Feature array manages an ordered list of 2d feature points. Each feature point has a 2D location that is represented as non-normalized floating point coordinates. Each feature also has a status flag indicating if whether this feature has been successfully tracked.
Feature history array manages a history of FeatureArray, there are maxHistory time slices in the whole history during tracking, so that user can access older feature records. It also provides APIs for users to extract a particular feature array in Time(t) from feature history.
Detector runs a Harris/Fast9 Corner implementation on the GPU or PVA to detect features. For Harris Corner implementation, detector adds new features to the end of the given list of feature points. For example, if the maximum feature count is 2000 and the list has 1500 features, currently only up to 500 features will be added, starting from index 1500 onwards. The decision if a new feature is added is dependent on proximity to features already in the list as well as a threshold on the corner response function. For Fast9 Corner implementation, detector adds detected features to the start of given list of feature points while users are free to decide how to combine newly detected features with previously detected features.