Overview of the Polyline labeling tool in Ango Hub

The Spline labeling tool allows you to draw splines on images and videos. Splines are similar to polylines, with the exception that they smoothly curve along keypoints rather than being jagged.

How to add a Spline tool to your project

From the project’s Settings tab, enter the Label Set section.

Click on Add Category. From the list that appears, click on Spline.

A new row will appear named Spline. Click on it to expand it.

Give your Spline tool a title and description.

Enable the Required toggle if you want to force labelers to create a spline on every asset. When the toggle is disabled, labelers will be able to save and move to the next asset without creating a spline label using this class.

If you would like to ask labelers further questions, for example, if you want to show a further radio after drawing the spline, click on Add Classification and add a further classification. More on nested classifications here.

How to Draw a Spline

Click on the image where you’d like the first point of the spline to be. Click again where you’d like the second point to be, and so on. When you are done, click on the first point again or press on N on your keyboard to close the spline.

You may resize the width of each point on the spline by using the grab points on the side.

To edit a spline's points, select it by clicking on it, then drag the spline itself or one of its points.

To add new points, select the spline, then press and hold Ctrl on your keyboard, then click on the spline where you'd like to add the point.

To remove a point, select the spline, then right-click on the point you wish to delete.

You may use the keyboard shortcuts Y and U to lenghten/shorten the current point's width by 1 pixel, or Alt+Y and Alt+U to do so by 0.5 pixels.

Edge Sharing

As you draw a spline, you may activate the Edge Sharing functionality. If you do so, Ango Hub will allow you to snap the point you are about to create to the existing point of another spline.

As you draw, use the keyboard shortcut "E" or click on the "Edge Sharing" button on the top of the editor. Then, as you draw, move your cursor close to a point of an already existing spline. Ango Hub will highlight that point and allow you to, if you choose to click, quickly snap your new point to it.

Marking spline points

After having drawn a spline, you may mark certain points. This mark may have any meaning you choose to assign to it. It can, for example, be used to mark that a certain road marking is occluded in the current view.

To mark a certain point on a spline, after you have drawn a spline, click it to select it. Then, hover over the point you'd like to mark and press "B" on your keyboard. The point will be marked. You may unmark a point the same way.

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