The language of architecture is three-dimensional form and space. But the language of the architect is two-dimensional drawing. Architects use a broad range of drawing systems and representations at different times throughout the design to communicate information and ideas. It is essential to understand both the different drawing systems and then when they are used, to communicate efficiently and effectively and resolve the disconnect between the three-dimensional realm of architecture and the the two-dimensional realm of the architect and paper.
Drawing systems are classified based on the method of projection.
Projection is the way a three-dimensional object is represented by projecting all the points in three-dimensional space onto a two-dimensional, flat plane or picture plane.
The picture plane is the two-dimensional plane of the drawing sheet or piece of paper.
There are three major types of drawing systems that use different types of projections methods:
- Multiview drawings (orthographic projections)
- Paraline or oblique drawings (axonometric projections)
- Perspective drawings
01 | Multiview Drawings (Orthographic Projections)
Multiview drawings include the drawings we know as plans, elevations and sections. These are multiple views of a building, object or form that read together help us understand its three-dimensions. Each of these drawings is an orthographic projection.
Orthographic projection is a way of representing a three-dimensional in which the object is viewed from a position perpendicular to the drawing plane being viewed. For example, a house or a box would normally have a top view, a front view and a side view.Orthographic projections are flat and to scale. They do not have any perspective or depth of field in them. Depth is created through line types, line weights and drawing styles.
A plan is a view of an object projected horizontally, or from above. In architectural drawing, this is known as a top view or top plan. Other architectural plans are cut horizontally through the building or object, usually at a height of about 1200mm above the ground or a floor plane.
An elevation is a vertical view of an object projected onto a picture plane. An elevation may be the front, side or back view depending on how we position ourselves relating to the object.
A section is an orthographic projection of an object as if it would appear cut vertically by an intersecting plane.
It is much easier to understand in a drawing, so please check out the examples below and try to find the different drawing types...
02 | Paraline Drawings (Axonometric Projections)
Paraline drawings include a group of orthographic projections called axonometric projections which include the isometric, dimetric and trimetric as well as oblique projections. Paraline drawings communicate the three-dimensional nature of an object in a single drawing rather than multiple views, like multiview drawings. In paraline drawings, parallel lines remain parallel and do not disappear to a vanishing point, like in perspective.
In an axonometric projection, all three axes are drawn with dimensions to the correct scale and three faces of the object are shown. A picture plane such as a plan or elevation is set on an angle and drawn to true scaled dimensions. The other planes are then projected usually at an angle not 90 degrees to the original face using the same scale for dimensions. Three types of axonometric projections include:
- In an isometric projection, the direction of viewing is such that the three axes of space appear equally foreshortened, and there is a common angle of 120° between them.
- In a dimetric projection, the direction of view is such that the three axes appear equally foreshortened.
- In a trimetric projection, the three axes appear unequally foreshortened.
An oblique projection starts with a plan or elevation with true dimensions. All other faces are extruded away from the original face with parallel lines at a certain angle, often 30, 45 or 60 degrees. These lengths are usually reduced to a consistent proportion. The presence of one or more 90-degree angles is usually a good indication the drawing is oblique. In architectural graphics, the main types of oblique projection are plan and elevation obliques.
In an elevation oblique, an elevation is drawn to scale and the three dimensions of the object extruded backward, usually at 30,45 or 60 degrees to their correct dimensions.
In a plan oblique, a plan is rotated 30,45 or 60 degrees and drawn to scale, and the three dimensions of the object extruded upwards, or downwards to their correct dimensions. Plan obliques can therefore be developed from above as a bird-eye view, or below as a worm-eye view.
Again, drawings explain things much clearer so try to find each example and define what makes them different in terms of the angles and views used...
03 | Perspective Drawings
Perspective is the description of three-dimensional volumes on a two-dimensional surface using lines that converge and recede into the depth of a drawing.
Unlike multiview and paraline drawings, perspective drawings are much closer to what the eye would sense and perceive. Perspective allows us to place a three-dimensional object in space and view it as if it were diminishing in size the further away it is from the eye. There are three types of perspective:
- In a one-point perspective, the cube, object or building is viewed horizontally and perpendicular to one of its faces and as if one were looking into the inside of a cube or room. All the internal walls or planes appear to converge into one central point.
- In a two-point perspective, the cube, object or building is viewed horizontally but obliquely with two external faces in view. The two sets of horizontal lines of these faces seem to converge in two opposite directions. This is similar to standing on a street corner looking down two right-angled streets.
- In a three-point perspective, three faces of a cube, object or building are exposed as the viewpoint moves up or down. All three faces seem to disappear into three different points.
Look to the examples below for the different perspective types...
All the drawings we produce at all stages of the design process are a version of Multiview, paraline or perspective drawing. While multiview plans, sections and elevations are the most commonly used, most people not engaged in the architectural or building professions will not understand these. They will most connect with the three-dimensionality of paraline drawings, or more likely the familiarity of perspective drawings.
It is important to add all these drawing systems to our tool kit and learn to use them in different ways depending on what we want to communicate.
Liz at ArchiMash
PS…If you have any questions or thoughts about architectural drawing systems or drawing in general, let me know at archimash.com/askliz.