Andrew Blake & Michael Isard 
Active Contours [PDF ebook] 
The Application of Techniques from Graphics, Vision, Control Theory and Statistics to Visual Tracking of Shapes in Motion

Active Contours deals with the analysis of moving images – a topic of growing importance within the computer graphics industry. In particular it is concerned with understanding, specifying and learning prior models of varying strength and applying them to dynamic contours. Its aim is to develop and analyse these modelling tools in depth and within a consistent framework.