Muscle Wrapping

Archive AnyScript Yahoo archive
1

Hello, I am currently studying a PhD in medical engineering at the
Centre for Medial Engineering and Technology at the University of
Hull, United Kingdom, and using AnyBody to model the biomechanics of
the juvenile pelvis.

I am currently constructing a biomechanical model of the hip joint
within AnyBody. I have appled muscle wrapping through
AnyShortestPathMuscle to accurately model the musculoskeletal
features. However, this is proving challenging due to complex
geometry and muscle interaction.

Therefore, I am investigating using AnyViaPointMuscle and specifying
via points (rather than wrapping to bone). However, I am unsure if
AnyViaPointMuscles wrap around the via points (similar to
AnyShortestPathMuscle wrapping around bone) or if the muscle is split
into different segments (visually the graphics display the muscle in
two different strands). I would be grateful of any information
regarding this topic.

Many Thanks
Pete Watson

2

Hello Pete,

Welcome to the group!

Here is a section from the muscle tutorial describing the properties of the
AnyViaPointmuscles:

Via point muscles pass through a set of at least two points on their way
from origin to insertion. Each of the

via points must be attached to a segment or the global reference frame of
the model. The first and the last

of the point sequence are special because the muscle is rigidly fixed to
them and hence transfers forces in

its local longitudinal direction to them. Conversely, the muscle passes
through the interior via points like a

thread through the eye of a needle. This means that the muscle transfers
only forces to interior via points

along a line that bisects the angle formed by the muscle on the two sides of
the via point.

In fact the AnyShortestPathMuscles work pretty much the same. Once in
contact they transfer the forces in the same manner as through ViaPoints.

I hope this helps, please ask again if not.

Best regards,

Sebastian

From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of dc_pete
Sent: 11. november 2008 16:33
To: anyscript@yahoogroups.com
Subject: [AnyScript] Muscle Wrapping

Hello, I am currently studying a PhD in medical engineering at the
Centre for Medial Engineering and Technology at the University of
Hull, United Kingdom, and using AnyBody to model the biomechanics of
the juvenile pelvis.

I am currently constructing a biomechanical model of the hip joint
within AnyBody. I have appled muscle wrapping through
AnyShortestPathMuscle to accurately model the musculoskeletal
features. However, this is proving challenging due to complex
geometry and muscle interaction.

Therefore, I am investigating using AnyViaPointMuscle and specifying
via points (rather than wrapping to bone). However, I am unsure if
AnyViaPointMuscles wrap around the via points (similar to
AnyShortestPathMuscle wrapping around bone) or if the muscle is split
into different segments (visually the graphics display the muscle in
two different strands). I would be grateful of any information
regarding this topic.

Many Thanks
Pete Watson

[Non-text portions of this message have been removed]

3

Hi,

Thanks for answering my earlier question on muscle wrapping.

I have one more question. I have a model where a muscle wraps over two
objects - bone (inported as stl) and a clyinder (created in Anybody as
an AnySurf). However, the muscle will not wrap over both objects at the
same time, and an error is returned. Will this problem be solved if the
two objects are merged into one AnySurf file rather then two
independant ones. If so, is there an file converter/merger which may be
able to help.

Thanks,
Pete Watson

4

Hello Pete,

The problem is that it cannot wrap over the imported bone geometry. Here’s
another section from the tutorial giving more detail:

The wrapping algorithm in AnyBody will in principle work with any sort of
surface including real bone surfaces, but for the time being only parametric
surfaces are used. The reason is that the bony surfaces are really a lot of
small planar triangles, and the corners and edges of the triangles will
cause the muscles to slide discontinuously over the surface, which disturbs
the analysis result. The parametric surfaces currently available are
cylinders and ellipsoids.

Best regards,

Sebastian

From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of dc_pete
Sent: 12. november 2008 16:01
To: anyscript@yahoogroups.com
Subject: [AnyScript] Muscle Wrapping

Hi,

Thanks for answering my earlier question on muscle wrapping.

I have one more question. I have a model where a muscle wraps over two
objects - bone (inported as stl) and a clyinder (created in Anybody as
an AnySurf). However, the muscle will not wrap over both objects at the
same time, and an error is returned. Will this problem be solved if the
two objects are merged into one AnySurf file rather then two
independant ones. If so, is there an file converter/merger which may be
able to help.

Thanks,
Pete Watson

[Non-text portions of this message have been removed]

5

Hi Sebastian,

Thanks for the reply. The model im working on has managed to wrap the
muscle over the bone geometry (it has a minimum of 100000 faces with
a smooth surface) and does not seem to disturb the result. The
problem is that if I create a solid cylinder next to the bone, and
specify the muscle to wrap over both surfaces, it will only recognize
one surface (either wrap to only bone or only cylinder). As it will
wrap over each surface when specified independently, is there a way
to merge the ANYSURF files so AnyBody reads the bone and the cylinder
as the same geometry.

Thanks

— In anyscript@yahoogroups.com, Sebastian Dendorfer
<anyscriptsup@…> wrote:
>
> Hello Pete,
>
> The problem is that it cannot wrap over the imported bone geometry.
Here’s
> another section from the tutorial giving more detail:
>
> The wrapping algorithm in AnyBody will in principle work with any
sort of
> surface including real bone surfaces, but for the time being only
parametric
> surfaces are used. The reason is that the bony surfaces are really
a lot of
> small planar triangles, and the corners and edges of the triangles
will
> cause the muscles to slide discontinuously over the surface, which
disturbs
> the analysis result. The parametric surfaces currently available are
> cylinders and ellipsoids.
>
>
>
> Best regards,
>
> Sebastian
>
>
>
> _____
>
> From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com]
On Behalf
> Of dc_pete
> Sent: 12. november 2008 16:01
> To: anyscript@yahoogroups.com
> Subject: [AnyScript] Muscle Wrapping
>
>
>
> Hi,
>
> Thanks for answering my earlier question on muscle wrapping.
>
> I have one more question. I have a model where a muscle wraps over
two
> objects - bone (inported as stl) and a clyinder (created in Anybody
as
> an AnySurf). However, the muscle will not wrap over both objects at
the
> same time, and an error is returned. Will this problem be solved if
the
> two objects are merged into one AnySurf file rather then two
> independant ones. If so, is there an file converter/merger which
may be
> able to help.
>
> Thanks,
> Pete Watson
>
>
>
>
>
> [Non-text portions of this message have been removed]
>

6

Hey Pete,

Well, it’s surprising for us that it actually works with the stl file. Even
so the algorithm is made in a way that it could handle it in general, it
will deliver wrong results due to the rough surfaces, therefore it should be
disabled. And this will also be the case in your applications. Even so the
position analysis works - you can see the wrapping - it will not give you
correct results for the muscle activations.

But why it doesn’t work for both surfaces together is another thing. And to
be honest I don’t know. So the remedy is that you should try to recreate the
bone surface you want to wrap on with cylinders and this should work in
using more than one.

Best regards,

Sebastian

From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of dc_pete
Sent: 13. november 2008 10:14
To: anyscript@yahoogroups.com
Subject: [AnyScript] Re: Muscle Wrapping

Hi Sebastian,

Thanks for the reply. The model im working on has managed to wrap the
muscle over the bone geometry (it has a minimum of 100000 faces with
a smooth surface) and does not seem to disturb the result. The
problem is that if I create a solid cylinder next to the bone, and
specify the muscle to wrap over both surfaces, it will only recognize
one surface (either wrap to only bone or only cylinder). As it will
wrap over each surface when specified independently, is there a way
to merge the ANYSURF files so AnyBody reads the bone and the cylinder
as the same geometry.

Thanks

— In anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com,
Sebastian Dendorfer
<anyscriptsup@…> wrote:
>
> Hello Pete,
>
> The problem is that it cannot wrap over the imported bone geometry.
Here’s
> another section from the tutorial giving more detail:
>
> The wrapping algorithm in AnyBody will in principle work with any
sort of
> surface including real bone surfaces, but for the time being only
parametric
> surfaces are used. The reason is that the bony surfaces are really
a lot of
> small planar triangles, and the corners and edges of the triangles
will
> cause the muscles to slide discontinuously over the surface, which
disturbs
> the analysis result. The parametric surfaces currently available are
> cylinders and ellipsoids.
>
>
>
> Best regards,
>
> Sebastian
>
>
>
> _____
>
> From: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com
[mailto:anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com]
On Behalf
> Of dc_pete
> Sent: 12. november 2008 16:01
> To: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com
> Subject: [AnyScript] Muscle Wrapping
>
>
>
> Hi,
>
> Thanks for answering my earlier question on muscle wrapping.
>
> I have one more question. I have a model where a muscle wraps over
two
> objects - bone (inported as stl) and a clyinder (created in Anybody
as
> an AnySurf). However, the muscle will not wrap over both objects at
the
> same time, and an error is returned. Will this problem be solved if
the
> two objects are merged into one AnySurf file rather then two
> independant ones. If so, is there an file converter/merger which
may be
> able to help.
>
> Thanks,
> Pete Watson
>
>
>
>
>
> [Non-text portions of this message have been removed]
>

[Non-text portions of this message have been removed]