CGAL users discussion list

[Andreas Fabri <>]

Hi Matthias,

As I answered Lionel's mail (who also didn't get an answer) :  There are
almost no stupid questions, only it is an effort to give a reasonable
answer, this takes time, and people are free to allocate their time
as they want or as it is imposed by constraints.

For the concrete problem,  maybe have a look at the 
Constrained_delaunay_triangulation_2.cpp
demo in demos/Triangulation_2

This demo allows to enter a polygon with the mouse, and then
inserts the edges of the polygon as constraints in a triangulation.

It will still triangulate the area inside the polygon as well as
the outside, so you have to identify the triangles inside by doing
a graph traversal on them.

If your input is not a polyline, but only points then you might
have a look at the Alpha Shape package. This supposed that you
have a rather uniform sampling density for the points on the contour.

hope this helps.


andreas



Matthias Dörfelt wrote:
> Is this question too simple, or maybe not accurate enough? If so, please 
> let me know.-
>
> Thanks!
>
> Am 23.09.2009 um 20:28 schrieb 
> <>
>  
> <>:
>
> > Hi,
> >
> > I am new to cgal and could finally make it work on my mac. I want to 
> > use it for
> > some 2D triangulation tasks and I basically got a simple example to 
> > work. Even
> > though, right now it just traingulates the convex hull (i think thats 
> > what its
> > calles) of all triangles. I want to create concave shapes though, 
> > based on the
> > outlines I draw with my mouse (similar to vector programs, when i 
> > click i add a
> > new point that should connect with the last on and be the outline of the
> > shape). I figgured, that i would propably have to use constrained 
> > triangulation
> > for that purpose but I could not wrap my head around it. I would be 
> > really
> > thankful if someone could point me into the right direction, or maybe 
> > give a
> > small example!
> >
> > Thank you!
> > --
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