Hi Hossi,
Welcome to the AnyScript forum!
- The origin of each segment (or segmental frame) depends mainly on how the stl files were generated. Typically, a part of the cadaver will be scanned and the scan will have a common origin for multiple bones. So, this is normal that when you find the origin by making a new node with sRel = {0,0,0} on a set of segments, they end up at the same point. This will happen, however, only in the neutral posture (or the posture in which the scan was made). If you want to capture the movement at the spine, please attach the reference nodes on the corresponding segment.
- If you make the node on a specific segment, it will follow the movement of that segment and will always be attached to that segment.
- Again, yes, if you make nodes on different segments, their distance to L4-L5 disc will change depending on the movement at the spine.
The only issue at the moment is that the entire thorax (T12 to T1) is modelled as a single rigid segment currently. So, there will be no relative motion between T9 and T12. However, we are currently working on a detailed thorax model that will be available in the future.
I hope this helps.
Best regards,
Dave