CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Iterate over edges and connect if the two faces incident
do not belong to the same segment then put a 1 in
the matrix.

Sebastien.

On 06/24/2016 05:00 PM, Sukhraj Singh wrote:
> Hello,
>
> I am trying to create an adjacency matrix for the segments.(undirected)
>
> I tried following code snippet, (the code isnt perfect though)
> The segment_ids ,contains the ids of the segments, its populated in the
> Surface Mesh Segmentation Plugin.
> ====================================================================================
>
>
>      int  current_segment  =  -1;
>
>      int  prev_segment  =  -1;
>
>
>      int  adjmat[10][10]  =  {0};
>
>      for(Polyhedron::Facet_iterator  facet_it  =  polyhedron->facets_begin();
>
>          facet_it  !=  polyhedron->facets_end();  ++facet_it)
>
>      {
>
>          current_segment  =  segment_ids[facet_it];
>
>          if(current_segment  !=  prev_segment)
>
>          {
>
>              //std::cout  <<  std::endl;
>
>              //std::cout  <<  "  segment:  "<<  prev_segment  <<  "  and  "  <<  "  
> segment:  "  <<  current_segment;
>
>              //std::cout  <<  "  Are  adjacent"  <<  std::endl;
>
>              adjmat[current_segment][prev_segment]  =  1;
>
>              prev_segment  =  current_segment;
>
>
>          }
>
>      }
>
> ===========================================================================================
>
> The output of adjmat is
>
> 0 1 1 1 1 1 0 0 0 1
> 1 0 1 1 1 1 0 0 0 0
> 1 1 0 1 1 1 0 0 0 0
> 1 1 1 0 1 1 0 0 0 0
> 1 1 1 1 0 1 0 0 0 0
> 1 1 1 1 1 0 0 0 0 0
> 0 0 0 0 0 0 0 0 0 0
> 0 0 0 0 0 0 0 0 0 0
> 0 0 0 0 0 0 0 0 0 0
> 0 0 0 0 0 0 0 0 0 0
>
> No. of segments were six, that's why > 6,6 elements are ale zeros
>
>
> Looks like the facet iteration is not "from one facet to neighboring
> facet" ? I assumed, I could record that particular jump from a facet to
> other that leads to segment id change , and make those segments as adjacent.
>
> Thanks to check the fallacy in my approach.
>
> --
> Sukhraj Singh