2 - Projection Methods

Abstract

This chapter discusses the way to draw layout rules, which define the projection methods used to describe artifacts and the way 3D views are represented on a 2D paper. These rules are presented in terms of first and third angle orthographic projections, sections and cutting planes, auxiliary projections, as well as trimetric, dimetric, isometric, and oblique projections. Engineering drawings are divided into pictorial projections or orthographic projections. The pictorial projections are nonspecific but provide visualization and can be subdivided into perspective, axonometric, and oblique projections. In pictorial projections, an artifact is represented as it is seen in 3D but on a 2D paper. In orthographic projections, an artifact is drawn in 2D on a 2D paper. Orthographic means a “correct drawing,” which prevents confusion. Thus, they can be termed “a true specification” because orthographic projections”are clearly defined by International Standards Organization (ISO) standards. Orthographic projections can be subdivided into first- and third- angle projections.