Individual marker trajectories and auto-labeling

[dlabbe]

Hi,

We purchased Optitrak (and TrackingTools) for bimechanical analysis. As such, we often do not work with "trackable" clusters. We follow the current literature in placing individual markers at different anatomical locations (e.g. on the malleoli, femoral condyles, etc.).

We need to export, preferably in c3d format, the x,y,z positions of each of these markers. Our problems are :

- We cannot assign a name (label) to a marker without creating a "trackable"

- One we export to a c3d file, we need to do the equivalent to Vicon's auto-labeling. That is to say, we need an algorithm that can merge trajectories for a single marker.

Could you tell me which one of your products would allow me to do this? I tried to explain this on the phone and was told labeling and tracking an individual marker was not supported. I'm hoping I hadn't explained correctly because I can't imagine such a basic and important feature is not available?

If such is the case, do you know of a third party software we could purchase to do this?

Thanks,

David

[beckdo]

When you use Tracking Tools to export C3D, it will trajectorize and assign labels to all markers. Markers that are part of a rigid body are guaranteed to stay the same even if they go out of view. Individual markers that go out of view (even if only for a single frame), will be relabeled with a new label when they return to the scene.

[dlabbe]

Thanks for your response. I have already figured out that it works as you describe.

My question relates to the produced c3d file. Is there no way for me to apply an algorithm which would merge these markers that go out of view for a few frames? No way for me to assign my own labels to markers?

If not, can you suggest an alternative method?

And I respectfully suggest these features be included in future versions.

Thanks again,

David

[Birch]

The labeling of individual markers as they exit and re-enter the point cloud is very challenging. That is why they are often clustered into rigid bodies or other hierarchies (such as a skeleton) to assist in identifying them. Without some kind of context or reference for the marker it will typically require human intervention to do the labeling. The Tracking Tools software is targeted at, and sold as, a solution for tracking rigid bodies.

Our Arena software supports full body tracking with the use of a skeleton hierarchy, however you must use one of its pre-defined marker sets as a base since it doesn't support custom ones at this time (you can add extra markers to it though). Arena also provides tools for manually editing and re-labeling of marker tracks.

Visual3D is a 3rd Party biomech software package from C-Motion which imports C3D. It may have built-in support for labeling marker tracks or point clouds, but you'd need to check with them.
http://www.c-motion.com/