Apple Shake 4 - Manual (Page 726)

726 Chapter 25 Image Tracking, Stabilization, and SmoothCam
matchSpace The pixels are matched according to the correlation between the selected
color space—luminance, hue, or saturation. When an image has roughly the
same luminance, but contrasting hues, you should switch to hue-based
tracking.
You can also adjust the weight of the color channels in the matchSpace
subtree.
referenceTolerance A tracking correlation of 1 is a perfect score—there is an exact match between
the original reference frame and the sampled area. When the
referenceTolerance is lowered, you accept greater inaccuracy in your track. If
tracked keyframes are between the referenceTolerance and the
failureTolerance, they are highlighted in the Viewer. Also, in some cases,
referenceBehavior is triggered if the tracking correlation is below the
referenceTolerance.
referenceBehavior This behavior dictates the tracking area reference sample. By default, the
reference pattern is the first frame that the track is started, not necessarily the
first frame of the trackRange. The last two behaviors in the referenceBehavior
list measure the tracking correlation and match it to the referenceTolerance to
decide an action.
use start frame The new samples are compared to
the reference pattern from the first
frame of the track. If you stop tracking
midway, and start again at a later
frame, the later frame is used as the
reference sample.
update every frame The source sample is updated from
the previous frame. This usually
creates an inherent drift in the track,
as tiny errors accumulate. This
method is for movements that have
drastic changes in perspective and
scale.
update from keyframes If you are using a failureBehavior of
“predict location and don’t create
keys” or “don’t predict location,” a
keyframe is not necessarily saved
every frame. In this case, you may
only want to update from the last
frame with a valid keyframe.
update if above reference tolerance This updates the reference sample
from the previous frame if the
correlation is above the
referenceTolerance. The intent is to
update every frame unless you know
the point is obscured. If you use a
predict mode and know there are
obstructions, it keeps the reference
area from updating if the point is
completely obscured.
Parameter Description