Manually label a trial

The recommended workflow for Nexus 2 is to use a ROM trial and dynamic calibration as this enables the use of automated labeling (for more information on this workflow, see Calibrate a labeling skeleton using a ROM trial). However, on occasions, you may need to supplement automated labeling with manual labeling, or to use manual labeling where automated labeling gives insufficiently accurate results.

You manually label reconstructed trial data using the tools in the Label/Edit Tools pane.

Manual labeling involves associating the markers defined in a Vicon labeling skeleton template (.vst file) with reconstructed markers displayed in the 3D Perspective view. Manual labeling is then used when the .vst file is scaled to fit the subject wearing the marker set described in the .vst file, during subject calibration. In subsequent movement trials, Nexus uses the resulting subject-specific Vicon labeling skeleton (.vsk file) to automatically label the subject wearing the same marker set.

To manually label 3D marker reconstructions:

1. In the Communications pane, on the Data Management tab, open the trial file that contains reconstructed markers.
2. On the time bar, move the current time indicator (vertical blue line) to the first frame of the trial in which the subject is standing in a stationary neutral pose.
   This is typically a T-pose or 'motorbike' pose, in which the subject stands in the basic neutral pose and raises the arms out straight to the sides with palms facing down in a position in the shape of a T. If the subject is not able to attain the T-pose, they can use any neutral pose where all of the markers are visible to the cameras so that they will be able to be reconstructed.
3. In the Subjects Resources tree, ensure that the subject node you created from the template is the only entry enabled for capture. (When enabled, there is a check mark in the check box.)
4. At the top of the Label/Edit Tools pane, from the Subject list select the subject to be manually labeled.
   Labels for the markers defined in the .vst file are displayed in the list in the Manual Labeling section.
5. By default, the Whole button is selected, so trajectories are labeled in both directions. This ensures that, when you label a marker at the current frame, the same marker is labeled throughout the trial. However, if you want the marker to be labeled from this point forward (or backward) only, for example, if you are resolving an overlapping trajectory, click the Backward or Forward button before proceeding.
6. In the Manual Labeling section, ensure Auto advance selection is selected to have Nexus automatically select the next label in the list after you have assigned a label to a marker.
   

7. In the list in the Manual Labeling section, click on the label you want to use.
   The shape of the pointer changes to include a tooltip that identifies the selected label to guide you in assigning labels to markers in the 3D Perspective view.

   Tip: To help you apply labels to the correct markers, on the view pane toolbar, click the Split vertically button and in the second pane, open a Subject Viewer. Any marker you select in the Label/Edit Tools pane is highlighted in the Subject Viewer, so that you can see where to place it on the figure in the 3D view.
   
8. In the 3D Perspective view click on the marker to which you want to assign the label.
   The next label in the list is selected and the tooltip changes to indicate that label. As you label more markers, a colored line is drawn between each marker until a stick figure appears.
   

   Tip: If you move the mouse to another area of the Nexus workspace while a marker is selected in the Manual Labeling section, the cursor retains the tooltip, indicating that Nexus is still in labeling mode. If you need to do something else in Nexus before marker labeling is complete, you can turn off labeling mode in one of these ways:

   • Press the ESC key.
   • Click on the Label/Edit icon, or any of the other icons in the Tools pane toolbar.
9. Repeat steps 7-8 until you have assigned all of the labels to markers.
   The stick figure in the 3D Perspective view should resemble a skeleton of the subject type defined in the .vst file.
   
10. To verify that the manual labeling was successful, check that all the markers are connected by sticks and that the sticks on the left side of the subject are red and those on the right side are green.
    

    Tip: To find the next unlabeled marker, you can also use the Find Next Unlabeled Trajectory button. Nexus searches from the current frame forward until it finds an unlabeled marker. When found, the marker is selected and centered in the view pane.

11. To save the labeling information with the trial, on the Nexus toolbar, click the Save button.