Apple Shake 4 - Manual (Page 744)

744 Chapter 25 Image Tracking, Stabilization, and SmoothCam
• update if above reference tolerance: This option 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, this option keeps the reference area from
updating if the point is completely obscured.
• update if below reference tolerance: This option updates the reference sample from
the previous frame if the correlation is below the referenceTolerance. This option
basically says, “If I can’t get a good match, then resample.” This approach is
excellent for gradual perspective and scale shifts in the tracking area.
• failureTolerance: If the correlation value of the tracker’s analysis falls below this value,
Shake initiates the failureBehavior.
• failureBehavior: A pop-up menu containing the following options:
• stop: The tracker stops if the correlation is less than the failureTolerance. You can
also press Esc to manually stop tracking.
• predict location and create key: If a failure is detected, then the tracker predicts the
location of the keyframe based on a vector of the last two keyframes, and
continues tracking in the new area.
• predict location and don’t create key: Same as above, but it merely predicts the new
search area and does not create new keyframes until a high correlation is obtained.
This is excellent for tracked objects that pass behind foreground objects.
• don’t predict location: In this case, the tracker merely sits in the same spot looking
for new samples. New keyframes are not created.
• use existing key to predict location: This allows you to manually create keyframes
along your track path. You then return to the start frame and start tracking. The
search pattern starts looking where the preexisting motion path is.
limitProcessing
This button sets a Domain of Definition (DOD) around the bounding boxes of all active
trackers. Only that portion of the image is loaded from disk when tracking, so the track
is faster. This function has no effect on the final output image.
preProcess
This button toggles preprocessing on and off for the tracking area. This applies a slight
blur to reduce fluctuations due to grain. To control the blur amount, open the
preProcess subtree.
• blurAmount: A subparameter of preProcess. Sets the amount of blur applied when
preprocessing.