An event is a single action in the time span of a trial, for example, a foot contacting the floor during a walking trial, or a knee angle exceeding a particular angle.
Events are normally added to your trial data automatically as part of the capture workflow, when you run Plug-in Gait Dynamic or other dynamic pipelines that include Detect Events From Forceplate and Autocorrelate Events. For more information, see step 7 of Capture the required movement.
However, if events are not automatically detected, or are only partially detected, you will need to enter event identification mode and add them manually. This is likely to be necessary in the following scenarios:
- If you are not using a force plate; or
- The floor is not flat (ie, the movement being captured involves stepping, climbing, etc); or
- The trial includes movement that is not a cyclical gait movement (for example, some sports movements)
If your trial type does not allow the automatic addition of events, you can add them manually, using the timebar as described below.
For more information on working with events, see:
Add events to trial data
To add events to motion capture trial data:
- From the Data Management tab, open the required trial, ensuring that it contains no gaps or other issues (see Review data quality and Fill gaps in trial data).
- Display the desired view (3D Perspective, 3D Orthogonal, Camera, or Graph).
To automatically display a specified view type when you enter event identification mode, in the Options dialog box (F7), select Event Identification View Options on the left, and in the Properties on the right, change View Type to On and in the User-Specified Event Identification View field, select the required view type.
- Enter event identification mode in either of the following ways:
The mouse pointer changes to a vertical arrow, to indicate that you are now in event identification mode.
- On the time bar, click the Enter Event Identification Mode button; or
- Press CTRL+E.
You can control zooming into the time bar in Event Identification mode:
- In the Options dialog box (F7), select Time Bar and in the Properties pane on the right, scroll to Event Identification Mode and select or clear Zoom to Event.
- When Zoom to Event is selected, you can specify the Zoom Range (the number of frames) either side of the event that you zoomed to in the time bar. The default is 20 frames.
- On the time bar, zoom in or out on the timescale (right-click and drag) to adjust the time span of data displayed in the view pane and move the current time indicator (blue line) along the time bar to locate the desired frame.
- Lock the event context by positioning the mouse pointer over the desired Left, Right, or General line on the selected frame (the line for a context is highlighted when the mouse pointer hovers over it) and pressing the UP ARROW or DOWN ARROW key. When the event context is locked, moving the mouse does not change the context.
- Set a new event in the current context on the selected frame by either left-clicking or pressing ENTER and then selecting the desired command from the context menu
- Create Event Foot Strike Creates a foot strike event at the selected frame.
- Create Event Foot Off Creates a foot strike event at the selected frame.
- Create Event General Creates a general event at the selected frame, represented by a vertical bar on the timeline. You cannot name general events and they are not saved to the event creation menu for future use.
- Create Custom Event Creates a custom event at the selected frame that you can name, represented by a caret ( ^ ) on the timeline. When you create and name a custom event, it is added to the event creation menu, so you can select it again in future.
- Navigate existing events in either of the following ways:
- In the time bar controls, click the Jump to the previous event or Jump to the next event button; or
- Press CTRL+LEFT ARROW or CTRL+RIGHT ARROW to go the previous or next event.
- If required, you can:
- Move an existing event to another frame by clicking in it with the left mouse button, holding the button down, dragging it left or right along the timeline.
- Move the event at the current frame in the current context back or forward one frame by pressing ALT+Left- or Right-arrow key.
- Delete existing events:
- Single event: On the time bar, click the event or press ENTER, and from the context menu select Delete Event <Type>.
- All events on current frame: On the time bar, click the desired event or press ENTER, and from the context menu select Delete All Events at Frame x.
- All events in trial: On the time bar, right-click anywhere and from the context menu point to Clear Events, then select Clear All Events.
- All events for one context only (ie, for left, right, general and custom events): On the time bar, right-click anywhere and from the context menu point to Clear Events, then select the required context option.
Note that you can also use the Delete Timebar Events pipeline operation (available on the Pipeline Tools pane, under Events & Timebar) to delete events from a selected range of frames and/or a specified context. See Events & Timebar operations in the Vicon Nexus Reference Guide.
- When you have finished editing the current event context, unlock the event context by either moving the mouse over a different context or using the Up/Down arrow keys on the keyboard.
- Repeat steps 5-9 for each event context you wish to edit.
- When you have finished editing all events, exit event identification mode in any of the following ways:
- In the timebar controls, click the Enter Event identification mode button again; or
- Press CTRL+E; or
- Press ESC
If you add gait cycle events before you crop a trial, you probably want to delete events that are outside the cropped region. (For information on cropping trial data, see Crop trials.)
Delete events that are outside the region of interest
If you crop a trial after you have added events to it, events may be retained in the discarded (cropped) region of the trial. To remove these events, do either of the following:
To delete events that are outside the region of interest:
- Do either of the following:
- Right-click on the time bar of the cropped trial and click Delete Events Outside Region of Interest; or
- In the Pipeline Tools pane, from the Events & Timebar operations, select Delete Timebar Events and in the Advanced Properties, select whether to delete events inside or outside of the specified region.
- Run the Delete Timebar Events operation to remove the unwanted events.
Customize event identification mode
To customize options that affect event identification mode:
- Open the Options dialog box (press F7).
- On the left of the dialog box, click Time Bar.
- In the Event Identification Mode section on the right, select (or clear) Focus on marker and enter or select the markers to focus on for Left and Right contexts.
Customize cycle visualization
By default, all the cycles (gait or other) that have been defined by sets of time bar events, are displayed on the time bar.
This provides an easy way to identify:
- How many cycles are defined
- Where they are temporally
- Whether they are associated with force plate activity (indicated by solid color instead of colored outline only)
- How large they are (number of frames)
- Whether the left or right side is indicated:
To turn the visual display on or off or to change the default color options and other visual indicators, in the Options dialog box (press F7), on the left side click Time Bar and change the required properties on the right.
To turn on or off the display of the frame count, right-click on the time bar and select or clear Show Cycle Frame Count.
Calculate step width and limp index
If your trial includes Foot Strike and Foot Off events, you can use the Calculate Gait Cycle Parameters pipeline operation to calculate step width and limp index.
To calculate step width and limp index:
- Ensure your trial data includes both Foot Strike and Foot Off events. If it doesn't, either recapture the data or add the missing events.
- Add the Calculate Gait Cycle Parameters operation to your current pipeline in the usual way.
- In the Properties pane, ensure that the units for the Stride/Step Length/Width setting are as required.
- Run the Calculate Gait Cycle Parameters operation on your data.
In the Subjects Resources pane, the Analysis Outputs include both step width and limp index.
On the Log tab, the step width and limp index data is displayed.