Abstract: A computer system for aiding in the design of an object, comprising a first sensor representing the object and adapted to be moved in three dimensions in a work area by a designer, the first sensor providing signals to the computer system that indicate its position and orientation in the work area, and a second sensor adapted to be moved by the designer in three dimensions in the work area, the second sensor providing signals to the computer system that indicate its position and orientation in the work area; the computer system responds to the signals from the first and second sensors by creating a displayed image corresponding to a three-dimensional model of the object in a virtual work area that corresponds to the designer's work area, the model comprising lines that each have a shape and position that corresponds to movement by the designer of at least one of the sensors, and by controlling the position and orientation of the model in the virtual work area in accordance with the motion of at least one of t