Question about TetrahedronFEMForceField(FEM) component

[ldi4]

HI all,

When I try to add TetrahedronFEMForceField(FEM) component to my scene, there is an error message keeps displaying:

[ERROR] [TetrahedronFEMForceField(FEM)] object must have a tetrahedric topology. The component is inactivated. To remove this error message please add a tetrahedric topology component to your scene.

I implemented subTopo component like this:

def createScene(rootNode):
    rootNode.addObject('VisualStyle', displayFlags='showForceFields showBehaviorModels')
    rootNode.addObject('RequiredPlugin', pluginName='SoftRobots SofaPython3')
    rootNode.addObject('RequiredPlugin', name='Sofa.Component.AnimationLoop')  # Needed to use components [FreeMotionAnimationLoop]
    rootNode.addObject('RequiredPlugin', name='Sofa.Component.Constraint.Lagrangian.Correction')  # Needed to use components [LinearSolverConstraintCorrection]
    rootNode.addObject('RequiredPlugin', name='Sofa.Component.Constraint.Lagrangian.Solver')  # Needed to use components [GenericConstraintSolver]
    rootNode.addObject('RequiredPlugin', name='Sofa.Component.Engine.Select')  # Needed to use components [BoxROI]  
    rootNode.addObject('RequiredPlugin', name='Sofa.Component.IO.Mesh')  # Needed to use components [MeshSTLLoader,MeshVTKLoader]
    rootNode.addObject('RequiredPlugin', name='Sofa.Component.LinearSolver.Direct')  # Needed to use components [SparseLDLSolver]
    rootNode.addObject('RequiredPlugin', name='Sofa.Component.Mapping.Linear')  # Needed to use components [BarycentricMapping]
    rootNode.addObject('RequiredPlugin', name='Sofa.Component.Mass')  # Needed to use components [UniformMass]  
    rootNode.addObject('RequiredPlugin', name='Sofa.Component.ODESolver.Backward')  # Needed to use components [EulerImplicitSolver]
    rootNode.addObject('RequiredPlugin', name='Sofa.Component.SolidMechanics.FEM.Elastic')  # Needed to use components [TetrahedronFEMForceField]
    rootNode.addObject('RequiredPlugin', name='Sofa.Component.SolidMechanics.Spring')  # Needed to use components [RestShapeSpringsForceField]
    rootNode.addObject('RequiredPlugin', name='Sofa.Component.StateContainer')  # Needed to use components [MechanicalObject]
    rootNode.addObject('RequiredPlugin', name='Sofa.Component.Topology.Container.Constant')  # Needed to use components [MeshTopology]
    rootNode.addObject('RequiredPlugin', name='Sofa.Component.Visual')  # Needed to use components [VisualStyle]  
    rootNode.addObject('RequiredPlugin', name='Sofa.GUI.Component')  # Needed to use components [AttachBodyButtonSetting] 
    rootNode.gravity.value = [-9810, 0, 0]
    rootNode.addObject('AttachBodyButtonSetting', stiffness=10)
    rootNode.addObject('FreeMotionAnimationLoop')
    rootNode.addObject('GenericConstraintSolver', tolerance=1e-7, maxIterations=1000)
    catheter = rootNode.addChild('catheter')
    catheter.addObject('EulerImplicitSolver', rayleighStiffness=0.1, rayleighMass=0.1)
    catheter.addObject('SparseLDLSolver', template='CompressedRowSparseMatrixd')
    catheter.addObject('MeshVTKLoader', name='loader', filename='my_SOFA_proj/mesh/catheter_ascii.vtk')
    catheter.addObject('TetrahedronSetTopologyContainer', name='topo', src='@loader')
    catheter.addObject('TetrahedronSetTopologyModifier', name="Modifier")
    catheter.addObject('TetrahedronSetGeometryAlgorithms', template="Vec3" ,name="GeoAlgo")
    catheter.addObject('MechanicalObject', name='tetras', template='Vec3', showObject=True, showObjectScale=1)
    catheter.addObject('UniformMass', totalMass=0.04)
    # catheter.addObject('TetrahedronFEMForceField', template='Vec3', name='FEM', method='large', poissonRatio=0.3,
    #                    youngModulus=1)
    boxROISubTopo = catheter.addObject('BoxROI', name='boxROISubTopo', box=[-7, -25,-7 , 7, 30, 7], strict=False,drawBoxes=True)
    boxROI = catheter.addObject('BoxROI', name='boxROI', drawBoxes=True)
    catheter.addObject('RestShapeSpringsForceField', points=boxROI.indices.linkpath, stiffness=1e12, angularStiffness=1e12)
    catheter.addObject('GenericConstraintCorrection')


    modelSubTopo = catheter.addChild('SubTopology')
    modelSubTopo.addObject('MeshTopology', position='@loader.position', tetrahedra=boxROISubTopo.tet
[SOFA.zip](https://github.com/sofa-framework/sofa/files/14542811/SOFA.zip)
rahedraInROI.linkpath,
                           name='container')
    modelSubTopo.addObject('TetrahedronFEMForceField', template='Vec3', name='FEM', method='large', poissonRatio=0.3,
                           youngModulus=1500)

I go through the source code and understand that the error message is caused by not detecting any tetrahedron in my mesh, But i generated my mesh using gmsh and it looks to me do have tetrahedron. I attached my code and mesh below. Very appreciate if i can get any form of help. Similar discussion are #3580 and #2732 but no apparent solution found.

SOFA.zip

[hugtalbot]

Hi @ldi4

This error seems quite explicit: a volumetric mesh including tetrahedra is needed in order to compute a linear elasticity material with the TetrahedronFEMForceField. Make sure your file mesh (catheter_ascii.vtk) contains tetrahedra and sub-topologies (triangles, edges and vertices).

Hope this helps

[epernod]

Hi,

some quick questions to identify where could be the error:

1. I see in your scene that you commented a first TetrahedronFEM in the parent Node (not inside the subtopo). Do you confirm this one was working fine ? This would mean the mesh is fine.
2. Then could you check the BoxROI component and check that the Data tetrahedraInROI is not empty ? This would mean the ROI is correct
3. Then could you check the MeshTopology in your child node and check that the Data: position and tetrahedra are not empty.

Best regards,

[ldi4]

Hi All, problem solved by regenerating vtk mesh directly from stl file instead of igs file. New mesh works but have [Cannot find triangle in tetrahedron] issue, but I will start a new discussion on this. Thank you guys for all your help!