Towards embodied 3D isovists Incorporating cognitively-motivated semantics of 'space' and the architectural environment in 3D visibility analysis

Krukar J., Schultz C., Bhatt M.

Abstract

Isovist analysis is being increasingly applied to the third dimension. However, this transition seems to be driven by a direct extrapolation of the 2D isovist concept, along with a variety of implicit assumptions that are only valid in the top-down 2D case. This results in definitions that make the 3D isovist equivalent to the geometric volume of 'space' visually accessible from the generating point in the 3D building environment. Such a concept neither adequately reflects the strategy of human visuo-locomotive exploration, nor does it account for the resulting mental representation of the explored space. We review two reasons for the dissimilarity between the 2D and 3D conceptualisations of isovists: (1) The quantity, and characteristics, of visual information relevant to the human everyday experience is different in the vertical and horizontal plane. (2) The left/right symmetry in accessing and interpreting visual information is not comparable to the top/down asymmetry of visual information. As a result, the difference between the experience of being above an object versus being below the object is incomparable, in contrast to experiencing an object from the left side versus the right side. Thus, a 3D isovist derived by (naively) extrapolating from its 2D counterpart limits its applicability in the studies of human cognition inside 3D environments. We propose a cognitively motivated extension of a general 3D isovist that accounts for these phenomena.