New techniques to measure 2D and 3D visibility over urban spaces are presented in this paper. The concept of the isovist, that is, the visible space from a vantage point, could help in providing a quantifiable basis for Lynch's urban analysis, as outlined in his book [Lynch, 1960 The Image of the City (MIT Press, Cambridge, MA)]. We also expand on the concept of 3D isovists and develop a new technique to calculate them on digital elevation models, whereby the same input information can be processed easily in pixel coordinates and in voxel space, that is, a 3D array of urban-visibility measures. The investigation of what we have called the ‘isovisimatrix’ seems to allow a very useful interpretation of visibility from a visual-perception viewpoint. The approach presented here suggests helpful applications for urban design, in particular for predicting the visual impact of new buildings on the physical context and understanding how open spaces may be used by people depending on visibility features.

The paper presents the core methodology for assessing solar radiation and energy production on building rooftops and vertical facades (still rarely considered) of the inner-city. This integrated tool is based on the use of LiDAR, 2D and 3D cadastral data. Together with solar radiation and astronomical models it calculates the global irradiance for a set of points located on roofs, ground and facades. Although the tool takes simultaneously roofs, ground and facades, different methods of shadow casting are applied. Shadow casting on rooftops is based on image processing techniques. On the other hand, the assessment on facade involves first to create and interpolate points along the facades and then to implement a point-by-point shadow casting routine. The paper is structured in five parts: (i) state of the art on the use of 3D GIS and automated processes in assessing solar radiation in the built environment, (ii) overview on the methodological framework used in the paper, (iii) detailed presentation of the method proposed for solar modelling and shadow casting, in particular by introducing an innovative approach for modelling the Sky View Factor (SVF), (iv) demonstration of the solar model introduced in this paper through applications in Geneva’s building roofs (solar cadaster) and facades, (v) validation of the solar model in some Geneva’s spots, focusing especially on two distinct comparisons: solar model versus fisheye catchments on partially inclined surfaces (roof component); solar model versus photovoltaic simulation tool PVSyst on vertical surfaces (facades). Concerning the roof component, validation results emphasize global sensitivity related to the density of light sources on the sky vault to model the SVF. The low dense sky model with 145 light sources gives satisfying results, especially when processing solar cadasters in large urban areas, thus allowing to save computation time. In the case of building facades, introducing weighting factor in SVF calculation leads to outputs close to those obtained by PVSyst. Such good validation results make the proposed model a reliable tool to: (i) automatically process solar cadaster on building rooftops and facades at large urban scales, (ii) support solar energy planning and energy transition policies.

Perceptual simulation represents an attempt to anticipate physical reality, whereby people can experience and interpret future environments from a subjective perspective. Working on experiential simulation for urban and landscape design requires an understanding of the relationship between man and the environment from a perceptual and cognitive standpoint. In fact, only by investigating the sensing and cognitive processes behind perception can we establish an informed approach to simulation of places and their ambiances. In particular, we propose a parallelism between man/environment and man/simulation relationships, aiming at giving back a framework for replicating in simulation the multisensory aspects that occur in the perception of the physical world. Hence, the objective of this article is to present how we approach the dimension of perceptual simulation within our research and professional work as urban designers. From a methodological point of view, we explored the topic through two main tasks, namely the selection and reconstruction of the research context and the key issues of perceptual simulation finalized in the second task, i.e. the construction of a set of simulation tools for urban design, intended as a matrix of possible practical applications. In particular, the theoretical framework presented in this work consists of a selection and overview of references relevant to urban design, comprehension of the research context and delivery of the set of tools implemented within our research unit. This matrix of tools represents the novelty of this work and is intended as a practical reference for orienting the choice among different simulation tools within the urban design practice. For instance, it is important to highlight the efficacy of each type of simulation in mimicking the man/environment relationship.