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Visual Dynamics of Architecture

As we navigate through the built environment and interact with it, we are continuously involved in the processing of spatial information. Visual perception appears to be simple and effortless and yet is, in fact, extremely complex. To understand the effect that architectural design decisions have upon patterns of navigation and way-finding it is necessary to first understand the process of environmental cognition and then to develop tools to analyze the built environment that surrounds us.

It seems natural to develop tools that can help us understand the experience of the environment, either to help modify or improve the environment itself. Visibility analysis is an intuitively attractive way to investigate the environment as it gives one the perspective view of the occupant. It allows us to make rigorous mathematical statements about systems, and thus it allows us to apply mathematical certainty to the experience of urban and building environments. We might use visibility analysis to talk about properties of the built environment, or to talk about how people can move or interact within the visible space, or to discover the significance of objects placed within that space.

In the search of work related to spatial analysis, many researchers have built their analysis around the psychological theories of James J. Gibson, who was an American psychologist considered one of the most important 20th century psychologists in the field of visual perception. Gibson's theories were mainly focused on the idea that observers sample information from the outside visual environment. Many of Gibson's initial ideas about perception were developed during his time directing aviation training during World War II, where it was critical that pilots orient themselves based on the characteristics of the ground surface observed visually. Gibson discovered invariants in the terrain and sky that were used as the primary perceptual source.

Rather than beginning his studies with the sense organs, or with the whole organism (human being or animal) that is the perceiver, Gibson begins with the environment to be perceived. Thus, the questions he asked were not how does the perceiver construct the world from sensory input and past experience, but rather what information is directly available in the environment when a person or animal interacts with it. Gibson suggested that perceptual systems are attuned to the invariants and variables in the environment, and that this information is actively sought through interaction. For Gibson, the environment contains objective information, "invariants" that allow recognition of the properties of surfaces, objects, and so forth. "When no constraints are put on the visual system, people look around, walk up to something interesting and move around it so as to see it from all sides, and go from one vista to another. That is natural vision..."

In this book "The Perception of the Visual Word", Gibson studies the field of view of an observer distinguishing between the visual world and the normal visual field. He describes the visual world as "the familiar, ordinary scene of daily life, in which solid objects look solid, square objects look square, horizontal surfaces look horizontal and the book across the room looks as big as the book laying in front of you" . The normal visual field has boundaries. When measured, it extends about 180 degrees laterally and 150 degrees vertically. It is sharp, clear and fully detailed at the center, but progressively more vague and less detailed toward its boundaries. The visual field, therefore, possesses a central to peripheral gradient of clarity. The visual world does not. It does not even have a centre, which agrees with the fact that it does not have boundaries. One is aware of a world which extends backward behind the head as well as forward in front of the eyes. The world in other words, surrounds us for the full 360 degrees. The world is ordinarily perceived by scanning, by moving the eyes rapidly from point to point, and the objects and surfaces which compose it are always clear and fully detailed.

The distance between the various objects and surfaces that surround us on all sides is also an important study that influences the visual perception of our environment. We relate to these environmental features in terms of their positions relative to us (above or below, to the left or to the right, in front or behind) and also in terms of their distances from us (touching, adjacent, near, away, far, beyond and remote). Given the difficulty of estimating distances accurately, and because of the false impression of accuracy given by expressing such estimates in terms of metrical units, Gibson divides the range of everyday space into the two categories of "aerial space" and "local space". Aerial space can be defined as the visual surroundings extending away from the observer and bounded in any direction by the horizon, the surface of the earth and the sky. It can be distinguished from local space primary by its volume and long range of distances. Local space is the kind of space to which we are accustomed, it is enclosed and restricted by walls. Even outdoors, in a civilized environment the spatial environment is cut up and limited to localized areas by buildings and other objects which erase the horizon. He also points out: "Persons who are adapted to going about and making the ordinary judgments of distance in the city are usually misled by the extent of distances in the desert, mountains on water or from a plane. Generally, aerial distances are poorly estimated by such persons because they are unfamiliar with the visual cues present in the situation for space" .

It is important to distinguish between those spaces we occupy at a given moment and those we do not at that same moment. For example, we occupy a local space at a given moment only when the elements that establish that space are visible across the entire (180 degrees) normal visual field. But if through an opening in this enclosed local space, the occupant has a glimpse of the aerial space on the outside, we term this relationship a view. The occupant has less than a 180 degree view of the elements that establish the aerial space and therefore, does not occupy. Views are thus mediators between local spaces and aerial space, between here and there.

Views have a direct relationship with the location of the observer within the space. The observer does not have the same view of the outside space by looking through a window from the right corner of the room than from the left corner, as by changing their location within the occupied space, their field of view also changes. The area in a spatial environment directly visible from a specific location within the occupied space is called "isovist".

An isovist is "the set of all points visible from a given vantage point in space and with respect to an environment". Isovists offer the great chance to describe spatial properties of environments, and explore how the form and configuration of a space influence the experience and behavior of the users. Benedikt considers geometric properties of isovists, such as area and perimeter. Thus he begins to quantify space, or what our perception of space might be, and the potential for its use. When, for example, people enter an empty restaurant, they do not sit down at an arbitrary place, but carefully choose a seat in relation to the surrounding architectural features.

I find that the study of isovist lacks a tool that can adequately represent a space as visually experienced by its users as there are no means of perceptually or conceptually simulating the continuous, comprehensive, real-time appearance of the environment for people moving through it at normal eye levels, with actual fields of view and at given rates of motion .It is perhaps, this direct relationship between vision and movement, that I am really interested in. How our movement and path through an environment is related to our perception of it.

In the search of work related to the dynamic experience of the environment I have found the work of Philip Thiel, who is a French Architect that believes that design should be based on the eye level experience of the users in the course of their movements though the environment, and also argues that the primary concern when designing should be the needs and preferences of the users.

His study began in 1951 as a consequence of an urban design thesis concerning the visual redevelopment of a sector of the city of Boston. This project proposed to increase the visitor's experience of the historically important buildings and sites in the area, by organizing their viewing sequence along a pedestrian pathway. While working on this project he realized that conventional design tools, well adapted for the description of static objects from static viewports (perspectives, plans, sections and elevations), was inadequate for this special task of representing the environment from moment to moment as one moves through it with actual fields of view and at different speed. For example, a pedestrian moving at the rate of 4 km per hour has an entirely different kind of experience (he can be aware of small details) from a motorist driving at 50 km per hour, who has only a very general idea of his surroundings as they rush past him, unless he is wholly concentrated on the roadway and other vehicles. No film director would compose a film running at a speed of 4km per hour just like one running at 50 km per hour, but town-planners do this constantly as long as they treat sidewalks and roadways on an equal footing, that is to say, lay them out side by side.

One of Thiel's main concerns is that there are rarely transition spaces from buildings to the city and the immediate surroundings, just break-off points, walled, raised, separated or terminated with antiseptic plazas, rather than treated as a point of junction with the scale, function and spirit of the setting. "...I honestly don't think individual buildings are as important anymore. Penzoil Place is beautiful, but who cares? You get into your car and drive past ugly parking lots and junky stores to get there. You drive into a subterranean parking lot and walk through grimy tunnels. Or you walk above ground or sidewalks that are not wide enough. By the time you reach the building you don't care if it's beautiful or not. How you get there and what you have to look at on the way are as important as having beautiful buildings in a city."

With this idea in mind Thiel developed a series of studies to help us understand the dynamic experience of the environment. He proposes a sequenced notation of spaces where the details of the viewers experience can be recorded by paths as they progress through different spaces.

First Thiel describes what he calls the Space Establishing Elements which are, as described by Gibson, the three generic elements that define a space: objects, surfaces and screens. Objects may be thought as a two or three dimensional forms existing as separate, discrete visual entities in a larger space than the one they help establish. Surfaces are two dimensional forms limited in spatial effect to the space they help establish. Screens as perforated surfaces or closely spaced objects, obviously are an intermediate type between the other two as limiting conditions. These three elements then are the generic agents which perceptually delimit a portion of the great void of space and which occur, as the figure suggest, as both natural and built forms.

Thiel also studies the way in which these elements interact with each other and then assigns a numerical value to the different configurations of surfaces, represented from the occupant's field of view. These configurations vary from a complete openness to a complete enclosed space, where 0 would be the complete opening and 100 a complete enclosure. The spaces situated in the columns between 0 and 100 increase gradually by 10 depending on its sense of enclosure. The spaces with a percentage higher than 30 are suggested spaces, spaces higher than 70 are called volumes and the spaces in between are called sketch spaces.

The next concept of space determination deals with the dimensions of the analyzed space and its "enclosed character". There are three key factors in this study: the space determination, the proportions of the Space Established Elements, and the absolute volume of the space. The "enclosed character" of a space vary from 0 to 10, where 0 represents a claustrophobic space and 10 a complete open environment. This feeling of enclosure is obtained by using both the volume of the space analyzed and its space determination value. The volume of the space is set in which the length is equal to 1.6 times the width, and the width is equal to 1.6 times the height. This ratio is approximately "the golden mean", and the space form so proportioned is assumed as a default reference base. Thiel gives a minimum habitable height of 1.8m which has a volume of 28.6m³, a maximum length of 4500m corresponding to the maximum distance seen by the human eye on the horizon from the ground and has a volume of 22.245 x 10000000000m³.

In order to obtain the feeling of enclosure, the volume of the analyzed space should be divided by 2.86m³ getting a value between 0 and 10. Using this value and the value taken from the space determination process, a sense of enclosure value will be calculated. For example, a room with a volume of 40m³ will be divided by 28.6m³ to give 1.38m³, and a space determination value of 60 will get a level of enclosure of 3.

If we study two spaces, each with the same space determination value, but with a different volume, the feeling of enclosure within each space will differ to the other. At the same time if both of the spaces have the same volume but a different space determination value, the sense of enclosure would also be different. Therefore, both are as important as the other and rely on each other to provide an accurate quantitative value of the space occupied.

The study suggested by Thiel is a tentative first approximation of the dynamic experience of different spaces, as it lacks of very important factors such as the color and texture of the Space Establishing Elements and the level and type of illumination in the spaces, the temperature and humidity, the arrangements, the types of furnishing and the human activity in or associated with the space. But it starts to suggest its application when designing in order to achieve a harmonic transition between open and enclosed spaces, which could be used in the same way musical notations control the harmony or sudden change of music, which has an impact on the audience's experience. "Architecture may well be 'frozen music' like a photograph record; but man is the pickup whose movement realizes the experience".

The main objective of my dissertation will be the practical verification of the systems developed by James Gibson, Philip Thiel and Michael Benedikt, whose purpose is an attempt to rationalise how we can use visibility analysis to explore architectural spaces by the codification and valuation of relative parameters to the physical environment. Applying them to different unban environments in order to investigate the possibilities and limitations of these methodologies. It is difficult to affirm that the systems presented in this paper have a great exactitude, giving their subjectivity, but it will prove interesting to test their accuracy and see how useful they prove to be.


  • Thiel P, 1961, "A sequence experience notation for architectural and urban space" Town Planning Review 32 (33-52)
  • Thiel P, 1998, "People paths and purposes: Notations for a Participatory Envirotecture" (University of Washington Press, Seattle, WA)
  • Benedikt M L, 1979, "To take a hold of space: isovists and isovists fields" Environment and Planning B: Planning and Design 6 (47-65)
  • James J. Gibson, "The Perception of the Visual World" (Boston: Houghton Miffin, 1950)
  • James J. Gibson, " The Ecological Approach to Visual Perception" (Boston: Houghton Miffin, 1979)