Adjust object positions in SOFA at runtime

[nikhunziker]

Hi everyone,

I'm working on a project where I aim to manipulate the position of objects during runtime in SOFA inside Unity. The idea is that these changes are also reflected in real-time in Unity while running the simulation and I have a few questions in this regard:

1. I believe it is best to use python for changing the positions of a collision model during runtime, but I am wondering how that is exactly done. Where can I use that python code while running Unity?
2. If there is a better option, how else can I adjust object positions in SOFA so that Unity updates the scene at runtime?

Any advice, examples, or documentation references would be greatly appreciated!

[damienmarchal]

Hi @nikhunziker,

I think for Unity related question @epernod is the one that has the knowledge.

If python is possible in Unity, then you should use what is called a Controller.

"""Demonstrate how to change a sofa component variables using a custom controller"""
import Sofa.Core
import math

class MyController(Sofa.Core.Controller):
       """A controlling accepting a mechanical object and changing its state"""
       def __init__(self, *args, **kwargs):
              Sofa.Core.Controller.__init__(self, *args, **kwargs)
              self.target = kwargs.get("target")
              self.currenttime = 0 

       # This method is called automatically at the end of each simulation step.    
       # Have a look at example the following example for other possible callback method:
       # https://github.com/sofa-framework/SofaPython3/blob/master/examples/emptyController.py
       def onAnimateEndEvent(self, event): 
              # Update internal "timing" to make cos/sin happy 
              self.currenttime += event["dt"]
       
              # Here we change the position of the "target" object. 
              self.target.position.value = [[math.cos(self.currenttime),math.sin(self.currenttime),0
                                             ,0,0,0,1]] 
               
def createScene(root : Sofa.Core.Node):     
       # Adds the mechanical object with a single 3d frame 
       root.addObject("MechanicalObject", name = "mo", template="Rigid3", position=[[0,0,0,0,0,0,1]])

       # Make the mechanical object visible. 
       root.mo.showObject.value = True
       root.mo.showObjectScale.value = 1.0

       # add the controller and pass the mechanical object as target
       root.addObject(MyController(target=root.mo))