CGAL users discussion list

[Sebastien Loriot <>]

I'm sorry but I don't understand what you are trying to achieve and what 
does not work.

Could you provide a complete minimal example (with data) that I can
compile and run and ideally have an error message/assertion showing
what does not work?

Thanks,

Sebastien.

On 5/13/23 16:12, "蓝色追风" ( via cgal-discuss Mailing 
List) wrote:
> 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
>
>
> <https://wx.mail.qq.com/home/index?t=readmail_businesscard_midpage&nocheck=true&name=%E8%93%9D%E8%89%B2%E8%BF%BD%E9%A3%8E&icon=https%3A%2F%2Fthirdqq.qlogo.cn%2Fg%3Fb%3Doidb%26k%3Dwic8g7X3V7SJGQtsmZpeoCg%26s%3D0&mail=534121639%40qq.com&code=hfAScRQS-WLnPbqomOz9eik53dpK9F7uARW_9kmmLmn4MrVtp2hS6oBkagGbyl_mL-pgi3Blkh39QseGO54MXw>
>
>
>
>
> 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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