Capture the required movement

After you have calibrated the labeling skeleton for your subject (see Calibrate a labeling skeleton), you can capture the required trials.

You can stream motion data in real time and/or capture raw camera data for offline processing. You can capture a trial manually (see below), or configure Nexus to start/stop capture automatically (see Automatically start and stop capture).

To quickly capture sequences of trials using the same setup information for each trial, see Use Simple Capture Mode.

Before capturing a movement trial, ensure that you have already:

• Created or opened a session in the database in which you want to store the trial data, and ensured that it is the active session. For more information, see Prepare a data management hierarchy to store your files.

• Loaded an existing .vsk file for the subject whose motion is to be captured. If you have just created your VSK (see Calibrate a labeling skeleton), the correct VSK is already loaded. If not, in the Subjects Resources pane, click the Load an existing subject button and open the required .vsk file.

• Attached the Vicon markers to the subject in accordance with the marker arrangement used in the labeling skeleton (.vsk) file (if you are using Plug-in Gait, see Attach Plug-in Gait markers to a patient).

To capture movement trials:

1. In the Resources pane, ensure Nexus is in Live mode.
2. Display a 3D Perspective view.

3. In the Capture Tools pane, select an existing capture configuration for the trial from the Trial Type list or save as a new one.

   

4. In the Next Trial Setup section, complete the details for storing your trial data in the active session.
   Naming sessions and trials: When you enter a name in the Trial Name field, do not give the trial the same name as the session as this can cause confusion when you select files in Data Management and may also cause issues if your Vicon Nexus system includes FLIR cameras.
   In the Data Source Setup section, ensure Optical Camera Data, Video Camera Data, and Device Data are selected as required.
5. If you want capture to start and/or stop automatically, specify the required settings in the Auto Capture Setup section. (For more information, see Automatically start and stop capture.)
6. If you are conducting clinical gait trials for kinetic analysis involving one or more force plates and want Nexus to automatically assess whether the foot is correctly positioned and is producing valid data for your live trials, ensure that in the Options dialog box (F7), Footstrikes is selected. For more information, see Automatically assess foot strikes.
7. In the Post-Capture Pipeline Setup section, specify any pipelines containing operations to be run automatically on the trial data when the capture is complete. (For example, if you are using Plug-in Gait, you could select Run pipeline after capture and then select the Reconstruct And Label and Plug-in Gait Dynamic pipelines. This automatically reconstructs and labels the data and then runs filtering, event detection, modeling and export operations.) However, to start with, you will probably prefer to leave this option cleared, so that you can run each operation separately and observe their effects.
8. In the System Resources tree, select Local Vicon System and then in the Properties pane, in the General section, set Processing Output Level to Labels.

9. In the capture volume, have the subject perform the movement that is to be captured.
   Nexus automatically reconstructs, labels, and fits the Vicon labeling skeleton created in the previous stage (see Prepare a subject) to the subject in real time.

   Tip: If a labeling error is obvious or persistent, restart the labeler by right-clicking Local Vicon System node and then clicking Reboot Core Processor (CTRL+R).

   If the subject steps on the force plates, the force vector is also shown in real time.
10. On the Capture Tools tab, unless you have specified a time or trigger on which to start capturing (see step 5), in the Capture section, click Start to begin capturing and in the capture volume, have your subject wearing the appropriate marker set for your VST perform the required motion.

11. Unless you have specified a time or trigger on which to stop capturing in the Auto Capture Setup section, when the subject has completed the required motion, click Stop.
    If you specified a post-capture pipeline (see step 7), Nexus automatically switches to Offline mode, displays the subject data in the 3D Perspective view, and automatically performs any operations contained in any pipelines selected in the Post-Capture Pipeline Setup section. Otherwise the system remains Live, ready to capture the next trial.

    Tip: If events are not automatically detected, or are only partially detected, you will need to add them manually (see Add events to trials). You will probably need to do this in situations such as: trials without force plates; movements that are not on a flat surface, such as stepping up/down/over, climbing, etc; pathological or non-cyclical gait movement.

12. Repeat steps 9–11 until you have obtained the required number of trials.

You can now reconstruct and label the trials. For more information, see Reconstruct and label movement trials.