User Guide

CHAPTER 13
406
Using Property and Tracking Controls (PB only)
• To correct a single frame, drag the feature region or track point to new locations. Alt-
drag (Windows) or Option-drag (Mac OS) the feature region to move it without moving
the track point. Use the Details section of the window to monitor the feature region
position. The tracker automatically updates the previous tracking data to this new feature
region/track point position.
• To correct several contiguous frames, drag the feature region or track point to new
locations as described above and click Analyze. Watch the tracking to make sure it is
accurate. If not, press any key to stop tracking, adjust the feature region, and begin again.
3 To preview tracking, press the spacebar.
4 When you are satisfied with the track, click Apply to copy keyframes to the selected
layer.
To correct drifting by modifying tracking settings:
1 Drag the current-time indicator to the last well-tracked frame.
2 Click Options and change the following settings:
• If colors change in the feature region, increase the Track Adaptiveness value.
• Select Process Before Match, select Blur, and then type a value of 2 to 3 pixels. Select
Enhance if the edges of the feature are fuzzy. Deselect the Blur option if you want to use
Subpixel Matching.
• Choose a value from 1/2 to 1/16 for Subpixel Matching. A smaller fraction increases the
accuracy of the tracker but also increases tracking time.
• If the area to be tracked has high contrast, change the Use option to Luminance. Try
Saturation if the area has a high concentration of color.
• If the area is partially obscured during tracking, set a tolerance value for Extrapolate
Motion if Accuracy Is Below_%. Determine the proper value by creating a trial track and
then examining the accuracy displayed in the Tracker controls panel for any frames with
an obscured feature region. Type a value that is slightly larger than the largest accuracy
value for the problem frames.
• If you can clearly track backward from some point at the end of the motion, select Track
in Reverse. When used with forward tracking, Track in Reverse can help isolate problem
areas where the Tracker controls can’t maintain a good track.
UG.book Page 406 Wednesday, February 21, 2001 12:05 PM