CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Your question is not clear at all. You talk about Delaunay triangulation 
(which is unique in non-degenerate situations)
and the code you post use arrangement and surface_mesher.

You should clarify what you want to do.

Sebastien.

On 03/25/2012 09:13 PM, RAGHU PRASAD wrote:
> Hi All,
>
>
> My Delaunay Trian-gulation assumes a given set of points, and it is
> always convex. Cuts result in non-convex boundaries, so the standard
> Delaunay Triangulation in CGAL is not directly usable.Thefore I am
> trying to use the edge flip technique to locally improve the mesh.
>
>
> My apparoach works as follows: when cutting, the cutting tool is
> attached to a node, the active node, so moving the scalpel moves the
> active node. The
> active node is always part of the boundary, so it is incident to two
> boundary edges, the cut edges. During a cut, these edges almost coincide
> geometrically,
> and form an incision. I call triangles incident with the active node
> active triangles. The active node is moved, and after each movement,
> local remeshing
> should be applied to the active triangles.
> *
> My question is does CGAL Dealunay has any re meshing mechanism .The
> remeshing process should perform the following*
>
> Edges are flipped to improve the element angles.If another node is found
> close to the active node, it is removed. When the incision becomes too
> large, it is split thus introducing new nodes to approximate the cutting
> tool path
>
> #include <CGAL/Exact_predicates_inexact_constructions_kernel .h>
> #include <CGAL/Arr_non_caching_segment_traits_2.h>
> #include <CGAL/Arrangement_2 .h>
> typedef CGAL: : Exact_predicates_inexact_constructions_kernel Kernel ;
> typedef Kernel : :FT Number_type ;
> typedef CGAL: : Arr_non_caching_segment_traits_2<Kernel> Traits ;
> typedef Traits : : Point_2 Point ;
> typedef Traits : :X_monotone_curve_2 Segment ;
> typedef CGAL: :Arrangement_2<Traits> Arrangement;
> typedef Arrangement : : Vertex_handle Vertex_handle;
> typedef Arrangement : : Halfedge_handle Halfedge_handle ;
> typedef Arrangement : : Face_handle Face_handle
> typedef CGAL::Surface_mesh_default_triangulation_3 Tr;
> typedef Tr::Geom_traits GT;
>
>
> // Insert isolated points .
> Arrangement arr ;
> Face_handle uf = arr . unbounded_face ( ) ;
> Vertex_handle u1 = arr . insert_in_face_interior(Point (3 , 3) , uf ) ;
> Vertex_handle u2 = arr . insert_in_face_interior(Point (1 , 5) , uf ) ;
> Vertex_handle u3 = arr . insert_in_face_interior(Point (5 , 5) , uf ) ;
> // Insert four segments that form a square−shaped face .
> Point p1(1 , 3) , p2(3 , 5) , p3(5 , 3) , p4(3 , 1);
> Segment s1 (p1 , p2) , s2 (p2 , p3) , s3 (p3 , p4) , s4 (p4 , p1 ) ;
> Halfedge_handle e1 = arr . insert_in_face_interior( s1 , uf ) ;
> Vertex_handle v1 = e1−>source ( ) ;
> Vertex_handle v2 = e1−>target ( ) ;
> Halfedge_handle e2 = arr . insert_from_left_vertex ( s2 , v2 ) ;
> Vertex_handle v3 = e2−>target ( ) ;
> Halfedge_handle e3 = arr . insert_from_right_vertex( s3 , v3 ) ;
> Vertex_handle v4 = e3−>target ( ) ;
> Halfedge_handle e4 = arr . insert_at_vertices( s4 , v4 , v1 ) ;
>
> Tr tr;
> C2t3 c2t3 (tr);
>
> Gray_level_image image("data/skull_2.9.inr", 2.9f);
>
>
> GT::Point_3 bounding_sphere_center(122., 102., 117.);
> GT::FT bounding_sphere_squared_radius = 200.*200.*2.;
> GT::Sphere_3 bounding_sphere(bounding_sphere_center,
> bounding_sphere_squared_radius);
>
>
> Surface_3 surface(image, bounding_sphere, 1e-5);
>
>
> CGAL::Surface_mesh_default_criteria_3<Tr> criteria(30.,
> 5.,
> 5.);
>
>
> CGAL::make_surface_mesh(c2t3, surface, criteria, CGAL::Manifold_tag());
> std::ofstream out("out.off");
> CGAL::output_surface_facets_to_off (out, c2t3);
> std::cout << "Final number of points: " << tr.number_of_vertices() << "\n";
>
>
> Perform Re-mesh
>
> {
>
>
> }
>
>
>
>
>
>
>
>
>
> --
> Warm Regards
>
> Raghu Prasad