CGAL users discussion list

["chen wenyu" <>]

Ok, it works. thx

 

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From:  Monique Teillaud <>
Reply-To:  
To:  
Subject:  Re: [cgal-discuss] get vertex handle from a facet
Date:  Mon, 15 Jan 2007 10:02:14 +0100
>well, I am not familiar with Alpha_shape_3, but at least I am afraid
>there is no Face_handle in Triangulation_3...
>
>Still, you can get the vertices of a facet, see the user and ref manual
>of TriangulationDataStructure_3:
>typedef std::pair<Cell_handle, int> Facet;
>(c,i) is the facet of c opposite to the vertex of index i.
>
>So, f.first->vertex( (i+1)&3 ) gives the first vertex of facet f.
>Same with (1+2) and (1+3) for the next two vertices.
>
> Monique Teillaud
>
>Mariette Yvinec wrote:
> > use fh->vertex(int i)> > where fh is a Face_handle.
> > See the doc of Triangulation_3 and Trriangulation_data_structure_3
> >
> > chen wenyu wrote:
> >
> >> Hi,
> >>
> >> How can I get the vertex handle from a facet.
> >>
> >> Facet f = ....;
> >>
> >> // how to get the three vertex handles of this facet f
> >>
> >>
> >> For example:
> >>
> >> -------------------------------------------------------
> >>
> >>// examples/Alpha_shapes_3/example_weight.C
> >>
> >>#include <CGAL/Exact_predicates_inexact_constructions_kernel <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Kernel_23_ref/Class_Exact_predicates_inexact_constructions_kernel.html#Cross_link_anchor_17>.h>
> >>#include <CGAL/Weighted_alpha_shape_euclidean_traits_3 <fi! le:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_ 3_ref/Class_Weighted_alpha_shape_euclidean_traits_3.html#Cross_link_anchor_804>.h>
> >>#include <CGAL/Regular_triangulation_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Triangulation_3_ref/Class_Regular_triangulation_3.html#Cross_link_anchor_762>.h>
> >>#include <CGAL/Alpha_shape_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_3_ref/Class_Alpha_shape_3.html#Cross_link_anchor_799>.h>
> >>#include <list>
> >>
> >>typedef CGAL::Exact_predicates_inexact_constructions_kernel <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Kernel_23_ref/Class_Exact_predicates_inexact_constructions_kernel.html#Cross_link_anchor_17> K;
> >>
> >>typedef CGAL::Weighted_alpha_shape_euclidean_traits_3<K> <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_3_ref/Class_Weighted_alpha_shape_euclide! an_traits_3.html#Cross_link_anchor_804> Gt;
> >>
> >>typedef CGAL::Alpha_shape_vertex_base_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_3_ref/Class_Alpha_shape_vertex_base_3.html#Cross_link_anchor_801><Gt>         Vb;
> >>typedef CGAL::Alpha_shape_cell_base_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_3_ref/Class_Alpha_shape_cell_base_3.html#Cross_link_anchor_800><Gt>           Fb;
> >>typedef CGAL::Triangulation_data_structure_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/TriangulationDS_3_ref/Class_Triangulation_data_structure_3.html#Cross_link_anchor_785><Vb,Fb> Tds;
> >>typedef CGAL::Regular_triangulation_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Triangulation_3_ref/Class_Regular_triangu! lation_3.html#Cross_link_anchor_762><Gt,Tds>    ;    Triangulation_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Triangulation_3_ref/Class_Triangulation_3.html#Cross_link_anchor_759>;
> >>typedef CGAL::Alpha_shape_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_3_ref/Class_Alpha_shape_3.html#Cross_link_anchor_799><Triangulation_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Triangulation_3_ref/Class_Triangulation_3.html#Cross_link_anchor_759>>        Alpha_shape_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_3_ref/Class_Alpha_shape_3.html#Cross_link_anchor_799>;
> >>
> >>typedef Alpha_shape_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_3_ref/Class_Alpha_shape_3.html#Cross_link_anchor_799>::Cell_handle          Cell_handle;
> >! >typedef Alpha_shape_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_3_ref/Class_Alpha_shape_3.html#Cross_link_anchor_799>::Vertex_handle        Vertex_handle;
> >>typedef Alpha_shape_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_3_ref/Class_Alpha_shape_3.html#Cross_link_anchor_799>::Facet                Facet;
> >>typedef Alpha_shape_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_3_ref/Class_Alpha_shape_3.html#Cross_link_anchor_799>::Edge                 Edge;
> >>typedef Gt::Weighted_point <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Triangulation_2_ref/Class_Weighted_point.html#Cross_link_anchor_750>  &nbs! p;           &n bsp;   Weighted_point <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Triangulation_2_ref/Class_Weighted_point.html#Cross_link_anchor_750>;
> >>typedef Gt::Bare_point                      Bare_point;
> >>
> >>int main()
> >>{
> >>  std::list<Weighted_point <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Triangulation_2_ref/Class_Weighted_point.html#Cross_link_anchor_750>> lwp;
> >>
> >>  //input : a small molecule
> >>  lwp.push_back(Weighted_point <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Triangulation_2_ref/Class_Weighted_point.html#Cross_link_anchor_750>(Bare_point( 1, -1, -1), 4));
> >>  lwp.push_back(Weighted_point <file:///C:/Program! %20Files/CGAL-3.2.1/doc_html/cgal_manual/Triangulation_2_ref/Class_Weighted_point.html#Cross_link_anchor_750>(Bare_point(-1,  1, -1), 4));
> >>  lwp.push_back(Weighted_point <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Triangulation_2_ref/Class_Weighted_point.html#Cross_link_anchor_750>(Bare_point(-1, -1,  1), 4));
> >>  lwp.push_back(Weighted_point <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Triangulation_2_ref/Class_Weighted_point.html#Cross_link_anchor_750>(Bare_point( 1,  1,  1), 4));
> >>  lwp.push_back(Weighted_point <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Triangulation_2_ref/Class_Weighted_point.html#Cross_link_anchor_750>(Bare_point( 2,  2,  2), 1));
> >>
> >>  //build alpha_shape  in GENERAL <file:///C:/Program%20Files/CGAL-! 3.2.1/doc_html/cgal_manual/Alpha_shapes_2_ref/Class_Alpha_shape_2.html #Enum_Mode> mode and set alpha=0
> >>  Alpha_shape_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_3_ref/Class_Alpha_shape_3.html#Cross_link_anchor_799>  as(lwp.begin(), lwp.end(), 0, Alpha_shape_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_3_ref/Class_Alpha_shape_3.html#Cross_link_anchor_799>::GENERAL <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_2_ref/Class_Alpha_shape_2.html#Enum_Mode>);
> >>
> >>  //explore the 0-shape - It is dual to the boundary of the union.
> >>  std::list<Cell_handle> cells;
> >>  std::list<Facet>       facets;
> >>  std::list<Edge>        edges;
> >>  as.get_alpha_shape_cells(std::back_inserter(cells),
&g! t; >>    Alpha_shape_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_3_ref/Class_Alpha_shape_3.html#Cross_link_anchor_799>::INTERIOR <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_2_ref/Class_Alpha_shape_2.html#Enum_Classification_type>);
> >>  as.get_alpha_shape_facets(std::back_inserter(facets),
> >>     Alpha_shape_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_3_ref/Class_Alpha_shape_3.html#Cross_link_anchor_799>::REGULAR <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_2_ref/Class_Alpha_shape_2.html#Enum_Classification_type>);
> >>  as.get_alpha_shape_facets(std::back_inserter(facets),
> >>     Alpha_shape_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_3_ref/Class_Alpha_shape_3.html#Cross_l! ink_anchor_799>::SINGULAR <file:///C:/Program%20Files/CGAL-3.2.1 /doc_html/cgal_manual/Alpha_shapes_2_ref/Class_Alpha_shape_2.html#Enum_Classification_type>);
> >>  as.get_alpha_shape_edges(std::back_inserter(edges),
> >>    Alpha_shape_3 <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_3_ref/Class_Alpha_shape_3.html#Cross_link_anchor_799>::SINGULAR <file:///C:/Program%20Files/CGAL-3.2.1/doc_html/cgal_manual/Alpha_shapes_2_ref/Class_Alpha_shape_2.html#Enum_Classification_type>);
> >>
> >>//start here
> >>
> >> std::list<Facet>::iterator fbeg = facetr.begin();
> >> std::list<Facet>::iterator fend = facetr.end();
> >>
> >> for (int i = 0; fbeg != fend; fbeg++)
> >> {
> >>     Facet f = (Facet)fbeg;
> >>
> >>     ........................
> >>
> >> &nb! sp;   // how to get the three vertex handles of this facet
> >> }
> >>
> >>}
> >>
> >>
> >>
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