[vtkusers] smoothing by AntiAliasBinaryImageFilter, Gaussian blur or windowedSincFilter

[Karthik Krishnan]

Merry christmas.

The Anti-alias smoothing filter in ITK uses a level set to "smooth
out" the voxel values so that the subsequent isosurface generator will
generate a smooth image, with fewer jagged edges etc.

Gaussian smoothing on the image domain would be another way to
accomplish the same thing.

Now, the smoothing the image may end up displacing the object's
boundary from the true boundary. The Anti-alias smoother ensures that
this displacement is no more than half a voxel. For the gaussian
smoother, this depends on the kernel sigma, no bounds here. You can
easily work this out.

--
karthik

On Fri, Dec 25, 2009 at 12:11 PM,  <lynx.abraxas at freenet.de> wrote:
> Hello!
>
>
> Let's  say  I  have  a  Platonic  solid  as a mesh (or even simpler a plane in
> [1,1,0] or [1,1,1] direction) I voxelize that to get a 3d-binary image. Then I
> wonder  what  would  be  the  best way to get back to a mesh who's shape is as
> close as possible to the original mesh.
> Just using marching cubes introduces uneven surfaces. From the vtk users  guid
> I  know gaussian smoothing the binary image can create a much smoother result.
> I was told AntiAliasBinaryImageFilter does something similar and then there is
> also the possibility to use some mesh smooting filter like Laplacian smoothing
> (vtkSmoothPolyDataFilter, used in vtk-book) and vtkWindowedSincPolyDataFilter.
> So  there  are two different classes of filter 1. voxel filter 2. mesh filter.
> Now I wonder:
>
> - Which one is the best for my problem?
> - Would it make sense to use more than one filter?
> - How can the voxel filter result in a  smoother  mesh  without  the  need  to
> subsample  the  voxel data? Or asked differently: How can the mesh be smoother
> altough the voxel discretisation stays the same???
> - What is the difference between Laplacian and Sinc smoothing or what type  is
> better?
> -  What  is  the difference between Gaussian and AntiAliasBinaryImageFilter or
> which one is better?
> - What filter is least dependant on abritrary chosen parameters?
>
>
> Sorry for the many questions but I'd be very thankful for any answers.
> Lynx
>
>
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-- 
_________________________________
Karthik Krishnan
R&D Engineer,
Kitware Inc.
Ph: +1 5188814919, +91 9538477060