Opensim wrapping

[Yanis AMMOUCHE]

Dear all,

I'd like to add some wrap surfaces to my model in order to have realistic moment arms during high flexion of the knee/hip. When looking at a template model that have some wrapping surfaces I found something strange :
for the muscle you want to be wrapped, you need to specify on which suface it will wrap, which algorithm will be used and the range (see in attachment).

This range is usually -1 -1, and I really have no clue about what it means. Someone has an idea about what it means ?

Best regards

[Dimitar Stanev]

This is used by the wrapping algorithm for calculating the wrapping of the muscle. This property is initialized internally and should not be exposed:

https://github.com/opensim-org/opensim- ... Wrap.h#L65

More details on muscle editor which may be of interest:

http://simtk-confluence.stanford.edu:80 ... cle+Editor

[Yanis AMMOUCHE]

Thanks for your quality answer M.Stanev,

Basically the -1,-1 range means that all segments are "allowed" to wrap on the obstacle. If we have an muscle that have 3 pathpoints indexed by 1, 2 and 3, there is in a case an equivalence between (-1,-1) and (1,3).

If we want only the last segment to be checked for a wrap then we have to specify (2,-1) or (2,39.

In the documentation they are talking about an ellipsoid wrapping algorithms, but if the obstacle is the cylinder, the algorithm stay the same ?

To have a global understanding of this algorithm, the new path computed is the shortest that do not penetrate the obstacle ?

Best regards,

Yanis