[ITK] Questions about ITK-Snap gaussian smoothing

[Dženan Zukić]

Hi Benedikt,

if you are asking about which mesh smoothing algorithm is used, I think
this source code file answers that:
https://sourceforge.net/p/itk-snap/src/ci/master/tree/Logic/
Mesh/VTKMeshPipeline.cxx#l167

Its declaration
<https://sourceforge.net/p/itk-snap/src/ci/master/tree/Logic/Mesh/VTKMeshPipeline.h#l122>
says it is an vtkImageGaussianSmooth
<http://www.vtk.org/doc/nightly/html/classvtkImageGaussianSmooth.html>. If
documentation is not enough, you can find its source code
<https://gitlab.kitware.com/vtk/vtk/blob/master/Imaging/General/vtkImageGaussianSmooth.cxx>
in VTK.

As the sigma is passed into there as a parameter, I believe the
user-modifiable preferences in the program control it.

Paul (CC'd) might have more explanations.

Regards,
Dženan Zukić, PhD, Senior R&D Engineer, Kitware (Carrboro, N.C.)

On Tue, May 30, 2017 at 4:42 AM, Beyer, Benedikt Alexander <
benedikt.beyer at rwth-aachen.de> wrote:

> Dear ITK community,
>
> I am currently writing an academic thesis at the RWTH Aachen University
> and I work with STL-data that is exported with ITK-Snap. A segmented
> structure is exported as an STL-file and then analyzed with VG Studio MAX.
> The data is used to determine measurement uncertainties created by gaussian
> filtering. To determine this uncertainty, I compare smoothed data to
> unsmoothed data.  I have a few questions regarding the gaussian image
> smoothing setting.
>
>
>    1. What gaussian filter algorithm does this option use? Eg. Recursive,
>    discrete, robust, etc.
>    2. Is this filter a linear or surface filter?
>    3. How big is the gaussian kernel? Eg. 3x3, 5x5, etc.
>    4. What does the “approximation error max” option do? It has no visual
>    effect on the segmentation.
>    5. There seems to be a threshold of the standard deviation at around
>    0.67. It seems that below this number no smoothing is applied. Is this
>    specific to the program, or is this depended on the voxel size?
>    6. Are there any known influences on measurement uncertainty by
>    gaussian smoothing?
>
>
> Thank you in advance and with kind regards
> Benedikt Beyer
>
>
>
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