Rigid body Assisted Labeling
Rigid body assisted labeling helps auto-labeler to create more stable trajectories by referencing individual markers to a rigid body location in post-processing of captured data. This feature could be beneficial when tracking multiple small markers (e.g. facial marker tracking) where marker swaps are more likely to occur. Small marker clusters can be trajectoried and labeled in a more stable manner by allowing the rigid body assisted labeling feature to provide more specific constraints.
Rigid body assisted labeling can be enabled under the Reconstruction settings.
Notes:
This feature does not assign actual marker labels, but it improves interconnection of reconstructed markers within different frames so that they are more clearly defined and less vulnerable to mislabeling errors. After the stable trajectories have been obtained, unlabeled markers can be manually labeled in the post-processing.
When labeling facial markers, use 4 to 5 normal size markers(larger than 10 mm) in an asymmetric pattern for the head and small face markers for the face.
Steps
1. Create an RB with the headband markers
2. Capture a recording of a cluster of small-sized markers (e.g. facial markers) next to a rigid body.
3. On reconstruction tab, set Rigidbody Assisted Labeling option to True
4. Configure other options to match your setup. A sample configuration for facial tracking is shown in the screenshot.
5. Now, you need to auto-label the Right-click the take on the project panel, Delete Marker Labels to remove the live labels, then Auto-Label. It should label face markers without swapping.
Rigid Body Assisted Labeling Settings
Default: OFF
Rigid Body Assisted Labeling can be used to optimize the labeling of markers within a region defined by a rigid body. The first step in using this feature is to create a rigid body from markers that are visible and rigidly connected. The example shown in the figure below demonstrates this for hand tracking. Five white markers are selected on the top of the wrist - which is rigidly defined. The black markers on the fingers are not rigidly defined in any fashion but are within the boundary of the Rigid Body Assisted Labeler. Labeling continuity is improved for the markers on the fingers which are given automatic labels.
Tracking of organic or flexible objects - that do not have a tracking models like the face and hand, are good candidates for Rigid Body Assisted Labeling.
Rigid Body Volume Radius
Default: 300 mm
The rigid body volume radius defines the region of space where the rigid body assisted labeling is applied. Increasing this radius will increase time needed for the auto-labeling so care should be made when setting this property.
Maximum Assisted Labeling Gap
Default: 30 frames
The maximum gap frames property defines the maximum number of frames a marker can be hidden before it is truncated or unlabeled. Increase this value if larger gaps are to be anticipated. Increasing the assisted labeling gap will increase the processing time of reconstruction. ↑
Prediction Radius (mm)
Default: 10 mm
The predication radius defines the size of the bounding region used to label markers. When labeling a marker from one frame to the next, a bounding region, relative to the rigid body, is created around each labeled marker. The labeling continuity is restricted to the bounding region from frame to frame. Increasing this can allow markers to swap if there are occlusions in the data. Decreasing this restricts labeling from frame to frame but may lead to an increase in broken trajectories. ↑
Discard External Markers
Default: False
Discards markers outside of rigid body volume.
Maximum Gap Frames
Default: 30 frames
The maximum gap frames property defines the maximum number of frames a marker can be hidden before it is truncated. Increase this value if larger gaps are to be anticipated. Increasing this setting will require longer processing time of reconstruction and auto-labeling. ↑
Discard External Markers
Default: OFF
Enabling this property will eliminate marker reconstructions outside of the region defined by the Rigid Body Volume. ↑
Dynamic Translational Constraint
Default: None
Prevents the rigid body from moving/rotation more than specified amount per frame. ↑
Max Translation (mm)
Default: 100
Distance for Dynamic Translation Constraint option.
Max Rotation (deg)
Default: 30
Angle for the Dynamic Rotation Constraint option.
Minimum Tracking Frames
Default: 20
Dynamic constraints are enabled when the rigid body is consecutively tracking more than this frame count.
Marker Filter Diameters
Default: False
Markers less than this diameter will not be used for rigid body tracking.
Minimum Diameter (mm)
Default: 10 Diameter used for Marker Filter Diameter option.
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