Autodesk 62205-051408-9001 User Guide - Page 717

Tracker Data, Tracking Strategies, x, y pair, expressing the motion of the reference

Page 717 highlights

Advanced Tracking Techniques ❚❘❘ Tracker Data Tracker data contains information about the Trackers and their frame-to-frame movements during the analysis. This data appears in the Timeline Tracker category when you add a Tracker. This data is used to apply motion to the element that you are tracking. The Tracker category contains a Reference folder, a Track folder, a Shift folder, and a Tolerance channel. (x,y) pair, expressing the motion of the reference feature between two frames. You can watch the shift values update dynamically as the track progresses to help you gauge how steady the track is. Note: When you turn off the Tracker, the data is no longer needed and the Tracker category is removed from the Timeline. To watch the shift values dynamically update: 1. In the Timeline, open the folder(s) for the Tracker(s) you want to monitor, and then open the Shift folder to see the shift values. 2. Start tracking and note how the shift values update as you track. The Reference folder contains channels for the position of the reference box, its width, its height, and its type. It also contains delta X and delta Y channels. The Track folder contains channels for the position of the center of the tracker box, its width, and its height. The Shift folder contains channels for the X and Y shift values, and a channel for confidence. Confidence is a measure of how much confidence the Tracker has in the match it finds. Shift values are values, in pixels, of how much the reference feature has moved. The shift values are an Tracking Strategies In most of these strategies, you pause the analysis and then return to a previous frame, erasing bad keyframes as you go. Use this Strategy When Change reference feature The Tracker loses its reference feature early on in the analysis. Example: the chosen reference feature moves too unpredictably and abruptly. See Changing the Reference Feature. Adjust size of tracker box The reference feature moves outside of the tracker box from frame to frame, but the motion of the reference feature is predictable. Example: a child on a see-saw. See Adjusting the Size of the Tracker Box. Adjust tolerance The reference feature is hidden by another object for several frames and it does not change direction while it is hidden. Example: a car passing behind a tree. See Adjusting Tolerance. Change reference type to Roaming The appearance of the reference feature gradually changes as the clip advances. Example: a dramatic lightening or darkening of the reference feature takes place. See Using a Roaming Reference Box. 701

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Advanced Tracking Techniques
701
❚❘❘
Tracker Data
Tracker data contains information about the
Trackers and their frame-to-frame movements
during the analysis. This data appears in the
Timeline Tracker category when you add a Tracker.
This data is used to apply motion to the element that
you are tracking.
The Tracker category contains a Reference folder, a
Track folder, a Shift folder, and a Tolerance channel.
The Reference folder contains channels for the
position of the reference box, its width, its height,
and its type. It also contains delta X and delta Y
channels.
The Track folder contains channels for the position
of the center of the tracker box, its width, and its
height.
The Shift folder contains channels for the X and Y
shift values, and a channel for confidence.
Confidence is a measure of how much confidence
the Tracker has in the match it finds.
Shift values are values, in pixels, of how much the
reference feature has moved. The shift values are an
(x,y) pair, expressing the motion of the reference
feature between two frames.
You can watch the shift values update dynamically as
the track progresses to help you gauge how steady
the track is.
Note:
When you turn off the Tracker, the data is no
longer needed and the Tracker category is removed
from the Timeline.
To watch the shift values dynamically update:
1.
In the Timeline, open the folder(s) for the
Tracker(s) you want to monitor, and then open
the Shift folder to see the shift values.
2.
Start tracking and note how the shift values
update as you track.
Tracking Strategies
In most of these strategies, you pause the analysis
and then return to a previous frame, erasing bad
keyframes as you go.
Use this
Strategy
When
Change
reference
feature
The Tracker loses its reference feature
early on in the analysis.
Example: the chosen reference feature
moves too unpredictably and abruptly.
See
Changing the Reference Feature
.
Adjust size of
tracker box
The reference feature moves outside of
the tracker box from frame to frame, but
the motion of the reference feature is
predictable.
Example: a child on a see-saw.
See
Adjusting the Size of the Tracker Box
.
Adjust tolerance
The reference feature is hidden by
another object for several frames and it
does not change direction while it is
hidden.
Example: a car passing behind a tree.
See
Adjusting Tolerance
.
Change
reference type
to Roaming
The appearance of the reference feature
gradually changes as the clip advances.
Example: a dramatic lightening or
darkening of the reference feature takes
place.
See
Using a Roaming Reference Box
.