > > > > >,
                    CGAL::Vector_3<CGAL::Epick> >&,
                    CGAL::HDS_graph_traits<CGAL::Polyhedron_3<CGAL::Epick>

                        ::vertex_descriptor&,


            CGAL::Type_equality_wrapper<CGAL::Cartesian_base_no_ref_count<double,
                    CGAL::Epick>, CGAL::Epick>::Vector_3&)’
                         put(vnm, v, vec);
                            ^
                    That propably means that the put fuction cannot
            recognize vnm ( I
                    passed) as a valid argument?



                    On 1 November 2016 at 09:50, Sebastien Loriot
            (GeometryFactory)
                    < <mailto:>
            <mailto: <mailto:>>
                    <mailto:
            <mailto:> <mailto:
            <mailto:>>>> wrote:

                        A writable property map, as describe in the
            concept of the
                    boost web
                        site is a mecanism that allow to generically
            associate a
                    property
                        (the value type) to a given object (the key).

                        If you want to associate a normal to a facet of a
                    Polyhedron, here
                        is a simple example (not tested):


                        struct Poly_normal_map{

                          typedef Polyhedron::Facet_handle key_type;
                          typedef Kernel::Vector_3 value_type;
                          typedef boost::writable_property_map_tag category;

                          std::map<Polyhedron::Facet_handle,
            Kernel::Vector_3>* normals;

                          Poly_normal_map() : normals(NULL)
                          {}

                          Poly_normal_map(std::map<Polyhedron::Facet_handle,
                                                   Kernel::Vector_3>& n)
                            : normals(*n)
                          {}

                          friend void put(Poly_normal_map pnm,
                                          Polyhedron::Facet_handle fh,
                                          const Kernel::Vector_3& n
                          {
                            CGAL_assertion(pnm.normals!=0);
                            pnm.normals.insert( std::make_pair(fh, n) );
                          }
                        };

                        std::map<Polyhedron::Facet_handle,
            Kernel::Vector_3> normals;
                        Poly_normal_map vpm(normals); //vpm is you
            writable property map


                        If you want to make the property map read-write,
            you can add
                        a get function:

                          friend const value_type& get(Poly_normal_map pnm,

             Polyhedron::Facet_handle fh)
                          {
                            CGAL_assertion(pnm.normals!=0);
                            return pnm.normals[fh];
                          }

                        and update the category tag.

                        Note that the code I've written is roughly
            equivalent to using a
                        boost::associative_property_map


            (http://www.boost.org/doc/libs/1_62_0/libs/property_map/doc/associative_property_map.html
            <http://www.boost.org/doc/libs/1_62_0/libs/property_map/doc/associative_property_map.html>

            <http://www.boost.org/doc/libs/1_62_0/libs/property_map/doc/associative_property_map.html
            <http://www.boost.org/doc/libs/1_62_0/libs/property_map/doc/associative_property_map.html>>


            <http://www.boost.org/doc/libs/1_62_0/libs/property_map/doc/associative_property_map.html
            <http://www.boost.org/doc/libs/1_62_0/libs/property_map/doc/associative_property_map.html>

            <http://www.boost.org/doc/libs/1_62_0/libs/property_map/doc/associative_property_map.html
            <http://www.boost.org/doc/libs/1_62_0/libs/property_map/doc/associative_property_map.html>>>)
                        :

                        std::map<Polyhedron::Facet_handle,
            Kernel::Vector_3> normals;
                        boost::associative_property_map<
                                 std::map<Polyhedron::Facet_handle,
                                          Kernel::Vector_3> > vpm(normals);

                        If you're not stuck with Polyhedron_3, you can
            use class
                        Surface_mesh that comes with its own property
            mechanism
                        as illustrated in this example:



            http://doc.cgal.org/latest/Polygon_mesh_processing/Polygon_mesh_processing_2compute_normals_example_8cpp-example.html
            <http://doc.cgal.org/latest/Polygon_mesh_processing/Polygon_mesh_processing_2compute_normals_example_8cpp-example.html>

            <http://doc.cgal.org/latest/Polygon_mesh_processing/Polygon_mesh_processing_2compute_normals_example_8cpp-example.html
            <http://doc.cgal.org/latest/Polygon_mesh_processing/Polygon_mesh_processing_2compute_normals_example_8cpp-example.html>>


            <http://doc.cgal.org/latest/Polygon_mesh_processing/Polygon_mesh_processing_2compute_normals_example_8cpp-example.html
            <http://doc.cgal.org/latest/Polygon_mesh_processing/Polygon_mesh_processing_2compute_normals_example_8cpp-example.html>

            <http://doc.cgal.org/latest/Polygon_mesh_processing/Polygon_mesh_processing_2compute_normals_example_8cpp-example.html
            <http://doc.cgal.org/latest/Polygon_mesh_processing/Polygon_mesh_processing_2compute_normals_example_8cpp-example.html>>>

                        Sebastien.



                        On 10/31/2016 12:46 PM, Iason Manolas wrote:

                            Hi,

                            I am new to CGAL. I have constructed a
                    CGAL::Polyhedron_3 and
                            now I want
                            to compute the normal vector for each of its
            vertices. So I
                            found the
                            Polygon Mesh Processing package which
            happens to have a
                    function


            <http://doc.cgal.org/latest/Polygon_mesh_processing/group__PMP__normal__grp.html#gad46aaf003999b2939f3f9e4f6fa58d0e
            <http://doc.cgal.org/latest/Polygon_mesh_processing/group__PMP__normal__grp.html#gad46aaf003999b2939f3f9e4f6fa58d0e>

            <http://doc.cgal.org/latest/Polygon_mesh_processing/group__PMP__normal__grp.html#gad46aaf003999b2939f3f9e4f6fa58d0e
            <http://doc.cgal.org/latest/Polygon_mesh_processing/group__PMP__normal__grp.html#gad46aaf003999b2939f3f9e4f6fa58d0e>>


            <http://doc.cgal.org/latest/Polygon_mesh_processing/group__PMP__normal__grp.html#gad46aaf003999b2939f3f9e4f6fa58d0e
            <http://doc.cgal.org/latest/Polygon_mesh_processing/group__PMP__normal__grp.html#gad46aaf003999b2939f3f9e4f6fa58d0e>

            <http://doc.cgal.org/latest/Polygon_mesh_processing/group__PMP__normal__grp.html#gad46aaf003999b2939f3f9e4f6fa58d0e
            <http://doc.cgal.org/latest/Polygon_mesh_processing/group__PMP__normal__grp.html#gad46aaf003999b2939f3f9e4f6fa58d0e>>>>
                            doing exactly what I want . In the above
            link I found
                    out that the
                            second argument was of type  VertexNormalMap
            which is a
                    model of
                            WritablePropertyMap. There was a link


            <http://www.boost.org/doc/libs/1_62_0/libs/property_map/doc/WritablePropertyMap.html
            <http://www.boost.org/doc/libs/1_62_0/libs/property_map/doc/WritablePropertyMap.html>

            <http://www.boost.org/doc/libs/1_62_0/libs/property_map/doc/WritablePropertyMap.html
            <http://www.boost.org/doc/libs/1_62_0/libs/property_map/doc/WritablePropertyMap.html>>


            <http://www.boost.org/doc/libs/1_62_0/libs/property_map/doc/WritablePropertyMap.html
            <http://www.boost.org/doc/libs/1_62_0/libs/property_map/doc/WritablePropertyMap.html>

            <http://www.boost.org/doc/libs/1_62_0/libs/property_map/doc/WritablePropertyMap.html
            <http://www.boost.org/doc/libs/1_62_0/libs/property_map/doc/WritablePropertyMap.html>>>>
                            to boost libraries explaining(?) what
            writable property
                    map is .

                            Unfortunately this is my first encounter
            with property
                    maps and
                            consequently I am a bit confused..
                            I also had a look at cgal's explanation of
            property maps
                    page

            <http://doc.cgal.org/latest/Property_map/index.html
            <http://doc.cgal.org/latest/Property_map/index.html>
                    <http://doc.cgal.org/latest/Property_map/index.html
            <http://doc.cgal.org/latest/Property_map/index.html>>

            <http://doc.cgal.org/latest/Property_map/index.html
            <http://doc.cgal.org/latest/Property_map/index.html>
                    <http://doc.cgal.org/latest/Property_map/index.html
            <http://doc.cgal.org/latest/Property_map/index.html>>> >, but I
                            did not
                            understand much..

                            Could anyone suggest a way of creating the
            property map
                    I need?

                            Best Regards,
                            Iason



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                --
                Andreas Fabri, PhD
                Chief Officer, GeometryFactory
                Editor, The CGAL Project

                phone: +33.492.954.912 <tel:%2B33.492.954.912>
            <tel:%2B33.492.954.912>    skype: andreas.fabri

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