Labeling
This page provides basic description of marker labels and instructions on labeling workflow in Motive.
Labeling: Basic Concept
Marker Label
Marker labels are basically software name tags that are assigned to trajectories of reconstructed 3D markers so that they can be referenced for tracking individual markers, Rigid Bodies, or Skeletons. Motive identifies marker trajectories using the assigned labels. Labeled trajectories can be exported individually, or combined together to compute positions and orientations of the tracked objects. In most applications, all of the target 3D markers will need to be labeled in Motive. There are two methods for labeling markers in Motive: auto-labeling and manual labeling, and both labeling methods will be covered in this page.
Monitoring Labels
Labeled or unlabeled trajectories can be identified and resolved from the following places in Motive:
Labeling Methods
There are two approaches to labeling markers in Motive:
Auto-label pipeline: Automatically label sets of Rigid Body markers and Skeleton markers using calibrated asset definitions.
Auto-label
Rigid body and Skeleton asset definitions contain information of marker placements on corresponding assets. This is recorded when the assets are first created, and the auto-labeler in Motive uses them to label a set of reconstructed 3D trajectories that resemble marker arrangements of active assets. Once all of the markers on active assets are successfully labeled, corresponding Rigid Bodies and Skeletons get tracked in the 3D viewport.
The auto-labeler runs in real-time during Live mode and the marker labels get saved onto the recorded TAKs. Running the auto-labeler again in post-processing will basically attempt to label the Rigid Body and Skeleton markers again from the 3D data.
Auto-labeling Steps
From Data pane
Right-click to bring up the context menu
Click reconstruct and auto-label' to process selected Takes. The this pipeline will create a new set of 3D data and auto-label the markers from it.
This will label all the markers that matches the corresponding asset definition.
Auto-labeler Settings
Marker Sets
Since creating rigid bodies, or skeletons, groups the markers in each set and automatically labels them, Marker Sets are not commonly used in the processing workflow. However, they are still useful for marker-specific tracking applications or when the marker labeling is done in pipelines other than auto-labeling. Also, marker sets are useful when organizing and reassigning the labels.
Create MarkerSet
Adding Labels
Labels pane
QuickLabel Mode
Labeling using the QuickLabel Mode
Under the drop-down menu in the Labels pane, select an asset you wish to label.
All of the involved markers will be displayed under the columns.
From the label list, select unlabeled or mislabeled markers.
Hiding Marker Labels
General Labeling Steps
Labeling Tips
When working with skeleton assets, label the hip segment first. The hip segment is the main parent segment, top of the segments hierarchy, where all other child segments are associated to. Manually assigning hip markers sometimes help the auto-labeler to label the entire asset.
Using Combined Reconstruction and Auto-label Pipeline
Step 4. Select an asset that you wish to label.
Step 5. From the label columns, Click on a marker label that you wish to re-assign.
Step 6. Inspect behavior of a selected trajectory and its labeling errors and set the appropriate labeling settings (allowable gap size, maximum spike and applied frame ranges).
Step 7. Switch to the QuickLabel mode (Hotkey: D).
Step 9. When all markers have been labeled, switch back to the Select Mode.
Using Standalone Reconstruction Pipeline and Auto-label Pipeline Separately
Step 1. Start with 2D data of a captured Take with model assets (Skeletons and Rigid Bodies).
Step 3. Examine the reconstructed 3D data, and inspect the frame range where markers are mislabeled.
Step 5. Unlabel all trajectories you want to re-auto-label.
Step 6. Auto-Label the Take again. Only the unlabeled markers will get re-labeled, and all existing labels will be kept the same.
Step 7. Re-examine the marker labels. If some of the labels are still not assigned correctly from any of the frames, repeat the steps 3-6 until complete.
Labeling Error Fix
The general process for resolving labeling error is:
Identify the trajectory with the labeling error.
Determine if the error is a swap, an occlusion, or unlabeled.
Resolve the error with the correct tool.
Swap: Use the Swap Fix tool ( Edit Tools ) or just re-assign each label ( Labels panel ).
When manually labeling markers to fix swaps, set appropriate settings for the labeling direction, max spike, and selected range settings.
Occlusion: Use the Gap Fill tool ( Edit Tools ).
Unlabeled: Manually label an unlabeled trajectory with the correct label ( Labels panel ).
Sample Scenarios and Tutorial Videos
Sample Scenario 1 :: All Good
When recorded 3D data have been labeled properly and entirely throughout the Take, you will not need to edit marker labels. If you don't have 3D data recorded, you can reconstruct and auto-label the Take to obtain 3D data and label all of the skeleton and rigid body markers. If all of the markers are well reconstructed and there are no significant occlusions, auto-labeled 3D data may be acceptable right away. In this case, you can proceed without post-processing of marker labels.
Recorded 3D data has no gaps in the labels, or the Reconstruct and Auto-label works perfectly the first time without additional post-processing.
Done.
Sample Scenario 2 :: Labeling errors in the middle of a Take
When skeleton markers are mislabeled only within specific frame ranges of a Take, you will have to manually re-label the markers. This may occur when a subject performs dynamic movements or come into contact with another object during the recorded Take. After correcting the mislabeled markers, you can also use the auto-labeler to assign remaining missing labels.
Start with recorded 3D data or Reconstruct and auto-label the Take to obtain newly labeled 3D data.
Inspect the Take to pick out the frame ranges with bad tracking.
Scrub the timeline to a frame just before the bad tracking frame range.
Scrub the timeline to a frame after the bad tracking frame range.
Manually label the same skeleton.
Auto-label the Take.
Check the frames again and correct any remaining mislabels using the Labeling pane.
Sample Scenario 3 :: Skeletons never acquire perfectly throughout a Take
For Take(s) where skeletons are never perfectly tracked and the markers are consistently mislabeled, you will need to manually assign the correct labels for the skeleton asset(s). Situations like this could happen when the skeleton(s) are never in an easily trackable pose throughout the Take (e.g. captures where the actors are rolling on the ground). It is usually recommended that all skeleton ‘’Takes’’’ start and end with T-pose in order to easily distinguish the skeleton markers.
This also helps the skeleton solver to correctly auto-label the associated markers; however, in some cases, only specific section of a Take needs be trimmed out, or including the calibration poses might not be possible. Manually assigning labels can help the auto-labeler to correctly label markers and have skeletons acquire properly in a Take.
You will get best results if you manually label the entire skeleton, but doing so can be time-consuming. You can also label only the mislabeled segment or the key segment (hip bone) and run the auto-labeler to see if it correctly assigns the labels with the small help.
Start with recorded 3D data or Reconstruct the Take.
Check to see if all markers are correctly assigned throughout the take. If not, re-label or unlabel, any mislabeled markers and run auto-label again if needed.
Sample Scenario 4 :: Mislabeling/unlabeling of a marker due to occlusions
Marker occlusions can be critical to the auto-labeling process. After having a gap for multiple frames, occluded markers can be unlabeled entirely, or nearby reconstructions can be mistakenly recognized as the occluded marker and result in labeling swaps or mislabels. Skeleton and rigid body asset definitions may accommodate labeling for such occlusions, but in some cases, labeling errors may persist throughout the Take. The following steps can be used to re-assign the labels in this case.
Start with recorded 3D data or Reconstruct and auto-label the Take
Examine through the Take, and go to a frame where markers are mislabeled right after an occlusion.
Using the Quick Label Mode, correct the labeling errors.
Move onto next occluded frames. When the marker reappears, correct the labels.
After correcting the labels, Auto-label the Take again.
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