These features can be curve segments like line segments, circles, ellipses etc. However, the RHT can also be applied to motion estimation. Moving objects are assumed to be rigid and a number of moving objects to be unknown.
Objects can be partially non-rigid or distorted.
There are moving objects in the gray-level image sequence shown below. Consecutive image frames are examined frame by frame. Using edge points of gray-level pictures, translational motion of moving objects is estimated. Motion is detected first, and only after that objects are segmented for tracking and recognition. Two moving objects are found.