Work with objects

To enable object tracking, you create objects in Tracker. The controls for creating and managing objects are all found within the Tracking panel (View > Tracking).

Objects are saved in .vsk format and contain information about their specific marker orientation relative to their local coordinate system.

For guidance on how to create and manage objects, see the following topics:

Create objects

To extract pose data from a set of markers, you create an object in Tracker.

To create an object:

1. Place the object with markers attached in the volume

   Tip: If you don't see anything in the 3D View, ensure that these options are selected:

   • In the View Filters, ensure Unlabeled Markers is selected.
   • In the Processing panel, ensure thatEnable Unlabeled Reconstructions is selected.

   Both of these settings are selected in the Default system file.

2. Select at least four (five or more is recommended) unassigned marker trajectories by doing one of the following:
   • To select markers individually, press and hold the CTRL key while you click on each marker.
   • To select a group of markers, press and hold the ALT key while you drag around the markers to form a box around them.

3. In the Tracking panel, in the Object field, specify a unique name and click Create. (If you forget this step, see Manage Objects to learn how to rename an object after it has been created.)

   

   A new object is created with labeled markers and sticks.

   

   The origin of the object is the mean point of all markers. If necessary, you can change this later (see Change an object's origin).

   The orientation of the object is aligned to the orientation of the global coordinate system on the frame it was created. If necessary, you can change this later (see Changing an object's alignment).

   Tip: If you enter review mode (ie, pause the live data) to create your object, a warning is displayed in the Workspace.

   

   To see the current pose of the newly created object, you must exit review mode. Although you can create multiple objects while paused, you cannot see the markers, sticks or local coordinate system for the object(s) until you exit review mode.

   In the Tracking panel, the newly created object is displayed in the Objects list.

   

   Tip: If your new object has a warning symbol (yellow triangle) next to it, to view information about the issue, hover the mouse pointer over the symbol. For more information, see Understand object evaluation.

Add or remove a marker on an object

When an object has been created, you can either add or remove a marker to/from that object.

To add a marker:

1. In either the Tracking panel or the 3D View, select the object.

2. Hold CTRL, select the marker you want to add and then in the Tracking panel, click Add Marker.

   You can only add a single marker per operation.

To remove a marker:

• Select the marker and in the Tracking panel, click Remove Marker.

  If the removal of the selected marker results in the object having fewer than four markers, you cannot remove the marker.

Create an object preset

An object preset is a set of object-specific properties that enables you to control the amount of filtering performed on a given object. This can help to reduce any jitter or systematic noise in an object, particularly if a marker on the object becomes occluded. It can also help ensure that objects are properly recognized. For information on using an object preset to ensure Tracker recognizes differences between similar objects, see also Resolve issues with object similarity.

To create an object preset:

1. In the Objects list in the Tracking panel, ensure that the object to which you want to apply the preset is selected.

2. In the object's Properties below, ensure the advanced parameters are displayed .

3. Depending on whether you want to use an existing object preset for this object, do one of the following:

   • If you want to use an existing object preset, in the Object Preset list, select the required preset.
   • If the required object preset does not exist, to the right of the Object Preset list, click Manage and in the Object Presets dialog box, enter a name in the Create New Preset field and then click Add.

4. In the Object Presets list at the top of the dialog box, select the new preset, then change the properties as required.

   For information on object tracking and the Entrance Threshold, see Why is the Entrance Threshold important?

   The following steps describe how to set the smoothing properties for translation and rotation.

5. To use 1-Euro filtering for the selected object, select Filtering Enabled.

   For detailed information on the 1-Euro filter and how to adjust these settings, visit www.lifl.fr/~casiez/1euro/.

6. With Translation Beta set to its default value, change the value of Translation Min Cut-Off to eliminate jitter during very slow movements.

   Note that decreasing the value of Translation Min Cut-Off reduces jitter but increases lag.

7. When you have finished adjusting the Translation Min Cut-Off value, increase the value of Translation Beta by very small increments to eliminate lag during faster movement.

   Note that 0 = filtering on all translation motion; 1 = filtering on very slow translation motion only.

   Follow the same procedure for adjusting the Rotation Min Cut-Off and Rotation Beta.

8. If you want Tracker to detect the object as static, select Motion Model.

9. When you have finished adjusting the properties, click Close.

10. In the Tracking panel, make sure that in the Object Preset list, the required preset is selected.

Add a mesh to an object

A mesh is a 3D model representation with a root bone that specifies its own coordinate system.

Adding meshes to objects enables you to better visualize them in the Workspace to check that they are correctly aligned and that they give the result that you want.

1. In the Tracking panel, in the Objects list, select the object to which you want to add a mesh.

2. In the object's Properties below, from the Mesh list, select the required mesh.

   

   Tracker accepts any mesh in the FBX file format. You can use the installed meshes, or your own FBX files. To choose your own FBX file, click the Import mesh button next to the Mesh list. This enables you to choose an FBX file from its saved location.

   The file is copied to the prop mesh folder:
   (C:\Users\Public\Documents\Vicon\PropMeshes)

   It is also added to the Mesh list and is set as the current mesh.

   Your mesh is displayed in the 3D View.

Change an object's origin

The object manipulator enables you to specify an object's origin (ie, the center of the physical object in relation to the marker pattern that is tracked by Tracker). You can also change the alignment of its local coordinate system (see Change an object's alignment).

1. Activate the object manipulator:
   1. To pause the live stream, press the space bar or click the Enter Review button at the bottom right of the Workspace.
   2. Select the object.

   3. In the 3D View, click the object manipulator button.

      

      Tip: If you click on the object manipulator while not in Review mode, the dialog box does not appear until you click Enter Review.

2. Ensure Global or Local (either the local or global reference frame, as required) is selected. For details, see Understand local vs. global reference frames.

3. In the 3D View either:

   • Drag an axis to move the origin to the required location; or

   • Enter values in the Translation fields;

     

     When you resume streaming (ie, un-pause), the object's orientation is updated.

     Tip: To scale the Manipulator, on the numeric keypad, press + (scale up) or - (scale down).

Understand local vs. global reference frames

Note that the manipulator operates with respect to either the local or global reference frame (corresponding to the object coordinate system or the world coordinate system, respectively). To switch between the two:

• Click the required icon at the top right of the Object Manipulator.

  

Using the global reference frame, you can also move the origin of the object to the global origin by clicking Translation .

If you use the local reference frame, note the following behavior:

• If you drag an axis, its translation in that axis is noted. When you start streaming again, this resets the local reference frame to this new location (ie, origin Translation is reset to (0, 0, 0)).
• If you enter a numerical value into one of the axis fields, the axis is translated by the specified amount. When you start streaming, the initial origin location persists so the translation still shows the amount specified for the remainder of that sync session.

Change an object's alignment

The object manipulator enables you to change an object's alignment or orientation (ie, to modify its local coordinate system). You can either align each axis manually or use one or more markers or axes to help align your local coordinate system.

For either method, make sure you first pause the live stream.

Align objects manually

With the object manipulator enabled and an object selected, you can either:

• Rotate an axis directly in the 3D workspace; or

• Enter a value in the rotation fields for each axis. You can also specify whether you want this to be a local or global rotation using the reference frame buttons (see Change an object's origin).

  If the global reference frame is selected, each axis identifier within Rotation changes to an active state (eg, ). Selecting one of these axes aligns it to its corresponding global axis.

Align with marker or axis

To align an object with a marker or axis:

1. Ensure the object manipulator is enabled and the required object is selected.

2. Click the alignment tool (for more information, see Understand the alignment tool).

3. Set your primary axis. To do this:

   • In the Primary Axis line, select the target type ( Axis , Marker or Center ), followed by the target.
     • If you chose Axis, you choose the target from a drop-down menu.
     • If you chose Marker or Center, you are prompted to select one or more markers.
   • Select the axis (X, Y or Z) and its direction (+/-)

4. Repeat step 3 for the Secondary Axis.

   Note that if the Axis or Target in the Secondary Axis is the same as Primary Axis, the Align button is unavailable.

5. Click Align.

   Tip: With the system still paused, you can undo (CTRL+Z) or redo (CTRL+Y) the most recent alignment.

Manage objects

Objects and their properties are displayed in the Tracking panel according to Tracker's AutoSave behavior (see Tracker fundamentals).

For further control of each object in the Objects list in the Tracking panel, right-click one or more objects to display a context menu. This enables you to use these options:

• Rename: Enables you to rename the selected object. You can also double-click to rename or select the object and press F2 or change its name in the Object field.
• Remove: Removes the selected object(s) from the tracking list.
• Enable: Activates the selected object(s).
• Disable: Deactivates the selected object(s).
• Export: Exports the object as a .vskfile with the name you have given the object. By default, objects are exported toC:\Users\Public\Documents\Vicon\Objects, but the dialog box enables you to save to any location. You can change the default location within the preferences (see Preferences options).
• Use for Camera Calibration: Enables you to use a custom calibration object. See Create a custom calibration object.

Manage tracking configurations

The top of the Tracking panel displays the controls that enable you to manage your objects. This includes being able to import an object, load a set of objects, or save a set of objects.

To import an object, click . You can import any object in .vsk format.

When you have finished creating your objects, you can save them to a tracking configuration file (MCP file format).

To do this, at the top of the Tracking panel, click the Save tracking configuration button:

The default location for tracking configuration files is: C:\Users\Public\Documents\Vicon\Tracker4.x\Tracking

When you want to re-use your tracking configuration, click the Load tracking configuration button to re-load the file.

Export an object as a VSK

To export an object as a Vicon Skeleton (VSK) file:

1. In the Tracking panel, go to the Objects list, right-click on the required object and then select Export.

2. In the Export dialog box, browse to or enter the location for the object.

   The default location is: C:\Users\Public\Documents\Vicon\Objects

3. Save the VSK.

Create a custom calibration object

You can use a Vicon Active Wand to set up your volume coordinate system quickly and easily (see Set the volume origin). However, using a larger calibration object (for example, markers embedded in the volume floor and wall) can improve calibration stability and consistency over time.

You can create and export a custom calibration object from any object as described in Create objects and Export an object as a VSK.

When you export the VSK, save it to your calibration objects folder.

The default location is: C:\Users\Public\Documents\Vicon\CalibrationObjects

You can use the custom calibration object to set the origin of your volume.

For detailed information on how to create and use a custom calibration object, see Scale calibration and set a fixed origin.