The main methods for creating designs are solid modeling and surface modeling. Surface modeling was the earliest form of CAD.

It is based on shaping surfaces by pulling, bending, twisting and stretching them until the required shape is created. The surfaces can be joined together to enclose a volume and so represent complete objects. Solid modeling is based principally on standard geometric shapes, which can be combined in various ways, mainly developed from the Boolean operations of subtraction, addition and intersection. When they were first introduced almost 20 years ago, solid modelers had the advantage of being much easier to learn and use, but they lacked the flexibility of surface modelers in creating complex shapes. Since then, the developers of surface modelers have made their systems much easier to use, while the suppliers of solid modelers have added more flexible modeling tools. Thus, the distinction between the two types of system is now not so clear-cut.