From 3-DoF to 6-DoF: New Metrics to Analyse Users Behaviour in Immersive Applications

This work focuses on enabling user-centric immersive systems, in which every aspect of the coding-delivery-rendering chain is tailored to the interactive users. Understanding the actual interactivity and behaviour of those users is still an open challenge and a key step to enable such a user-centric system. Our main goal is to enable user behavioural analysis in the case of 6 degree-of-freedom (DoF) systems by extending the applicability of existing behavioural methodologies adopted for studying user behaviour in 3-DoF settings. Specifically, we deeply analyse 6-DoF navigation patterns with comparisons to the 3-DoF counterpart. Then, we define new metrics aimed at better modelling users similarities in a 6-DoF system. We validate and test our solutions on real navigation paths of users while displaying dynamic volumetric media in 6-DoF Virtual Reality conditions. To show the flexibility and generality of our proposed metrics, we also test their performance on navigation trajectories collected in a 6-DoF Augmented Reality settings. Our results show that metrics that consider both user position and viewing direction better perform in detecting user similarity while navigating in a 6-DoF system. Having easy-to-use but robust metrics that underpin multiple tools and answer the question "how do I detect if two users look at the same content?" open the gate to new solutions for a user-centric system.