Calibration Pane
Overview
Calibration is essential for high quality optical motion capture systems. During calibration, the system computes position and orientation of each camera and amounts of distortions in captured images, and they are used constructs a 3D capture volume in Motive. This is done by observing 2D images from multiple synchronized cameras and associating the position of known calibration markers from each camera through triangulation.
Please note that if there is any change in a camera setup over the course of capture, the system must be recalibrated to accommodate for changes. Moreover, even if setups are not altered, calibration accuracy may naturally deteriorate over time due to ambient factors, such as more or less light entering the capture volume as the day progresses and fluctuation in temperature. Thus, for accurate results, it is recommended to periodically calibrate the system.
Starting a New Calibration
New Calibration
To begin a new Calibration click New Calibration
Load Calibration
If you already have a previous calibration you wish to load, click Load Calibration.
This will open the Calibrations folder.
From here you can choose a Calibration you wish to load.
Each time you create a new calibration in Motive, it will automatically save in the Calibrations folder.
Open Calibration Folder
If you wish to view calibrations in File Explorer, click the Open Calibration Folder. You cannot load a calibration from this window. The purpose of opening the Calibration folder is to manipulate the files separately from Motive. For instance, you may want to delete old Calibrations that are no longer relevant to your current camera setup.
Place your cameras
Aim and Focus
Masking
Before performing system calibration, all extraneous reflections or unnecessary markers should ideally be removed or covered so that they are not seen by the cameras. If this is not possible, extraneous reflections can be ignored by applying masks over them in Motive.
Masks can be applied by clicking Mask in the calibration pane, and it will apply red masks over all of the reflections detected in the 2D camera view. Once masked, the pixels in the masked regions will entirely be filtered out from the data. Please note that Masks get applied additively, so if there are already masks applied in the camera view, clear them out first before applying a new one.
Clear Masks
This will help remove masks that are no longer useful or need to be reset in order to cover new reflections.
Cancel
This button will allow you go back to the Calibration pane's default window.
Mask
This button will auto-apply masks to objects in the capture volume.
You can always click Clear Masks then Mask again to reapply new Masks if you're unhappy with the initial masking or to reset the masks from a previous calibration.
Continue
This button will continue with the Calibration process with the masks applied.
Wand the Volume
Calibration Type:
Full
When Full is chosen from the dropdown, this will allow for a full volume calibration where each camera is used for the calibration.
Refine
Wand:
Cancel
This button allows you to go back to the masking window incase you need to make changes to your masks.
Start Wanding
This button will initiate the calibration with all previous settings applied.
Once you begin to wand the camera squares in the Calibration pane will turn dark green when a camera has begun successfully collecting samples, but still does not have a sufficient amount of samples collected. Once there is a sufficient amount of samples collected the square will turn light green. Once all the camera squares have filled in light green the Start Calculating button will be enabled.
Show list
This will show the amount of samples a camera has captured. Typically you want around 1,000-4,000 samples. Samples above this threshold are unnecessary and can oftentimes be detrimental to a calibration's accuracy.
Start Calculating
This button will start calculating the samples taken during the wanding stage. During this the camera squares will cycle through red, dark cyan, and light cyan.
Red
Calibration samples were Poor and have a high Mean Ray Error.
Light Red
Grey
Calibration samples are Good
Dark Cyan
Calibration samples are Excellent.
Light Cyan
Calibration samples are Exceptional.
Setting the Ground Plane
Type of Ground Plane
Auto (default setting)
When chosen from the dropdown, Motive will automatically recognize the ground plane you are using.
Detected Device
On occasion Motive will recognize a ground plane as a different ground plane. When this occurs, you can choose the appropriate ground plane from the Detected Device's dropdown.
Custom
You can create your own custom ground plane by positioning three markers in a right triangle shape. To refine the position, change the vertical offset (how far from the ground are the markers on its base.
Rigid Body
It is also possible to create a ground plane from a Rigid Body. Select the Rigid Body you wish to use. Motive will use the pivot point of the Rigid Body as the ground plane.
Refine Ground Plane
By toggling the white dot at the bottom of the Calibration pane, you can access the Refine Ground Plane window.
It is possible to refine the ground plane. To do this, you'll want to lay out additional markers in the capture volume. It is important to use markers of the same dimension and height for an accurate refinement. This allows Motive to make sure that the ground plane is level.
Translate and Rotate
By further toggling the white dot at the bottom of the Calibration pane, you can access the Translate and Rotate window.
To further position the ground plane, you can manually enter translate and rotate values. This step is typically not necessary for an accurate ground plane placement.
Continuous Calibration
Enabled
Status
Idle
When the status is Idle, Motive is waiting to initiate continuous calibration.
Sampling
Motive is sampling the position of at least four markers.
Evaluating
Motive is calculating the newly acquired samples.
Anchor Markers
By toggling the white dot at the bottom of the Calibration pane, you can switch to the anchor marker window.
Active anchor markers can be set up in Motive to further improve continuous calibration. When properly configured, anchor markers improve continuous calibration updates, especially on systems that consists of multiple sets of cameras that are separated into different tracking areas, by obstructions or walls, without camera view overlap. It also provides extra assurance that the global origin will not shift during each updates; although the continuous calibration feature itself already checks for this_._
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