Analysis of the influence of time and sight trajectories on daylight glare probability in office environments

Abstract To quantify and characterise the perception of brightness in visual activity is still a challenge for researchers, mainly because it is a subjective parameter, dependent on the active position of the occupant. The aim of this study was to consider dynamic users in work environments and verify the influence of viewing time and sight direction on glare probability. The data were collected in a real environment where 26 volunteers were monitored while performing common office tasks. The gaze movements were recorded with an Eye-Tracker device. Through High Dynamic Range (HDR) images the surfaces’ brightnesses were mapped and the glare probability index (DGP) was calculated. Those data were correlated with the users' satisfaction answers obtained through questionnaires. The researchers found that, when performing a task, users keep their eyes fixed on the task surface, and during break periods, the sight became more dispersed. The windows were mainly visualised when they were part of the task’s background or when their luminance values were low. The conclusion was that DGP weighted values were closer to the satisfaction votes expressed by the participants, emphasising the importance of considering vision directions and viewing time in this analysis.