Imposing a defined force to a body

[andersonnardin]

Hello all,

I have two very practical and simple questions:

1. Is there an example where I can impose a defined force on an object on the scene? For example, I want 3N applied to this point of my body.
2. Is there a documentation reference where I can find a list of all available components? I used to refer to this from @damienmarchal, but it seems it is not working anymore.

In advance, thank you for your support.
Anderson

[andersonnardin]

I guess it can be done with the component ConstantForceField; please correct me if I am wrong.
What about components like LinearForceField, SphereForceField, etc.? Are they deprecated?
Another thing, about the SurfacePressureForceField, how is it different from the SurfacePressureConstraint?

Thank you again, I am looking forward to seeing your answer.

[EulalieCoevoet]

Hello,

1. Yes you can use ConstantForceField to apply a defined constant force on an object.
2. I was using the bin/Modeler to see all the available components, but I see it's no longer there. @hugtalbot is there another tool to list the components ?
3. For the components LinearForceField and SphereForceField, the examples from sofa/examples/Component/MechanicalLoad/ seem to work fine and do not show any message about deprecation. You can have a look at these examples and the description of the components.
4. SurfacePressureConstraint is for a constraint based approach, in this case the pressure is a Lagrange multiplier.

Hope this helps.

[andersonnardin]

Hi,

1. Thank you for your answer.
2. I await @hugtalbot to give a suggestion about how to list components.
3. In sofa/examples/Component there is no such folder called MechanicalLoad. In version 22.12, I have:
   
4. I am familiar with the concept of Lagrange multiplier, but I still did not get the point about the practical difference between using ForceField and Constraint components. When should I use each of them? Could you give an example?

Thank you very much again.
Anderson

[hugtalbot]

Hi @andersonnardin

Some additional info:

1. the ConstantForceField applies the same nodal force on all nodes (or a set of nodes if you specify the datafield indices)
2. currently, I would say no : the best way to know which objects are available you could just browse the repository: e.g. looking for all engines would be simple, you just open the folder Sofa/Component/Engine/ and you will find them in category.
3. The folder example is now in the master branch following the same architecture than the code. However, the examples are still have the old sort in the v22.12 release. The v23.06 will update this
4. ForceFields apply physical (surface / volume) forces to the objects. Constraints - in the sense of the Lagrange-multiplier constraint resolution - are a way to solve some laws that you want to fulfill in your simulation taking into account the physics of your objects : contact, attachment, insertions etc. Note that we have dedicated trainings on these topics.

Hope this helps