Motion
Motion is another aspect of 3-D vision that humans are able to interpret with ease. This chapter studies the basic theoretical concepts and then tackles real problems where motion is crucial, including the monitoring of traffic flow and the tracking of people.
• the basic concepts of optical flow and its limitations.
• the idea of a focus of expansion.
• identification of the ground plane as an early stage in the analysis of many types of scene incorporating motions.
• the need for “occlusion reasoning” when objects repeatedly pass behind one another and then reemerge.
• how serious studies of the motions of complex objects may have to take into account 3-D articulated models of linked parts.
• the important status of the Kalman filter in motion applications.
Note that although this is only an introductory chapter on 3-D motion, it can demonstrate methods that can be used to perform vital surveillance tasks. Chapter 20 will take this work further—into the area of egomotion—once invariants have provided the means to take useful shortcuts in the analysis.