| dc.description.abstract | The immersive experience of 360-degree video in virtual reality headsets expands the limits of innovative human-computer interactions, necessitating a comprehensive understanding of the intricate interaction process for the optimisation of 360-degree content. Despite its significance to the user, current research has remained predominantly focused on the technical challenges, neglecting the impact of content-specific aspects on user behaviour. This thesis employs a content-aware approach to discern the independent role of spatial- and temporal properties of a 360-degree video sequence in shaping gaze behaviour. By employing spatiotemporal image complexity, this work reveals the intricate dynamics between content-specific attributes, gaze behaviour, cognitive perceptions and usability context. Instrumental to this thesis was the introduction and formulation of the quadrifactorial exploration index Nψ, a novel metric to quantify complex gaze patterns. By integrating computer vision techniques and eye-tracking data, the index measures gaze patterns based on extent, intensity, variability and randomness. Moreover, an initial framework, utilising another unique metric δ, was devised to examine the confounding influence of diegetic artefacts in 360-degree videos on user gaze. Utilising a mixed-methods design, 52 participants were observed viewing six 360-degree videos with varying spatiotemporal image complexities via a head-mounted display, while seated on either fixed or rotating chairs. The interaction was captured utilising eye-tracking technology and subjective user evaluations. The results demonstrated a negative correlation between temporal complexity – the rate of visual change over time in consecutive frames – and the extent of user gaze. In contrast, spatial complexity – the level of visual richness in each frame – did not significantly impact the user gaze, seemingly attributed to underlying cognitive factors. An observed dichotomy between objective gaze metrics and subjective user experiences further emphasises the role of cognition in the observed spatial- and temporal effects on gaze behaviour. In addition, it was found that these effects were significantly moderated by the different seating types. The employment of oculesics, computer vision and user-centric evaluations revealed the autonomous significance of 360-degree video content within the multifaceted interaction model, while taking into account cognitive and usability influences. The insights provide a theoretical understanding of gaze dynamics during 360-degree video interaction, as well as carry significant implications for the development of more engaging 360-degree content and immersive VR environments. | |
