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646 Chapter 12: Animation
process. This mechanism allows you to match a
move in which the view passes through a field
of features with only some of them (at least six)
visible at any time.
6. (Optional) Set up manual key frames for each
tracker at f rames in which the feature radical ly
changes motion or shape or is briefly occluded
and so might be difficult for the computer
to track. If you want, you can do this after
a tracking attempt indicates where tracking
errors occurred.
7. Perform the feature track using the Batch
Trackrollout.Thisisoftenaniterativeprocess:
correcti ng for t r acking errors by tuning start
and stop f r ames or manually repositioning the
gizmo and mot ion search b oxes at error frames.
When you reposition a gizmo at some frame,
you establish a new target feature image and
subsequent frames up to the next keyframe will
be retracked. You can use the error detecting
features in the tracker to step through possible
tracking errors. When complete, this process
builds a table of 2D motion positions for each
feature. You can save this to disk using the Save
button on the Movie rollout.
8. Choose the camera that will be matched in
theMatch-Moverollout,selectwhichcamera
parameters you want to estimate, set the
movieandsceneanimationframerangesand
perform the match. This generates a keyframed
animation of the selected camera parameters.
After camera tracking, scene geometry (the character)
matches the filmed background.
9. Check the match for obvious errors and review
the tracker gizmo positions at these frames.
You can manually adjust gizmos at these frames
and the matcher interactively recomputes the
camera position.
10. (Optional) Apply smoothing to selected camera
parameters and recompute a compensating
match for the other parameters.
The Camera Tracker also has the ability to animate
3ds Max geometry to follow or match the video by
followingthemovementofatrackerina2Dplane.
For this type of animation scene measurements
aren’t required. Use the Object Pinning rollout of
the Camera Tracker to create this type of tracking.
R equi rement s for Camer a Tra ck i ng
Tousethecameratracker,youneedthefollowing:
• Moviefootageinoneofthefileformatsthat
3ds Max supports such as AVI, MOV, or FLC.
If you have sequential still images, you can use
anIFL(ImageFileList).Thefileselectorcan
automatically generate an IFL file by selecting
thefilenameandturningonthesequence
button. Or use the
IFL Manager Ut i lit y (page
3–668)
to create an IFL file.