Solve Problems with Nulls

Solve Problems with Nulls

I almost always apply track data to a null object layer and
then use parenting to apply the motion to other layers.
This offers a bunch of advantages:
. Offset and relocate tracks: It doesn’t matter whether
the track attach point is in the right location; the
null picks up the relative motion, and any layer parented
to it can be repositioned or animated on its own
(Figure 8.9).
. Optionally lock the tracked layer once you’re happy
with it, so you don’t inadvertently move it.
. Use a Stabilization track to peg multiple object to a
scene (next section).
. Parent one motion track to another if you need to
switch to a different track target mid-shot.

One common problem is that a track is good only until a
given point in the scene, and if you then move the tracker
to search a different location, the whole track jumps. By
adding a new track and another null, you can create and
apply as many individual tracks as you like, parenting one
to the next.