Fractal Dimension Calculation and Visual Attention Simulation: Assessing the Visual Character of an Architectural Façade

Ju Hyun Lee,Michael J Ostwald

doi:10.3390/buildings11040163

Abstract

The design of a building façade has a significant impact on the way people respond to it physiologically and behaviourally. Few methods are available to assist an architect to understand such impacts during the design process. Thus, this paper examines the viability of using two computational methods to examine potential visual stimulus-sensation relationships in facade design. The first method, fractal analysis, is used to holistically measure the visual stimuli of a design. This paper describes both the box counting (density) and differential box counting (intensity) approaches to determining fractal dimension (D) in architecture. The second method, visual attention simulation, is used to explore pre-attentive processing and sensation in vision. Four measures—D-density (Dd), D-intensity (Di), heat map and gaze sequence—are used to provide quantitative and qualitative indicators of the ways people read different design options. Using two façade designs as examples, the results of this application reveal that the D values of a façade image have a relationship with the pre-attentive processing shown in heat map and gaze sequence simulations. The findings are framed as a methodological contribution to the field, but also to the disciplinary knowledge gap about the stimulus-sensation relationship and visual reasoning in design.

Highlights

The architectural façade, or external face of a building, is the first, physical interface most people engage with as they approach a building, providing important visual clues about its functionalities
Creating the façade is an important part of the design process, for aesthetic reasons, and because the façade is central to the relationship between visual character and human response
To begin to fill this gap, this paper presents two computational approaches to examine the stimulus-sensation relationship at the early design stage: (i) measuring the visual characteristics of façade design and (ii) capturing intrinsic visual engagement without conscious awareness

Summary

Introduction

The architectural façade, or external face of a building, is the first, physical interface most people engage with as they approach a building, providing important visual clues about its functionalities. Creating the façade is an important part of the design process, for aesthetic reasons, and because the façade is central to the relationship between visual character and human response. Stamps [1], for example, uses participants’ ratings of 16 computer-generated façade drawings to examine human visual preferences for architectural façades, with a focus on three types of stimuli (silhouette complexity, surface complexity and facade articulation). As authors acknowledge such rating methods have unavoidable limitations including innate and selection biases Psychological evaluations of this type depend on participants’ life experiences and cultural backgrounds. Observational research potentially offers an insightful approach to understanding dynamic and emotional responses to building design and can provide indicators about the impact of a façade on people’s daily activities. Observer bias in such studies is difficult to control [7] and individuals’ own perspectives are often ignored [8]

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