Re: [pgrouting-dev] Re: [postgis-users] Diagram of Voronoï to Squelettisation of polygon

[Stephen Woodbridge]

It might be simpler than this. Assign_vertex_id only need to be called 
once for any given data set as this creates the data that a network is 
created from. Our wrapper routines then use the start and end to create 
a bounding box and then expand the bounding box to collect the sub-set 
of the total graph data that is needed to build a graph for a given 
solution.

So for the voronoi diagram, you could write a new wrapper function where 
you pass in two corners of a bounding box, that would then collect the 
graph data and build the graph for the Voronoi solver which would then 
return polygons of the solution.

-Steve

On 12/13/2010 10:18 PM, Daniel Kastl wrote:
> Hi Jérôme,
>
> As you said the idea would be to add a function that calculates a
> skeleton from a polygon.
>
> Currently pgRouting contains a couple of functions
> (http://www.pgrouting.org/docs/1.x/index.html), but all of them require
> network data with at least information about "start" and "end" ID of a
> linestring. If the information about "start" and "end" ID doesn't exist
> yet, you can run a function called "assign_vertex_id". But what you need
> is network data.
>
> Your skeleton function now would allow users to add one more step before
> and retrieve a network from polygon data. So one could first run the
> skeleton function, then the "assign_vertex_id" function and finally have
> all the routing functions available even if the original data was of
> polygon shape.
>
> pgRouting has it's source code on GitHub
> (https://github.com/pgRouting/). The "assign_vertex_id" function is
> here:
> https://github.com/pgRouting/pgrouting/blob/master/core/sql/routing_topology.sql.
> Though I'm not sure it wouldn't be a good idea to reorganize this a bit.
> Well, I think we might better discuss details on the pgRouting list:
> http://lists.osgeo.org/mailman/listinfo/pgrouting-dev
>
> Best regards,
> Daniel
>
>
>
> 2010/12/11 j.rolland <jrmrolland at aol.com <mailto:jrmrolland at aol.com>>
>
>
>     Hi Daniel,
>
>     Of course that I am interested, say me how I can contribute my share.
>     As I indicate it in my blog, I can develop a function which turns
>     over the
>     skeleton from a polygon. Give me your specifications and I would
>     study them.
>
>
>     cordially,
>     Jérôme
>
>
>     Daniel Kastl-3 wrote:
>      >
>      > Salut Jérôme,
>      >
>      > Thank you for sharing your blog article!
>      > I tried to recall my French from high school and thanks to nice
>      > screenshots
>      > and code samples I think I could mostly understand.
>      >
>      > Well, I thought your functions might be an interesting
>     contribution to
>      > pgRouting project (http://www.pgrouting.org).
>      > We're trying to collect various routing and network analysis related
>      > functionality. Some voronoi and skeleton addition would for sure
>     suite
>      > well.
>      > That way users could build some routable network out of river
>     polygons for
>      > example. It might also help to build a routable graph for  maritime
>      > navigation. Probably there are a lot more use cases.
>      >
>      > Let me know if you're interested.
>      >
>      > Daniel
>      >
>      >
>      > 2010/12/9 j.rolland <jrmrolland at aol.com <mailto:jrmrolland at aol.com>>
>      >
>      >>
>      >> hi,
>      >>
>      >> I have just set up on my blog at the following address
>      >> http://ageoguy.blogspot.com/2010/12/squ… ation.html
>      >> http://ageoguy.blogspot.com/2010/12/squ… ation.html  a tutorial (in
>      >> french)
>      >> which presents an algorithm of surface squelettisation of waterway
>      >> (POLYGON).
>      >> I provide an example like all the necessary functions and
>     requests which
>      >> will enable you to obtain the skeleton of the waterway as you
>     can see it
>      >> in
>      >> the capture below :
>      >>
>      >> http://old.nabble.com/file/p30413623/skeleton5.jpg
>      >>
>      >>
>      >> regards,
>      >> Jérôme
>      >> --
>      >> View this message in context:
>      >>
>     http://old.nabble.com/Diagram-of-Vorono%C3%AF-to-Squelettisation-of-polygon-tp30413623p30413623.html