Autodesk 62205-051408-9001 User Guide - Page 701

Snap, Tolerance, Auto Snap, Analyze Controls, Snapping to, Update the Reference Box

Page 701 highlights

Tracker Interface ❚❘❘ Roaming. It is also less flexible since it assumes little or no change to the reference feature. Roaming-Updates the contents of the reference box at each frame. Use this option when the reference feature undergoes significant changes in luma or shape cues during the clip. For example, if the reference feature undergoes lighting changes, choosing Roaming increases the chances of finding a match at each frame. Roaming is slower than Fixed since the reference box must be updated at each frame. Note: Results are often not as accurate with Roaming because very small errors in the analysis are compounded. Snap Use this button to update the contents of the reference box at the current frame. See Snapping to Update the Reference Box for a discussion of when you might use this. Tolerance Use Tolerance to set how much tolerance for error there is in locating a match for the reference box. A keyframe is only set for the frame if a match is found. If Tolerance is set to 100%, a match is always found, regardless of how wrong it may be. If Tolerance is set to 0%, a keyframe is only set for the frame if an exact match for the reference box is found. A good rule of thumb is to leave Tolerance set to 100% and then lower it if necessary. It can save time to play your clip through several times and note where 100% Tolerance might cause the Tracker to lose the reference feature. You can then lower the setting for these portions of the clip. For more information, see Adjusting Tolerance. Auto Snap If you enable Auto Snap when the Tracker does not have enough confidence to set a keyframe, it updates the contents of the reference box with the last good match, and then searches for a match on the updated contents. Analyze Controls Use the Analyze controls to start, pause, and restart the analysis, as well as to advance the analysis by a single frame. Track Forward-Starts the analysis forward . Click the button again to toggle tracking on and off. Track Backward-Starts the analysis backward . Click the button again to toggle tracking on and off. For information on when to use Track Backward, see Analyzing Backward. One Frame Forward-Advances the analysis forward by a single frame . For information on when to use analyze One Frame Forward, see Editing the Tracker's Path. One Frame Backward-Advances the analysis backward by a single frame . For information on when to use analyze One Frame Backward, see Editing the Tracker's Path. Tracking forward and then backward, or vice versa, or omitting frames in the middle of your sequence without setting a new reference will produce incorrect results. 685

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Tracker Interface
685
❚❘❘
Roaming. It is also less flexible since it assumes little
or no change to the reference feature.
Roaming
—Updates the contents of the reference
box at each frame. Use this option when the
reference feature undergoes significant changes in
luma or shape cues during the clip. For example, if
the reference feature undergoes lighting changes,
choosing Roaming increases the chances of finding a
match at each frame.
Roaming is slower than Fixed since the reference box
must be updated at each frame.
Note:
Results are often not as accurate with
Roaming because very small errors in the analysis
are compounded.
Snap
Use this button to update the contents of the
reference box at the current frame. See
Snapping to
Update the Reference Box
for a discussion of when
you might use this.
Tolerance
Use Tolerance to set how much tolerance for error
there is in locating a match for the reference box. A
keyframe is only set for the frame if a match is found.
If Tolerance is set to 100%, a match is always found,
regardless of how wrong it may be. If Tolerance is set
to 0%, a keyframe is only set for the frame if an exact
match for the reference box is found.
A good rule of thumb is to leave Tolerance set to
100% and then lower it if necessary. It can save time
to play your clip through several times and note
where 100% Tolerance might cause the Tracker to
lose the reference feature. You can then lower the
setting for these portions of the clip.
For more information, see
Adjusting Tolerance
.
Auto Snap
If you enable Auto Snap when the Tracker does not
have enough confidence to set a keyframe, it updates
the contents of the reference box with the last good
match, and then searches for a match on the updated
contents.
Analyze Controls
Use the Analyze controls to start, pause, and restart
the analysis, as well as to advance the analysis by a
single frame.
Track Forward
—Starts the analysis forward
.
Click the button again to toggle tracking on and off.
Track Backward
—Starts the analysis backward
. Click the button again to toggle tracking on
and off. For information on when to use Track
Backward, see
Analyzing Backward
.
One Frame Forward
—Advances the analysis
forward by a single frame
. For information on
when to use analyze One Frame Forward, see
Editing
the Tracker’s Path
.
One Frame Backward
—Advances the analysis
backward by a single frame
. For information
on when to use analyze One Frame Backward, see
Editing the Tracker’s Path
.
Tracking forward and then backward, or vice versa,
or omitting frames in the middle of your sequence
without setting a new reference will produce
incorrect results.