For an in-depth explanation of this tool, please refer to the Tracker documentation in this manual.

The differences between a Tracker Modifier and a Tracker Tool are as follows.

• The tracker modifier can only track a single pattern.
• A source image must be set for the tracker modifier.
• The tracker modifier can only output a single value and cannot be used for complex stabilization procedures.
• The default source image for the modifier is the tool immediately upstream of the tool that contains the modifier (i.e. when adding a tracker modifier to a glow tool with a loader as its input, the tracker source input will default to the output of the loader). Set a different source image for the tracker modifier by typing in the name of the tool. Alternately, drag and drop the source tool from the flow into the text box control.

Imagine that you needed to track an actor's eyes so that an unearthly, alien glow could be applied to the eyes. Add a glow tool and then create an ellipse mask in the shape of the eye.