[Insight-users] Level Set Bahaves Differently for 2D/3D?

[Sah Rayman]

I did a little more explore. 

1. SetMaximumIterations(1) and examine the level set
output (before binary thresholding). 

In a narrow band (2~3 pixels wide) of 0 level set, 2D
and 3D version gives exactly the same level set
output. 

2. SetMaximumRMSError(-1) so that it never functions.
For 3D version, compare the level set output (let's
call it ls_out) of Iteration=1 and Iteration=100. 
For outside area: ls_out=4, inside:ls_out=-4, narrow
band: -4<ls_out<4

And I discovered that, 
(ls_out_iter_is_1 < 4) = (ls_out_iter_is_100 < 4)

meaning that the narrow band is NOT updated for the 3D
version.

Does it mean  I have to manually update the narrow
band, how? Why in 2D case, it is obviously update
automatically?

Thanks.
Sah


--- Sah Rayman <sahrayman at yahoo . com> wrote:
> I applied the example code, 
> ThresholdSegmentationLevelSetImageFilter.cxx to my
> 3D
> image data and got some wierd results.
> 
> As a "debug", I created a 2D mhd file as input.
> Re-complied
> ThresholdSegmentationLevelSetImageFilter.cxx for a
> 2D
> and a 3D version. Then run them on the same 2D data.
> 
> 
> The 2D output looks very nice; but seems the 3D
> level
> set stopps even when the speedMap is obviously
> bigger
> than 0. It just stoppes after a few iterations after
> start, leaving an output quite close to input.
> 
> Advection, curvature and Laplacian weights are all
> set
> to 0, and therefore there is only propagation terms.
> 
> 
> Also, I use SetMaximumPropagationTimeStep() to set a
> same time step for 2D/3D cz their defaults are
> different.
> 
> It there any reason the 2D/3D still behaves
> different? 
> 
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