Brandstätter, Klara;
(2025)
Facilitating the Creation of Expressive Non-Player Characters Using Immersive Single-User Record and Replay.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Non-player characters (NPCs) are an essential element of many 3D and virtual reality (VR) experiences. Animation for NPCs is often motion-captured using expensive hardware, and the post-processing steps are time-consuming, especially when capturing multiple people simultaneously. Using record and replay techniques in VR can offer a cheaper and easier method of motion capture, as these devices are consumer-grade and already require user movements to be tracked. We present three studies to assess the viability of single-user record and replay for creating expressive NPCs. We also include an open-source record and replay tool for users to create their own animations in VR. In the first set of user studies (N=47 and N=42), we compare single-user recordings with conventional multi-user recordings. Our results suggest that participants cannot distinguish between characters recorded by a single user and characters recorded by two users. Consumer VR devices typically track the user’s head and hands. Software approaches are required to transform this input into full-body motion for animation. In a subsequent user study (N=53), we implement five avatar representations and assess how well their generated motions can convey emotions. Our findings suggest that, from the perspective of emotion expressivity, connected upper-body parts that provide visual continuity improve clarity, and that current techniques for algorithmically animating the lower body are ineffective. Based on these findings, we expand the functionality of our record and replay technique to facilitate editing of existing recordings and capture more expressive full-body avatars with hand, face, and eye tracking. We then study the effect of rerecording scenarios multiple times on perceived interactivity between multiple NPCs (N=144). Our results show that one recording is enough for scenarios where characters are not in close contact with each other, and that two recordings are more appropriate for close-contact group interactions.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Facilitating the Creation of Expressive Non-Player Characters Using Immersive Single-User Record and Replay |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2025. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/deed.en). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| Keywords: | Character Animation, Non-Player Characters, Record and Replay, Virtual Reality |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Computer Science |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10217838 |
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