[Insight-users] Levelsets-v4 curvature term drives circles to squares (2-D) (+other issues)

[Bill Lorensen]

A simple example would make a great itk wiki example. We need some
levelset examples. If you can post a fully compilable example, I'll be
happy to add it to the wiki examples.

On Mon, Dec 17, 2012 at 10:58 AM, Arnaud Gelas <arnaudgelas at gmail.com> wrote:
> Hi Vaaksiainen,
>
> As Bill mentioned, to get the best performance make sure to build your
> program in Release. It can make a huge difference.
>
> Now speaking about the performance of the v4 framework, it is not
> multi-threaded for all level set representations as it was for the previous
> implementation; and some there is still some work to be done on that matter.
> Also for some of the sparse cases, there are still some optimizations to be
> made in the code.
>
> I will try to look at some of these issues during the holidays...
>
> ---
>
> Meanwhile, could you make a minimal example with one image to reproduce this
> behavior, please?
>
> Thanks,
> Arnaud
>
>
>
> On 12/17/2012 04:45 PM, Bill Lorensen wrote:
>>
>> Make sure you build your program Release and not Debug.
>>
>> On Mon, Dec 17, 2012 at 10:02 AM, Vaaksiainen <vaaksiainen at gmail.com>
>> wrote:
>>>
>>> Update to this question and some credit to authors :) now that I've
>>> tried it, Chan-Vese levelset works nicely, and although a single
>>> iteration is slowish, the convergence is very fast from the initial
>>> circle initialization (~comparable with v3 snake in total time). I
>>> remark, that default value of Heaviside epsilon is kinda high, so
>>> changing that was my first solution. The original question with plain
>>> curvature or geodesic active contour remains open still.
>>>
>>> I try not to profile spammer, so I also attach here my thanks to
>>> Arnaud regarding my previous question
>>> (LevelSetEquationTermContainer->SetInput() ? ).
>>>
>>> Best,
>>>
>>> -Vaaksiainen
>>>
>>> 2012/12/17 Vaaksiainen <vaaksiainen at gmail.com>:
>>>>
>>>> Hi,
>>>>
>>>> I'm learning Levelsets-v4 hard. Currently, after not getting the
>>>> convergence appreciated, I tried the following:
>>>>
>>>> I set up LevelSetEvolution following the
>>>> itkSingleLevelSetDenseImage2DTest -example, but I use only propagation
>>>> or curvature terms one at a time. I set the feature images unitary,
>>>> and initialize the levelset as small circles (equi-spaced).
>>>>
>>>> Problem: curvature term drives circles towards squares (really
>>>> sharp-edged NxN pixel squares eventually), while obviously should not.
>>>> Somewhat similar happens with the propagation term alone, where I find
>>>> speed along coordinate axes to be dominative.
>>>>
>>>> What I might be doing wrong here?
>>>>
>>>> Another question, is it possible to obtain (approximately) similar
>>>> behaviour using GeodesicActiveContourLevelSetImageFilter and
>>>> Levelsets-v4 framework with propagation, curvature and advection
>>>> terms. I tried, but obvious reasons (mentioned above) already
>>>> cancelled this study. Also: number of iterations per time unit seems
>>>> to be drastically lower (hundred folds) with the new framework.
>>>>
>>>> -V
>>>
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>>
>>
>



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