1. A computing system, comprising: a depth image analysis module to track a world-space pose of a human in a fixed, world-space coordinate system; an interaction module to establish a virtual interaction zone with a moveable, interface-space coordinate system that tracks the human and moves relative to the fixed, world-space coordinate system; and a transformation module to transform a position defined in the fixed, world-space coordinate system to a position defined in the moveable, interface-space coordinate system.