Autodesk 62205-051408-9001 User Guide - Page 718

26 Tracking Use this Strategy Snap to update reference box Apply effect before tracking Delete bad keyframes and let Tracker interpolate Continue analysis with a different reference feature Analyze backward When The appearance of the reference feature changes suddenly one or more times in the clip. Example: a bird flaps its wings, then folds them. See Snapping to Update the Reference Box. The quality of the reference feature is too poor for the Tracker to track it. For example, you can produce a highcontrast version of the source clip using a Color Correction filter, track the reference feature in this version, and then remove the effect when the tracking is finished. See Using Filters to Ease Tracking. The Tracker is setting incorrect keyframes and the motion of the reference feature is sufficiently predictable for Combustion to interpolate between two good keyframes. For example, find the previous good keyframe and the next good keyframe, removing all bad keyframes in between them, and let Combustion interpolate between the two good keyframes. See Deleting Bad Keyframes and Letting the Tracker Interpolate. The reference feature moves off the frame before the end of the clip. The reference feature changes to such a degree it is no longer usable. For example, an extreme zoom where the first and last frames have almost nothing in common (except perhaps a central point). See Continuing the Analysis with a Different Reference Feature. The feature you want to track grows larger or is off screen at the beginning of the clip. For example, all of your required reference features may not be visible on the first frame. Tracking backwards helps in many cases. See Analyzing Backward. Use this Strategy Edit Tracker's path manually Analyze one frame at a time Track manually When A portion of the clip cannot be tracked, or an adequate track cannot be "locked down". Example: one or two bad keyframes are throwing off your track. Edit or remove these keyframes manually. See Editing the Tracker's Path. The Tracker should be checked on each frame. Example: use for very intricate tracks where extreme precision is required, such as tracking blue eyes onto a brown-eyed actor. See Analyzing One Frame at a Time or Tracking Manually. The reference feature is hidden by another object for several frames, and its motion is not predictable. The reference feature moves outside the range of the tracker box and its motion is not predictable. See Analyzing One Frame at a Time or Tracking Manually. Changing the Reference Feature Change the reference feature and reset the Tracker when the Tracker loses its reference feature early in the analysis and there is a better reference feature you can use. To change the reference feature: 1. Pause the analysis. 2. Return to the reference frame. 3. Click the Reset Tracker button in the Tracker panel. See Reset and Select Options for more information. 4. Position the Tracker over the new reference feature. 5. Restart the analysis. Adjusting the Size of the Tracker Box Adjust the size of the tracker box if the reference feature moves outside the tracker box, causing the 702