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674 Chapter 12: Animation
trackerasthisautomaticallyestablishesaninitial
search bound for the tracker gizmo.
Delete Track er—Deletes the selected tracker from
thelistandtheMoviewindow.
Tracker Setup group
Sets up the parameters for the cur rently selected
tracker.Anytrackeryoucreatewilltakeitsinitial
parameters f rom the cur rent va lues in this g roup.
Scene object—Associates a tracker with a scene
pointobjectthatcorrespondstotheimagefeature
in the Mov ie window. Pressing this button puts
3ds Max into standard object picking mode. When
you’ve selected the object, the entry in the t racker
listandthetextinthebuttonchangetothenameof
the s elected object. You can change the connected
object at any time by pressing this button.
It’s recommended that you use point or CamPoint
helper objects, although you can use any 3ds Max
object. The tracker uses the pivot point of the
selected object as the correlation reference point
during the match computation.
When you set up a tracking project, you can make
the t racker save the setup in a .mot settings file.
The association b etween tracker and scene point
object that you set up here is saved as a scene
objectname.Ifyoureloadthemovieinthetracker,
the object association is reestablished using the
object’s name. This means you must be careful to
name the point objects uniquely, otherwise you
might establish incorrect associations. Further,
you must load the working scene in 3ds Max before
opening the movie in the camera tracker utility, s o
the named objects can be found. If you happen
to open the movie first, the object names in the
Tracker list will all read "<none>". Simply reopen
the movie in the tracker and it will establish the
connections correctly.
Match weight—Sets the camera matching priority
separately for each tracker. Use this to improve
the m atch accuracy for features close to where
a computer g r aphics generated element will b e
inserted. It helps to minimize sliding and jitter in
that part of the scene.
The match-move algorithm works by adjusting
the camera to min imize the error between the
featu re objects seen through the camera and
their ass ociated feature points in the movie
plate. With all weights set to 1 , the algorithm
randomly distributes the error between all t he
object projections and their tracking features.
If you bump the Match Weight of a tracker, it
redistributes the error in favor of that track er,
reducing the distance between that tracker’s
feature and object projection, while possibly
increasing the er ror in other trackers. If you bump
weights on two or more features, the locking
may progressively lessen, since the a lgorithm
distributes the improvements be tween the
high-weight trackers. Use weights of two to six to
get a good lock.
Ma x M ov e/Fr a me—Sets the maximum number
of pixels that the tracked feature moves f rom
frame-to-frame over the entire tracking range
and establishes an init ial motion search bounds
box for newly created t r ackers. You can also set
thisdynamicallybyadjustingthemotionsearch
bounds box directly in the Movie window.