Question Scaling

Hello,

I am currently comparing how scaling works in different biomechanical modeling systems.

My questions are:

  1. Do I understand correctly that AnyBody allows rigid, affine, as well as deformable scaling, the latter two being based on landmarks?

  2. When scaling a segment based on landmarks, how are the wrap objects scaled? Can they also undergo affine/deformable transforms?

Thank you very much!
Eva

Hi Eva,

  1. That is correct. Technically, you can also do rigid body transformation using landmarks. There is RBF scaling using landmarks and finally there is also RBF scaling using stl.
  2. Generally, the wrap surfaces are defined using some nodes (or landmarks) on the segments. These landmarks are also scaled with the scaling of the segment. So, the wrap surfaces will be scaled accordingly. Please note that the wrap surfaces are analytical surfaces (e.g., cylinders) that are calculated as best fitting from these scaled landmarks. The shapes will not be deformed (a cylinder will still be a cylinder) but only the landmarks used for estimating these shapes will be scaled before the estimation of the wrap surface.

Finally, you can also create your own scaling functions to be used with the segments.

Best regards,
Dave

Thank you so much Dave. That is very helpful to know!

Since the wrap surfaces are analytical surfaces, does this mean you could not, for example, end up with a sheared cylinder?

Best,
Eva

Hi Eva,

That is correct. You will always have a regular cylinder and not a sheared cylinder. And likewise for other types of wrapping surfaces.

Best regards,
Dave

Hi Dave,
Great, thank you very much!
Best,
Eva