In
this example, you want the object to track only the changes in position
of the reference feature. The object follows the X and Y motion
without undergoing changes in scale or rotation.
For example, you have
footage of a bird flying and you want to attach a small blue arrow
to the to top of the bird's wing. You can add an image of an arrow from
the File browser to the footage. You need to track the arrow to
one point on the wing. Note in this example there are no scale or
rotation changes to the wing.
NoteAlthough this example
uses the 2D transform tool, there are many other tools that have
position and translation parameters that can be tracked, such as Reaction,
Panner, the Garbage Mask, Remove Dust tool, and the Warp 2D tool.
To track position:
- Play the footage a few times to evaluate
what reference feature you want to use and if there are any foreseeable
problems for the tracking.
- Determine a good reference frame. In
this example, it is the first frame of the footage.
- From the Tools tab, drag a Tracker Analyzer
tool to Schematic. You do not need to attach it directly to the
dependency graph as it is not going to be modifying the image but
rather, you will be using data associated with that tracker. Once
you have finished tracking, you can remove the tracker tool from
the dependency graph.
- Position the Reference and Analyzer boxes
on the position you want tracked. In the case below, the tip of
the bird's wing has been selected.
- Click Analyze Forward to track reference
position in the footage.
- From the Tools tab, open the Composition
folder and drag a Blend and Comp node to the dependency graph between
the footage node and the Output node.
- Connect the bird footage to the Back
input of the Blend and Comp node.
- The image of the arrow is then dragged
into Schematic and linked to the composition and attached to the
Front input of the Blend and Comp node.
- A 2D Transform tool is then added between
the arrow image and the Blend and Comp node. Select the 2D Transform
node.
- From the 2D Transform tool UI, select
1 Point from the Transform Type menu. The Source and Destination
coordinate value editors appear.
- The Source X and Y coordinates are set
to 0, 0 fixing the center of the arrow image exactly at the center
of the tracker.
- To set the Destination transform, right
click on the Destination label and select Set Tracker. The Tracker
Selector appears. Expand the Tracker and select the Tracker Analyzer.
- Enable Use Offset and click the Link
button.
The arrow is tracked
to the tip of the bird's wing. Play the footage.
