74 Chapter 5
drawing” has come into general use, indicating that more than one view is used to illustrate an object,
but the terms are essentially synonymous. “Orthographic” comes from the Greek word for “straight writ-
ing (or drawing).” Orthographic projection shows the object as it looks from the front, right, left, top, bot-
tom, or back, and different views are typically positioned relative to each other according to the rules of
either first-angle or third-angle projection. Ortho views depict the exact shape of an object seen from one
side at a time as you are looking perpendicularly to it without showing any depth.
A single view of an object is rarely adequate to show all necessary features. Figure 5.3 is an exam-
ple of orthographic projection showing the six principal views used by architects and engineers in con-
struction and industrial drawings.
Common types of orthographic drawings include plans, elevations, and sections. The most obvious
attribute of orthographic drawing is its constant scale—that is, all parts of the drawing are represented
without foreshortening or distortion, retaining their true size, shape, and proportion. Thus, in an ortho-
graphic drawing, a window shown to be 8 feet wide by 4 feet high will always be drawn at this size, no
matter how far it is from our viewpoint (Figure 5.4).
Plans are really orthographic views of an object as seen directly from above. Floor plans are the
most common form of plan; they delineate the layout of a building. A floor plan is represented by a hor-
izontal section taken through the building or portion of a building just above the windowsill level. In ad-
dition to the arrangement of rooms and spaces, floor plans need to show the location of various archi-
tectural elements such as stairs, doors, and windows and details such as wall and partition thickness.
Generally, the greater the scale of a drawing, the more detail that it is expected to contain (Figure 5.5).
Thus, a drawing at a scale of 1/4” = 1’0” will typically contain more information and show more detail than
a drawing at a 1/8" = 1'0" scale. Likewise, a scale of 1:2 is greater than that of 1/4 inch = 1 foot, 0 inches.
Other types of plans used in building construction may include site plans, which typically show the lay-
out of a site; foundation plans. which show the building structure; and reflected ceiling plans, which are
normally used to locate light fixtures and design features.
Two important rules that must be adhered to in orthographic drawing are the placement and align-
ment of views, depending on the type of projection to be used. These rules are discussed below. In ad-
dition, projection lines between the views must be aligned horizontally and vertically.
Orthographic (multiview) projection is a generally accepted convention for representing three-di-
mensional (3D) objects using multiple dimensions (2D) of the front, top, bottom, back, and sides of the
object. In practice, the minimum number of views possible is used to describe all the details of the ob-
ject. Usually, a front view, top, and single side view are sufficient and are oriented on the paper accord-
ing to accepted convention. Figure 5.6 represents a multiview projection for a simple house. The projec-
tion clearly shows that it is a form of parallel projection, and the view direction is orthogonal to the
projection plane. Isometric projection attempts to represent 3D objects using a single view. Instead of
the observer viewing the object perpendicular to it, the object is rotated both horizontally and vertically
relative to the observer. There are rules and conventions to guide the creation of both types of projec-
tions. Additionally, either of them can be supplemented with various types of dimensions.
First-Angle Projection.
First-angle projection is the ISO standard and is used mostly in Europe and Asia. If we imagine project-
ing a 3D object into a transparent plastic cube, the main object surfaces are projected onto the cube’s
walls so that the top view is placed under the front view and the right view is placed at the left of the front
view, a two-dimensional representation of the object is formed by “unfolding” the box and viewing all of
the interior walls as is shown in Figure 5.7A.