User Manual

Using the Pattern Flipbooks
Each pattern has a pair of thumbnail windows shown in the Inspector. The left window shows
the selected pattern, while the right window is updated during the track to show the actual
pattern that has been acquired for each frame.
The Tracker Pattern Selection and Flipbook thumbnails.
Each pattern that’s stored is added to a Flipbook. Once the render is complete, you can play
this Pattern Flipbook to help you evaluate the accuracy of the tracked path. If you notice any
jumps in the frames, then you know something probably went wrong.
Using Adaptive Pattern Tracking
Even the most ideal pattern will usually undergo shifts in profile, lighting conditions, and other
variables. These can adversely affect pattern recognition to the point that a pattern becomes
unusable. The Tracker offers three modes of pattern acquisition during tracking that can help to
correct these conditions. The modes can be set using the Adaptive Mode options in the
Inspector.
The Adaptive Mode options.
None
When the Adaptive mode is set to None, the pattern within the rectangle is acquired when the
pattern is selected, and that becomes the only pattern used during the track.
Every Frame
When Every Frame is chosen, the pattern within the rectangle is acquired when the pattern is
selected, and then reacquired at each frame. The pattern found at frame 1 is used in the search
on frame 2, the pattern found on frame 2 is used to search frame 3, and so on. This method
helps the Tracker adapt to changing conditions in the pattern.
Every Frame tracking is slower and can be prone to drifting from sub-pixel shifts in the pattern
from frame to frame. Its use is therefore not recommended unless other methods fail.
Best Match Tracking
Best Match tracking works in much the same way as Every Frame tracking; however, it will not
reacquire the pattern if the difference between the original pattern and the new one is too
great. This helps to prevent cases where transient changes in the image cause the Tracker to
become confused.
As a comparison between the two Adaptive modes, if a shadow passes over the tracker point,
the Every Frame tracking mode may start tracking the shadow instead of the desired pattern.
Chapter – 73 Using the Tracker Node 1500