[vtkusers] Marching cubes with ITK data: Problems with negative indices, possible bug?

Matthias Riechmann riechmann at ira.uka.de
Mon Sep 1 13:51:00 EDT 2008


Hi,

I tried to create polgon models with marching cubes from ITK-data using 
the ITK-VTK bridge. To force the marching cubes to close the polygons I 
applied the "itk::ConstantPadImageFilter" on my original image data to 
extend it by a couple of pixels. The way this filter does the job, is to 
assign negative pixel coordinates (indices) in order not to have to 
recalculate the image's origin.
VTK's marching cube worked quite fine with it, ony on some images I 
discovered a nasty phenomenon: The resulting polygon was split into 
separate segments. This was not visible at first but after some 
filtering holes startet to appear on the surface. A test using the 
vtkConnectivityFilter showed the polydata really was split into several 
pieces.
Is it possible the ITK-VTK-bridge cannot handle the negative indices 
properly? As a workaround I started extending my images using the 
itk::PasteImageFilter, which which works out fine with the marching cubes.


Matthias




-- 
Dipl.-Inform. Matthias Riechmann
Institut für Prozessrechentechnik, Automation und Robotik
Medizin-Gruppe
Universität Karlsruhe (TH)
Gebäude 40.28, Zimmer 103
Engler-Bunte-Ring 8
76131 Karlsruhe

Fon: +49 (721) 608-4049
Fax: +49 (721) 608-7141

Web: http://wwwipr.ira.uka.de/~richmann
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