Calibrate a subject
- Adaptavist ScriptRunner for Confluence Cloud (Unlicensed)
- Dev Ops
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.
Before starting calibration, the performer needs to stand in an A-pose so Shogun’s calibrator can identify the markers on the subject in a pose that the software is familiar with.
During the ROM, ensure that the performer goes through a full range of movement for every limb and joint to be captured. The purpose of a ROM is to help the calibration process estimate both the bone length and pose of the skeleton within the selected marker set. The more accurate the ROM is, the more accurate this estimation will be.
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 correct parts of the performer.
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:
The number of markers in a specified marker set at the start of the calibration. These numbers are displayed as:
Required – The number of markers in the selected template.
Labeled – The number of labeled markers found by the cameras that match the corresponding marker in the selected template. This number does not include cluster markers.
If any joint is out-of-range during the A-pose booting process as well as any markers that are missing from the selected template.
The calibration status. This can be one of the following:
Finding A-Pose...
A-Pose cannot be identified, please check marker placement.
A-Pose cannot be identified, please check subject pose.
A-Pose found, awaiting boot...
A-Pose found, awaiting Accept...
Calibrating...
If 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.
When you have created a subject, perform a live subject calibration:
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.
After you have clicked Calibrate, the Subject Calibration Feedback panel appears and displays information such as:
The calibration status. At this stage, it should say Finding A-Pose or A-Pose found, awaiting Accept…
Which markers are missing (if any) from the selected skeleton template.
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. In this case, the calibration status would say either A-Pose cannot be identified, please check marker placement or A-Pose cannot be identified, please check subject pose.
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.
While the performer is still in the A-pose, visually check that all the markers have been labeled and everything looks OK.
Reminder: The number of Labeled markers does not include markers that are associated with a labeling cluster attached to the subject.
After you’ve checked that the labels are correct and that the pose of the skeleton looks reasonable, you can begin the calibration process. To do this go to 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 A-Pose found, awaiting Accept... 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, displaying the advanced options and in the Capture section, selecting Capture Canceled Calibrations. Then refer to Troubleshoot subject calibration.
Get the performer to perform a ROM that includes all the required movements.
If you're using one of the high-fidelity finger 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 finger 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
When the ROM is complete and you are satisfied with the coverage, click Stop Calibrating.
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.
An alternative to live solving subject calibration
In Shogun 1.6 and later, if you find that after Live calibration the solve requires much tweaking, for a post-processed alternative, try Auto-Skeleton in Shogun Post. For information, see Use Auto-Skeleton in Getting more from Vicon Shogun. See also the Vicon video: How do I optimize my live solve using Auto-Skeleton?
More information on the Subject Calibration Feedback panel
In Shogun 1.12 and later, the Subject Calibration Feedback panel displays the number of visible markers and lists the joints requiring calibration.
For the best calibration, the number of labeled markers must match the number of required markers. The Labeled field is displayed in green if these marker numbers match.
If the cameras cannot find all the required markers, the Labeled field is displayed in red.
Use the Subject Calibration Feedback panel to guide the performer during their ranges of motion to ensure the joints are fully covered.
Each joint appears with a progress bar showing the proportion of the joint template range covered by the range of motion.
What is coverage?
Every joint in a template has a set of statistics for how the joint can perform, such as how far a joint can stretch, the angles at which it can bend, etc. When a performer is conducting a Range of Motion (ROM), the calibration process is comparing the joints on the performer with the joint statistics in the software. The term coverage refers to how well the ROM of the performer matches (ie, covers) the ROM of the corresponding joint statistics.
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.
Note
Coverage for toes is often low. This is usually caused by toe markers being placed on shoes, resulting in limited dexterity.
For good coverage, aim for between 30% to 60%. Joints that have at least 30% coverage perform much better and we recommend you aim for at least 30% coverage on as many joints as possible.
When 30% is reached, the bar turns green and a check mark appears 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 additional 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.
