External_force_fields are 0 in grasp_elastic.py

[Uber0802]

I observed that when running grasp_elastic,py, the force map is empty without representing the force. I wrote a function that print out the external_force_fields in each step at line 545 in grasp_elastic.py. It turns out 0 as the picture I attached shows. below is the function I wrote

def print_external_force_fields(contact_model, step):
    print(f"External Force Field at Step {step}:")
    fem_sensor1_forces = contact_model.gripper.fem_sensor1.external_force_field.to_numpy()
    fem_sensor2_forces = contact_model.gripper.fem_sensor2.external_force_field.to_numpy()

    print("FEM Sensor 1 External Forces:")
    print(fem_sensor1_forces)

    print("FEM Sensor 2 External Forces:")
    print(fem_sensor2_forces)

[Uber0802]

after some debugging effort, we found the bug. It seems that the code lacks a line between line 568 and line 569. It might require contact_model.gripper.fem_sensor1.extract_markers(0) to let the visualization work. and also the external_force_field seems to be so sparse that it turns out to be almost all zeros. the attached graph is the debugged visualization.