Instance Segmentation

Annotating instance segmentation involves drawing polygons. Simply click on the image to start a label, and close the path to finish drawing. Double-click on a label to select it.

Dragging the midpoint on an edge turns the midpoint into a vertex. Click the midpoint of an edge while pressing c makes the edge a bezier curve. You can adjust the control points to get tight-fitting curves. To revert back to a normal edge, click on a control point while pressing c.

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Drawing a segmentation label

Sometimes an instance can be divided into multiple parts in the image due to occlusion. To link different polygons, select a segmentation label, and press Ctrl-L (Cmd-L for Mac users) or the Link button to start linking. Click all labels that you want to link, and hit Enter to finish linking.

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Linking segmentation labels

Segmentation labels often share borders with each other. To make segmentation annotation more convenient, Scalabel supports vertex and edge sharing. When drawing a segmentation label, adding a new vertex at the position of an existing vertex shares the reference of the two vertices. The edge between two vertices that are both shared by two segmentation labels will also be shared. When adjusting a vertex or an edge with shared reference, all segmentation labels involved will be changed accordingly.

Quick Draw is a useful tool for border sharing. When drawing a segmentation label that needs to share a border with an existing label, press Ctrl-D (Cmd-D for Mac users) or the Quick Draw button to start Quick Draw mode. First select a polygon to share the border with, and then select the starting vertex and the ending vertex of the shared border. Press Alt to toggle between two possible shared paths. Hit Enter to end Quick Draw.

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Quick Draw

To delete a single vertex, click on the vertex while pressing d. When drawing a segmentation label in progress, pressing d deletes the last vertex drawn on the image.

Lane Marking

Lane marking is similar to segmentation labeling, except that the path is not closed. Hit Enter to finish drawing a label.

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Lane marking

Drivable Area

Similarly as other instance segmentation tasks, you can annotate the drivable area in the image. Details about the drivable area can be found in this blog.