Attach a rigid cube to flexible FEM body

[Haitham]

Hi All,

Sorry for my naive question, I have just started using SOFA!

I have a *.msh file representing a flexible rod that I have inserted into sofa. I need to attach a rigid cube or cylinder to its tip to move with the rod. I am using python and I already wrote the code for both objects but they are separate.

Thanks

[Hugo]

Dear @haithamhussien

Welcome on the forum, it is a place for both naive and advanced questions. So no need to apologize.

Repost from #15863 : Depending on the type of animation loop you are using, I would have two main solutions:
– the most appropriate constraint to attach physically two objects would be the BilateralInteractionConstraint (requiring a FreeMotionAnimationLoop)
– the second would be the AttachConstraint, a project constraint ensuring that at the end of the time step, the desired points of both objects are in the same location.

You could also set StiffSprings between your objects, but in this third solution would not ensure the exact connection at each time step.

Anyway, you connect two objects they also need to have the same DOFs (Vec3d/Rigid..). If one object is deformable while the other is rigid, you might have to create a dedicated subnode to connect the two models.

Do not hesitate to take a look at the associated scene examples:
– examples/Components/constraint/BilateralInteractionConstraint.scn
– examples/Components/constraint/AttachConstraint.scn
– examples/Components/forcefield/StiffSpringForceField.scn

I hope this helps.
Best wishes,

Hugo

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