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["蓝色追风" <>]

Hi again, 

 

Sorry for the delay response. This is a simple example code for my problem. It’s about the intersection between two boxes. 

 

//// 

read_obj("box.obj");///A simple function read shape information from OBJ file generated from Blender

std::vector<std::array<FT,3> > points;

std::vector<CGAL_Polygon> polygons;

 for(int i=0; i<vertices.size(); i++)

 {

      points.push_back(CGAL::make_array<FT>(vertices[i].x, vertices[i].y, vertices[i].z));

 }

   

 for(int i=0; i<triangles.size(); i++)

  {

      CGAL_Polygon p;

      p.push_back(triangles[i].v1);

      p.push_back(triangles[i].v2);

      p.push_back(triangles[i].v3);

      

      polygons.push_back(p);

  } 

Mesh mesh; 

PMP::polygon_soup_to_polygon_mesh(points, polygons, mesh); 

Mesh mesh_copy = mesh; 

 

PMP::transform(CGAL::Aff_transformation_3<Kernel>(CGAL::Translation(), Kernel::Vector_3(0.0, 0.3, .5)), mesh); 

PMP::transform(CGAL::Aff_transformation_3<Kernel>(0,-1,0, 

                                               1,0,0, 

                                               0,0,1,1), mesh); 

 

Mesh out1; 

 

Mesh::Property_map<Mesh::Face_index, int> mesh1_id = mesh.add_property_map<Mesh::Face_index, int>("f:id", -1).first; 

Mesh::Property_map<Mesh::Face_index, int> mesh2_id = mesh_copy.add_property_map<Mesh::Face_index, int>("f:id", -1).first; 

Mesh::Property_map<Mesh::Face_index, int> out1_id = out1.add_property_map<Mesh::Face_index, int>("f:id", -1).first; 

     

 for(Mesh::Face_index f : faces(mesh)) 

 { 

    mesh1_id[f] = 1; 

 } 

 for(Mesh::Face_index f : faces(mesh_copy)) 

 { 

    mesh2_id[f] = 2; 

 } 

     

 Visitor visitor; 

 visitor.properties[&mesh] = mesh1_id; 

 visitor.properties[&mesh_copy] = mesh2_id; 

 visitor.properties[&out1] = out1_id; 

 

bool valid_intersect = PMP::corefine_and_compute_intersection(mesh, mesh_copy, out1, CGAL::parameters::visitor(visitor)); 

 

Mesh out1_part1; 

for(Mesh::Face_index f : faces(out1)) 

{ 

    if(out1_id[f] == 2) 

    { 

           std::vector<Mesh::Vertex_index> tmp; 

           auto tp = CGAL::vertices_around_face(out1.halfedge(f), out1); 

           for(auto vd:tp) 

           { 

                  Kernel::Point_3 tmp_P = out1.point(vd); 

                  Mesh::Vertex_index index = out1_part1.add_vertex(tmp_P); 

                  tmp.push_back(index); 

           } 

           out1_part1.add_face(tmp[0], tmp[1], tmp[2]); 

    } 

  } 

////

 

Here are the two boxes (mesh and mesh_copy) and the intersection polyhedron (out1). But the above code can only capture two triangles(out_part1) from Box 2. While for the command “:corefine_and_compute_union”, the above code works very well. Do you have any suggestions regarding this problem? 

 

Thanks again. 

 

Best wishes, 

Daye 

mesh and mesh_copy

out1

out_part1

---

蓝色追风

Original Email

Sender:"cgal-discuss"< >;

Sent Time:2023/5/11 8:35

To:"cgal-discuss"< >;

Subject:Re: [cgal-discuss] Have trouble usingNamedParameters"face_index_map" in "corefine_and_compute_intersection"

The code used is exactly the same, so if you made it work with one
function it should work with the second one. I suggest you look at the
difference you have in function calls to see where it could come from.
Without a minimal example showing the problem it would be hard to help more.

Best,

Sebastien.

On 5/10/23 14:32, "蓝色追风" ( via cgal-discuss Mailing
List) wrote:
> Yes, with "PMP::corefine_and_compute_union" I can distinguish which
> sub-mesh of the union belongs to which original mesh, just like the
> example code you sent me. But it seems that this does not work with
> "corefine_and_compute_intersection". Is it because some meshes are
> recreated during the intersection operation? Do you have any suggestions
> on how to distinguish the faces in the resulting mesh after "intersection"?
>
> Best wishes,
> Daye
> ------------------------------------------------------------------------
>
>
> 蓝色追风
>
>
>
>
>
>
>
> Original Email
>
> Sender:"cgal-discuss"< >;
>
> Sent Time:2023/5/10 11:27
>
> To:"cgal-discuss"< >;
>
> Subject:Re: [cgal-discuss] Have trouble using
> NamedParameters"face_index_map" in "corefine_and_compute_intersection"
>
>
> The corresponding mesh is passed as a reference in visitor calls so you
> can compare the address of the mesh with the one you are interested in.
>
> Best,
>
> Sebastien.
>
> On 5/10/23 11:19, "蓝色追风" ( via cgal-discuss Mailing
> List) wrote:
> > Hi, again,
> >
> > I tried your suggestion and implemented the example code you gave me.
> > However, for many faces of intersection, the visitor cannot recognize
> > whether they come from "mesh1" or "mesh2". Taking this example
> >
> (https://github.com/CGAL/cgal/blob/master/Polygon_mesh_processing/examples/Polygon_mesh_processing/corefinement_mesh_union_with_attributes.cpp ) as an example, many "out_id" of the intersected mesh are "-1". Do I need to handle the intersected mesh specially for a relatively complicated mesh?
> >
> > Thanks again.
> >
> > Best wishes,
> > Daye
> > ------------------------------------------------------------------------
> >
> >
> > 蓝色追风
> >
> >
> >
> >
> >
> >
> >
> > Original Email
> >
> > Sender:"cgal-discuss"< >;
> >
> > Sent Time:2023/5/10 8:48
> >
> > To:"cgal-discuss"< >;
> >
> > Subject:Re: [cgal-discuss] Have trouble using Named
> > Parameters"face_index_map" in "corefine_and_compute_intersection"
> >
> >
> > face_index_map is not an output parameter. It is used internally by the
> > code to avoid using a hash map. If you want to track correspondance
> > between input and output, you should use the visitor:
> >
> >
> https://doc.cgal.org/latest/Polygon_mesh_processing/classPMPCorefinementVisitor.html
> >
> >
> https://github.com/CGAL/cgal/blob/master/Polygon_mesh_processing/examples/Polygon_mesh_processing/corefinement_mesh_union_with_attributes.cpp
> >
> > Best,
> >
> > Sebastien.
> >
> > On 5/9/23 21:43, "蓝色追风" ( via cgal-discuss Mailing
> > List)
> > wrote:
> > > Hi, all,
> > >
> > > I am currently using the CGAL command
> > > "corefine_and_compute_intersection" to compute the intersection between
> > > two surface meshes. At the same time, I want to determine the face
> index
> > > of the intersection mesh in the original mesh. I noticed that the
> > > "face_index_map" in the Named Parameters of
> > > "corefine_and_compute_intersection" seems to be able to achieve this
> > > functionality, but I am having trouble using it. Could you please
> > > provide me with an example code to help me use the "face_index_map"
> > feature?
> > >
> > > Thank you for your time and help!
> > >
> > > Best wishes,
> > > Daye
> > >
> > > --
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> >
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> >
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>
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