Point cloud Object tracking

Create object tracks to track them across frames and use automatic interpolation to drastically reduce annotation time.

If you want to identify an object that appear across multiple frames and label it with a consistent ID, use tracking. When setting up the ontology, you can mark a label as a Track . When you annotate an object with a class marked as Track, it is automatically converted to a Track object. Currently, tracks are only supported for Cuboid annotations.

All the usual methods of drawing a cuboid are available for tracks as well.

Label Settings

In addition to marking an object as a track, you can also lock the dimensions of a label and specify its default dimensions.

Lock dimensions (Only applicable to tracks)

Many objects in the real world are rigid - that is, their shapes and dimensions do not change over time. For example, a car's position and orientation may change over time, but its dimensions will stay the same. When a label's dimensions are locked, all objects of that class will maintain the same dimensions across all frames. If you update the size of an object in one frame, the same size will be automatically applied to all the frames the object appears in. An object with locked dimensions is specified with a lock icon in its annotation card.

Default dimensions

You can specify reference dimensions for a label if you expect all objects in your dataset to be of roughly the same size. You can then draw cuboids of this size by holding Shift and placing the cuboid anywhere in the point cloud. More details here.

Managing a track annotation object

When you draw the initial cuboid in a track, it will be automatically copied to all the subsequent frames. All these cuboids will have the same object ID.

Ending a track

To mark the end of a track, simply click on the End track icon - this is the right most icon the tool panel in the bottom section of the card, as shown above. Note that you should end the track in the frame after the last frame an object appears in. For example, if a car last appears in frame 12, you should end the track in frame 13.

Labeling static objects

If an object appears in multiple frames, but its position relative to the ego-vehicle does not change, you can mark it as a static object by clicking on the Lock button located on the right end of the section with object dimensions.

Occluded objects

If an object disappears for a frame but is otherwise part of the track, you can mark it as occluded. To do this, use the button to the left the End track button.

Navigation

A frame in which you make any changes to an object is called a key-frame. You can navigate between the key-frames by using the next and previous buttons, located either side of the lock icon.

The frames on either side of these navigation icons, take you to the first and last frame of the track.

You can hover over any button to display a Tooltip specifying what the button does.

Automatic Interpolation

Automatic interpolation is automatically started as soon as you label at-least 2 frames in a track.

Interpolation can be used in two labeling flows:

Labeling flow 1

1. Label the first frame in which an object appears.

2. Adjust its position/size in the next frame.

3. Automatic interpolation will now adjust the cuboid in all subsequent frames.

4. If you adjustments in any of the subsequent frames, other frames will also be automatically adjusted.

Labeling flow 2

1. Label the first frame in which an object appears.

2. Skip a few frames.

3. Adjust the cuboid/size after a few frames.

4. All frames in between will be automatically adjusted.

5. Any subsequent frames will also be adjusted automatically.