Keyframe Interpolation
Keyframe Interpolation
Keyframe interpolation is the process of creating intermediate values between a set of keyframes. The keyframes are specified by you and then the values in the frames between the keyframes are automatically filled in.
In the iMerit Point Cloud tool, keyframe interpolation is used for object labels that change over time. For example, in a sequence with a moving car, the cuboid around the car moves in each frame. With keyframe interpolation, you only need to specify the label at certain key times, and the intermediate labels are created automatically.
Note: Keyframe interpolation is available for 3D cuboids (instance classes).
View the Keyframes of an Object
In the context of interpolation, a keyframe is a marker that indicates that at that frame, the state of the object is defined by the user. In other frames (that are not keyframes), the state of the object label is calculated automatically through interpolation.
Select the annotation
The keyframes are now visible in the timeline at the bottom of the editor. A normal keyframe is shown with a blue underline under the frame it belongs to.
Add a Keyframe
In the current frame
Select the object.
Make a change to the object in the editor. A keyframe containing the new changes is added automatically.
Or,
Select the object.
Press K. Without making changes, the keyframe captures the state of the object label at that frame. This means the object will not change.
Remove a keyframe
Select the object.
Go to a frame that is a keyframe
Press K
Label Occluded Objects
Sometimes an object might be occluded, in which case you might want the object to not be present in certain frames and reappear in other frames.
Create the cuboid on the object
Go to the frame where the object is last visible (in above example, frame 3)
Press K
Go to the frame where the object reappears (in above example, frame 7)
Press K
Contextual click the annotation and go to Add/Delete Annotations
Select the option which allows you to delete between the two keyframes (#4 to #5)
There are various ways to use the contextual menu of ‘Add/Delete Annotations’ to delete annotations from certain frames.
Use Instance IDs in Sequences
An Instance ID is an identifier assigned to each labeled object in a sequence. This instance ID can be used to track an object over multiple frames.
View the Instance ID of an Object
The instance ID of an object is displayed in the Class List on the left along with the classname.
When an object is selected, it is also displayed on the Status box.
Add a Instance ID to an Object
When creating an object, the user is asked to select a missing ID or create a new one.
Change the Instance ID of an Object (In all Frames)
Select the object.
Open the Annotation Details pop-up
Select +Create new.
Save. The new Instance ID replaces the old Instance ID in all frames.
Merge an Instance into another Instance
Select the object you want to merge into another instance.
Open the Annotation Details pop-up
From the Select missing instance, select the other objects instance ID
Note: Merging instances is only possible when both instances have no overlapping keyframes.
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