Modelling / 3.2 /
Graphical Modelling

Graphical models are used to communicate design ideas. Graphical models can take many forms, but their prime function is always the same—to simplify the data and present it in such a way that understanding of what is being presented aids further development or discussion. Designers utilize graphical modelling as a tool to explore creative solutions and refine ideas from the technically impossible to the technically possible, widening the constraints of what is feasible.

3.2.1 | 2D and 3D graphical models

Orthographic projections of an iron

Graphical modelling represents objects on a medium that physically has only two dimensions (2D) - most commonly paper or a computer screen. Graphical models are restricted in that they can only provide the beholder with the stimulus of sight.

Graphical models can take many forms, but their prime functions are:

To present information in a way that allows easy insight.
To aid discussion and development of what is being presented.
To refine ideas to the technically possible.

Graphical models are different from concept models in that they try to accurately define design features rather than merely provide directionality.

2D graphical models are often diagrammatic - They provide a 'flat view' of an object annotated with labels indicating for instance dimensions, material choices or construction techniques.

The most commonly used form of 2D graphical modelling in the design of physical objects is an orthographic projection. In architecture orthographic projections of buildings are called elevation views. Another common 2D projection is the section view - a view that shows the inside of an object.

Architectural elevation view

Architectural section view

Architectural plan view

A Light Plan by Luke McLindon on Behance

Detailed technical drawing of the Apple Watch, with several orthographic projections - Hackster.io

Despite the medium of graphical models being two-dimensional, an impression of the third dimension (3D) can be provided through the use of perspective or a combination of projections from different sides of a design.

When creating graphical models on a computer these can be animated to give the viewer the illusion of being able to orbit around a design or even see parts move. Because of advances in computer-aided design (CAD), in many industries, orthographic projections (and other 2D graphical models) are usually generated from objects that are modelled in 3 dimensions first.

Sophisticated Computer-Aided design can bring 3D graphical models quite close to what a final product in the real world would look like. Software can calculate the effect of different light sources on a modelled object. This process, called rendering, not only calculates where shadows are, but also the reflection of light of parts of the object (that in turn might cause shadows on other objects). Photo-realistic rendering is very resource intensive (needs a good graphic card and powerful computer) and the algorithms calculating the light effects are proprietary and often expensive to use.

3.2.2 | Part and assembly drawings

An assembly drawing shows how parts of a product fit together. They are commonly used to show how to assemble parts of model kits or flat-pack furniture.

There are two types of assembly drawing:

A fitting assembly drawing shows the parts put together and can be in 2D or 3D.
An exploded assembly drawing that shows the parts separated, but in the correct orientation for fitting together. Usually drawn in 3D.

A parts drawing provides the information to assemble a product in a similar way that an assembly drawing does but with the additional benefit of a List of Parts (LoP) or a Bill of Materials (BoM). These parts lists provide detailed information about the parts, materials, and quantity required to assemble the product.

Ikea Kura Reversible Bed full assembly instructions. Click here to see the full detailed assembly instructions. Note how the instructions are communicated graphically, with no words.

2D fitted assembly drawing.

3D parts assembly drawing.

3D parts drawing with Bill of Materials (BoM).

3.2.3 | Perspective, projection and scale

Three dimensions can be simulated on a two-dimensional medium by drawing in perspective. There are several types of perspective drawings. Some are easier to construct than others. At the early stages of the design process, designers will prefer quicker methods over more sophisticated methods, even though the latter might provide a more realistic view of an object. The most common perspective drawing types are:

Oblique
Isometric
One-point perspective
Two-point perspective
Three-point perspective

The last three listed types of perspective drawings attempt to represent space by foreshortening through the use of vanishing points.

Projections are two-dimensional views of an object. Where a perspective drawing displays an object from a single viewpoint, projections look the same as long as the beholder remains in the same plane (usually perpendicular to the object).

There are different standards for projecting views. The most common are first and third angle projections. In order to prevent misunderstandings about a design presented with projections, the designer will always indicate which standard is used.

When producing a graphical model on paper in a context where the dimensions of the object are under scrutiny, a designer will attempt to draw all parts of the object to scale. This means the designer chooses a fixed ratio between the size of any element in the drawing and the size of that same element in real life.

Scale statements are found on most more formal design drawings (assembly drawings, maps, etc.). The most common format is the representative fraction. A scale of 1:4 means that one length unit in the drawing is equivalent to 4 length units in real life.

When using CAD software, the scale ratio is automatically calculated for the output medium. E.g. if a designer prints a design on an A3 sheet of paper, the software will determine the scale of the end result and print that on the drawing.

3.2.4 | Formal and informal drawing techniques

Almost all examples of graphical models presented above are forms of formal drawing techniques. They are constructed following (strict) standards of a particular industry or standardizing institution. These standards are helpful as the interpretation of graphical models needs to be the same across countries and industries. This is mainly the case because the purpose of these drawings is to convey technical details. Formal drawings are often made with the use of technical aids such as drafting tables, t-squares and protractors.

When designers produce freehand sketches they often include brief notes or annotations to help explain the thinking behind the visual image. A range of freehand techniques can be used in the early stages of the design process to explore shape, aesthetics, relative parts and basic assembly.