simtk.org

Hi,

I am using the C++ API to build and solve a model.
I would like to assign weights to the coordinates of my model.
I saw that it is possible when I look at the detailed description section of the InverseKinematicsSolver class (https://simtk.org/api_docs/opensim/api_ ... olver.html). I can see W_qj which contains the weights for the coordinates.

Unfortunately, I did not find a proper way to do it as compared with marker weights (there is a method to update the marker weights in the InverseKinematicsSolver class).
I found that one can create a CoordinateReference and set weights to it and include it as a third input argument of the InverseKinematicsSolver class (https://simtk.org/api_docs/opensim/api_ ... rence.html). However, one has to specify a Function for the desired value of this CoordinateReference which is not what I want because I do not know what the value should be (this is what I am trying to find actually by using the InverseKinematicsSolver class).

So I am a bit confused and any help to clarify how i can set weights to the coordinates of my model will be appreciated.

Thank you

Vincent

The Coordinates are handled by the AssemblySolver class (parent to InverseKinematicsSolver), which may provide the functionality you're looking for.

Thanks Thomas. I will look into it

Hi again,

I had a look at the AssemblySolver class but the problem remains the same.
I still cannot add only a weight to a Coordinate without giving a value to it.
This approach is therefore not appealing to me since the Coordinate values is what I am trying to get through the inverse kinematics process.
I would like to give a weight to each coordinate so it has more or less importance when the solver is trying to find a solution (minimising the error).
I really thought it was possible

Thanks anyway

Vincent

Please see the description of the algorithm on the "How Inverse Kinematics Works" page in the documentation (https://simtk-confluence.stanford.edu/d ... tics+Works). If the InverseKinematicsSolver class doesn't meet your specific needs, you could extend it (e.g., by creating a C++ plugin), or suggest an enhancement on the GitHub page (https://github.com/opensim-org/opensim-core/issues).

Thank you Thomas.
This webpage has more information and explains the weights on the coordinates.
I was misled by the previous documentation page of the C++ API.
I understand now that this is doing something different from what I thought.
I will reflect and see if I want to investigate the other options you mentioned.

Regards

Vincent