1. A system for tracking the location and orientation of a user's feet, comprising: a depth sensor operable to generate a depth map of a scene within the field of view of the depth sensor, the field of view containing at least a portion of the user; a camera for imaging the scene, the image data generated by the camera having a predetermined relationship to the depth map generated by the depth sensor; a display device; and a processor; and a computer-readable memory storing instructions which, when executed by the processor, cause the processor to: identify a portion of the depth map as a candidate object for foot tracking; convert the identified portion of the depth map to a binary mask; apply a distance transform to the binary mask; identify local maxima from the output of the distance transform; determine a line representation connecting the identified local maxima as a central skeleton representation of the identified portion; determine a location of a toe of the user's foot and a location of an ankle of the user's foot, based on the central skeleton representation; calculate an orientation of the user's foot based on the determined locations of the toe and the ankle; overlay a representation of an item of footwear over the image data generated by the camera based on the determined toe location and orientation of the user's foot; and output the resulting image to the display device for display on the display device.