What marker-set is used on the example of a gait model?

Hi,

I’m Donghwan Lee.

I have some questions,

  1. I’m curious what marker-set is used from “FullBody.main” on the “Plug-in-gait-Simple” file.

a) Are values(degree, velocity, acceleration, force, moment) changed if I use different marker-set
compared to “FullBody.main”?

  1. If I remove skull markers(RFHD, LFHD, RBHD, LBHD), it can’t run ‘Parameter Identification’.
    a) If my model has no skull markers, how can I run ‘Parameter Identification’?
    b) How can I remove the skull on “FullBody.main”?

Thank you

Best regards,

Donghwan Lee

Hi,

You can enable a driver for the head by driving it to 0, assuming that the head does not move wrt to the thorax. Update Plug-in-gait_Simple\Setup\ExtraDrivers.any with these lines:

#define BM_MANNEQUIN_DRIVER_SKULL_THORAX_LATERALBENDING ON
#define BM_MANNEQUIN_DRIVER_SKULL_THORAX_ROTATION ON
#define BM_MANNEQUIN_DRIVER_SKULL_THORAX_FLEXION ON

Kind regards,
Pavel

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Hi Pavel,

Thank you for your answer.

I still have a question what “driving it to 0” means?
Is it OFF?

#define ~ OFF
#define ~ OFF
#define ~ OFF

Best regards,
Donghwan Lee

Hi Donghwan,

It means we define motion (kinematic constraints) as not moving and staying at the “neutral” position (flexion/lateral bending/rotation of the neck and rotation of the head being 0 degrees). We do that by using default mannequin drivers - please go through the tutorials to catch up with the terminology.
AMMR Documentation

Setting it to ON means we will enable default drivers and they will using values from the Mannequin file.

Kind regards, Pavel

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Great thank you, Pavel!

It was very helpful for me.

By the way,

Could you explain what marker-set is used on “FullBody.main”?

Thank you,

Donghwan Lee

I believe it is Vicon’s Plug-In Gait marker protocol

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Isn’t it the company name of motion analysis? My question is what marker-set is used obviously.

HI, Donghwan,

You are looking for the names and placement of Plug-in-gait Markers?

Best Regards,
Lee

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“Plug-in gait” is the name of the marker set/protocol as suggested by Vicon. I think our examples are consistent with this protocol or may have been a little adapted to produce better results.
You can see the marker placement scheme kindly provided by Lee, or download the official documentation from Vicon’s website for some extra information.

Regards,
Pavel

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Hi Lee,

Thank you for your answer.

I think my question is too general.

What I really want to know is how I can modify the marker-set.

I use Helen Hayes marker set, and it is totally different from Plug-in-gait marker placement especially the direction of the axis. (see What marker-set is used on the example of a gait model?)

I’m trying to do modeling using ‘FullBody.main’ which is in the ‘Plug-in-gait-Simple’ file.

The problem is the axis of force plate is auto-detected but body markers are not such as the foot.

So, my model has a different axis between the force plate and body markers.

  1. Could I modify c3d using Mokka or other tools?
  2. Do I have to modify the axis using AnyBody?

Best regards,

Donghwan Lee

Hi Donghwan,

I believe the orientations of markers are as same as the referenced segment’s anatomicalFrame.

You could find the detail information about how to define the markers in AnyMocapMpdel.any - ClassTemplates.any - CreateMarkerDriverClass.any.

Best Regards,
Lee

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You don’t need to change orientation of the markers.

1 Like