[Insight-users] Adaptive Meshing for FEM - Registration

[Markus Weigert]

Hi Nick,

if I see this the right way, the only way to achieve this kind of meshing would
be to use the ITK - Mesh and create a mesh - input file from this mesh, which the FEM - Filter 
can read, right?
I didn't have a look at the itk mesh yet, but is it appropriate for tatrahedral mesh generation which
can be used to create a fem - mesh?

Further question:

What is the concrete function of these lines (taken from software guide), why two different
membrane - types, which one is actually created?:

 typedef itk::fem::Element3DC0LinearHexahedronMembrane   Element3DType;
 typedef itk::fem::Element3DC0LinearTetrahedronMembrane  Element3DType2;

  {
//  Software Guide : BeginCodeSnippet
  Element3DType::LoadImplementationFunctionPointer fp = 
    &itk::fem::ImageMetricLoadImplementation<ImageLoadType>::ImplementImageMetricLoad;
  DispatcherType::RegisterVisitor((ImageLoadType*)0,fp);
//  Software Guide : EndCodeSnippet  
  }
  {
  Element3DType2::LoadImplementationFunctionPointer fp =
    &itk::fem::ImageMetricLoadImplementation<ImageLoadType>::ImplementImageMetricLoad;
  DispatcherType2::RegisterVisitor((ImageLoadType*)0,fp);
  }


Regards,
Markus
  ----- Original Message ----- 
  From: Nicholas Tustison 
  To: Markus Weigert 
  Cc: insight-users at itk.org 
  Sent: Monday, June 12, 2006 5:41 PM
  Subject: Re: [Insight-users] Adaptive Meshing for FEM - Registration


  Hi Markus,


  A straightforward conversion between an ITK mesh and a FEM mesh is non-existent.  I'm reworking the FEM mesh class now and maybe I'll come up with something but until then...


  The current FEM framework allows for an external mesh to be brought into the FEM project but that, in addition to the default rectilinear mesh that is created when no external mesh is specified, is the extent of the current FEM library meshing capabilities.  


  Nick Tustison




  On Jun 12, 2006, at 11:32 AM, Markus Weigert wrote:


    Hi all,

    in the insight book ("Insight into Images") from Terry S. Yoo,
    there is a nice example of adaptive lung meshing (page 331).
    My question is, how can such a meshing be obtained with ITK in 3D?
    I suppose, one can use the ITK - Mesh framework for this task,
    but the ITK Mesh would need to be casted to a FEM - Mesh.
    Can this casting be done in a straight forward way, or is it more complicated?

    Also, this would be interesting because one could start to segment an image
    and mesh individual surfaces to model each tissue with different elasticity.
    Any idears on this???

    Regards,
    Markus



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