La freccia e il cerchio
anno 7, numero 7, 2016
pp. 183-186

Manuela Piscitelli
Perceptive deceptions in architecture

   Sight is the sense through which we receive the most information about reality that surrounds us. However, we do not always work out this information correctly, returning a mental image that corresponds exactly to the original, but sometimes misled by false clues, we fall into perceptual illusions that make us recognise objects and spaces differently from the real ones.
   The human perceptual system recognises the shape and size of objects through soalled “depth clues”, such as the overlap of the elements in the foreground to those in the background, the shading, and above all, the apparent decrease in size that makes us think smaller the distant objects, as a result of our visual system that is essentially in perspective. To these clues, we should add the so-called “perceptual constants”, which allow us to recognise regular shapes that actually look distorted or foreshortened because of the perspective view.
   In fact, the perceptive system, consisting of the eye and mind, processes information in order to connect prospectively deformed objects and spaces to regular shapes of which we have seen before. It therefore differs from the simple optical vision, as it is a coding of images coming from our visual system, subject to a cultural judgment. This means that we interpret images basing on previous experience and knowledge of the characteristics of objects and spaces.
   What we perceive is then an apparent space or from our experience, we consider the most likely space corresponding to the image formed upon the retina, but does not always coincide with the real space, as will be shown in the following examples.
   In fact, artists and architects have often intentionally exploited these ambiguities inherent to the human perceptive system in order to “deceive” the viewer, leading him to see a different space from the real one. A well-known example in graphics are the so called impossible images, widely disseminated by the extraordinary work of the artist Maurits Escher, produced by presenting a series of data incompatible with each other, according to which the perception is deceptive because it does not allow us to refer to an object that our intellect considers real or achievable.
   In the architectural field, deceptions can be of different types. Egyptian and Greek sacred architecture already used optical corrections. The painted architecture, which was already present in Roman times and used greatly in the Baroque culture, creates illusory spaces in continuity with real spaces. The deformation of the architectural space deceives the observer suggesting a different spatiality from the real one. Finally, in recent years, the most sophisticated form of illusion ever conceived has added to previous concepts, where the simulation of immersive virtual spaces means the user has the feeling of moving as they would in a real space.
   The optical corrections are a simple case of perceptive deception, but they surprise us for the precocity of application, that testifies the understanding of the vision mechanism in Egyptian and Greek times. Knowledge in optics allowed the Greeks to construct temples that cancelled the aberration effects on the shape resulting from the perception.
   In particular, the long lines of the horizontal elements, such stylobate, architrave and frame, suffered a perceptive curvature with the concavity facing upwards. To achieve the illusion of horizontality, in many examples including the Parthenon, they made these elements slightly curved, with the concavity facing downwards in order to compensate perceptive errors. Similarly, to avoid the optical effect of divergence of columns and to obtain an illusion of verticality, they made the column axes converging upwards, with a maximum inclination in the corner columns, and gradually smaller towards the centre of the facade.
   We should find a higher level of sophistication in the creation of perceptive deceptions in the painted architecture, starting from the painting of gardens, which was widespread in the Roman world since the first century B.C. under the influence of the Hellenistic scenography. Salvatore Settis argues that the genre of garden painting is the result of a fusion between pictorial fiction and reality, in order to suggest the illusion of a real garden. In support of this hypothesis, he gives the example of the underground nympheum of Livia’s villa at Prima Porta in Rome, where an amazing fresco painting of a garden, dated to 40-20 B.C., is preserved.
   The lack of light and air in the underground environment is in stark contrast to the subject of the paintings, an airy garden depicted in detail with great variety of plants and birds, life-size and without interruption even at the edges. In the absence of vertical architectural elements such as columns or pillars, the garden perspective is cleverly obtained by the representation of horizontal elements: the fence of reeds and willow branches in the foreground, and a marble balustrade in the background. Between these two elements, the garden comes to life with trees rich in colourful flowers and fruits, and birds of different species. The double fence has the function of defining the green space in an illusionary way, moving the viewer away from the plants placed over the balustrade.
   Other devices further enhance the sense of spatial depth. The reduction of plant details, highly accurate for those in the foreground, allow a precise botanical analysis of each plant, and become gradually less accurate and faded in the distance, is a depth clue. A rare and innovative atmosphere is obtained thanks to the colour variations ending in an airy turquoise sky, the last frontier of the view. The presence of birds in flight and branches with the tops bent by the wind give the feeling of movement.
   The composition of the garden, like in a real garden, is organised according to a symmetrical scheme: the main trees are placed at the centre of the painted wall, joined by other trees in a balanced composition, according to precise rules. It is a clearly defined space, as a real garden would be, in the sense that the extension of the represented garden is limited. On the contrary, the spatiality of the nymphaeum is deceptively extended, denying the walls as if they were broken through by painting, or as if it were a glass pavilion surrounded by a real garden. Such examples can be found frequently in Roman architecture, such as in the House of the Golden Bracelet at Pompeii, where painting dematerialises the walls, creating a deceptive spatiality with a fine line between the real space and the illusory perspective in the painting garden.
[…]