1. An image processing method, comprising: receiving, from an infrared (IR) camera, a signal encoding an IR image including a plurality of IR pixels, each IR pixel specifying one or more IR parameters of that IR pixel; identifying, in the IR image, IR-skin pixels that image a human hand; for each IR-skin pixel, estimating a depth of a human hand portion imaged by that IR-skin pixel based on the IR parameters of that IR-skin pixel; and deriving a skeletal hand model including a plurality of hand joints, each hand joint defined with three independent position coordinates inferred from the estimated depths of each human hand portion.