Gazing into space: perceiving another’s gaze vergence and fixation distance in three-dimensional space

Understanding the eyes of others is vital for navigating the complex social world around us. Where someone is looking provides information about not only the focus of their attention, but also their current thoughts, emotions and intentions. Shifts in another’s gaze direction can reflexively orient our attention towards the object of their fixation, an effect known as “gaze cueing” (Friesen and Kingstone, 1998). Despite much research on perceiving gaze direction, little is known about gaze vergence. Our eyes converge as the object of our fixation moves closer to us and become parallel as that object moves farther away. Fixation distance information obtained from perceiving gaze vergence could potentially allow us to refine a general sense of the direction in which a person is looking to recover a more precise point of fixation in three-dimensional space. The experiments in this thesis utilise a three-dimensional stereoscopic display to investigate how observers perceive the gaze vergence of a computer-generated avatar and whether gaze vergence can cue attention to locations in depth. Chapter One finds that when perceiving another’s gaze vergence, fixation distance is systematically underestimated, especially when the avatar’s gaze is averted downwards. Chapters Two to Five apply this stereoscopic setup to gaze cueing and find that the gaze direction cueing effect persists in a three-dimensional environment. However, shifts in another’s gaze vergence do not reflexively orient attention to locations in depth, even across several temporal and spatial variations. Nevertheless, a significant stimulus location effect persists across these experiments, whereby the object closer to the avatar is detected more quickly than the farther object, irrespective of the avatar’s gaze fixation location. This effect was explored in Chapter Six. Participants’ reaction times are increased when the avatar’s eyes are open, regardless of the object’s location. The mere presence of open eyes can therefore capture attention even when detrimental to the task at hand. Overall, the results suggest that despite our ability to discriminate gaze vergence precisely, vergence cues may not be utilised readily in daily life to facilitate attention or to locate others’ precise fixation location in three-dimensional space

Blickpunktabhängige Computergraphik

Contemporary digital displays feature multi-million pixels at ever-increasing refresh rates. Reality, on the other hand, provides us with a view of the world that is continuous in space and time. The discrepancy between viewing the physical world and its sampled depiction on digital displays gives rise to perceptual quality degradations. By measuring or estimating where we look, gaze-contingent algorithms aim at exploiting the way we visually perceive to remedy visible artifacts. This dissertation presents a variety of novel gaze-contingent algorithms and respective perceptual studies. Chapter 4 and 5 present methods to boost perceived visual quality of conventional video footage when viewed on commodity monitors or projectors. In Chapter 6 a novel head-mounted display with real-time gaze tracking is described. The device enables a large variety of applications in the context of Virtual Reality and Augmented Reality. Using the gaze-tracking VR headset, a novel gaze-contingent render method is described in Chapter 7. The gaze-aware approach greatly reduces computational efforts for shading virtual worlds. The described methods and studies show that gaze-contingent algorithms are able to improve the quality of displayed images and videos or reduce the computational effort for image generation, while display quality perceived by the user does not change.Moderne digitale Bildschirme ermöglichen immer höhere Auflösungen bei ebenfalls steigenden Bildwiederholraten. Die Realität hingegen ist in Raum und Zeit kontinuierlich. Diese Grundverschiedenheit führt beim Betrachter zu perzeptuellen Unterschieden. Die Verfolgung der Aug-Blickrichtung ermöglicht blickpunktabhängige Darstellungsmethoden, die sichtbare Artefakte verhindern können. Diese Dissertation trägt zu vier Bereichen blickpunktabhängiger und wahrnehmungstreuer Darstellungsmethoden bei. Die Verfahren in Kapitel 4 und 5 haben zum Ziel, die wahrgenommene visuelle Qualität von Videos für den Betrachter zu erhöhen, wobei die Videos auf gewöhnlicher Ausgabehardware wie z.B. einem Fernseher oder Projektor dargestellt werden. Kapitel 6 beschreibt die Entwicklung eines neuartigen Head-mounted Displays mit Unterstützung zur Erfassung der Blickrichtung in Echtzeit. Die Kombination der Funktionen ermöglicht eine Reihe interessanter Anwendungen in Bezug auf Virtuelle Realität (VR) und Erweiterte Realität (AR). Das vierte und abschließende Verfahren in Kapitel 7 dieser Dissertation beschreibt einen neuen Algorithmus, der das entwickelte Eye-Tracking Head-mounted Display zum blickpunktabhängigen Rendern nutzt. Die Qualität des Shadings wird hierbei auf Basis eines Wahrnehmungsmodells für jeden Bildpixel in Echtzeit analysiert und angepasst. Das Verfahren hat das Potenzial den Berechnungsaufwand für das Shading einer virtuellen Szene auf ein Bruchteil zu reduzieren. Die in dieser Dissertation beschriebenen Verfahren und Untersuchungen zeigen, dass blickpunktabhängige Algorithmen die Darstellungsqualität von Bildern und Videos wirksam verbessern können, beziehungsweise sich bei gleichbleibender Bildqualität der Berechnungsaufwand des bildgebenden Verfahrens erheblich verringern lässt