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678 Chapter 12: Animation
can u se this detection can be us ed both during a
manual tracking review (see Batch Track Rollout
(page 2–678))orduringactualtrackingtocorrect
errors using the Resample On Error control in the
Motion Trackers setup rollout (page 2–673).
Inter face
Match Error—A sum-of-differences-squared
measureinRGBspaceofthebestmatchin
thecurrentframetothefeaturetargetfrom
the previous keyframe. The error shown is a
percentage of the maximum possible image
difference. Good matches are usually below 0.05
percent.
Variance Delta—The difference in RGB color
variance b etween the feature target image and
the current b est match. This measures whether
the t arget and match have similar color ranges
and can compensate for m istakes made by the
sum-of-differences measure.
Jump Delta—The tracker computes a moving
average for the preceding five frames and measures
the difference between that average and the jump
in the current frame. If this difference exceeds the
current Jump delta threshold, a potent ial error is
flagged. If the threshold is set to five, any jump
inthecurrentframethat’sfivepixelsmorethan
the average jump in the last five frames is flagged.
This picks up sudden accelerations rather than just
large jumps.
You can adjust the thresholds as needed and enable
or disabled individual measures in the detector
using the check boxes to the left of each measure.
Camera Track er: Batch Track
Rollout
Utilities panel > Utilities rollout > More button > Utilities
dialog > Camera Tracker > Batch Track rollout
The Camera Tracker utility’s Batch Track rollout
performs feature hands-off tracking once the
trackers have been set up. You c an set up a set of
trackers, start a batch tracking of them all, and
then use the other tools in this p anel to check for
and review detected tracking errors. This panel
also checks for tracking completion.
Procedure
To review and cor rect track ing errors:
1.
Select an error in the list.
2. Browse through the er rors in sequence by
repeatedly clicking Next, under the l ist.
3. When you’ve selected an er ror, the associated
tracker gizmo is selected and brought into view
andthemovieissettotheframeatwhichthe
potent ial error was detected.
4. If there is indeed an error, adjust the gizmo
in the Movie window to correct it, and place
anewkeyframe.
5. If inspection shows that there isn’t an er ror,
the thresholds may be set too finely, so try
adjusting the associated threshold and running
CheckStatusagain. Thisisoftenagoodway
tocalibratethethresholdsforyourscene,but
be careful not to increase them too much and
miss a real error.
6. To clear an entry out of the list, click the Clear
button. This is basically a cosmetic action
that removes items from the l ist t hat you’ve
either fixed or determined are not errors while
working through the potential errors. If you
perform a Check Status again, some of the
errors ma y show up as well.