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This information is for Vicon Tracker 3.4. For up-to-date help, see the latest Tracker documentation.

You view and manipulate various values of one or more selected items (such as the x, y, and z components of a marker trajectory) against time.

The Graph view pane contains the following components.

Component

Description

Graph view pane tool bar

You manage the display of graph data in the workspace with the following controls and buttons on the Graph view pane tool bar at the top of the view pane. The Graph view pane tool bar is designed to lead you left to right through the normal flow of operations required to plot a graph for the selected elements.

Graph type

You select the type of graph to be displayed in the workspace from under the categories in this drop-down list (graph types that are not available for the current selection are dimmed):

Devices

Components – Displays graphs for the components of analog signals from force plates, or other analog devices, such as EMG devices or accelerometers.

Trajectories

  • Components – The X, Y, and Z position of a trajectory over time.
  • Distance From Origin – The linear distance between a trajectory and the origin.
  • Distance Between – The distance between two selected trajectories.
  • Distance Between (xyz) – The absolute distance (as a vector) between two selected trajectories.
  • Angle Between – The angle between three selected trajectories.
  • Trajectory Count – The number of trajectories being reconstructed.

Metrics

  • Latency – A measure of the time taken by Tracker to perform some task. As data is received from the hardware and is processed, Tracker takes timestamps that are used to calculate the latency estimate.There are two different kinds of latency that are graphed if you are using Firmware 222.
  • Data Delivered – The amount of time taken between the sync packet being received and the data for that frame being delivered from the hardware. This is the integration period of the camera - the time that it takes the camera to process the sample and any Ethernet overheads.  
  • Data Processed – The amount of time between the sync packet being received and the completion of data processing.

Object

Quality – The RMS error of a rigid body compared to its model (VSK).

Segments

  • Global Angle – The global position and orientation of a rigid body.
  • Relative Pose – The difference in orientation between two objects. The relative pose graph shows the transformation from object A (the first object selected) relative to object B (the second object selected).

Differentiate the Graph 

You specify for the displayed graph the current variable, its first derivative (velocity or angular velocity), or its second derivative (acceleration or angular acceleration) by selecting the desired options from this drop-down list:

  • x (none)
  • x' (velocity)
  • x" (acceleration)
    A graph of a trajectory will have X, Y, and Z axes, but when differentiated to x' (velocity) will change to X', Y', and Z' axes.

Graph Components 

You specify the components of the selected graph type to be plotted in the active Graph view pane by selecting the required options from this drop-down list (only components that you have selected for graph view are available):

  • Components - Dependent on the type of graph you have chosen. For example, the count for the Trajectory Count graph.
  • Select None
  • Select All
    This option enables you to focus on a component of particular interest, which occupies more of the workspace. When multiple components are plotted, each is always shown on a separate axis, and the components shown are applied to all channels visible in the workspace. The number of vertically stacked graphs displayed in the workspace depends on the type of graph selected and the number of components selected from this component list.

Rotation Order 

If you select an object on the Object tab in the Resources pane, you can select Global Angle from the Graph view tool bar. This enables the Rotation Order button. Clicking on the Rotation Order button lists the angle convention choices of Helical (default), XYZ, XZY, etc. This enables you to choose either a Helical or an Euler angle convention. The Euler angle convention itself has multiple rotation order conventions represented by XYZ, XZY, etc.

Show Legend 

This button allows you to show a legend to the right of the graph trace for each component being plotted.

Scaling

You manage the scale of the graph (to ensure that the desired portions of the selected traces are visible) with these buttons:

Fit Horizontally 

Zoom out the x-axis to show the complete range of the trace for 100 frames. This is useful if you have zoomed in a long way and now want to quickly see the entire graph again.

Lock Horizontal Axis 

Lock the horizontal graph axis so that the current zoom level is maintained.

Fit Vertically 

Scale the y-axis so that all the data in selected traces for the currently visible x-axis is visible. If there are multiple traces in the selected components, they are all set to the same range required to show all the data for all traces.

Lock Vertical Axis 

Lock the vertical graph axis so that the current zoom level is maintained.

Fit Both Horizontally & Vertically 

Scale the x and y axes simultaneously to fit the horizontal and vertical ranges of data.

Lock/Unlock Selection Set 

Lock the current Graph view pane, so that it is effectively detached from the selection set and is not affected by any subsequent selections in other open view panes. This is useful for displaying different elements in multiple Graph view panes.

Graph view pane workspace

You view and manipulate graph data in the workspace.

The workspace contains rulers and axes along the right and bottom edges and graph traces for the item being plotted.

The y-axis vertical ruler is on the right side of the graph and the x-axis horizontal ruler is below the graph. The y-axis represents the selected component. The x-axis represents the time (in frames). It starts on the right side, which is labeled 0 (current frame) and is labeled from right to left with decreasing negative values to reflect the number of frames away from the live frame.

Tips:

  • To change the default number of samples to display when a new real-time graph is opened, press F7 to open the Options dialog box, click Graph on the left, and on the right side, change the Default X-axis length value.
  • When zooming into or out of graph data, the display of grid lines in the workspace can be set to guide the eye toward the selected area of focus. Major grid lines remain at their normal weight, while any minor grid lines gradually fade. To obtain this behavior, press F7 to open the Options dialog box, ensure Graph is selected and in the Properties area, select Show Minor Grid Lines.

Viewing data in Graph view

You can display graphs of motion capture data in the Graph view pane.

The Graph view pane displays graphs for the types of data that can be produced in a motion capture trial.

Graphs of trajectories data display three graphs of the X, Y, and Z components of trajectories for two or more selected 3D markers, or a single graph of the trajectory count for all 3D marker trajectories, against time. This is useful for analyzing 3D marker trajectories and identifying gaps to be filled.

To view 3D trajectories in a graph:

  1. Stream live camera data.
  2. Select the markers to be graphed in either of the following ways. (The number of markers you select depends on the type of graph you want to view, as described in step 3 below.)
    • On the Objects tab in the Resources pane, expand the required Object node, expand the Markers node, and then select one or more markers; or
    • In a 3D Perspective view pane, select one or more markers.
  3. From the view pane tool bar, select Graph. A single Graph view pane is displayed with the default Components graph type plotting the X, Y, and Z components of each selected marker.

    Tip

    When you have displayed a Graph view pane, you can select additional markers to add to the Graph view pane. Each trajectory is displayed in a different color trace. To identify the color trace used for each trajectory, click the Show Legend button  (or hover the mouse pointer over it) in the Graph view pane tool bar. If the trace for any additional markers is not visible, use the Fit Horizontally, Fit Vertically, or Fit Both Horizontally and Vertically buttons.

  4. From the Graph Type list in the Graph view pane tool bar, select another option under the Trajectories section to plot the selected marker trajectories in a different type of graph:
    • Distance From Origin: Plots the distance from the capture volume origin to each selected marker. This is useful for later plotting velocity or acceleration of markers.
    • Distance Between: Plots the absolute distance between two selected markers. This is useful, for example, for seeing how the distance between two markers that are assumed to have a rigid relationship, changes over time.
    • Angle Between: Plots the angle between the two vectors formed by three selected markers. This is useful for seeing how the group of markers move over time.
    • Trajectory Count: Plots the total number of trajectories over time visible to the Vicon cameras (if streaming Live data in real time) or processed in trial (if viewing previously captured data in a file).
  5. If you want to save a particular graph view (for example, specific trajectories that you have selected), save your configuration using the view pane configuration management controls.