3
Architectural Drawing
Systems
The central task of architectural drawing is representing three-dimensional
forms, constructions, and spatial environments on a two-dimensional surface.
Three distinct types of drawing systems have evolved over time to accomplish
this mission: multiview, paraline, and perspective drawings. This chapter
describes these three major drawing systems, the principles behind their
construction, and their resulting pictorial characteristics. The discussion does
not include media that involve motion and animation, made possible by computer
technology. Nevertheless, these visual systems of representation constitute a
formal graphic language that is governed by a consistent set of principles.
Understanding these principles and related conventions is the key to creating
and reading architectural drawings.
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PROJECTION DRAWING
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All three major drawing systems result from the way
a three-dimensional subject is projected onto a twodimensional
plane of projection, or more simply, onto
the picture plane.
¥ Projectors transfer points on the subject to the
picture plane. These projectors are also called
sightlines in perspective projection.
¥ The drawing surface or sheet of paper is the virtual
equivalent of the picture plane.
Three distinct projection systems result from the
relationship of the projectors to each other as well
as to the picture plane.
Orthographic Projection
¥ Projectors are parallel to each other and
perpendicular to the picture plane.
¥ Axonometric projection is a special case of
orthographic projection.
Oblique Projection
¥ Projectors are parallel to each other and oblique to
Perspective Projection
¥ Projectors or sightlines radiate from a central
point that represents a single eye of the observer.
Once the information for a three-dimensional
construction or environment has been entered into
a computer, 3D CAD and modeling software can
theoretically present the information in any of these
projection systems.
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PICTORIAL SYSTEMS
ARCHITECTURAL DRAWING SYSTEMS / 25
Projection Systems
Axonometric Projection
These pictorial views are
available in most 3D CAD
and modeling programs.
The terminology, however,
may differ from what is
presented here.
When we study how each projection system represents the same subject, we
can see how different pictorial effects result. We categorize these pictorial
systems into multiview drawings, paraline drawings, and perspective drawings.
Pictorial Systems
Multiview Drawings
¥ Plans, sections, and elevations.
¥ The principal face in each view is oriented parallel to the picture plane.
Paraline Drawings
¥ Isometrics: The three major axes make equal angles with the
picture plane.
¥ Dimetrics: Two of the three major axes make equal angles with the
¥ Trimetrics: The three major axes make different angles with the
¥ Elevation obliques: A principal vertical face is oriented parallel to
¥ Plan obliques: A principal horizontal face is oriented parallel to
Perspective Drawings
¥ 1-point perspectives: One horizontal axis is perpendicular to the picture
plane, the other horizontal axis and the vertical axis are parallel with the
¥ 2-point perspectives: Both horizontal axes are oblique to the picture
plane, and the vertical axis remains parallel with the picture plane.
¥ 3-point perspectives: Both horizontal axes as well as the vertical axis
are oblique to the picture plane.
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MULTIVIEW DRAWINGS
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Orthographic projection represents a threedimensional
form or construction by projecting lines
¥ Projectors are both parallel to each other and
¥ Major faces or facets of the subject are typically
oriented parallel with the picture plane. Parallel
projectors therefore represent these major faces in
their true size, shape, and proportions. This is the
greatest advantage of using orthographic
projectionsÑto be able to describe facets of a
form parallel to the picture plane without
foreshortening.
Ambiguity of depth is inherent in any orthographic
projection, as the third dimension is flattened onto
¥ Lines that are perpendicular to the picture plane
are projected as points.
¥ Planes that are perpendicular to the picture plane
are projected as lines.
¥ Curved surfaces and those that are not parallel to
the picture plane are foreshortened.
¥ Note that the projected size of an element remains
constant regardless of how far forward or back it is
from the picture plane.
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Any single orthographic projection cannot convey facets of a subject that are oblique or
perpendicular to the picture plane. Only by looking at related orthographic projections
can this information be discerned. For this reason, we use the term Òmultiview drawingsÓ
to describe the series of orthographic projections necessary to fully and accurately
describe a three-dimensional subject.
¥ If we enclose an object within a transparent picture-plane
box, we can name the images projected orthographically
onto the principal picture planes.
¥ Top views are orthographic projections cast onto the
horizontal picture plane. In architectural drawing, top
views are called plans.
¥ Front and side views are orthographic projections cast
onto the vertical picture planes. In architectural drawing,
front and side views are called elevations.
¥ See Chapter 4 for floor plans and sections, which are
orthographic projections of cuts made through a building.
¥ To make it easier to read and interpret how a series of
orthographic projections describes a three-dimensional
whole, we arrange the views in an orderly and logical
fashion.
¥ The most common layout results when we unfold the
transparent picture-plane box into a single plane
represented by the drawing surface. The top or plan view
revolves upward to a position directly above and vertically
aligned with the front or elevation view, while the side
view revolves to align horizontally with the front view. The
result is a coherent set of related orthographic views.
¥ Although these three objects have different forms,
their top views appear to be identical. Only by looking at
related orthographic projections are we able to
understand the three-dimensional form of each object.
We should therefore study and represent threedimensional
forms and constructions through a series of
related orthographic projections.
¥ The mind must be able to read and assemble a set of
multiview drawings to fully understand the nature of the
three-dimensional subject.
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PARALINE DRAWINGS
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While orthographic projections describe a three-dimensional
subject through a series of distinct but related two-dimensional
views, paraline drawings convey the three-dimensional nature of a
form or construction in a single pictorial view. Properly speaking,
any orthographic projection is a paraline drawing. However, we use
the term Òparaline drawingÓ to refer specifically to those single
pictorial views described below.
Types of Paraline Drawing
¥ Axonometric projections can produce isometric, dimetric,
or trimetric views.
¥ Oblique projections can result in plan obliques or elevation
obliques.
¥ Unfortunately, CAD and modeling programs do not use these
terms for the different types of paraline drawings in a
consistent manner.
Pictorial Characteristics of Paraline Drawings
¥ Paraline drawings are always aerial or wormÕs-eye views.
¥ Parallel lines in the subject remain parallel in the drawing.
¥ All axial linesÑthose lines parallel to the major X-, Y-, and Zaxes
Ñare scalable. Conversely, nonaxial lines are never
scalable.
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An axonometric projection is an orthographic projection of a three-dimensional form that is inclined to
the picture plane in such a way that its three principal axes are foreshortened. The term ÒaxonometricÓ
is often misused to describe paraline drawings of oblique projections or the entire class of paraline
drawings. Strictly speaking, axonometric projection is a form of orthographic projection in which the
projectors are parallel to each other and perpendicular to the picture plane. The difference between
orthographic multiview drawings and an axonometric single-view drawing is simply the orientation of
the object to the picture plane.
Isometric Projection
¥ Isometric projection is an axonometric
projection of a three-dimensional subject
inclined to the picture plane in such a way that
its three principal axes make equal angles with
the picture plane and are equally foreshortened.
Dimetric Projection
¥ Dimetric projection is an axonometric projection
in which two of the principal axes are equally
foreshortened and the third appears longer or
shorter than the other two.
Trimetric Projection
¥ Trimetric projection is an axonometric
projection in which all three principal axes are
foreshortened at a different rate.
¥ Of these three, the most commonly used in
architectural drawing is isometric projection.
¥ All three axes receive equal emphasis.
¥ All axial linesÑthose parallel to the principal
axesÑare drawn to true length at
the same scale.
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Oblique projection represents a three-dimensional form or
construction by projecting parallel lines at some convenient
angle other than 90¡ to the picture plane. A principal face or
set of planes of the subject is usually oriented parallel to
the picture plane and is therefore represented in accurate
size, shape, and proportion.
¥ For convenience, the receding lines perpendicular to the
picture plane are typically drawn to the same scale as the
lines parallel to the picture plane.
¥ The receding lines may be foreshortened to 3/4 or 1/2 their
true scaled length to offset the appearance of distortion.
In architectural drawing, there are two principal types of
oblique drawings: plan obliques and elevation obliques.
Plan Obliques
¥ Plan obliques orient the horizontal planes of the subject
parallel to the picture plane. These horizontal planes are
therefore shown in true size and shape, while the two
principal sets of vertical planes are foreshortened.
¥ Plan obliques have a higher angle of view than isometric
drawings.
¥ An advantage in constructing plan obliques is the ability
to use floor plans as base drawings.
Elevation Obliques
¥ Elevation obliques orient one principal set of vertical
planes of the subject parallel to the picture plane. This set
is therefore shown in true size and shape, while the other
vertical set and the principal horizontal set of planes are
both foreshortened.
¥ The face selected to be parallel to the picture plane should
be the longest, the most complex, or the most significant
face of the building or construction.
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PERSPECTIVE DRAWINGS
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Perspective projection portrays a three-dimensional form or
construction by projecting all of its points to a picture plane (PP)
by straight lines that converge at a fixed point representing a
single eye of the observer.
¥ While we normally see through both eyes in what
we call binocular vision, perspective projection
assumes we view a three-dimensional subject or
scene through a single eye, which we call the
station point (SP). Unlike the parallel projectors
in orthographic and oblique projections, the
projectors or sightlines in perspective projection
converge at this station point.
Pictorial Characteristics of Perspective Drawings
The converging sightlines in perspective give rise to
the two principal pictorial characteristics of
perspective drawings: convergence of parallel lines
and reduced size with distance.
¥ Parallel lines in the subject or scene appear to
converge when they are perpendicular or oblique
to the picture plane (PP).
¥ The size of an element or object appears to
decrease as it recedes from the observer.
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A well-drawn perspective excels in conveying the
experience of being in a three-dimensional spatial
environment.
¥ The experiential nature of a perspective drawing relies
on our ability to define at least three layers of depth
within a scene: a foreground, a middleground, and a
background.
¥ Perspective drawings assume there is an observer
located at a specific point in space and looking in a
specific direction.
¥ Multiview and paraline drawings, on the other hand,
do not make reference to the point of view of an
observer. We can view the drawings from various
angles and be comfortable in reading the objective
information. Our eyes can roam over the expanse of
a plan or paraline drawing and be able to correctly
interpret the graphic information.
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¥ We can use a series of perspectivesÑwhat we call
serial visionÑto convey the experience not only of
being in a place but also of moving through a
sequence of spaces.
¥ 3D-modeling programs often have the ability to
create a sequential series of perspective views and
animate a walk-through or fly-through of a building
or spatial environment. There is an ongoing question
regarding how to use these capabilities to simulate
more effectively the way we experience space.
¥ There is little advantage in drawing a perspective of
a small-scale object, such as a chair or structural
detail, unless it exists in a spatial environment. At
these scales, the degree of convergence of parallel
lines is so slight that a paraline view is usually a
better and more efficient choice.
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COMMUNICATING DESIGN IDEAS
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We use architectural drawings to initiate, explore, develop, and
communicate design ideas. No one drawing can ever reveal everything
about its subject. Each pictorial system of representation provides
an alternative way of thinking about and representing what we see
before us or envision in the mindÕs eye. The choice of a particular
drawing system influences how we view the resulting graphic image,
establishes which design issues are made visible for evaluation and
scrutiny, and directs how we are inclined to think about the subject
of the drawing. In selecting one drawing system over another,
therefore, we make conscious as well as unconscious choices about
what to reveal as well as what to conceal.
Point of View
¥ Multiview drawings represent a three-dimensional subject through
a series of distinct, but related, two-dimensional views.
¥ These are abstract views that the viewer must assemble in the
mind to construct an objective reality.
¥ Paraline drawings describe the three-dimensional nature of the
same subject in a single view.
¥ These views combine the scalability of multiview drawings and the
easy-to-understand, pictorial nature of perspectives.
¥ Perspectives are experiential views that convey a sense of being
present in a spatial environment.
¥ Perspectives depict an optical reality rather than the objective
reality of multiview and paraline drawings.
¥ It is a paradox that multiview drawings are relatively easy to
develop but often difficult to interpret, while perspective drawings
are challenging to construct but usually easy to understand.
Digital Views
A distinct advantage of digital drawing over traditional drawing
is the ability to experiment with design modifications, study...
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