In some
cases, you may want the object to track only a rotational change. The
Tracker requires two tracker boxes to track rotation. The first
Tracker goes over the pivot point of the rotation you want to track.
You place the second over an area that describes the axis of the
rotation you want to apply to the object.
NoteYou can also use
the 2D Transform, and the rotation parameter controls of the Garbage
Mask, Remove Dust and Warp2D tools.
To track changes in rotation only:
- Determine a good reference frame and
position the footage at that frame.
- Select the Tracker Analyzer tool from
the Tools tab and drag it 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.
- Attach the composition to the input of
the tracker.
- Add a second Tracker Analyzer
- Place the first Tracker over the pivot
point of the rotation you want to track.
- Click Analyze Forward to analyze the
footage.
- Go back to the first frame.
- Place the second tracker over an area
that describes the axis of the rotation you want to apply.
- Click Analyze Forward to analyze the
footage.
- Drag a Reaction tool from the Tools tab
and place it on the dependency graph between the footage node and
the Output node.
- With the cursor over the Reaction node,
right-click and select Add Source.
- To associate a layer with the source
you just created, select Bilinear at the bottom of the Layer Editor
and click Create.
- In the Layer Editor, right-click inside
the Z field under Rotation and select Track Rotation.
The Tracker Selector
browser appears.
- Using Ctrl +
click, select both the trackers then click Link.
The rotation has been
tracked.
NoteWhen tracking data
needs to applied to more than one layer in a composition, add an
extra axis node to the dependency graph and connect it to the appropriate
layers. Linking the axis to several layers facilitates panning multiple objects
inside a reaction. In this case, you would then click the axis node
at step 13 instead of the Layers node, and continue the procedure.
