Car design. Computer artwork of computer-aided design (CAD) of a car body. The computer screen at right shows the car body from three different angles, allowing a three-dimensional model to be built. This model (red) can be used to test the structural strength of the car, and to gain information on its aerodynamics and stability. CAD is an important tool in mechanical design, allowing the vehicle to be viewed from any angle. Changes to the detailed structure may be made rapidly, and the effect on the rest of the design calculated quickly.