Create and calibrate a subject

After you've attached the markers to the performer(s) (see Place markers on a performer), you can create a subject to represent the performer in Shogun Live, and then calibrate it.

During live subject calibration, labels are automatically assigned to the subject markers based on the selected subject template and the assumed position of these markers (calibrating the subject finds the actual position of the markers). When the performer is in an A-pose, Shogun Live can easily assign the labels to the right parts of the performer.

Calibrating a subject involves the performer (wearing the corresponding marker set) standing in an A-pose and then performing a Range of Motion (ROM) in the capture volume. During the ROM, ensure that the performer goes through a full range of movement for every limb and joint that is to be captured. The purpose of a ROM is to help the calibration process estimate both the pose of the subject’s joint centers and also the position of the markers with respect to the joints. The more accurate the ROM is, the more accurate this estimation will be.

Use the Subject Calibration Feedback panel to see which joints require further motion (this is measured in "coverage", see Subject Calibration Feedback for a definition). The Subject Calibration Feedback panel also indicates whether:

• Any markers are missing from the specified marker set at the start of the calibration.
• Any joint is out-of-range during the A-pose booting process.
• One or more labeling clusters have been attached to the subject.

For a good calibration, aim to have a coverage of at least 30% for each joint. For more information, see Subject Calibration Feedback.

Before you begin

Before calibrating a subject, complete the following steps and checks:

Place and pose your performer

Get your performer to enter the volume and stand in an A-Pose (see the following example).

Shogun Live indicates when a subject is in an A-pose and enables you to click Accept A-Pose to assist in the calibration.

Always start the calibration by accepting the A-pose. This loads the subject into Shogun Live and automatically assigns the correct labels to the marker reconstructions. Also, the pose chosen as the A-pose is used to enforce some constraints on the subject. Taking these constraints into account as early as possible increases the accuracy of the calibration.

If you have multiple subjects to calibrate, you must calibrate them separately. Have the performers enter the volume one at a time and select the corresponding labeling cluster for the subject you want to calibrate.

Give the clearest view of the subject

To give the clearest view of the subject:

1. At the top of the 3D View, ensure View Filters is selected.

2. Under the Volume options, clear Cameras.

3. In the Subject View Presets section, select Solve.

4. In the Subjects (Solve) options matrix, in the S column, ensure Skins is selected (in addition to any other options you may want to use). In this example, Markers is selected also.

Use offset markers

To help Shogun Live boot the subject and label the subject markers, it is recommended to place the markers on the upper arms and legs in an asymmetrical manner. This offset helps identify the left and right-side of the subject and speeds up the calibration.

Check you have enough processing power

Using high-density marker sets (such as high fidelity fingers marker sets) creates a greater processing demand. This means you may experience dropped frames, especially when using more than one actor.

Ideally, first test the makers set with a single actor on a high-spec, multi-core machine.

To improve processing, you can run reconstruction, labeling, solving and/or retargeting over multiple machines. For information, see Run Shogun processing on multiple machines in Getting more from Vicon Shogun.

Check the marker count of the current selection

The Marker Selection counter enables you to easily check the number of markers currently selected. This is a useful quick check before you start calibrating a subject, as you can see if the required number of markers have all been placed on a subject, or the markers are within their correct marker set (for example, facial markers).

To display the number of selected markers:

1. In the 3D View, display the View Filters and in the Overlays section, select the Selected Marker Count option.

   

   At the bottom right of the view pane, the Marker Selection count is displayed. If no markers are currently selected, a zero is displayed.

   

2. As you select markers in the view pane, the Marker Selection counter changes to display the number of selected markers.

   

Check for missing markers

To view missing markers, ensure that Missing Markers is enabled (3D View > View Filters > Data > Missing Markers).

If a marker is completely hidden it turns red and glows.

Calibrate your subject

To perform a live subject calibration:

1. In the Tracking panel, on the Setup tab go to the Subject section and in the Template field, choose the appropriate template for your subject. If you're using side waist markers and/or finger markers, choose the templates that include side waist markers and/or fingers (indicated by their names). The example in this guide uses the FrontWaist10Fingers template.

2. In the Skin field, ensure the required mesh is selected. The default mesh is ViconActor. If you can't see this field, display the advanced properties by clicking Advanced parameters at the top right of the Setup tab.

   The selected mesh is used for the solving skeleton.

3. (Optional) If you are tracking multiple subjects, they must be calibrated separately with each subject assigned to their own labeling cluster(s). In Labeling Cluster Selection, choose from the following:

   • All: Any currently unattached labeling clusters are attached to the subject. Select this option if you are only calibrating one subject.

   • Selected: Only the cluster(s) selected at the start of calibration are attached to the subject. Select this option if you need to calibrate multiple subjects.

   • None: No labeling clusters are used for calibration.

4. In the Subject field, enter a name for the new subject and click Create.

   Tip: To begin calibrating the subject as soon as you create it, select Calibrate on create.

   

   The subject is calibrating and the menu bar, above the workspace, now reads Subject Calibration Active and a flashing red circle is displayed along with the Subject Calibration Feedback panel.

5. Check the performer is standing in an A-pose, with the hands flat. The following are examples of what an A-pose looks like depending on the solving options you have selected.

   

   Tip: If you're using a template that includes fingers, also ensure that:

   • The wrists are straight, not bent to either side or up or down.
   • The fingers are straight, with a natural spread, and no bend.
   • The thumb is held tight against the index finger. Ensure that the thumb and the fingers all point in the same direction.

   The Subject Calibration Feedback panel appears and displays information such as which markers are missing (if any) or which joints are out-of-range (compared to the A-pose). The following is an example of a bad A-pose that causes Shogun Live to struggle to find the joints required for calibration.

   

   When the subject has booted, the coverage percentage of every joint is displayed in the Subject Calibration Feedback panel. For more information on the coverage percentage, see Subject Calibration Feedback.

   Tip: If you have issues booting the subject, see Troubleshoot subject calibration.

6. While the performer is still in the A-pose, visually check that all the markers have been labeled and everything looks OK.

   

7. After you're happy with the position of the joints and the labeling solution for the booted pose, in the Tracking panel, below the Subject field, click Accept A-Pose to proceed with calibrating your subject.

   

   The Subject Calibration Feedback panel status is updated from Accept A-Pose to Calibrating.

   Tip: If you're using an offset and left and right markers (see the guidance on marker placement) but are still experiencing problems with subject booting, cancel the calibration by going to the Tracking Setup panel, display the advanced options and in the Capture section, select Capture Canceled Calibrations. Then refer to Troubleshoot subject calibration.

8. Get the performer to perform a ROM (Range Of Motion) that includes all the required movements.

   If you're using one of the high-fidelity fingers templates, include some finger movements as part of this process. Include bending and spreading the fingers as well as poses of the hand to obtain a good calibration of the articulated hand. A good hand calibration is required for accurate labeling and solving.

   The Subject Calibration Feedback panel indicates the joints that require more motion (ie, coverage). For more information on the optimum coverage, see Subject Calibration Feedback.

   

   For high-fidelity fingers templates, include the following in your ROM:

   • Bunch hands into fists
   • Wiggle the fingers
   • Touch the tip of the thumb against the tip of each digit of the same hand:
     • Thumb to index finger
     • Thumb to middle finger
     • Thumb to ring finger
     • Thumb to little finger

9. When the ROM is complete and you are satisfied with the coverage, click Stop Calibrating.

   Tip: Aim for a joint coverage average score of 60%.

   

In the 3D View, you can see the mesh and solving skeleton of the subject.

Tip: If you cannot see your subject, you may need to change the display. Click View Filters and choose the required options).

The subject is now fully calibrated. Find your subject on the Tracking panel in the Subject section, where it is displayed together with a node representing its labeling cluster (if any).

You can now use the subject in captures as required (for example, if you're using it for retargeting, see Load a retargeting setup (optional)).

If you have difficulty with calibrating your subject satisfactorily, see Troubleshoot subject calibration.

Subject Calibration Feedback

In Shogun 1.12 and later, the Subject Calibration Feedback panel lists the joints requiring calibration. Each joint appears with a progress bar showing the proportion of the joint template range covered by the range of motion.

The progress bar is displayed in red if the joint range coverage is below 30%. Joint coverage under this threshold means the skeleton calibration is more strongly influenced by the predefined statistics for the joint compared to the recorded ROM of the performer. This is to compensate for the lack of varied data. Although there is nothing wrong with low coverage (due to hindering factors such as a restrictive costume that prevents moving some limbs), anything under 30% does not produce optimal calibrations.

For good coverage, aim for between 30% to 60%. Joints that have at least 30% coverage will perform much better and it is encouraged to reach at least 30% on as many joints as possible.  

When 30% is reached, the bar will turn green and a tick will appear on the right -hand side of the panel.

When joint coverage reaches 60 %, the green tick is replaced with a star. You're welcome to perform more range of motions at this point, but at 60% coverage you have already achieved optimum results for that joint so further motion is not critical.  

Generally speaking, encourage your performers to do the best range of motion they can, as more ROM flexibility will increase the quality of their subject’s labeling and solving post-calibration.

The overall coverage is displayed as an average at the top of the Subject Calibration Feedback panel.