With the help of CAD systems, designers and architects can create and design products and buildings in virtual space. Complex shapes and structures are no longer just in the mind of the designer, but are becoming visible on the screen. However, unusual shapes are like special components that can hardly be produced automatically and are therefore very costly to manufacture. A construction method is needed that will allow a wide variety of designs to be created while at the same time enabling these to be produced cost-effectively.
This led to the development of parametric CAD systems at the start of the seventies. These were used for constructing machines and vehicles and were mostly intuitive to operate. The product model is no longer saved as a precise geometry. Instead, its shape is stored in the computer as a combination of parameters and numerical variables that specify its size. A cube-shaped object, for instance, is defined by the parameters length, width and height, a cylinder by diameter and height.