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Transparency effect: Urban design definition

"Transparence" signifie perception visuelle simultanée de différentes aires ou couches spatiales." Gyorgy Kepes
"L'avenir se présente sous la forme de la transparence" Walter Benjamin, 1929

Transparency: Quality of a substance (...) which (...) lets light rays pass. 1591. 
Transparent: 1. through which it is possible to see (... c Authorizing the passage of the light by interstices (rare). 1693. 

One will speak about transparency effect when a building or a layout enables the walker to have his/her sight extended through a grouping of urban spaces. 
Transparency only exists in relation to opaque elements. 
The word transparency is rather recent, and the transparency seems to be, until the 16th century, a more or less involuntary effect, a side effect, born from an intention which is foreign for/to him, generally of a functional nature.
Since ancient times, the colonnades of the temple or agora have given an effect of transparency. These features are used for promenading, for public life, and therefore require a fluid pedestrian circulation and some opening. The relation between the degree of opacity and the function is even more obvious in this opposition: "The Doric order organises in the light the transparency of the colonnade, opposed by Hegel to the hermetism of the pyramid. " Field of death, the pyramid excludes any opening. 
In the same way, the monumental gates of the Roman cities firstly mark the symbolic crossing of a city limit. The transparency effect is only a consequence, it is not an aesthetic aim. This idea is led to the extreme in the Eastern culture, with the system of doors and gantries (1), the use of which is often purely symbolic. They materialize the passage from a world to another, from a world down here to the next world.

In the Early Middle Ages, the transparency of the garden fence complements a functional purpose. Low openwork wooden palisades delimit the Hortus conclusus. The limit can thus be indicated while leaving the garden visually open. 
The Gothic cathedral of the 13th century introduces transparency into the city. The flying buttresses express the sophistication of the structure, and break with the massiveness hitherto inherent to architecture. The Romance buttresses are succeeded by openwork volumes, which create an effect of transparency all around the building. The stained glasses, as for them, bring transparency inside the building.
In 1380, an important stage was reached in France: the appearance of the word transparence (transparency), which comes down to saying that the concept got formulated. 
It would seem that, from this moment on, the transparency is explicitly conceived as a plastic element. 
At the 15th century Renaissance, as the models were drawn from the Antiquity, one re-used the transparency effect of elements like the colonnade or the portico. First in Italy, with Palladio, Bramante and Bernin, the frontage gives a new relationship between building and urban space. Its elements - especially colonnades and windows - create a physical and visual transition between inside and outside, between private and public. 
In parallel, the Italian gardens open, on the surrounding landscape, windows of cut plants. One finds the principle of visual transition.

In the 17th century, transparency enters the vocabulary of architecture: the substantive "transparent" indicates "a very thin ornamental panel lit from behind (1762); it applies to a decorative openwork motif, used in both architecture and sculpture (in particular in the Spanish baroque style)" 
In the 18th century, the effect of transparency takes a moral connotation. This will have an echo in the 20th century. The return to transparency wants then to be a "new social order". One compares the physical transparency to the ethical transparency.
the 19th century, the Haussmann's boulevards give an urban scale to transparency. They break with the winding streets inherited from the Middle Ages. They have an objective which is above all very functional: to regulate traffic problems. But, in fact, they offer long continuous prospects which bring depth to the perception of the town (2) 
Moreover, the work of Haussmann systematizes the plantation of trees rows, which allows for another form of transparency: transparency effect of plants, variable according to the seasons (3).

At the beginning of the 20th century, transparency takes a major place, because of the relation which it creates between the sequences of public spaces, as well as between public space and private space. 
The piles are an essential tool of modernism, for they have the advantage to release some land (4). It is the beginning of a type of transparency which is independent of the volume of the building, and at the scale of both the city and the pedestrian. 
Glass construction, since the middle of the 19th century, has been made possible by metal structures (greenhouses of Kew Garden, 1848).
One sees once again the effect transparency acting on the private-public relationship, with the ambivalent inversion of the visual inside-outside relationship, between day and night (5).
The glazed building becomes the standard of international architecture, and finally leads, by multiplying an effect of reflection, to the construction of virtual urban landscapes (6).

The Jean Nouvel building for the Cartier foundation illustrates the current integration of transparency in urban production, by combining several properties. The filter frontage, sort of grid entry to the building behind it, manifests a limit, registered in the alignment of the Boulevard Raspail. The transparency effect makes it possible to build a transition between public space and the building (7).

The effect of transparency is today in the center of the development of a whole of space concepts, like the concept of filter, or that of framing, of urban window. The transparency effect is perceived as being able to qualify a space. This is why those transparency effects (fences, alignments, urban windows...), which will have as a finality to make the city breathe, will be recommended or preserved by the town planning documents. 
One measures well the progression of the effect of transparency: born from essentially functional intentions, it is now itself an object of regulation, of specific concerns. 

CF. TOWN GATE, FENCE, URBAN PROSPECT, ALIGNMENT / BUILDING LINE, VEGETAL/WOODY EFFECT, REFLECTION EFFECT, URBAN WINDOW, GRID

Source: Arturbain.fr