Access object data on the fly, sofaPython3

Dear all,

I want to propose a question of how to access/modify object data on the fly, for example index positions.

I’ve followed the example of “python controller” as https://github.com/sofa-framework/SofaPython3/blob/master/examples/liver-scriptcontroller.py, but still fail to stream position data when I trigger the event.

My code is attached as below, aiming to print out the position of the first tissue index on pressing “ctrl + “+””

In the createScene(root) function, I create the scene with root and tissue node

tissue = root.addChild('tissue')
tissue.addObject('MechanicalObject', name = "tissueDofs", src="@tissueMeshLoader")

root.addObject( KeyPressedController(name="tissueController") )

In the trigger function, I define

class KeyPressedController(Sofa.Core.Controller):
    def __init__(self, *args, **kwargs):
        Sofa.Core.Controller.__init__(self, *args, **kwargs)
        self.iteration = 0

    def onKeypressEvent(self, event):
        if event['key']=="+":
            root_now = self.getContext()
            tissue_now = root_now.tissue.tissueDofs
            with tissue_now.position.writeableArray() as wa:
                print(wa[0])

However, after I start the simulation and press “ctrl + “+””, I only received [INFO] [SofaViewer] QtViewer::keyPressEvent, CONTROL pressed but no position data was printed out. Could you help point out what might be the reason?

In addition, is there other way to trigger an event than pressing a key? For example, in a tissue cutting simulation in which only when the distance between scalpel and tissue surface is closer enough could a Topology modification event be triggered.

Cheers