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Graphic representation

Lesson 1:

What is graphic representation?

Graphic representation is a form of communication, just like written or spoken language, which allows us to transmit ideas in a very precise way through drawings, images, symbols … It is a language that has the great advantage of being universal, as it is understandable by anyone, regardless of where they come from. Think, for example, about how easy it is for a tourist, regardless of nationality, to move around a city with a tourist map like the one in the image:

(Eleldanense, CC BY-SA 3.0, Wikimedia Commons)

Or how much easier it is to assemble a piece of furniture with the help of some instructions that, in addition to written text, have drawings that show the different parts and their exact placement:


Graphic representation can be divided into:

  • Artistic drawing: which has the goal of transmitting emotions and feelings.
  • Technical drawing: which has the purpose of representing or describing a part of reality.

Below you can see two examples of graphic representation, both by the same author, Leonardo da Vinci. Despite having been made by the same person, his intention in the image on the left (artistic drawing) is quite different from the image on the right (technical drawing). While in the first it aims to awaken sensations in the viewer, in the second its objective is to accurately describe how some of the technological devices that he developed in his life work:

(Left: Lady with an Ermine, Leonardo da Vinci, Wikimedia Commons; Right: Atlantic Codex, Leonardo da Vinci, Wikimedia Commons)

In the technology subject we will focus on the form of graphic representation that is used to describe reality in a precise way, that is, in technical drawing. This way of representation is widely used in the technological field mainly to design objects, pieces or structures that make life easier for us.

Think about how useful graphic representation can be, mainly technical drawing, when, for example, we need to design and manufacture a vehicle. The engineers in charge of the design of a car must have an idea of ​​the shapes, measures and other characteristics of the car in mind. However, they will need to represent that idea graphically or, otherwise, it will be very difficult to tell the workers how they must proceed.

Transmitting all the necessary information orally would be practically impossible and many mistakes would be made. For this reason, drawings like the one below are created to clearly describe how each of the parts must be manufactured and how they should be assembled later:

(Left: Pixabay; Right: Anyusha, Pixabay)

Sketches and plans.

In the design of any product (from a bicycle to a building), a process is followed in which its characteristics are progressively described with greater accuracy. Think, for example, of the process that takes place from the moment an architect has an idea for ​​a house until construction begins.

Probably, the architect will first draw a very simplified picture that roughly represents his idea. This initial representation is called a sketch.

A sketch is a drawing, usually without dimensions, that provides a general idea of the product or structure that is going to be created.

(Regina Cervantes Aceves, CC BY-SA 4.0, Wikimedia Commons)

A second step in the design process might be adding, by hand, some important dimensions to the sketch, in order to give some information about its size and how each of its parts is going to be assembled. This way, other people will be able to have a better idea of the final product, though still not a perfect one. As this kind of drawing requires a higher level of detail they usually represent specific parts of the complete design.

(Iria99, CC BY-SA 4.0, Wikimedia Commons)

The last step in the design process is to make drawings with a high level of detail that can represent the whole product or just a part of it. This kinds of drawings are called plans. In this case, all necessary measures must be included so that the workers in charge of manufacturing the product or constructing the building will know exactly how to proceed.

In this case, the need for precision calls for the use tools, such as a ruler, set square, protractor, compass… and currently the use of computer programs, known as CAD programs (Computer Aided Drawing). Below you can see the plan of a house:

(Cocoparisienne, Pixabay)

The previous process is carried out not only for the construction of houses but for the design of all kinds of products, from the simplest, such as a can of soda, to the most complex ones, like a telecommunications satellite or a spaceship, for example.

Types of technical drawing.

Two different way of representation are used in technical drawing.

The first one consists of drawing an object or building so that several angles can be seen at the same time. That is called perspective drawing. There are different ways to represent an object in perspective

Dentro del dibujo técnico, que como ya hemos explicado tiene la función de describir con precisión un objeto, nos encontramos con dos formas muy diferentes de representación.

  • Cavalier perspective.
  • Isometric perspective.
  • Conical perspective.

(Original images)

Cavalier perspective

Isometric perspective

Conical perspective

As you can see, perspective drawing gives us a general idea of ​​how the object or building that is being represented is. This kind of drawing allows us to see several angles of an object at the same time, that is why the result is similar to how we see objects in reality.

However, there is another form of technical drawing in which an object is represented as seen only from one of its angles. This form of representation is called multiview projection. The following images are examples of this kind of representation:

(Modified from: Pixabay)

(Wilder Llanes Méndez, CC BY-NC-ND 2.0, Flickr)

Typically, this type of representation is chosen when we want to describe the different parts of an object in detail. With a perspective drawing it is quite difficult to represent the smallest parts of an object, while when drawing only one of its sides it is much easier to increase the level of detail.

In the following pages we will learn to draw the views (multiview projection) of an object from a perspective drawing.

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