CGAL users discussion list

[Renato Poli <>]

Hi Sebastien,

I worked the past days on simplifying my problem and trying to understand
what is going on.
I made a very raw code (below) as an example.

Please find attached three pictures:
(1) the mesh without refinement
<http://cgal-discuss.949826.n4.nabble.com/file/t376144/cgal-mesh1.png> 

(2) the refined mesh after
/ typedef CGAL::Delaunay_mesh_size_criteria_2<CDT> Criteria;
     CGAL::refine_Delaunay_mesh_2(cdt,seeds.begin(), seeds.end(),
Criteria(0, 100));/
<http://cgal-discuss.949826.n4.nabble.com/file/t376144/cgal-mesh2.png> 

(3) the seed location (the extra point when compared to mesh1)
<http://cgal-discuss.949826.n4.nabble.com/file/t376144/cgal-mesh3.png> 

I dont understand
     (i) why the refiner changes the mesh beyond the shape and size
criteria? ; and 
     (ii) why the mesh refiner changes the area with a seed?

Is there any way to avoid those points and get more 'control' on the
meshing?

Thanks upfront,
Renato


==== Raw code for mesh creation
 40   typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
 41   typedef K::Point_2 CPoint;
 42   typedef CGAL::Polygon_2<K> CPolygon;
...
 44   typedef CGAL::Triangulation_vertex_base_2<K> Vb;
 45   typedef CGAL::Triangulation_face_base_with_info_2<FaceInfo2,K>    Fbb;
 46   typedef CGAL::Delaunay_mesh_face_base_2<K,Fbb> Fbbb;
 47   typedef CGAL::Constrained_triangulation_face_base_2<K,Fbbb>        Fb;
 48   typedef CGAL::Triangulation_data_structure_2<Vb, Fb> Tds;
 49   typedef CGAL::Exact_predicates_tag                               
Itag;
 50   typedef CGAL::Constrained_Delaunay_triangulation_2<K, Tds, Itag> CDT;
...
 56   typedef CGAL::Delaunay_mesh_size_criteria_2<CDT> Criteria;
...
 83   CPolygon pgn;
 84   pgn.push_back( CPoint(5.88643, 2.60851));
 85   pgn.push_back( CPoint(5.81283, 2.89567));
 86   pgn.push_back( CPoint(5.625, 3.125));
 87   pgn.push_back( CPoint(5.58073, 3.40017));
 88   pgn.push_back( CPoint(5.53646, 3.67535));
 89   pgn.push_back( CPoint(5.18695, 3.80367));
 90   pgn.push_back( CPoint(4.82072, 4.10386));
 91   pgn.push_back( CPoint(4.78469, 3.81578));
 92   pgn.push_back( CPoint(4.53348, 4.14603));
 93   pgn.push_back( CPoint(4.375, 3.75));
 94   pgn.push_back( CPoint(3.98473, 3.96918));
 95   pgn.push_back( CPoint(3.96882, 3.53733));
 96   pgn.push_back( CPoint(3.76489, 3.76106));
 97   pgn.push_back( CPoint(3.60312, 3.3071));
 98   pgn.push_back( CPoint(3.38327, 3.09255));
 99   pgn.push_back( CPoint(3.64059, 2.897));
100   pgn.push_back( CPoint(3.23544, 2.82327));
101   pgn.push_back( CPoint(3.43546, 2.57049));
102   pgn.push_back( CPoint(3.47702, 2.25083));
103   pgn.push_back( CPoint(3.69296, 1.91734));
104   pgn.push_back( CPoint(3.93944, 1.62403));
105   pgn.push_back( CPoint(4.26672, 1.81009));
106   pgn.push_back( CPoint(4.21836, 1.51922));
107   pgn.push_back( CPoint(4.51268, 1.50128));
108   pgn.push_back( CPoint(4.81592, 1.47285));
109   pgn.push_back( CPoint(5.08929, 1.60714));
110   pgn.push_back( CPoint(5.46234, 1.783));
111   pgn.push_back( CPoint(5.44254, 2.08688));
112   pgn.push_back( CPoint(5.69193, 2.26163));
113 
114   CPolygon ext_pgn;
115   ext_pgn.push_back( CPoint(1, 0) );
116   ext_pgn.push_back( CPoint(8, 0) );
117   ext_pgn.push_back( CPoint(8, 6) );
118   ext_pgn.push_back( CPoint(1, 6) );
119 
120   std::list<CPoint> seeds;
121   seeds.push_back( CPoint(2.68962, 2.55613) );
122 
123   CDT cdt;
124   cdt.insert_constraint(pgn.vertices_begin(), pgn.vertices_end(), true
);
125   cdt.insert_constraint(ext_pgn.vertices_begin(),
ext_pgn.vertices_end(), true );
126 
127 //  CGAL::refine_Delaunay_mesh_2(cdt,seeds.begin(), seeds.end(),
Criteria(0, 100));




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