Spatial representation in two dimensions - The why and how of projection

The perspective representation, which is also referred to as stereogram, is used when an object needs to be reproduced in a particularly descriptive and plastic way. In contrast to the technical drawing, which is defined in DIN 6 (ISO 5456-2) and divides the object into several independent views, the technical illustration combines all three sides of a workpiece in one representation. These advantages become especially evident, when the possibilities of digital photography cannot be applied for technical reasons. This happens, for example, when the object to be depicted is still in development and does not exist, yet.

The so-called exploded view drawings are used for spare parts illustrations and assembly instructions. The respective machine part is depicted with all its single components in a virtually emerged way. To the observer, the depicted machine part seems to "explode" in an ideal manner. Especially in this display format technical illustration is showing its supremacy over photography: A camera-compatible arrangement of the many single components of a complex assembly would demand a disproportionately high operating expense.

Another argument for technical illustrations is their good reproduction. While  a photograph, as a so-called halftone, needs to be prepared for printing with retouching, a technical illustration as a line-art model can be reproduced without any problems with all common printing and copying methods.  Perspective representations are successfully used in aerospace, the military, automotive and  all other manufacturing  industries.

The demands of ISO 9000 with regard to technical documentation ("Product Support") have created greater necessity for perspective projection. The term "Product Support", comprises the whole information and the service that a manufacturer offers to his customers. The information material published under this term ranges from simple instruction manuals, via maintenance manuals and spare parts catalogs up to complete documentation on microfilm. Nowadays, assembly operators must at any time be capable of maintaining and repairing even unknown machines and equipment. Here, documentation with perspective  representations specify theorder the machine components have to be assembled or dismantled. The same graphics help to identify a spare part or to initiate a repeat order. Furthermore, bidding documents, advertising for industrial products, projecting of equipment, maintenance manuals, spare parts catalogs, training material, cartoon representations, etc. shall also be mentioned in this context.

Source:
Hans-J. Engelke: "2D-Konstruktion mit AutoCAD 2002. Isometrisches Zeichnen für Einsteiger"
(Munich, Vienna: Carl Hanser Verlag, 2001), p. 3-4.

We thank Carl Hanser Verlag for their support and their consent to publish and translate this text excerpt. Further information on the book can be found at http://www.hanser.de/buch/2001/3-446-21777-0.htm.