# Axes - "rotational transformation matrix"

Hi All,

I am still working on driving an humerus-radius-ulna-hand model by
Vicon markers, and I have run into a problem setting up the initial
conditions. How can I calculate the Axes value for each segment from
the data I have? Can someone explain to me in easy-to-understand
steps how to transform the matrix of the segment to be relative to the
global reference, or recommend a paper that will help me?

Any help would be appreciated!
Sarah

Hi Sarah,

The new version 2.0 has a feature which was actually already
available in version 1.3 but was not documented. It is a function for
calculation of rotation matrices such as the Axis variable. Here’s an
example from a tutorial we are working on:

`````` AnySeg Arm = {
r = {0.500000, 0.000000, 0.000000};
Mass = 1.000000;
Jii = {0.100000, 1.000000, 1.000000}*0.1;
Axes = RotMat(20*pi/180,z);
AnyDrawSeg drw = {};
};
``````

The RotMat function rotates the position of the Arm segment 20
degrees about the z axis at load time. You can use the same function
for ARel specifications and other places where you may need a
rotation matrix.

Best regards,
AnyBody Support

— In anyscript@yahoogroups.com, “Sarah R. Sullivan” <sarsulli@e…>
wrote:
> Hi All,
>
> I am still working on driving an humerus-radius-ulna-hand model by
> Vicon markers, and I have run into a problem setting up the initial
> conditions. How can I calculate the Axes value for each segment
from
> the data I have? Can someone explain to me in easy-to-understand
> steps how to transform the matrix of the segment to be relative to
the
> global reference, or recommend a paper that will help me?
>
> Any help would be appreciated!