Stiffness issue

[JetsSimavDibris]

Hi there,
I'm trying to reproduce a nodule on SOFA v22.12.
I created the skin with a value of stiffness and a sphere inside with a different stiffness's value, but I'm not able to "feel" the latter. I mean I feel the skin through the Geomagic but not the sphere.
What can I do?

Here there's a piece of the code:

stiffness_nodule = 2000
def createScene(root):
    # Create two instances of Skin with different stiffness values
    skin_Up=suture_models.Skin(parentNode=root, 
        name='Dermal', 
        rotation=[0.0, 0.0, 0.0], 
        translation=[0.0, 0.0, 4.0], 
        sphere1Box=[1, 1, -0.1, 1, 1, -0.1], sphere2Box=[1, 1, -0.1, 1, 1, -0.1],
        #fixingBox=[-0.1, -0.1, -2, 10, 20, 0.1],
        scale3d=scale3d_skin)
    skin_Up.stiffness = 80
    print ('Dermal found')

    nodule=sphere(parentNode=root, name="sphere", translation=[0, 0, 0],scale3d="0.5 0.5 0.5", stiffness=stiffness_nodule)


def sphere(parentNode=None, name=None, translation=[0.0, 0.0, 0.0], scale3d=[0.0, 0.0, 0.0], color=[0.0, 0.0, 0.0], stiffness=None):

    name=parentNode.addChild(name)
    name.addObject('EulerImplicitSolver',  rayleighStiffness="0.1", rayleighMass="0.1" )
    name.addObject('CGLinearSolver', iterations="25", tolerance="1e-5" ,threshold="1e-5")
    name.addObject('MeshObjLoader' ,filename="mesh/sphere.obj" ,name="loader" )
    name.addObject('MechanicalObject', template="Rigid3d")
    name.addObject('UniformMass' , totalMass=5)
    name.addObject('UncoupledConstraintCorrection')
    name.addObject('BoxROI', name='boxROI', box=[13,10,2,5,4,4], drawBoxes='false', computeTriangles='true')
    name.addObject('RestShapeSpringsForceField', name='rest', points='@boxROI.indices', stiffness='1e12', angularStiffness='1e12')

    #name.addObject("Monitor", ID="1", stiffness=2000, template="Vec3d")
   
    Visu=name.addChild('Visu')
    Visu.addObject('MeshObjLoader' ,name="meshLoader_3", filename="mesh/sphere.obj", scale="0.5", translation=[10, 6, 4.9])#, handleSeams="1" )
    Visu.addObject('OglModel' ,name="VisualOGL" ,src="@meshLoader_3",material="Default Diffuse 1 0 0.5 0 1 Ambient 1 0 0.1 0 1 Specular 0 0 0.5 0 1 Emissive 0 0 0.5 0 1 Shininess 0 45")
    Visu.addObject('RigidMapping' ,input="@..", output="@VisualOGL")
    
    Surf=name.addChild('Surf')
    #Surf.addObject('MeshObjLoader' ,filename="mesh/sphere.obj" ,name="loader" )
    #Surf.addObject('MeshTopology' ,src="@../loader")
    Surf.addObject('MechanicalObject')#, src="@../loader")#, scale="1.1")
    Surf.addObject('SphereCollisionModel', radius=5, name="Torus2Triangle")
    Surf.addObject('RigidMapping')

[hugtalbot]

Hi @JetsSimavDibris

To create an heterogeneous object, you have two ways of doing it:

• either to define heterogeneous stiffness vector per tetrahedra like in this discussion
• or to map another object on the main one. For this an example below:

    yourSkin.addObject('EulerImplicitSolver', name="odesolver", rayleighStiffness="0.01", rayleighMass="0.01") #added the 2 params
    yourSkin.addObject('CGLinearSolver', iterations="25", name="EpiLinearsolver", tolerance="1.0e-9", threshold="1.0e-9")

    # Volumetric mesh loader
    yourSkin.addObject('MeshGmshLoader', name='volumeLoader', filename="C:\sofa\src\VirtualSkinV4\mesh\skin_volume_403020_05", scale3d=scale3d)

    # Tetrahedra container
    yourSkin.addObject('TetrahedronSetTopologyContainer', src='@volumeLoader', name='TetraContainer')
    yourSkin.addObject('TetrahedronSetGeometryAlgorithms', template='Vec3d')
    yourSkin.addObject('TetrahedronSetTopologyModifier')

    # Mechanical object and mass
    yourSkin.addObject('MechanicalObject', name='SkinMechObj',  template='Vec3d')
    yourSkin.addObject('DiagonalMass', name="SkinMass", massDensity="1.0")
    # Forces
    yourSkin.addObject('TetrahedronFEMForceField', template='Vec3d', name='FEM', method='large', youngModulus=skin_youngModulus, poissonRatio=skin_poissonRatio)
    yourSkin.addObject('LinearSolverConstraintCorrection')

    # Fixed box for constraints
    yourSkin.addObject('BoxROI', name='boxROI', box=fixingBox, drawBoxes='false', computeTriangles='true')
    yourSkin.addObject('RestShapeSpringsForceField', name='rest', points='@boxROI.indices', stiffness='1e12', angularStiffness='1e12')


    #SubNode with the sphere to add stiffness and mass
    stifferSphere = yourSkin.addChild("StifferSphereInsideSkin")
    stifferSphere.addObject('MeshGmshLoader', name='sphereLoader', filename="YourVolumetricMeshFileOfSphere.msh")
    stifferSphere.addObject('TetrahedronSetTopologyContainer', src='@volumeLoader', name='TetraContainer')
    stifferSphere.addObject('TetrahedronSetGeometryAlgorithms', template='Vec3d')
    stifferSphere.addObject('TetrahedronSetTopologyModifier')

    # Mechanical object and mass
    yourSkin.addObject('MechanicalObject', name='SphereMechObj',  template='Vec3d')
    yourSkin.addObject('DiagonalMass', name="SkinMass", massDensity="1.0")

    # Forces
    yourSkin.addObject('TetrahedronFEMForceField', template='Vec3d', name='FEM', method='large', youngModulus=sphere_youngModulus, poissonRatio=sphere_poissonRatio)
    yourSkin.addObject('BarycentricMapping', template='Vec3d', name='mapping', input='@.', output="@../")

I hope this helps

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@JetsSimavDibris
In accordance with our forum management policy, the last reply is more than 4 months old and is therefore closed. Our objective is to keep the forum up to date and offer the best support experience.

Please feel free to reopen it if the topic is still active by providing us with an update. Please feel free to open a new thread at any time - we'll be happy to help where and when we can.