How to create a marker on the head?

Main Forum
1

Hey, AnyBody support,

I want to use VICON to monitor the head movement with 4 markers on the head (2 on the front, and 2 on the back side).

I have no idea how to create the marker’s nodes on the head, I mean, the coordinates (x, y, z) of each marker.

I read the GaitUniMiamiTDRightLeg model, and its LocalMarkerCoordinatesAndSize file. I was wondering to know how to create such a folder like “LocalMarkerCoordinates” with so precise values for each marker?

Thank you!

Sincerely,

Cathy

2

Hi Cathy,

You can have a look at the GaitFullBody model, this one has four markers on the skull (RFHD, LFHD, RBHD, LBHD). You can take the coordinate values from here or place the nodes visualy yourself. And the coordinates don’t need to be extremely precise, 1 milimeter precision is certainly enough.

Best regards, Sylvain.

3

Hi, Sylvain,

I have one more question with the GaitFullBody model here:

On the basis of the GaitFullBody model, I replaced the original c3d file with my own c3d file data. I matched the marker labels with the marker names in the ModelSetup.any file.

Finally I can load the model successfully. But I failed in the time step 0 of initial conditions.

Could you please give me a hint to solve the problem? Thanks a lot!

Best regards,

Cathy

4

Hi Cathy

Usually this can happen if the initial posture of the model is too different from the location of the markers in the first timestep.

The remedy is to change the initial position of the mannequin, this is done in the TrialSpecific folder if you are using AMMR1.2 or in the mannequin.any file if you are using AMMR1.1. The posture need to be relative close to the markers, but usually a rough guess where the orientation of pelvis is ok will be enough.

Another root of errors could be a marker that have dropped out… so if one of the markers you are suing is in 0,0,0 when the analysis starts, it will cause problems, so you could try adding a little time to tStart to see if this is the problem, or check the markers.

It can also be the initial size of the subject which is too different to from the subject of the trail.

Best regards
Søren

5

Hey, Guys,

Thanks a lot for your help!

Cathy