Dafna Fisher-Gewirtzman

Spatial openness as a practical metric for evaluating built-up environments

This paper reports on a primary metric tool developed in a collaboration between an architecture researcher and a computer science researcher. The development of this tool emerged from the concept that the spatial openness (SO)—the volume of free space measured from all possible observation points—is an important quality indicator of alternative spatial configurations within given constraints; this concept is based on the idea that the geometry and morphology of the built-up environment influence perception. Previous work showed that comparative SO measurements in alternative spatial configurations are correlated with the comparative perceived density, and in particular that a higher value of SO indicates a lower perceived density. We present a feasible 3D computational method for measuring SO and demonstrate its potential use in the design process. The SO metric is a step towards the development of quantitative comparative evaluation of building shapes and spatial configurations related to the 3D observation of open space.

A 3-D Visual Method for Comparative Evaluation of Dense Built-up Environments

The work reported here is a contribution by the authors to the search for reliable metric method for spatial evaluation, related to human perception of ‘openness’ and to the development of evaluation tools for urban planning and design. A recent innovation, the ‘spatial openness index’ (SOI), a quantitative index, based on a three-dimensional visual analysis of space is applied here. This approach reflects the hierarchical order found in the urban environment: dwelling unit, building, neighbourhood, etc. This index expresses oppenness to natural light, air, and near and distant views, for each level in the hierarchical order. At the basis of this work is the assumption that the SOI is correlated with the ‘perceived density’, evaluated by people responding to alternative spatial configurations. A preliminary indication test was carried out in order to justify this assumption. In this test, groups of spatial configurations with equal built masses were ranked both by their calculated SOI and by statistical analysis of perceived density evaluated by participating individuals. Good agreement was found between pairs of results obtained for most of the spatial configurations.

To go where no man has gone before: Virtual reality in architecture, landscape architecture and environmental planning

Abstract The use of virtual reality has its roots in visual communication science but disparate mechanisms and applications set it apart from the many tools of visualization. This paper reviews the use of virtual reality (VR) environments for research and teaching in the context of three disciplines: architecture, landscape architecture and environmental planning. As opposed to other uses of virtual environments, for example, in the health sciences or engineering, simulations using virtual reality theatres or labs in the three fields we explore are used to display inaccessible realities. VR environments are typically used in these fields for planned and designed realities, not yet existent or with nonexistent components. Each field has different reasons for spatial or temporal inaccessibility to reality, prompting the need and eventually the capability to achieve various levels of accuracy in the virtual setting. We describe current VR research opportunities and challenges in each discipline and emphasize what they can gain from sharing virtual reality systems for research and education.

Visibility of urban activities and pedestrian routes: An experiment in a virtual environment

Abstract Patterns of pedestrian movement in cities are influenced by visibility of urban activities, among other factors. This paper describes a behavioral experiment in an immersive virtual reality, where individuals are exposed to visual stimuli and their route decisions are recorded. To evaluate the effect of urban visibility on the pedestrian route choices, we introduce visibility scores, such as a graph theoretical centrality measure, to represent the urban environment. Participants in the experiment select routes and the chains of their navigational decisions are then associated with the visibility scores. The selected routes in the virtual reality are compared with all possible routes, which are generated by computational random walk simulations. Statistical analysis suggests that pedestrian navigation choices are purposive and that they are influenced by the specific visibility attributes of the urban environment. Therefore, the research contributes toward development of a unified framework that incorporates the interaction of urban morphology and human spatial behavior. In addition, our experimental procedure and our results highlight the potential of a virtual reality laboratory as a research environment for complex urban situations.

Visual Exposure and Visual Openness: An Integrated Approach and Comparative Evaluation

This paper reports on the development of an integrated model analyzing Visual Exposure and Visual Openness in the urban environment. The authors propose a measurable morphological approach that could contribute to the planning and design process. High permeability to a view is one of the main objectives in the development of dense urban areas. It can influence a residents satisfaction and the real estate value. In addition, Visual Exposure, referring to privacy, is also a major aspect influencing quality of the human environment. Combining these two important factors and being able to measure and evaluate both of them in one model is of a great importance and can support a sustainable urban environment.

Different approaches of visibility analyses applied on hilly urban environment

Abstract The work reported in this paper is a contribution to the search for reliable visibility evaluation method for the urban environment. We examine three analysis models: 1. Point based visibility graph of street network based on , 2. Voxel based volumetric visibility analysis (Fisher-Gewirtzman et. al., 2013) and 3. Line Of Sight (LOS) based visibility analysis (Fisher-Gewirtzman and Elber, 2013). We compare between these models to explore their suitability to a hilly urban spatial configurations. We describe the similarities and differences. In this study we carry out a test comparing the value of visibility degree centrality for street network to the assessments of 3D Voxel and LOS visibility analyses. Our results demonstrate that junctions with similar rankings in all three models were located in a fairly flat topography and all the junctions with different rank were located on the border of a sloping topography. Their visibility was influenced by the changing topography. This preliminary study will be followed by more comprehensive research looking at a variety of urban, architectural and topographic conditions. These findings may provide planners and designers with information about factors that affect the visibility of the urban environment and may put forward new ideas to improve the existing measurement tools.

Can visibility predict location? Visibility graph of food and drink facilities in the city

Abstract The spatial arrangement of socio-economic facilities in the city is shaped by the interaction of many individuals in the context of a particular physical structure. The urban physical environment displays characteristics of networks (graphs) where nodes and edges are embedded in space. For decades, the analysis of urban network structure represents an attractive model for describing urban phenomena. This paper presents novel means of understanding how socio-economic activities are distributed in urban environment, what forces influence their spatial patterns and how urban structure and functions are mutually dependent. We investigate the functional aspect of urban spatial networks; specifically we study the spatial distribution of food and drink public facilities in the historical district of Tel Aviv-Yafo Israel. These places, cafés, coffee shops, restaurants and others are known as ‘third place’ in urban sociology and play an important role in establishing a sense of place. We propose a novel graph analytic framework in which the third places are incorporated by means of visual accessibility. The development of this framework emerged from the concept of Integrative Visibility Graph (IVG), a quantitative method, based on visibility analysis of urban structure and its functioning. Several centrality measures from complex network theory are applied to the proposed graphs in order to evaluate structural position of third place locations in the urban network. Our findings illustrate a strong correlation between street centrality values and third place distribution.

3D visibility analysis indicating quantitative and qualitative aspects of the visible space

This paper presents the development of a 3D visibility analysis model that consist a combination of objective calculations and a subjective evaluation, representing the value of the view and its possible impact on the perception of a viewer. The model, developed in Matlab, has default weightings for different elements of the view, which can be changed in accordance to future users. A bounding box, defined as working area consisting buildings and topography, is divided into equal-size voxels and sub-voxels for higher accuracy. This model may be further developed for use in practice to support a sustainable future urban environment.

Visuospatial search in urban environment simulated by random walks

Abstract Human spatial behavior, navigation and activity in cities are affected by the visibility of urban environment. In this paper pedestrian visual search for urban locations is conceptualized as a stochastic process and modelled by random walks (a succession of random steps). Urban environments are represented as a chain of navigational decisions forming a mathematical graph of visual connectivity. Random walkers wandering on the graph imitate aggregated visual search for urban activities in the case study, which is the historical district of Tel Aviv-Yafo. The study is then compared to a set of systematically generated computational patterns represented by various visibility graph models. The main result discloses a strong positive relation between local and global visibility properties. A positive global–local relationship of spatial networks is termed intelligibility in space syntax theory and is deemed a key determinant in human navigation and wayfinding. Additionally, we compare the first passage time, an outcome of stochastic simulation, with deterministic graph theoretic measures of centrality, namely closeness and betweenness centralities. Comparison of distinct visibility types aims to identify a navigational signature of the case study and allows measurement of visual distinction between different locations in the city.

The association between perceived density in minimum apartments and spatial openness index three-dimensional visual analysis

Small apartments exist in dense cities worldwide. Developing adequate quality small apartments in city centres would strongly attract current demand. Analysis, predictive tools and design concepts regulated for better interior design and lower perceived density would provide residential environments with happier tenants. This research evaluates perceived density and visual privacy in alternative minimum apartments based on the spatial openness index three-dimensional visibility analysis, i.e. their accumulated three-dimensional visibility calculations. The compatibility of the spatial openness index concept as predicting perceived density in minimum apartments was examined and assessed. An empirical study was conducted using a virtual reality experiment in a controlled environment – An immersive three-dimensional visualisation laboratory1, with more than 100 subjects participated in the experiment. Significant relations were found between perceived density and visual privacy for all apartments (single and double story). The measured volume of visible space from the door viewpoint (the entrance to minimum apartments) and the perceived density evaluated there by participants, and a general evaluation for the apartment are strongly related for both (single and double story groups). Strong correlation was found between visibility measurements from the door and the ‘visual privacy’ at the sofa/bed. According to assessment results the spatial openness index three-dimensional visibility analysis can predict the perceived density of minimum apartments.