Graphics is used to represent complex objects and structures that are created from simple geometric elements, such as lines, circles, and planes. Current 3-D CAD programs use these simple geometric forms to create more complex ones, through such processes as extruding, sweeping, and Boolean solid modeling operations. To fully exploit the use of CAD, you must understand geometry and be able to construct 2-D and 3-D geometric forms.

This chapter introduces the geometric forms useful in engineering design, from the simple to the complex. The chapter defines four engineering geometry categories, from simple 2-D elements to complex 3-D forms. The geometric elements and forms that are the basic components of engineering geometry are defined and illustrated, along with the application of these elements to engineering design. In addition, geometric conditions are defined and illustrated, and geometric construction techniques that are useful for engineering design are described.

The chapter is divided into two major sections: geometric construction and engineering geometry. Many of the geometric construction techniques described apply only to hand tools, because many CAD systems have commands that perform some of the steps automatically. However, the construction techniques are still valuable because the terminology and the descriptions of the various geometric forms are applicable to CAD. CAD systems become even more powerful in the hands of someone who understands 2-D and 3-D geometric forms.