82 Chapter 5
Features on both sides of a centerline shown on a drawing are the same size and shape. These
equal-length short, parallel lines are placed outside the drawing of the object on its centerline (Figure
5.9). A hidden detail may be straight, curved, or cylindrical. Whatever the shape of the detail and re-
gardless of the number of views, it is represented by a hidden edge or invisible edge line.
Three-View Drawings.
Regularly shaped flat objects that require only simple machining operations may often be adequately
described with notes on a one-view drawing. However, when the shape of the object changes, portions
are cut away, or complex machining or fabrication processes must be shown, the single view would
normally be inadequate to describe the object accurately. The combination of front, top, and right side
views represents the method most commonly used by drafters to describe simple objects (Figure 5.10).
For building construction, other views would typically be needed.
The Front View.
Before an object is drawn, it is examined to determine which views will best furnish the information re-
quired to construct the object. The surface shown as the observer looks at the object is called the front
view. To draw this view, the drafter goes through an imaginary process of raising the object to eye level
and turning it so that only one side can be seen. If an imaginary transparent plane is placed between
the eye and the face of the object and parallel to the object, the image projected on the plane is the
same as that formed in the eye of the observer.
The Top View.
To draw a top view, the drafter goes through a process similar to that required to obtain the front view.
However, in third-angle projection, instead of looking squarely at the front of the object, the view is seen
from a point directly above it. When a horizontal plane on which the top view is projected is rotated so
that it is in a vertical plane, the front and top views are in their proper relationship. In other words, the
top view is always placed immediately above and in line with the front view.
The Side View.
A side view is developed in much the same way that the other two views were obtained. That is, the
drafter imagines the view of the object from the side that is to be drawn and then proceeds to draw the
object as it would appear if parallel rays were projected upon a vertical plane.
Three-Dimensional Graphics.
Depicting three dimensions on a flat piece of paper is a very important skill for designers, enabling them
to communicate their ideas to other people. This is especially useful when showing your design to non-
professionals such as managers and marketing personnel.
There are several tried and tested three-dimensional drawing systems used to produce a realistic
representation of an object. Some techniques, such as isometric projection, are based on mathemati-
cal systems; others try to convey a larger degree of realism by applying perspective to the drawing.
Amongst the methods covered in this tutorial are oblique, isometric, axonometric, and perspective
drawing.