Maybe I’m doing something wrong here, but why the result does not seem right ? I’m doing a rotation of the humerus in the scapular plane but the unique axis appears to be far from normal to the scapular plane.

Can you tell me if my computation of the unique vector ‘n’ from the four parameters (e0 = GHRot2.Pos[0], e1 = GHRot2.Pos[1], e2 = GHRot2.Pos[2], e3 = GHRot2.Pos[3]) is ok ?

Thank you for your quick reply. I recheck my measure and the documentation of the function. I remembered that sometimes, although we provide the measure with local reference frames, the final measure is given with respect to the global reference frame. This is the case with those measures RotVector and EulerParameters, right ?

Thus, in order to obtain the right rotation axis, I just have to put back the global measure in local measure by multiplying it by the transpose of the rotation matrix of the local reference frame (scapula.GH), as follows:

Because the orientation of rotational axis from AnyKinRotational is a local one, you should specify ‘GlobalCoord=Off’ when you use that axis in your AnyDrawVector object.

I read from the ref manual that it is risky but still possible to drive a motion with Euler parameters. I have a situation in which I must pass in a singularity, which fails to work when I use any Euler rotation sequence. I also tried it with the rotation vector, without success.

Thus, I would like to know how I can drive my measure using the Euler parameters. When I try it, it does fails to apply the initial conditions.