Keypoint Connections

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What Is It?

Keypoint Connections is a feature within the Alegion video annotation platform that allows annotators to mark linked attributes throughout the duration of a scene. A common use case is that of a skeletal annotation that tracks different body parts as they move from frame to frame.


Where Is It?

Keypoint Connections can be enabled for a particular project by adjusting the project’s ontology to meet your needs. To use this feature visit Alegion Control and log in using your credentials. You will need to create a new project for this annotation, or open a previously created project in which the ontology has not yet been established. Then adjust the ontology following the steps below before importing the records you intend to annotate.


How do I Use It?

Project & Ontology

Entity Types

In Control, select the project you are wanting to annotate and navigate to the Ontology menu. There, under the Entity Types category, add a bounding box for the parent entity that all of your keypoints will be associated with (i.e. “Person 1”). Then add keypoints for all of the parts that need to be represented in the final annotation (i.e. “Left Hand”, “Left Knee”, etc.). 

Hierarchical Entity Types

To configure the connections, scroll down to the Hierarchical Entity Type section and select “Add hierarchical entity type”. From the menu that pops up, enter all of the relevant descriptors for the entity and make sure to check the “Skeletal Hierarchy” box. Under the Parent Entity Type dropdown box, select the bounding box that you created before. Then next to Child Entity Type, select the “Add new” button and select one of the keypoints you have created. The first child entity added will not yet have the ability for an adjacent entity to be selected, however, after adding a second child entity you will then be able to link the child entities to each other. Repeat this process until all related keypoints have been imported, and all adjacent entities have been marked. If you have another Hierarchical Entity that you would like to have annotated, the entire process can be repeated again using a new bounding box as a “Parent Entity Type” (i.e “Person 2). The various keypoints can be reused, but the connections will have to be reestablished for each Hierarchical Entity. 


Once all desired entities have been established and the connections configured, return to the records tab to import the assets you would like to annotate. Then either assign the task to a worker, or begin the annotation work yourself. 



Once in the annotation window, you will first need to draw the bounding box (the parent entity) for the hierarchical entity you are wanting to annotate. Once the bounding box has been established, switch to the hierarchy view on the left side of the screen. From here, you will be able to click “Add keypoint” for each keypoint that you want to be represented in the hierarchical entity. Lines will automatically populate between keypoints in accordance with the connections established in the ontology. Once placed, the keypoints can be dragged to their proper locations as the annotator moves throughout the frames. The keypoints will automatically move between their placements as the video is played, so the number of frames requiring manual placement will vary depending on the amount and fluidity of the movement in the video. Additionally, the visibility of the connections in the annotation window can be toggled by selecting the “Show Skeletons” icon on the right hand side of the screen.

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