[vtkusers] cleaning vtkSilhouette result

[Lars Friedrich Lars]

Hi nsarrasin,

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. See also: http://vtk.1045678.n5.nabble.com/projection-onto-a-plane-td1244478.html#a1244479 .

What about an approximate approach as follows in order to extract the external contour of a poly data object:
- render the poly data with the desired geometric setup (view plane, position ...)
- modify the poly data's material properties so that you gain a binary image at the end
- extract the rendered image using the vtkWindowToImageFilter  
- use the extracted 2D image as input for vtkContourFilter and simply set an appropriate isovalue that is suitable to extract the outer contour as poly data again

... I did not implement that myself, but I think this should work.

regards,
lars


-------- Original-Nachricht --------
> Datum: Fri, 5 Nov 2010 04:03:00 -0700 (PDT)
> Von: nsarrasin <nsarrasin at phenix-systems.com>
> An: vtkusers at vtk.org
> Betreff: [vtkusers] cleaning vtkSilhouette result

> 
> Hi all,
> 
> I'm using vtkSilhouette on a vtkPolyData to get its contours.
> It works well and you can see the result here :
> http://img143.imageshack.us/img143/8783/vtksilhouette.png
> 
> Now my goal is to clean the result to extract the external contour of this
> result , as if it was the shadow of the vtkPolyData.
> 
> vtkConnectivityFilter->ExtractLargestRegion() doesn't work here because
> there are some auto-intersected silhouettes.
> 
> I'm quite lost on this case because I'm pretty sure it's possible but
> don't
> know where to look.
> 
> Note that I've already posted a similar question but never find any
> answer,
> hope sometimes someone can advice me.
> 
> Thanks by advance
> -- 
> View this message in context:
> http://vtk.1045678.n5.nabble.com/cleaning-vtkSilhouette-result-tp3251639p3251639.html
> Sent from the VTK - Users mailing list archive at Nabble.com.
> _______________________________________________
> Powered by www.kitware.com
> 
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
> 
> Please keep messages on-topic and check the VTK FAQ at:
> http://www.vtk.org/Wiki/VTK_FAQ
> 
> Follow this link to subscribe/unsubscribe:
> http://www.vtk.org/mailman/listinfo/vtkusers

-- 
GMX DSL Doppel-Flat ab 19,99 &euro;/mtl.! Jetzt auch mit 
gratis Notebook-Flat! http://portal.gmx.net/de/go/dsl