CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 03/29/2012 04:26 PM, ayongwust_sjtu wrote:
> I stepped into<<  operator of Triangulation_3 with the predefined example :
> examples/Triangulation_3/simple_triangulation_3.cpp
>
> Here is the way the points were inserted in the example:
> -------------------------------
>    std::list<Point>  L;
>    L.push_front(Point(0,0,0));
>    L.push_front(Point(1,0,0));
>    L.push_front(Point(0,1,0));
>
>    Triangulation T(L.begin(), L.end());
>
>    Triangulation::size_type n = T.number_of_vertices();
>
>    // insertion from a vector :
>    std::vector<Point>  V(3);
>    V[0] = Point(0,0,1);
>    V[1] = Point(1,1,1);
>    V[2] = Point(2,2,2);
> -------------------------------
> When calling<<  operator, the triangulation object recursively retrieve all
> its vertex iterators, and
> copy them into a TV vector(std::vecotor<Vertex_handle>  TV(n+1)).
>
> Then, here are my questions:
> 1), Why an infinite vertex is defined as the first one of the triangulation?
> tr.is_infinite(TV[0]);
See this:
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Triangulation_3/Chapter_main.html#Section_39.1


> 2), Why the order of points of the triangulation is different with which
> they inserted?
see
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Triangulation_3_ref/Class_Delaunay_triangulation_3.html#Function_std::ptrdiff_t_insert6PointInputIterator_first+_PointInputIterator_last9;

And also this:
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Triangulation_3/Chapter_main.html#Subsection_39.5.3

for how to get the initial order.

Sebastien.

> The output order of points is:
> 1 0 0
> 0 0 0
> 0 1 0
> 1 1 1
> 2 2 2
> 0 0 1
>
> While the order in which points were inserted:
>    L.push_front(Point(0,0,0));
>    L.push_front(Point(1,0,0));
>    L.push_front(Point(0,1,0));
> .....
>    V[0] = Point(0,0,1);
>    V[1] = Point(1,1,1);
>    V[2] = Point(2,2,2);
>
>
> Best Regards,
> Xianyong Liu
>
> -----
> -------------
>
>   Regards,
>   Xianyong Liu
> --
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> http://cgal-discuss.949826.n4.nabble.com/How-are-points-in-triangulation-3-indexed-tp4515572p4515572.html
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