Finding the displacement of a bone between neutral and condition

[lassoan (Andras Lasso)]

For future reference the issue is discussed in this topic:

Creating a new coordinate system

Hello all, I am trying to create a local coordinate system within the global coordinate system in order to compute the displacement of a bone block between two different scans. The reason why the global coordinate system does not suffice is because I would like the rotational displacement of the bone block to be in terms of the orientation of the reference bone block rather than the global space. Could someone please provide some guidance on how to create a local coordinate system? Thank you …