For a few reasons, I ended up writing code in Matlab to get the gravity vectors without using the MEX interface. This way I don't need to have separate parallel instantiations of the model in C++ and Matlab. I have included the Matlab code below. I compared it to the output of my MEX interface code ...

Hi Sherm, Thank you for your response! The coupling that occurs physiologically is probably a combination of muscle coordination and ligaments/passive components. I imagine that the coupler constraints would be more representative of these passive components. However, I am specifically interested in...

I am working with the OpenSim neck model through the Matlab API. The neck model has 24 mobilities (8 joints, each with 3 rotational DOF). There are 18 coordinate coupler constraints, leaving 6 generalized coordinates (lower c-spine pitch2, roll2, yaw2; upper c-spine pitch1, roll1, yaw1). I am trying...

Hi Peter, I'm wondering if you had any success with this? I am attempting to do something similar with the neck model. I want to determine the wrench at the forehead when a particular muscle activation pattern is applied. However, the Jacobian is not invertible because is both not full rank and not ...

In case it is helpful to anyone, I was able to create the mex interface for Matlab to get the gravity term in the equations of motion. I have attached my c++ code "GravityEngine.cpp". Thank you for your help, Dimitar. I was able to base the structure off of your example code. It requires the mexplus...

Ah thank you Dimitar!

I will just create my own function to implement that functionality. Thanks for your help.

I am working with a version of the OpenSim neck model that has a BushingForce between each vertebral body. I need to populate a vector of the torques from the bushings to add to my equation of motion. The parent class of BushingForce is a templatized class TwoFrameLinker<Force, PhysicalFrame>. I am ...

Hi Dimitar, Thank you for your response. That is helpful and keeps me from wasting time trying to get a pointer to work. I have another question for you. I am using a model (the neck model available on OpenSim) that has 6 independent coordinates (roll, pitch, yaw of 2 joints) and 15 coordinates that...

Hi Dimitar, I have created a MEX interface to read in the gravity term for the equations of motion. I have some more work to do on it but I am getting a return value into matlab that makes sense. I currently am loading the model separately into Matlab and the MEX C++ function, so I have to do everyt...

I am just interested in the gravity term to update the equations of motion based on state (only realized to position stage). All I really need is that getGravityForce().getBodyForces(state) call so that I can put it into model.getMatterSubsystem().multiplyBySystemJacobianTranspose(). I've been playi...