Achieving a good quality calibration is essential to achieve good quality motion capture, so it's always worth trying to get the best quality calibration. The camera calibration tells the system the position & orientation of your cameras, so it can turn the 2D footage into 3D data when you process your motion capture action takes.
When your calibration has finished processing, here's what you should do:
If your calibration was successful, check out the Information On The Web App and the Calibration Report to ascertain the quality.
If your calibration failed, this usually indicates a critical error with file settings, check out Further Troubleshooting for more info on what to check.
Information On The Web App
There is some useful information on the Web App that you can use to check your calibration processed as expected.
Input Details
This window allows you to check the input settings you provided for the system to process the calibration.
Status
If you hover over the status, it will tell you the quality score of the calibration. This provides a rating, ranging from Excellent to Very Good, Good, Weak & Poor. The rating is determined based on many factors, including the reprojection error. If your calibration is Weak or Poor, please refer to the Further Troubleshooting section below.
This also provides a comment, to identify some common errors. Here's what they mean:
'Calibration is poor. One or more cameras have been skipped. Please check the following cameras [] before proceeding.'
If the data from some cameras doesn't agree with the others, they will be skipped. Try removing the respective cameras, by using the 'Create new from' button to duplicate your session with only the chosen cameras and process a new calibration. This could be because they couldn't see the actor clearly, or are a different model to other cameras.
'Cameras [] show bigger error than expected.
If the data from some cameras has a great pixel error when compared to other cameras, they may have negative impacts on the overall tracking. Try removing the respective cameras, by using the 'Create new from' button to duplicate your session with only the chosen cameras and process a new calibration. This could be because they couldn't see the actor clearly, or are a different model to other cameras.
'Calibration is poor. There is a mismatch in resolutions used and the camera type selected. Please check the following cameras [] before proceeding.'
In order to process the footage, all videos must be the same resolution and from the same camera model (unless using Experimental Mode).
Sync
This video contains the clip from the input videos trimmed to show only the part between the first and last clap time. Use this video to visually check that the system has synchronized the footage correctly. Ignore this if timesync'd cameras were used.
Camera layout
This 3D viewer allows you to see the recreation of your camera positions, with respect to the origin (where the actor began the Y-pose sequence). You can use this to visually check if the layout is as expected.
Download
Here you can download the JSON file of your camera positions.
Calibration Report
When your calibration finishes processing, you will receive an email. This email includes the status of the calibration, a link to the session and if the calibration was successful, it attaches the bespoke calibration report.
Overview
At the top, there will be a short overview of the calibration feedback, the same as is shown on the Web App.
Video Metadata
This table provides a brief summary of the files you selected. Here you can identify any obvious outliers, consider that framerate and resolution should always be consistent.
Camera Intrinsics
These are the lens distortion parameters used, determined based on which camera profile you chose for this session. This can be ignored.
Calibration Mosaic
This visualisation shows the overlay of the 2D and 3D tracking from each camera's perspective. The blue skeleton is the independent observation from each camera, whereas the red skeleton is the 3D estimation shown from each camera. If there is a large difference in the alignment of these skeletons in one/some cameras, this indicates an outlier, that you should consider removing from your session. If the skeletons are very close, this is a sign of a good calibration.
This can also be used to verify the framing of your cameras is adequate, as it is essential that at the beginning of the calibration Y-pose sequence, every camera can see the entire body of the person doing the Y-pose.
Active Area
When you perform a calibration, the system uses the starting location of the Y-pose sequence to define the origin of the 3D calibration. It will then track the furthest locations you walk in each direction away from the origin, to define the desired perimeter of the capture volume by connecting those locations in the form of a convex hull. This ensures that during the action takes, only actors within the capture volume will be tracked.
This visualisation shows the capture volume perimeter, overlayed in a black line on each camera view. It is strongly recommended that the entire capture volume can be seen in all cameras.
Further Troubleshooting
If you achieved a weak, poor or failed calibration, it's worth checking a few things to see if you can resolve this.
Check your input settings are correct:
Clap times (not necessary if footage is sync'd) - this window should contain all three claps.
Example - If you enter 00:03 - 00:06, it will use the audio from the entire 3rd, 4th, 5th and 6th second.
Y-pose sequence times - this window should begin when the actor is stood still in the Y-pose.
Example - If you started the Y-pose at 7 seconds and finished it at 32 seconds, you should enter 00:06 - 00:32.
Actor height - this should be the height of the actor, excluding footwear.
You should also check your videos are:
Named correctly & consistently
The same duration (at least within 2sec difference)
The same resolution
The same framerate
Uploaded correctly and can be previewed when selected for your Calibration
Matching the camera and resolution you chose for your Session