An examination of range effects when evaluating discomfort due to glare in Singaporean buildings

This article discusses ratings of visual discomfort from glare across different buildings located in Singapore. These data were used to determine if range effects influence the vertical illuminance values for the same ratings of visual discomfort when the category rating procedure is used. The effect occurs when maxima and minima vertical illuminance (i.e. the range) vary across buildings. Our analyses showed that with a higher vertical illuminance range in a building, the mean vertical illuminance value for the same criterion of visual discomfort also increased. The results suggest that the effect caused by different ranges of measured vertical illuminance present across the buildings biased the ratings of visual discomfort. Although these effects may be unavoidable in some buildings that have vastly different levels of light, the data suggest that the overall range of vertical illuminance must be carefully evaluated when predicting visual discomfort. Matching these conditions may enable vertical illuminance to provide more reliable evaluations of discomfort due to glare.

Pattern-Induced Visual Discomfort and Anxiety in Migraineurs: Their Relationship and the Effect of Colour

In migraineurs, coloured lenses were found to reduce the visual stress caused by an aversive pattern known to trigger migraines by 70%, but do such patterns also produce a low-level anxiety/fear response? Is this response lessened by colour? We sought to investigate this in a study comprising a broad screening component followed by a dot-probe experiment to elicit attentional biases (AB) to aversive patterns. Undergraduate psychology students completed headache and visual discomfort (VD) questionnaires (N = 358), thereby forming a subject pool from which 13 migraineurs with high visual discomfort and 13 no-headache controls with low visual discomfort, matched on age and sex, completed a dot-probe experiment. Paired stimuli were presented for 500 ms: aversive achromatic 3 cpd square wave gratings vs control, scrambled patterns. These conditions were repeated using the colour that was most comfortable for each participant. VD was greater in the more severe headache groups. On all measures, the migraineurs were more anxious than the controls, and a positive relationship was found between VD and trait anxiety. The 3 cpd gratings elicited an aversive AB in the migraine group which was somewhat reduced by the use of colour, and this was not seen in the controls. The results suggest a new role for colour in reducing visual stress via anxiety/fear reduction.

Visual Discomfort and Variations in Chromaticity in Art and Nature

Visual discomfort is related to the statistical regularity of visual images. The contribution of luminance contrast to visual discomfort is well understood and can be framed in terms of a theory of efficient coding of natural stimuli, and linked to metabolic demand. While color is important in our interaction with nature, the effect of color on visual discomfort has received less attention. In this study, we build on the established association between visual discomfort and differences in chromaticity across space. We average the local differences in chromaticity in an image and show that this average is a good predictor of visual discomfort from the image. It accounts for part of the variance left unexplained by variations in luminance. We show that the local chromaticity difference in uncomfortable stimuli is high compared to that typical in natural scenes, except in particular infrequent conditions such as the arrangement of colorful fruits against foliage. Overall, our study discloses a new link between visual ecology and discomfort whereby discomfort arises when adaptive perceptual mechanisms are overstimulated by specific classes of stimuli rarely found in nature.

Mitigating Visual Discomfort on Head Mounted Displays using Estimated Gaze Dependent Depth of Field

<p>Virtual Reality (VR) applications on Head Mounted Displays (HMDs) are now more common and accessible for personal viewing than before with the introduction of consumer-level devices like the Oculus Rift. However, exposure to VR applications on HMDs results in significant discomfort for the majority of people, the severity of which can both increase or decrease after repeated exposures. This is disadvantageous for the development and adoption of VR, as a long adaptation period cannot be relied on for making Virtual Environments palatable. Symptoms of discomfort caused by the viewing of content on VR devices including HMDs are historically described as “Simulator Sickness” and include eye fatigue, headaches, nausea and sweating; symptoms very similar to those experienced by sufferers of motion sickness. We refer to the specific subset of Simulator Sickness Symptoms caused by visual stimuli as symptoms of “Visual Discomfort”. A conflict between accommodation and vergence depth cues on stereoscopic displays is known to be a significant cause of visual discomfort. This report describes a psychophysical evaluation used for judging the effectiveness of dynamic Depth of Field (DoF) blurring on reducing visual discomfort caused by initial exposure to stereoscopic content on HMDs. Our DoF implementation adjusts the focal region of stereoscopic content based on an estimation of users’ view vectors in real time and is realised in a commercial game engine. Participants report a significant reduction of visual discomfort using a simulator sickness questionnaire when DoF blurring is enabled. On average, a 34% reduction in our sickness measure is observed, indicating that dynamic DoF blurring is an effective rendering technique for reducing visual discomfort.</p>

Mitigating Visual Discomfort on Head Mounted Displays using Estimated Gaze Dependent Depth of Field

<p>Virtual Reality (VR) applications on Head Mounted Displays (HMDs) are now more common and accessible for personal viewing than before with the introduction of consumer-level devices like the Oculus Rift. However, exposure to VR applications on HMDs results in significant discomfort for the majority of people, the severity of which can both increase or decrease after repeated exposures. This is disadvantageous for the development and adoption of VR, as a long adaptation period cannot be relied on for making Virtual Environments palatable. Symptoms of discomfort caused by the viewing of content on VR devices including HMDs are historically described as “Simulator Sickness” and include eye fatigue, headaches, nausea and sweating; symptoms very similar to those experienced by sufferers of motion sickness. We refer to the specific subset of Simulator Sickness Symptoms caused by visual stimuli as symptoms of “Visual Discomfort”. A conflict between accommodation and vergence depth cues on stereoscopic displays is known to be a significant cause of visual discomfort. This report describes a psychophysical evaluation used for judging the effectiveness of dynamic Depth of Field (DoF) blurring on reducing visual discomfort caused by initial exposure to stereoscopic content on HMDs. Our DoF implementation adjusts the focal region of stereoscopic content based on an estimation of users’ view vectors in real time and is realised in a commercial game engine. Participants report a significant reduction of visual discomfort using a simulator sickness questionnaire when DoF blurring is enabled. On average, a 34% reduction in our sickness measure is observed, indicating that dynamic DoF blurring is an effective rendering technique for reducing visual discomfort.</p>

Artificial Intelligence for Detecting Indoor Visual Discomfort from Facial Analysis of Building Occupants

Glare is a common local visual discomfort that is difficult to identify with conventional light sensors. This article presents an artificial intelligence algorithm that detects subjective local glare discomfort from the image analysis of the video footage of an office occupant’s face. The occupant’s face is directly used as a visual comfort sensor. Results show that it can recognize glare discomfort with around 90% accuracy. This algorithm can thus be at the basis of an efficient feedback control system to regulate shading devices in an office building.