[vtkusers] cleaning vtkSilhouette result

[Lars Friedrich Lars]

Nice to hear that this approach is sufficient for your needs!

In a non-VTK-based application at our institution we use a similar approach to extract the 'real' silhouette of polygonal 3D objects in perspective 2D projections. For us, this approach has appeared to be the only really robust one. Some years ago, we also tried to implement other - possibly faster - algorithms (comparable to the method you describe below), but all our algorithms suffer from occasional instabilities due to intersections and further 'epsilon'-problems.

If you find some time, it would be really nice if you could add a minimum example based on your app to the VTK examples wiki because there are quite a few postings on the silhouette-topic in the mailing list. I'm sure that it help a lot of people!

regards,
lars


-------- Original-Nachricht --------
> Datum: Fri, 5 Nov 2010 09:36:40 -0700 (PDT)
> Von: nsarrasin <nsarrasin at phenix-systems.com>
> An: vtkusers at vtk.org
> Betreff: Re: [vtkusers] cleaning vtkSilhouette result

> 
> > I'm not sure whether you recognized that the vtkPolyDataSilhouette
> filter
> does not generate an output that lies on the view plane (mapped to the 2D
> plane in 3D space) - it rather extracts edges of the 3D object - it will
> be
> difficult to infer "connectivity" from these 3D parts.
> 
> Yes I was aware of this but before launching connectivityfilter I
> projected
> the output on a plane.
> 
> My first idea was to project the output of vtkSilhouette on a plane (z=0)
> then triangulate with vtkDelaunay2D (and set the silhouette's output as
> both
> input and source to constraint the triangulation) and finally use
> silhouette
> again.
> 
> The problem is that vtkDelaunay2D didn't worked on the output of
> vtkSilhouette (still auto intersection problems I guess).
> 
> Anyway, than you very much Lars Friedrich Lars the combinaison of
> vtkWindowToImageFilter & vtkContourFilter, since I don't need a great
> accuracy, works perfectly !!
> 
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