8

Camera Tracker: Motion Trackers Rollout 651
New Tracker —
Creates a new movie feature tr acker.
This places a feature tracker gizmo in the center of
the Movie window and a new entry in the tracker
list. The new tracker takes on the parameters
currently displayed under Tracker Setup. You
can change these parameters after you create the
tracker, but it’s often useful to set the Max Move
Per Frame parameter prior to creating the new
trackerasthisautomaticallyestablishesaninitial
search bound f or the tracker gizmo.
Delete Track er—Deletes the selected tracker from
thelistandtheMoviewindow.
Tracker Setup group
Sets up the parameters for the currently selected
tracker.Anytrackeryoucreatewilltakeitsinitial
parameters from the current values in this group.
Scene object—Associates a tracker with a scene
pointobjectthatcorrespondstotheimagefeature
in the Movie window. Pressing this button puts
3ds Max into standard object picking mode. When
you’ve selected the object, the entry in the tracker
listandthetextinthebuttonchangetothenameof
the selected 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 tracker save t he setup in a
.mot settings fi le.
The association between tracker and scene point
object that you set up here is saved as a scene
object name. If you reload the movie in the tracker,
the object association is reestablished using the
object’s name. This means you must b e careful to
name the point objects uniquely, otherwise you
might establish incorrect associations. Fur t her,
you must load the working scene in 3ds Max before
opening the movie in the camera tracker utility, so
the named objects c an 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 match accuracy for features close to where
a computer graphics generated element w il l be
inserted. It helps to minimize sliding and jitter in
that part of the scene.
The mat ch-mov e algorithm works by adjusting
the camera to minimize the error between the
featu re objects seen through the camera and
their associated feature points in the movie
plate. With a l l weights set to 1, the algorithm
randomly distributes the error between all the
object projections and their tracking features.
If you bump the Match Weight of a tracker , it
redistributes the error in favor of that tracker,
reducing the distance between that tracker’s
feature and object projection, while possibly
increasing the error in other trackers. If you bump
weights on two or more features, the locking
may progressively lessen, since the a lgorithm
distributes the improvements between the