Importing Rotational and Translational Coordinates

[Hao Yang Chan]

Hi all, so what I've been doing is exporting the kinematics of a femur with a stationary tibia at certain degrees of flexion. Either I'm misinterpreting the way Opensim outputs translations and rotations or Opensim is reporting them wrongly.

I have been exporting the rotations by the having the center of rotation about the centroid of the body (however, this produces results skewed about at least one axis of rotation, meaning I have to manually correct it to what I think the proper rotation about the axis should be), would that be the proper way of exporting the kinematics? I've also tried rotating the body about the body about the joint center, however, that produces kinematics which are visibly wrong.

Any help would be much appreciated, thanks!

[jimmy d]

Are you trying to compare knee angles from some other measurement system to knee angles from an OpenSim modeled knee joint?

Does your other measurement system take into account constraints or coupled translations?

You will need to describe both the model you are using in OpenSim and the model of the knee that you originally got kinematics from

[Hao Yang Chan]

I figured it out, I was manually applying the transformations when I should have been creating a transformation matrix, thanks!