Position, Rotation, and/or Scale
You can’t uncheck the Position toggle in the Tracker panel(thus avoiding the unsolvable riddle, what is a motion
track without Position data?), but you can add Rotation
and Scale. Enable either toggle, and a second track point is
automatically added.
Additionally tracking rotation and scale data is straightforward
enough, employing two track points instead of
one. Typically, the two points should be roughly equidistant
from the camera due to the phenomenon of parallax.
Tracks that add rotation and scale usually have features
that change appearance through the course of the shot
(because they themselves may rotate and scale). Tracker >
Options contains the Adapt Feature on Every Frame toggle.
By default, the tracker is set to adapt the track feature
if confi dence slips below 80%. Adapt Feature on Every
Frame is like restarting the track on each and every frame,
comparing each frame to the previous one instead of the
one you originally chose. For ordinary tracks this adds an
unwanted margin of error, but in a case where a feature is
changing each frame anyhow, because the scale, orientation
or blurriness is in constant fl ux, this can help.
If a track keeps slipping going forward, try starting at the
end of the clip and tracking in reverse (note that the “play”
icons in Tracker Controls go both directions). It’s best to
start where your feature is largest and most prominent
so that it doesn’t outgrow the boundaries of the Feature
region.
