[Qgis-developer] fTOOLS Delaunay triangulation

[Carson Farmer]

kimaidou,
> Speaking about delaynay triangulation, voronoi diagram, etc... I am
> looking for a way to create concave (and not convex) hull of a set of
> points.  I have made several google searches, and what I need seems to
> be the implementation of alpha shapes. Basically, you define a
> parameters to tell how much you want the final polygone to be concave.
>
> Ok, I am trying to explain (english english) : I think when a delaynay
> triangulation is made for a set of points, we are very close to be
> able to male a concave hull, no ?
>   
Technically the plain delaunay will be a *convex* hull. But you can 
clearly see that with a little bit of work you can also generate a 
concave polygon, in fact:/ Basic alpha shapes/ are based on the Delaunay 
triangulation.

I don't know of any specific algorithms, but I imagine it wouldn't be 
too hard to come up with something if you were so inclined....

Carson

-- 
Carson J. Q. Farmer
ISSP Doctoral Fellow
National Centre for Geocomputation (NCG),
Email: Carson.Farmer at gmail.com
Web:   http://www.carsonfarmer.com/
       http://www.ftools.ca/