2011

feature to the element that you are tracking, so that the two appear locked
together.
In all tracking except for stabilizing, the Tracker applies the shift values without
modification.
With stabilizing, the Stabilizer operator inverts the shift values, resulting in a
negation (and therefore elimination) of the motion—see
Stabilizing on page
783.
Tracking Position
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.
NOTE Although 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:
1 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.
2 Determine a good reference frame. In this example, it is the first frame
of the footage.
3 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.
4 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.
770 | Chapter 32 Tracking and Stabilizing