Disclosed are systems, methods and circuits for human to machine interfacing using one or more 3D hand skeleton models, comprising an image acquisition circuit to acquire a 2D image of a hand, a hand feature identifier module to identify hand features in an acquired image and an image skeleton builder module to generate a 2D skeleton dataset of the hand using identified features. A 3D skeleton builder module is adapted to generate a 3D hand skeleton dataset by determining a configuration of some or all of the one or more 3D hand skeleton models whose 2D projection substantially corresponds to the generated 2D skeleton dataset.