{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,10]],"date-time":"2025-12-10T09:08:37Z","timestamp":1765357717528,"version":"3.44.0"},"reference-count":60,"publisher":"Association for Computing Machinery (ACM)","issue":"9","funder":[{"name":"European Commission Horizon Europe TRANSMIXR","award":["101070109"],"award-info":[{"award-number":["101070109"]}]}],"content-domain":{"domain":["dl.acm.org"],"crossmark-restriction":true},"short-container-title":["ACM Trans. Multimedia Comput. Commun. Appl."],"published-print":{"date-parts":[[2025,9,30]]},"abstract":"<jats:p>\n            The advent in our daily life of Extended Reality (XR) technologies, such as Virtual and Augmented Reality, has led to the rise of user-centric systems, offering higher level of interaction and presence in virtual environments. In this context, understanding the actual interactivity of users is still an open challenge and a key step to enabling user-centric system. In this work, our goal is to construct an efficient clustering tool for 6 df navigation trajectories by extending the applicability of existing behavioural tool. Specifically, we first compare the navigation in 6 df with its 3 df counterpart, highlighting the main differences and novelties. Then, we investigate new metrics aimed at better modelling behavioural similarities between users in a 6 df system. More concretely, we define and compare 11 similarity metrics which are based on different\n            <jats:italic toggle=\"yes\">distance features<\/jats:italic>\n            (i.e., user positions in the 3D space, user viewing directions) and\n            <jats:italic toggle=\"yes\">distance measurements<\/jats:italic>\n            (i.e., Euclidean, Geodesic, angular distance). Our solutions are validated and tested on real navigation paths of users interacting with dynamic volumetric media in both 6 df Virtual Reality and Augmented Reality conditions. Results show that metrics based on both user position and viewing direction better perform in detecting user similarity while navigating in a 6 df system. Such easy-to-use but robust metrics allow us to answer a fundamental question for user-centric systems: \u2018How do we detect if users look at the same content in 6 df?\u2019, opening the gate to new solutions based on users interactivity, such as viewport prediction, live streaming services optimised based on users behaviour but also for user-based quality assessment methods.\n          <\/jats:p>","DOI":"10.1145\/3701734","type":"journal-article","created":{"date-parts":[[2024,10,25]],"date-time":"2024-10-25T10:03:52Z","timestamp":1729850632000},"page":"1-27","update-policy":"https:\/\/doi.org\/10.1145\/crossmark-policy","source":"Crossref","is-referenced-by-count":2,"title":["A Clustering Approach to Unveil User Similarities in 6 df Extended Reality Applications"],"prefix":"10.1145","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2779-2314","authenticated-orcid":false,"given":"Silvia","family":"Rossi","sequence":"first","affiliation":[{"name":"Centrum Wiskunde and Informatica (CWI), Amsterdam, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8990-2665","authenticated-orcid":false,"given":"Irene","family":"Viola","sequence":"additional","affiliation":[{"name":"Centrum Wiskunde and Informatica (CWI), Amsterdam, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8441-8791","authenticated-orcid":false,"given":"Laura","family":"Toni","sequence":"additional","affiliation":[{"name":"University College London (UCL), London, United Kingdom"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1752-6837","authenticated-orcid":false,"given":"Pablo","family":"Cesar","sequence":"additional","affiliation":[{"name":"Centrum Wiskunde and Informatica (CWI), Amsterdam, The Netherlands and Technische Universiteit (TU) Delft, Delft, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"320","published-online":{"date-parts":[[2025,9,11]]},"reference":[{"key":"e_1_3_1_2_1","doi-asserted-by":"publisher","DOI":"10.1145\/3549529"},{"key":"e_1_3_1_3_1","first-page":"1","volume-title":"International Conference on Quality of Multimedia Experience","author":"Alexiou Evangelos","year":"2020","unstructured":"Evangelos Alexiou, Nanyang Yang, and Touradj Ebrahimi. 2020. 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