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676 Chapter 12: Animation
Set Stop—
Sets the end of the ac tive frame range
for a tracker .
You use the Set Start and Set Stop buttons in the
Setup box together with the Movie Stepper rollout
to set the active range. Pressing the buttons will
set the start or stop point at the frame currently
shownintheMovieStepper.
Tracke r Keyframes and Position D ata
Any time you manually position a tracker gizmo,
suchasatthefirstframeoratsometrackingerror,
youcreateaspecialkeyframeposition.Thetracker
never attempts to reposition these keyfra mes, but
uses them as start points for the frames that follow
them up to the next keyframe. At keyf rames, you
can adjust the position and the feature or search
bounds.
During tracking, the selected feature at a keyframe
is sampled and that feature becomes the search
target for subsequent frames. Using any adjusted
search bounds up until the next key f rame,
prov ides the star t point, target feature, and search
bounds box for the frames that follow.
Thepositiondataforeachframeineachgizmo
canbeoneofthreepossibilities:
•Akeyframedefininganewstartposition,target
feature image, and search bounds box.
• A tracked position.
•Unknown.
Allframepositionsexceptthefirstareinitially
unknown and will be named as t racking proceeds
or gizmos are posit ioned. When you manually
set a keyframe, any previously tracked positions
followingthatkeyframeupuntilthenextkeyframe
are deleted and so become unk now n . The
Complete Tracking button in the Batch Track
rollout searches for unknown positions in the
currently enabled trackers and tr acks those frames.
TheCheckStatusbuttoninthesamerollout
checks for any currently unknown positions as
well as tracking errors. See Batch Track Rollout
(page 2–678).
Camer a Tr ack er: M ovie Stepper
Rollout
Utilities panel > Utilities rollout > More button > Utilities
dialog > Camera Tracker > Movie Stepper rollout
The Camera Tracker utility’s Movie Stepper rollout
browses through the movie during the tracking
phase either to set start and stop frames, to review
tracking results or to manually perform a track
over a sequence of fr ames. The Movie Stepper
rollout consists of a frame counter, a set of stepper
buttons, and some option check boxes.
Interfa ce
Movie Frame Counter —Advances the Movie
window to the designated frame.
VCR controls—Navigates through the movie in the
Movie window:
<<—Steps to the start frame of the selected tracker.
<10—Steps back 10 frames.
<—Steps back one frame or keyframe if Step
Keyframesisturnedon.