How to get force by using LCPForcefeedback in Python?

[SangbaekYoo]

My objective is to get force data in specific position of device in simulation.

There are good examples (Geomagic Haptics), but it is difficult to find example in Python.

Currently, I am using Haptics plugin and LCPForceFeedback class.

I am success to define object in createScene(root) function as follows:

def createScene(root):
  ...
  device = root.addChild('device')
  ...
  device.addObject('MechanicalObject', name='instrument', template='Rigid3d')
  device.addObject('LCPForceFeedback', activate="true", forceCoef="0.005", name="haptic")

When scene is run, I want to read force in specific position of device. For this, I guess that I can use computeForce function which is public member function of LCPForceFeedback class.(I understand that computeForce function returns force information and it is also used in Geomagic cpp file.)
https://www.sofa-framework.org/api/master/sofa/html/classsofa_1_1component_1_1haptics_1_1_l_c_p_force_feedback.html#a9e888aee5f18b622f71e6dd42586fe43

I expect to get force in Python like below line,

print("Force:", self.rootNode.device.haptic.computeForce(input))

but there is error "attibuteError: unable to find attribute: computeForce".

I think I'm mistaken about how to use it in Python.
Can anyone give me advice how to use it?
Or is there any other method to get force in my own python code?

[jungjae01eng]

I haven't used the Haptics plugin before, so I'm not entirely certain. However, the computeForce function is a public member function, but it's also defined as a virtual void, which implies that it doesn't return any value, correct?

You mentioned the Geomagic Haptics example. In the Geomagic-RigidSkull.scn file, they have included the following code:

<LCPForceFeedback activate="true" forceCoef="1.0"/> <!-- ADDED : Compute a force-feedback for the device -->

Are you attempting to simply extract and print the forceCoef using Python?

[fredroy]

Hello @SangbaekYoo,

Looking at the source code of LCPFF, it seems that computeForce takes 6 Real as parameters (3 float to define the input position and 3 floats as reference for output force) so thats why maybe you could not call computeForce().
If you wish to use it like you did, you may need to add bindings (c++ to python3)

[hugtalbot]

Thanks @SangbaekYoo for the question and @fredroy for the reply.
Note that a dedicated page is available here: #3812

[github-actions[bot]]

⚠️ ⚠️ ⚠️
@SangbaekYoo
Feedback has been given to you by the project reviewers, however we have not received a response from you. Without further news in the coming weeks, this discussion will be automatically closed in order to keep this forum clean and fresh 🌱 Thank you for your understanding

[github-actions[bot]]

⚠️ ⚠️ ⚠️
@SangbaekYoo
In accordance with our forum management policy, the last reply is more than 4 months old and is therefore closed. Our objective is to keep the forum up to date and offer the best support experience.

Please feel free to reopen it if the topic is still active by providing us with an update. Please feel free to open a new thread at any time - we'll be happy to help where and when we can.