CGAL users discussion list

["Ch'Gans" <>]

On 24 March 2017 at 03:31, Andreas Fabri
<>
 wrote:
>
> Hello,
>
> In the pull request https://github.com/CGAL/cgal/pull/1991
> I added the graph_traits and free functions so that now
> all triangulation classes can be used with the BGL.

BTW, what is the rational behind all these 'copy/paste' in these
graph_traits, isn't it possible to parametrise the templates with a
triangulation instead of the triangulation own params?
eg:
template<class Triangulation>
struct graph_traits< Triangulation > {
typedef typename Triangulation::Vertex_handle vertex_descriptor;

}


Chris


>
> Concerning the edge weights, you might store them in
> a boost::unordered_map<edge_descriptor,double>,
> fill it as you like, wrap it in a boost associative
> property map, and then pass it to the MST algorithm,
> instead of redefining T2_edge_weight_map. The weight map
> is a parameter of the MST algorithm.
>
> best,
>
> andreas
>
>
> On 21/03/2017 03:34, Ch'Gans wrote:
>>
>> Hi there,
>>
>> I'm doing some experiment with CGAL Constrained Delaunay Triangulation
>> and boost graph Minimum Spanning Tree.
>>
>> The constrained edges of CDT correspond to path that already exist,
>> the non constrained edges of CDT are transient edges for the MST
>> algorithm.
>> To make sure that MST will use the constrained edges, i'm setting
>> their associated 'weight' (length) to zero,  and for the
>> non-constrained edges i'm setting their 'weight' to their squared
>> length.
>>
>> I'm currently doing all of these manually, including 'transforming'
>> the data structures between the steps of my 'pipeline'. I know it is
>> not optimal, but at least i am able to get the whole pipeline working.
>>
>> I went through the chapter 'CGAL and the Boost Graph Library' (BTW big
>> thumb up for the documentation!) and saw that CGAL provides all the
>> bolts and nuts to bind CGAL with boost graph. For example, CGAL
>> provide the edge weight map needed by MST, filters that allow to
>> filter out infinite edges, ...
>>
>> I am now wondering if I could use a filter to hide/proxy the weight of
>> the constrained edges or if i should use a different approach.
>> Maybe I should redefine T2_edge_weight_map
>> (CGAL/boost/graph/graph_traits_Triangulation_2.h) so that it takes a
>> CDT as a ctor argument...
>>
>> Actually it looks like i cannot use graph_traits_Triangulation_2.h or
>> graph_traits_Delaunay_Triangulation_2.h, i would need to write my own
>> version for CDT, do I?
>>
>> Any clarification or point out are very welcome,
>> Chris
>>
>
> --
> Andreas Fabri, PhD
> Chief Officer, GeometryFactory
> Editor, The CGAL Project
>
> phone: +33.492.954.912    skype: andreas.fabri
>
>
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