[SOLVED] Objects do not deform on collision when using FrictionContact response

[Scheikl]

Dear SOFA Community,
I created a scene file in SofaPython3, that uses the FreeMotionAnimationLoop, together with the GenericConstraintSolver in the root node and UncoupledConstraintCorrection in each object.

When choosing the response “default” (creating forces proportional to the detected interpenetration) in DefaultContactManager, the objects deformed on collision.
When using the response “FrictionContact” (constraint-based method) the models did not deform anymore.

@Hugo proposed the following solution that worked perfectly.
First: set the data compliance in the UncoupledConstraintCorrection to roughly 1/totalMass of the object. Now, all the models deformed on collision, but the behavior seemed a bit unstable.

Second: use PrecomputedConstraintCorrection instead of UncoupledConstraintCorrection in models with heavy deformation. That made everything much more stable.

I added the thread as [SOLVED], so that other people might find this solution when facing a similar problem.

Cheers,
Paul

SOFA version: v20.12_beta
SofaPython3 version: master (4566e4d83a126b7722cbeb824b38254e99d4cf73)

Minimal Scene:

root_node.addObject("FreeMotionAnimationLoop")
root_node.addObject(
    "GenericConstraintSolver",
    maxIterations=1000,
    tolerance=0.001,
    computeConstraintForces=True,
)
root_node.addObject("DefaultPipeline", name="CollisionPipeline")
root_node.addObject("BruteForceDetection")
root_node.addObject(
    "MinProximityIntersection",
    name="localmindistance",
    alarmDistance=0.2,
    contactDistance=0.1,
)

root_node.addObject(
    "DefaultContactManager", name="Response", response="FrictionContact"
)

... (solver, topology, mesh loader)

liver.addObject(
    "MechanicalObject", template="Vec3d", name="dofs",
)

liver.addObject("UniformMass", totalMass=1.5, name="LiverMass")

liver.addObject(
    "TetrahedronFEMForceField",
    template="Vec3d",
    method="large",
    name="FEMforcefield",
    poissonRatio=0.3,
    youngModulus=3000,
    computeGlobalMatrix=False,
)

liver.addObject("PrecomputedConstraintCorrection")

... (collision models and mapping)

[Hugo]

Thanks @scheikl for sharing everything (problem and solution!) on the forum!

Hugo

[Author]

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