1. An information input apparatus comprising: an observation unit configured to observe an environment including a user and one or more apparatuses to be controlled, the observation unit including a sensor; a learning unit configured to separate a foreground and a background from observation data obtained by the observation unit, the foreground including the user and the one or more apparatuses to be controlled, the background including the environment except for the foreground, and to learn three-dimensional models of the foreground and the background; a state estimation unit configured to estimate positions and postures of already modeled foregrounds in the environment; a user recognition unit configured to identify fingers of the user from the foreground and to recognize a shape, position, and posture of the fingers; and an apparatus control unit configured to: specify a depth to a three-dimensional user interface on a display, of an apparatus of the one or more apparatuses, based on an intersection of straight lines extending from the identified fingers of the user, and output a control command to the one or more apparatuses to be controlled on the basis of the depth, shape, position, and posture of the fingers recognized by the user recognition unit.