[vtkusers] filtering polygon surfaces

[Jeff Weiss]

I am using VTK to produce polygonal surfaces of bones from CT data.  I read the
data in (vtkVolume16Reader) and extract isosurfaces using marching cubes
(vtkMarchingCubes), smooth the resulting surface (vtkSmoothPolyFilter),
decimate the surface (vtkDecimate) and finally use the connectivity filter
(vtkConnectivityFilter) to grab the largest surface.

When using this technique on CT datasets of the distal femur and proximal
tibia, I often get a lot of "junk" on the inside of the bone's outer surface
(cancellous bone, etc.) that correspond to the isosurface value that I select.
 It almost appears that the stuff on the inside is branched from the main outer
surface of the cortex.

First, is it possible to generate non-manifold surfaces with marching cubes?
 If so, any way to cut the connections or filter the parts out that I don't
want using VTK?  If marching cubes in VTK doesn't generate non-manifold
surfaces, what other or tools in VTK might I use to avoid getting polygons
other than just the cortical surface when extracting isosurfaces from CT
datasets of bones?

Thanks,

Jeff Weiss


-- 

Jeffrey A. Weiss, Ph.D.
Department of Bioengineering, University of Utah
jeff.weiss at utah.edu   http://hodad.bioen.utah.edu/~weiss/mrl