[ITK-dev] itk FEM Solver

[Yusuf OEZBEK]

Dear ITK community,

I want to deform a 3D model using itk’s FEM module. For this I have implemented the following workflow:

1. Read CT data-set and create 3D iso-surface using vtkMarchingCubes (output is polydata)
2. Extracted the interested surface using vtkHardwareSelector (output is 2D polydata)
3. Converted the extracted surface to the unstructured gird using vtkUnstructuredGrid and vtkDelaunay3D in order to get a 3D tetrahedron as unstructured grid (output is 3D unstructured grid)
4. Converted the unstructured grid to the itk mesh, which contains tetrahedron cells (output is itkMesh object)
5. To convert the itk mesh to the FEM model, I have created FEM object (FEMObject<3>), which contains a material (MaterialLinearElasticity), elements and nodes (Element3DC0LinearTetrahedronStrain), boundary conditions within force (LoadBC) and to generate a solution for the formulation, I have created a solver (FEMSolver<3>).

My problem is:
If I call the update of solver “solver->Update()” I get the warnings “/itk-4.7.2/Modules/ThirdParty/VNL/src/vxl/core/vnl/algo/vnl_qr.txx: vnl_qr::solve() : matrix is rank-deficient by 3” and generated solutions are just zeros.

The test code can be found under the link:

https://www.dropbox.com/s/v8q5qdqg9ads33n/vtkUGridToFemMesh.zip?dl=0

Thank you for any help