Apple Motion 4 - Manual (Page 1302)

Some General Guidelines
The Motion tracker uses the source image for its tracking analysis. This means that the
tracker automatically uses the best search area, the best color, the best contrast, subpixel
accuracy, and so on in the clip to generate the best possible tracking data. Common
tracking strategies, such as using filter tricks, manually resizing a tracking “box” or search
area, or specifying a subpixel sampling amount are not required.
This does not mean that you do not have to work to achieve a perfect track, of course.
Use the following guidelines to help you decide what may and what may not assist you
in your tracking analysis.
What will help you:
• Removing interlacing (fields) from the footage prior to tracking. To remove the fields
from footage, select the footage in the Media tab of the Project pane, click the Media
tab in the Inspector, then choose an option from the Field Order pop-up menu.
Note: Interlacing can be present in clips stabilized using the automatic analysis mode
in the Stabilize behavior.
• Stabilizing a clip, exporting the clip, importing the clip, then stabilizing the clip again.
• Sharpening or blurring a clip or an object with a filter, exporting the clip, importing
the clip into the same group as the original footage, tracking the filtered clip, then
using that tracking data as the source for other tracking behaviors.
Note: Other filter tricks may also be helpful, such as using a filter to isolate a less-noisy
color channel of a clip or an object.
• Setting the View resolution to a lower setting, which may speed the tracking analysis
What will not help you:
• Applying any filter to a clip or object prior to tracking
• Soloing or isolating a tracked clip. This does not speed tracking analysis.
• Adding multiple Stabilize behaviors. This does not help to further stabilize an analyzed
clip, because the tracker analyzes the original source footage and not the result of an
analyzed clip (or a filtered clip).
• Converting a track to keyframes and stabilizing again
• Selecting a tracking reference feature that does not change perspective, scale, or
rotation. The Motion tracker is designed to handle changes in perspective, scale, and
rotation very well.
Tracking and Groups
There are a few special considerations when tracking groups.
1302 Chapter 19 Motion Tracking