Hi, Luis,
The dataset I used is "sphere.zip",
which can be downloaded from
http://appsrv.cse.cuhk.edu.hk/~dfwang/tmp/sphere.zip
(the size is about 30K). By uncompressing this file, you will see Analyze file
of "sphere.hdr" and "sphere.img".
The parameters I used are listed as
follows,
Internal Forces (Alpha): 0.8
External Forces (Beta):
0.8
Damping Forces (Gamma): 0.35
Range of Search: 2
Rigidity
(Regularizing): 0.5
Number of Iterations: 1
The parameters involved in
the gradient calculation of
DeformableModelSimplexMesh are keep unchanged.
That is, I did not make any
change to the source code of
DeformableModelSimplexMesh.
The steps to reproduce my results are listed
as follows,
1. "File/Load File", select "sphere.hdr";
2. left click
the center point of the upper left image, then click
"File/Create Mesh", you
will see a simplex spherical mesh in the window;
3. "File/Preprocess Image",
wait about two minutes to finish the preprocess;
4. Click "Settings/Deform
Mesh" about 25 times. Each time after your click,
you will see that the
simplex mesh deform. In this process, you can see the
problem I described in
my last email.
By the way, if I set the parameter of "Number of
Iterations: 1" to 25, and
click "Settings/Deform Mesh" only once. The result
I got seems quite
similiar to the initial mesh, and is not like the one got
by seting "Number
of Iterations: 1" to 1 and click "Settings/Deform Mesh" 25
times. I think
this is another bug in this program.
If any part in
the above desription is not clear enough, please let me know
and I will try
to provide more details.
Best wishes,
Defeng
----- Original
Message -----
From: "Luis Ibanez" <
luis.ibanez-5opLkZggLXlBDgjK7y7TUQ@public.gmane.org>
To: "Defeng WANG" <
dfwang-zYqom8TFGCeYwlIiWXL0Uw@public.gmane.org>
Cc: "Leila Baghdadi" <
baghdadi-R4eML03dpU13h0zPYw+Emw@public.gmane.org>;
<
insight-developers-RyaoCGfWeh4@public.gmane.org>; <
insight-users-RyaoCGfWeh4@public.gmane.org>
Sent: Friday, February 01, 2008 10:40
AM
Subject: Re: [Insight-developers] bug report on DeformableModelSimplexMesh
application
>
> Hi Defeng,
>
> Can you
please post in a public web site the image that
> you are using as input,
and the full set of parameters
> that you are using for running this
application ?
>
> Otherwise it is very hard for us to figure out how
far
> from the edge of the image you are seeing the final
> contour
stopping.
>
> Please give use a very clear sequence of step that
we
> could follow to reproduce your experience
here.
>
>
>
>
Thanks
>
>
>
Luis
>
>
> -------------------
> Defeng WANG
wrote:
>> Hi, Leila,
>>
>> Thanks for your reply. It
seems that the parameters in the UI of
>> DeformableModelSimplexMesh
are not related to the gradient calculation. I
>> read the source code
involved in DeformableModelSimplexMesh. As for the
>> gradient
calculation, three filters are used successively as
follows,
>>
>>
m_GradientMagnitude->SetInput(m_CastImage->GetOutput()
);
>>
m_GradientMagnitude->SetSigma(0.5);
>>
>>
m_SigmoidImage->SetInput(
m_GradientMagnitude->GetOutput());
>>
m_SigmoidImage->SetOutputMinimum(0);
>>
m_SigmoidImage->SetOutputMaximum(1);
>>
m_SigmoidImage->SetAlpha(230);
>>
m_SigmoidImage->SetBeta(1300);
>>
>>
m_GradientFilter->SetInput(
m_SigmoidImage->GetOutput());
>>
m_GradientFilter->SetSigma( 0.5);
>>
>>
>> I have
taken a look at the final gradent image. It seems that it is good
>>
enough to describe the
>> edge or boundary of a sphere. So what do you
think of this problem
>> existing
>> in this simple
example?
>>
>>
>> Look forard to your
response.
>>
>> Best wishes,
>>
Defeng
>>
>> ----- Original Message ----- From: "Leila
Baghdadi"
>> <
baghdadi-R4eML03dpU13h0zPYw+Emw@public.gmane.org>
>> To: "Defeng WANG" <
dfwang-zYqom8TFGCeYwlIiWXL0Uw@public.gmane.org>
>> Cc: <
insight-developers-RyaoCGfWeh4@public.gmane.org>; <
insight-users-RyaoCGfWeh4@public.gmane.org>
>> Sent: Thursday, January 31,
2008 10:54 PM
>> Subject: Re: [Insight-developers] bug report
on
>> DeformableModelSimplexMesh
application
>>
>>
>>> Hi
Defeng,
>>>
>>> Yes I have used that code many a times.
I am not sure if I understand
>>> what you mean by "it does not
converge".
>>>
>>> My understanding of deformable models
is
>>>
>>> 1. you must make sure your gradient image is
created properly. Use
>>> paraview to look at the vector
image
>>>
>>> 2. you must play with the parameters to
get the model to converge,
>>>
>>> This is a specific
type of deformable models which uses simplex mesh.
>>> I suggest you
read about this algorithm first. This is developed based
>>> on the
paper by Herve Delingette of INRIA
france.
>>>
>>>
>>>
Leila
>>>
>>> On Thu, 2008-31-01 at 22:29 +0800, Defeng
WANG wrote:
>>>
>>>> Hello, ITK users and
developers,
>>>>
>>>> I found that
DeformableModelSimplexMesh, provided in
>>>>
InsightApplications-3.4.0, does not converge. It seems that
the
>>>> deformable mesh will not stop near the boundary of one
object to be
>>>> segmented. I tried a very simple volume data
set containing a sphere
>>>> only. The initial mesh I used is a
spherical simplex mesh inside it.
>>>> However, by increasing the
number of iterations, the mesh will
>>>> continue to expand until
it reaches outside of the image and the
>>>> program reports
error.
>>>>
>>>> Is there anybody tried this
program successfully before? Or anybody
>>>> knows how to adjust
the parameters properly to get right
segmentation?
>>>>
>>>> Best
wishes,
>>>> Defeng
>>>>
_______________________________________________
>>>>
Insight-developers mailing list
>>>>
Insight-developers-RyaoCGfWeh4@public.gmane.org>>>>
http://www.itk.org/mailman/listinfo/insight-developers>>
>>
>>
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