A method for controlling operation of a 3D tracking device in tracking a 3D modeling instrument, the method comprising: - receiving coordinates of a plurality of vertices defining a plurality of edges or outer faces of an object with respect to a three-dimensional coordinate space; - tracking, and providing to an external 3D modeling process, coordinates of a current position of at least one 3D modeling instrument with respect to the coordinate space, based on received position data of a current position of at least one external pointing instrument in real space; - upon determining that any vertex, edge or face of the object qualifies as an activation vertex (1102.a), activation edge or activation face due to the current position of the 3D modeling instrument being in a predefined activation volume defined, with respect to the given vertex, edge or face, as a limited volume of the coordinate space in which the 3D modeling instrument can activate the external 3D modeling process: - activating an external 3D modeling process allocated to a combination of the 3D modeling instrument and the activation vertex, activation edge or activation face; - receiving, from the external 3D modeling process, modeling volume information defining, with respect to a current position of the activation vertex, activation edge or activation face, a limited active modeling volume of the coordinate space, in which the 3D modeling instrument can control the external 3D modeling process; - receiving, from the external 3D modeling process, changed coordinates defining a modeled position of the activation vertex (1102.b), activation edge or activation plane with respect to the coordinate space; and - deactivating the external 3D modeling process upon determining that the current position of the 3D modeling instrument is outside the active modeling volume. - receiving coordinates of a plurality of vertices defining a plurality of edges or outer faces of an object with respect to a three-dimensional coordinate space; - tracking, and providing to an external 3D modeling process, coordinates of a current position of at least one 3D modeling instrument with respect to the coordinate space, based on received position data of a current position of at least one external pointing instrument in real space; - upon determining that any vertex, edge or face of the object qualifies as an activation vertex (1102.a), activation edge or activation face due to the current position of the 3D modeling instrument being in a predefined activation volume defined, with respect to the given vertex, edge or face, as a limited volume of the coordinate space in which the 3D modeling instrument can activate the external 3D modeling process: - activating an external 3D modeling process allocated to a combination of the 3D modeling instrument and the activation vertex, activation edge or activation face; - receiving, from the external 3D modeling process, modeling volume information defining, with respect to a current position of the activation vertex, activation edge or activation face, a limited active modeling volume of the coordinate space, in which the 3D modeling instrument can control the external 3D modeling process; - receiving, from the external 3D modeling process, changed coordinates defining a modeled position of the activation vertex (1102.b), activation edge or activation plane with respect to the coordinate space; and - deactivating the external 3D modeling process upon determining that the current position of the 3D modeling instrument is outside the active modeling volume. - activating an external 3D modeling process allocated to a combination of the 3D modeling instrument and the activation vertex, activation edge or activation face; - receiving, from the external 3D modeling process, modeling volume information defining, with respect to a current position of the activation vertex, activation edge or activation face, a limited active modeling volume of the coordinate space, in which the 3D modeling instrument can control the external 3D modeling process; - receiving, from the external 3D modeling process, changed coordinates defining a modeled position of the activation vertex (1102.b), activation edge or activation plane with respect to the coordinate space; and - deactivating the external 3D modeling process upon determining that the current position of the 3D modeling instrument is outside the active modeling volume.