Confidence

Confidence

At the bottom of Motion Tracker Options is a submenu
of options related to After Effects’ mysterious Confi dence
settings. Every tracked frame gets a Confi dence setting, an
evaluation of how accurate the track was at that frame. This
may or may not be indicative of the actual accuracy, but my
experience is that you’re almost guaranteed to be fi ne with
values above 90%, and real problems will cause this value
to drop way down, even to 30% or less.

Depending on this setting, you can
. Continue Tracking. Just power ahead no matter what.
. Stop Tracking. So you can reset the tracker manually
right at the problem frame.
. Extrapolate Motion. Let After Effects guess based on
how it was moving on the previously tracked frames.

This is for cases where the tracked item disappears for
one or a few frames.
. Adapt Feature. The default behavior is to go ahead and
change the reference Feature region to the previous
frame if there is low Confi dence, indicating the feature
has suddenly changed appearance.



Whichever you choose, you also have the option to go back
to the frame where a track went wrong, reset the feature
region by hand, and restart the track.
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.
. 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.