# Segment Orientation

I am looking at using some of the data from the shoulder model for use
in Matlab, and I cannot find the place in the file structure where the
new segments orientations are defined. In previous musculoskeletal
modeling packages I have used, there was an explicit part of the
source code where a distal segment is defined in terms of a rotation
of the axes of a proximal segment about defined lines. These
rotations were often a function of a joint parameter like
glenohumeral’s plane of elevation or the shoulder elevation with
respect to the thorax, plane of elevation, etc. Where are these
definitions in ShoulderArm.root.any? I need to get explicit
mathematical relations between the orientations of the different
segments in the shoulder.

Nick

Hi Nick,

I am not sure what exactly you can find in the Body Model of the
repository.

As far as I understand from you description, AnyBody works slightly
different than the other system you have tried. The kinematics is
entirely based on inverse kinematics, i.e., each segment has
position coordinates and the kinematical constraints defined in the
model can be solved to find these positions. Therefore the angles
you speak of is not necessarily a part of a model, because they do
not need to be there to describe the kinematics.

Typically, there are some angle defintions in the model, which you
can use if you like them. Or you can create you own ‘measures’.
AnyBody uses a concept we call ‘kinematic measures’, i.e., measures
of motion. You can find them as derived classes of the AnyKinMeasure
class.
What you need is the AnyKinRotational, i.e., a measure of rotations.
This can be set up to use Euler Angles (or Cardan Angles) with any
sequence of axes (e.g. z,y,z as in the standard Euler angles).

In this class, you enter references to the two coordinates systems
you want to measure the rotation between, set up the Type
(=RotAngleAxes equivalent to Euler-like angles), and the sequence of
axes.

I you do not like the coordinate systems that are present in the

I hope this helps you on the way.

Michael
AnyBody Support

— In anyscript@yahoogroups.com, “stl_nick_gt” <nflieg@…> wrote:
>
> I am looking at using some of the data from the shoulder model for
use
> in Matlab, and I cannot find the place in the file structure where
the
> new segments orientations are defined. In previous
musculoskeletal
> modeling packages I have used, there was an explicit part of the
> source code where a distal segment is defined in terms of a
rotation
> of the axes of a proximal segment about defined lines. These
> rotations were often a function of a joint parameter like
> glenohumeral’s plane of elevation or the shoulder elevation with
> respect to the thorax, plane of elevation, etc. Where are these
> definitions in ShoulderArm.root.any? I need to get explicit
> mathematical relations between the orientations of the different
> segments in the shoulder.
>
> Nick
>