“…However, they are characterised by complex search and mapping processes. The model-free methods (e.g., [4,13,14,15,16,17,18,19,20,21,22,23]) analyse the spatio-temporal shape and motion characteristics of a subject's silhouettes without assuming any explicit model of the subject's body. Although the inter-subject discriminability of these methods are high, they are susceptible to variations in viewpoints and the subject's attire.…”