The paper proposes virtual input devices based on collision detection for easy construction of interactive 3D graphics applications which use a motion capture system as a real time input device. Each virtual input device is composed from several collision sensor objects and an actuator object. These objects are software components represented as a visible object which users can manipulate on a computer screen. Each virtual input device has a certain metaphor associated with its role that is determined by location and composition structure of its components. Therefore, it is possible to define various virtual input devices easily only by combining several sensor objects and an actuator object through direct manipulations on a computer screen. The paper presents a realization mechanism and actual examples of virtual input devices