Activate real time flag without GUI

[pablovasse]

Hi,
we are working with SofaPython3 and we need to run our simulations in real time. We have been using the GUI so far, but now we want to run from a python IDE and we don't need the GUI anymore. Is there a way to set the simulation in real time with a python command in our script or is it necessary to flag the box in the gui?

Thank you

[hugtalbot]

Hey @pablovasse
This is not bound in the python interface. However, this can be reproduced within your python script with a python controller : you can access the time step dt from the root node (root.dt.value), keep track of the time needed for the previous time step and update the simulation time step accordingly.
With a PythonController this should be easy to write.

However, do not forget to check my comment here on the risk related to time step modification.

[hugtalbot]

Part of the script would look something like :

import timeit

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

    def onBeginAnimationStep(self, dt):
        self.elapsedTime = timeit.timeit()

    def onEndAnimationStep(self, dt):
        self.elapsedTime = timeit.timeit() - self.elapsedTime
        self.getContext().getRootContext().dt.value = self.elapsedTime
        self.elapsedTime = 0.

[pablovasse]

Thanks @hugtalbot!
In your comment you suggest not to change the time step especially when using Lagrange multiplier, which we are using to solve the contact response. So, would you recommend to stick with the GUI and activate the real time flag through it?

[hugtalbot]

Hi @pablovasse
The real-time flag is actually changing the time step, I would therefore not advise this as well.

If changing the time step is compulsory (maybe regarding performances), what you could do is:

• to run a reference simulation with the smallest time step possible
• and then use the script given above to adapt the time step and compare the results accuracy