5
Paraline Drawings

Paraline drawings include a subset of orthographic projections known as axonometric projections—the isometric, dimetric, and trimetric projections—as well as the entire class of oblique projections. Each type offers a slightly different viewpoint and emphasizes different aspects of the drawn subject. As a family, however, they combine the measured precision and scalability of multiview drawings and the pictorial nature of linear perspective. Because of their pictorial quality and relative ease of construction, paraline drawings are appropriate for visualizing an emerging idea in three dimensions early in the design process. They are capable of fusing plan, elevation, and section into a single view and illustrating three-dimensional patterns and compositions of space. Portions of a paraline drawing can be cut away or made transparent to see inside and through things, or expanded to illustrate the spatial relationships between the parts of a whole. At times, they can even serve as a reasonable substitute for a bird's-eye perspective.

Paraline Drawings

Paraline drawings communicate the three-dimensional nature of an object or spatial relationship in a single image. Hence, they are also called single-view drawings to distinguish them from the multiple and related views of plans, sections, and elevations. They can be distinguished from the other type of single-view drawing, linear perspective, by the following pictorial effects.

Paraline drawings present either an aerial view looking down on an object or scene, or a worm's-eye view looking upward. They lack the eye-level view and picturesque quality of linear perspectives. They represent what we know rather than how we see, depicting an objective reality that corresponds more closely to the picture in the mind's eye than to the retinal image of linear perspective.

Types of Paraline Drawings

There are several types of paraline drawings, each named after the method of projection that is used to develop them. Two of the most common in architectural drawing are discussed in this chapter: isometric and oblique drawings.

In both isometric and oblique drawings:

All parallel lines in the subject remain parallel in the drawing.
All lines parallel to the principal X-Y-Z- axes can be measured and drawn to scale.

The images that emerge from oblique projections are distinct from isometric views that develop from orthographic projection. The ease with which we can construct an oblique drawing has a powerful appeal. If we orient a principal face of the subject parallel to the picture plane, its shape remains true and we can draw it more easily. Thus, oblique views are especially convenient for representing an object that has a curvilinear, irregular, or complicated face.

Plan Obliques

The principal set of horizontal planes oriented parallel to the picture plane is emphasized and can be represented in true size, shape, and proportion.
Plan views can be used as base drawings—a definite advantage when drawing horizontal planes with circular or complex shapes.
Plan obliques have a higher angle of view than isometric drawings.

Isometric Drawings

All three principal sets of planes share equal emphasis.
The angle of view is slightly lower than that of plan obliques.
Plans and elevations cannot be used as base drawings.

Elevation Obliques

The principal set of vertical planes oriented parallel to the picture plane is emphasized and can be represented in true size, shape, and proportion. The other vertical set and the principal horizontal set of planes are both foreshortened.
An elevation can be used as a base drawing. This view should be of the longest, the most significant, or the most complex face of the object or building.

Isometric Drawings

Isometric drawings establish a lower angle of view than plan obliques and give equal emphasis to the three principal sets of planes. They preserve the relative proportions of a subject or scene and are not subject to the distortion inherent in oblique views.

To construct an isometric drawing, first establish the direction of the three principal axes. Because they are 120° apart on the picture plane, if we draw one axis vertically, the other two axes make a 30° angle with a horizontal on the drawing surface.

Isometric drawings of forms based on the square can create an optical illusion and be subject to multiple interpretations. This ambiguity results from the alignment of lines in the foreground with those in the background. In such cases, a plan oblique might be a better choice.

Plan Obliques

Plan obliques present a higher angle of view than isometric drawings and emphasize the set of horizontal planes by revealing their true size, shape, and proportions.

Elevation Obliques

Elevation obliques orient a principal vertical face or set of vertical planes parallel to the picture plane and therefore reveal their true sizes, shapes, and proportions.

Constructing Paraline Drawings

There are three basic approaches to constructing the entire class of paraline drawings. When constructing and presenting a paraline drawing, keep in mind that paraline views are easiest to understand if vertical lines in space are also oriented vertically on the drawing surface.

Circles and Freeform Shapes

Any circles oblique to the picture plane appear as ellipses. To draw such a circle in a paraline drawing, we must first draw a paraline view of the square that circumscribes the circle. Then we can use either of two approaches to drawing the circle within the square.

Spatial Depth Cues

We can enhance the perceived depth of a paraline drawing by utilizing a hierarchy of line weights to distinguish between spatial edges, planar corners, and surface lines.

3D-modeling programs treat lines as the continuous edges of polygons. It may therefore be difficult to define this hierarchy of line weights without first transferring the graphic image to a two-dimensional environment.

To separate planes in space, to clarify their different orientations, and especially to distinguish between the horizontal and the vertical, we can use contrasting textures and patterns.

Paraline Views

Even though a paraline drawing always presents either an aerial view or a worm's-eye view of a subject, we can construct a paraline view in any of several ways to reveal more than the exterior form and configuration of a design. These techniques allow us to gain visual access to the interior of a spatial composition or the hidden portions of a complex construction. We categorize these techniques into expanded views, cutaway views, phantom views, and sequential views.

Expanded Views

To develop what we call an expanded or exploded view, we merely shift portions of a paraline drawing to new positions in space. The finished drawing appears to be an explosion frozen at a point in time when the relationships between the parts of the whole are most clear.

Expanded views are extremely useful in describing the details, layering, or sequence of a construction assembly. Remember that, as with other drawing types, the larger the scale of a paraline drawing, the more detail you have to show.
At a larger scale, expanded views can effectively illustrate vertical relationships in multistory buildings as well as horizontal connections across space.

Expanded Views

Cutaway Views

A cutaway view is a drawing having an outer section or layer removed to reveal an interior space or an internal construction. This strategy can also effectively manifest the relation of an interior to the exterior environment.

The simplest method for creating a cutaway view is to remove an outer or bounding layer of a composition or construction.

To reveal a more complex composition, the cut may follow a three-dimensional route. In this case, the trajectory of the cut should clarify the nature of the overall form building as well as the organization and arrangement of interior spaces.
Cuts should be clearly articulated by a contrast in line weights or tonal values.

Phantom Views

A phantom view is a paraline drawing having one or more parts made transparent to permit the presentation of internal information otherwise hidden from our view. This strategy effectively allows us to unveil an interior space or construction without removing any of its bounding planes or encompassing elements. Thus, we are able to simultaneously see the whole composition and its internal structure and arrangement.

Condominium Unit No. 5, Sea Ranch, California, 1963–65 Moore, Lyndon, Turnbull, Whitaker

Digital Views

The grouping and layering functions of 2D drawing and 3D CAD or modeling programs give us the ability to more easily create the different types of paraline views. By organizing elements and assemblies of a three-dimensional construction into separate groups or layers, we can selectively control their location, visibility, and appearance, as illustrated on this and the facing page.

We can hide or dim certain elements or assemblies to create cutaway views.
We can move selected elements or assemblies along axial lines to construct expanded views.

Sequential Views

While a paraline is a single-view drawing useful in displaying three-dimensional relationships, a series of paraline views can effectively explain processes and phenomena that occur in time or across space.