“…or appearance features representing the texture of the facial skin including wrinkles, bulges, and furrows. Typical examples of geometric-feature-based methods are those of Gokturk et al (2002), who used 19 point face mesh, of Chang et al (2006), who used a shape model defined by 58 facial landmarks, and of Pantic and her collegues (Pantic & Rothkrantz, 2004;Pantic & Patras, 2006;Valstar & Pantic, 2006a), who used a set of facial characteristic points like the ones illustrated in Figure 3. Typical examples of hybrid, geometric-and appearance-feature-based methods are those of Tian et al (2001), who used shape-based models of eyes, eyebrows and mouth and transient features like crows-feet wrinkles and nasolabial furrow, and of Zhang and Ji (2005), who used 26 facial points around the eyes, eyebrows, and mouth and the same transient features as Tian et al (2001).…”