Nanotilus: Generator of Immersive Guided-Tours in Crowded 3D Environments

Abstract
Immersive virtual reality environments are gaining popularity for studying and exploring crowded three-dimensional structures. When reaching very high structural densities, the natural depiction of the scene produces impenetrable clutter and requires visibility and occlusion management strategies for exploration and orientation. Strategies developed to address the crowdedness in desktop applications, however, inhibit the feeling of immersion. They result in nonimmersive, desktop-style outside-in viewing in virtual reality. This paper proposesNanotilus---a new visibility and guidance approach for very dense environments that generates an endoscopic inside-out experience instead of outside-in viewing, preserving the immersive aspect of virtual reality. The approach consists of two novel, tightly coupled mechanisms that control scene sparsification simultaneously with camera path planning. The sparsification strategy is localized around the camera and is realized as a multiscale, multishell, variety-preserving technique. When Nanotilus dives into the structures to capture internal details residing on multiple scales, it guides the camera using depth-based path planning. In addition to sparsification and path planning, we complete the tour generation with an animation controller, textual annotation, and text-to-visualization conversion. We demonstrate the generated guided tours on mesoscopic biological models -- SARS-CoV-2 and HIV viruses. We evaluate the Nanotilus experience with a baseline outside-in sparsification and navigational technique in a formal user study with 29 participants. While users can maintain a better overview using the outside-in sparsification, the study confirms our hypothesis that Nanotilus leads to stronger engagement and immersion.

Citation
Alharbi, R., Strnad, O., Luidolt, L. R., Waldner, M., Kouril, D., Bohak, C., … Viola, I. (2021). Nanotilus: Generator of Immersive Guided-Tours in Crowded 3D Environments. IEEE Transactions on Visualization and Computer Graphics, 1–1. doi:10.1109/tvcg.2021.3133592

Acknowledgements
The research was supported by the King Abdullah University of Science and Technology (BAS/1/1680-01-01) and KAUST Visualization Core Lab. We thank nanographics.at for providing the Marion software, Alex Kouyoumdjian for insightful comments, and Jules Verne for inspiration.

Publisher
Institute of Electrical and Electronics Engineers (IEEE)

Journal
IEEE Transactions on Visualization and Computer Graphics

DOI
10.1109/tvcg.2021.3133592

Additional Links
https://ieeexplore.ieee.org/document/9645360/

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