[SOLVED] Deleting Springs via SofaPython3

[Scheikl]

Dear SOFA Community,
I am trying to simulate two objects that are connected via connective tissue.
The easiest way to achieve a similar behavior is a StiffSpringForceField.
I would like to delete springs in this ForceField, when a certain force on the objects is exceeded. (Look into the mechanical object at specific indices, and trigger spring deletion, once force is too large.

body1.addObject(
    "StiffSpringForceField",
    template="Vec3d",
    name="SpringForceField",
    object1=body1.collisionMO.getLinkPath(),
    object2=body2.collisionMO.getLinkPath(),
    indices1=[78, 34],
    indices2=[88, 96],
    length=[28.4112, 29.8606],
    stiffness=1e04,
    damping=5
    )
body1.init()

When I create the scene via runSofa, the springs are visible in the object, and removing them during runtime works fine.

As a next step, I wanted to do the same thing from within a python script.
However, print(body1.SpringForceField.spring.value) returns [[], []] So the general shape of the DataField is correct, but I cannot access the springs.

What would be your approach to delete springs via python?
Deactivating all springs at once with body1.SpringForceField.isCompliance = True works fine, but I would like to delete individual springs.

Cheers,
Paul

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

[jnbrunet]

Hey @scheikl ,

I think this is because the data spring is a vector of sofa::component::interactionforcefield::LinearSpring objects, and the latter class hasn’t been bound to python3 yet, hence why you are seeing a vector of empty values (SofaPython3 detects that it is a vector, but cannot convert the LinearSpring class).

If you have some time, would you be able to create a very basic python 3 scene using the StiffSpringForceField. By basic I mean with the minimum number of components and plugins (for example, two objects attached and created from a RegularGridTopology so that we don’t have to add mesh files to the scene). I will try to add bindings for the LinearSpring class and this will help me to test the bindings.

J-N

[Scheikl]

Hi @jnbrunet,
sorry for the late reply!

Oh okay, that makes sense.

Would a scene with default meshes from sofa/share be okay?
https://cloud.ipr.kit.edu/s/STwn3oAHNn4dnnG

Cheers,
Paul

[jnbrunet]

Hi @scheikl,

Unfortunately, I haven’t had time to look at this yet. I just created a github issue here so that it doesn’t get lost.

Hopefully, I should be able to do it just after the holidays.

J-N

[Scheikl]

Hi @jnbrunet,
No worries!

Thanks, have a nice holiday! 🙂

Cheers,
Paul

[Scheikl]

Solved in https://github.com/sofa-framework/SofaPython3/pull/78 🙂

[Author]

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