Liu Ren Gregory Shakhnarovich Jessica K. Hodgins Hanspeter Pfister Paul A. Viola Learning silhouette features for control of human motion. 1303-1331 2005 24 ACM Trans. Graph. 4 http://doi.acm.org/10.1145/1095878.1095882 db/journals/tog/tog24.html#RenSHPV05