[Insight-users] DeformableModelSimplexMesh

[Luis Ibanez]

Hi Alex,

What you are undertaking is a very interesting effort.

We will be happy to assist you in the coding of these new Mesh
classes.  Please note that ITK has a backward compatibility
policy that states that we will keep in the toolkit classes
that have been made available in any previous release.

To be consistent with these policy, when we add new classes
that may be replacement for existing classes, we still keep
the original ones in the toolkit. That means that instead
of modifying the code of the deformable filters, what we
would like to do is to add new versions that are appropriate
for your new Mesh structure. In this way, both the old filter
and the new filters will be available to users.

You probably noticed that this approach was already used for
the Simplex mesh. The original deformable model filter was
written for the itkMesh, and when Thomas Boettger kindly
contributed the Simplex mesh to the toolkit, he also provided
a customized version of the Deformable Model algorithm, that
was adapted to work with the Simplex mesh.



Do you have a design for these classes ?

We will be very interested in looking at the hierarchy
that you are planning to implement.


One resource that you could use is to add a page in the ITK
Wiki (anybody has write access to it) describing the details
of your design and implementation.  We do this for any major
modification to the toolkit.

The page were you can add this proposal is:

  http://www.itk.org/Wiki/ITK_Oversight_Committee#Proposals


Also, since you are planning to contribute code to the
toolkit, we should probably move this discussion to the
developers list. You can subscribe to the list at the
following link:

http://www.itk.org/mailman/listinfo/insight-developers


You are also welcome to joing the weekly phone conferences
that are held on Fridays at 1:00pm EST. You will find
information about this at:

http://www.itk.org/Wiki/Telephone_Conference_Agendas_and_Minutes


Please let us know if you have any questions,


   Thanks


     Luis



-----------------------
alex. gouaillard wrote:
> Dear leila, dear all.
> 
> FYI, we are almost ready (one month) to release a new mesh structure in
> itk. This mesh structure for discrete surfaces is based on C-GAL and the
> so called "Quad-Edge" structure.
> The impact on the curent problem you're addressing here is twofold:
> 
> 1. This structure natively hold primal and dual connectivity information
> of the surface, making the actual simplex related classes kind of
> obsolete. I would like to volunteer to recode the existing classes
> (well, triangle to simplex and simplex to triangle are not necessary
> anymore) using the new structure and I was wondering if you would mind
> giving me some e-mail assistance if I have any problem? I plan to do
> that within the following 30 days.
> 
> 2. We are planing to port most of the surface processing filters from
> vtk to itk to be able to have all the surface processing done in itk,
> and only the vizualization in vtk. Has we implemented the euleroperators
> in the new structure, this work is made easier. We have already ported
> decimate (first version, no topology modification), smoothing, and
> implemented an improved version of connectivity filter. More are on the
> way. 
> 
> cheers,
> 
> alex
> 
> On Thu, 2006-08-24 at 02:50, Leila Baghdadi wrote:
> 
>>Hi Zein,
>>
>>I have done some further investigation with this and fixed a few minor
>>things which I will commit to cvs soon.
>>
>>However, the major issue which I still have not solved is as follows,
>>
>>As you know, this application reads a binary a image to be converted to
>>a mesh using the vtkMarchingCubes class. This class happens to create
>>4-5 triangles per voxel of image (i.e, a huge number of triangles)
>>converting such a mesh to a simplex mesh for deformation will result in
>>a disaster unless you have unlimited memory on your system. 
>>
>>So To avoid the above I placed the vtkDecimate class right after
>>vtkMarchingCubes for the sole purpose of reducing the number of
>>triangles by a huge number (i.e, creating a simplex mesh which can
>>easily be deformed for many iteration)
>>
>>Unfortunately, over the course of VTK going through major modifications
>>this class is replaced by vtkDecimatePro which according to my tests
>>does not do a good job of reducing the number of Triangles unless
>>PreserveTopology is Off at which case it creates holes in the mesh
>>(i.e., not usable for converting to simplex mesh and going through the
>>deformation)
>>
>>I have sent an e-mail to vtk list asking if the old class could be added
>>to vtk tree so I could modify my itk code to use the old class.
>>Meanwhile, I am going to have to think about this and see if I can
>>resolve this myself.
>>
>>Please continue using itk,
>>
>>Leila 
>>
>>_______________________________________________
>>Insight-users mailing list
>>Insight-users at itk.org
>>http://www.itk.org/mailman/listinfo/insight-users
> 
> 
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