I’m just worrying that I have fundamentally misunderstood
AnyShortestPathMuscle. I have uploaded files shippen1.bmp and
shippen2.bmp. This images are consecutive steps for a mild arm
movement.
The muscle shown in green is pectoralis_major_clavicular_part_2 which
wraps around surfaces ThoraxPectoralisEllipsoidRef (blue),
Pectoralis_minor2_cyl.Cylinder.Cyl.node1.CylSurf (cyan) and
coracoid_cyl2 (magenta).
Without doubting that the path of pectoralis_major_clavicular_part_2
from origin to insertion in minimal for both configurations shown,
for the left shoulder there appears to be an intermediate position
with significantly more potential energy as the muscles changes
wrapping sides of the cylinders.
Therefore my question is: in calculating the minimal path length is
the route of the muscle in the previous step used as a starting
orientation or it each step considered independantly?
Many thanks
James
PS I notice from the answer to Sarah’s question that the next version
of the Repositary is under-development. It is possible to say when
this will be released?
I have looked at the pictures you are right that the muscle has
flipped to the wrong side of the cylinder. The muscle path is
calculated as the shortest path, and it do use the position in the
previous timestep as the initial guess on the position. In some
cases, especially when the wrapping surfaces are thin and the motion
between each time step is large (in the direction of the normal of
the wrapping surface, where the muscle is wrapping) the muscle may
incidentially end up on the wrong side of the cylinder, this could be
the case here. So if in this case the uppper body has large forward
or backbackward motion between the timesteps, the muscle position
from the previous timestep is not always good enough to prevent the
muscle to flip to the wrong side.
The remedy is normally to use more timesteps, it may also help to
increase the SPLine.StringMesh variable of the muscle, this will
increase the discretization of the muscle.
Best regards
Søren, AnyBody support
— In anyscript@yahoogroups.com, “jamesshippen” <jamesshippen@…>
wrote:
>
> Hi
>
> I’m just worrying that I have fundamentally misunderstood
> AnyShortestPathMuscle. I have uploaded files shippen1.bmp and
> shippen2.bmp. This images are consecutive steps for a mild arm
> movement.
>
> The muscle shown in green is pectoralis_major_clavicular_part_2
which
> wraps around surfaces ThoraxPectoralisEllipsoidRef (blue),
> Pectoralis_minor2_cyl.Cylinder.Cyl.node1.CylSurf (cyan) and
> coracoid_cyl2 (magenta).
>
> Without doubting that the path of
pectoralis_major_clavicular_part_2
> from origin to insertion in minimal for both configurations shown,
> for the left shoulder there appears to be an intermediate position
> with significantly more potential energy as the muscles changes
> wrapping sides of the cylinders.
>
> Therefore my question is: in calculating the minimal path length
is
> the route of the muscle in the previous step used as a starting
> orientation or it each step considered independantly?
>
> Many thanks
>
> James
>
> PS I notice from the answer to Sarah’s question that the next
version
> of the Repositary is under-development. It is possible to say when
> this will be released?
>