Apple MA434Z/A User Manual - Page 749

• failureTolerance: If the correlation value of the tracker's analysis falls below the value in this field, Shake initiates the failureBehavior. • failureBehavior: A pop-up menu containing the following options: • stop: The tracker stops if the correlation is less than the failureTolerance. You can also press Esc to manually stop tracking. • predict location and create key: If a failure is detected, then the tracker predicts the location of the keyframe based on a vector of the last two keyframes, then continues tracking in the new area. • predict location and don't create key: Same as above, but this option merely predicts the new search area and does not create new keyframes until a high correlation is obtained. This option is excellent for tracked objects that pass behind foreground objects. • don't predict location: In this case, the tracker merely sits in the same spot looking for new samples. New keyframes are not created. • use existing key to predict location: This option allows you to manually create keyframes along your track path. You then return to the start frame and begin tracking. The search pattern starts looking along the preexisting motion path. limitProcessing This button creates a Domain of Definition (DOD) around the bounding boxes of all active trackers. Only that portion of the image is loaded from disk when tracking, so the track analysis is faster. This setting has no effect on the final output image. preProcess This button turns on preprocessing for the tracking area, applying a slight blur to reduce fluctuations due to grain. To control the blur amount, open the preProcess subtree. • blurAmount: A subparameter of preProcess that sets the amount of blur applied when preprocessing to improve the quality of tracks in clips with excessive grain or noise. trackRange The trackRange parameter is the potential frame range limit of your track. By default, the range is set to the clip range. For Shake-generated elements such as RGrad, this parameter takes a range of 1. You can set new limits using Shake's standard range description, for example, 10-30x2. If you stop tracking and start again, the analysis starts from the current frame until it reaches the lower or upper limit of your trackRange, depending on whether you are tracking forward or backward. Chapter 25 Image Tracking, Stabilization, and SmoothCam 749