# Subtitling 3D VR Content with Limited 6 DoF: Presentation Modes and Guiding Methods
## 5 Discussion
This reflects the potential of this mode, and the importance of undertaking further research to assess its benefits, and to ideally overcome some of its identified drawbacks (e.g., ease of reading, impact of distance and viewing modes, and content blocking). It should be also noted that the considered VR scenario creates its own specific conditions that may potentially impact the obtained results. First, all of the actions take place within a delimited area (inside the interrogation rooms), where the speakers do not significantly move. The area is also separated by a mirror from the user's area, so the users, for example, cannot move around the speakers. In addition, despite forcing camera movements, the scenario does not incite the users to navigate around the 3D VR environment, and therefore the scenario has limited 6 DoF. Nonetheless, evaluation of these types of test sequences is valuable, because they are very common in, and applicable to, a wide variety of use cases, such as e-learning, content watching, and sports/cultural events. Regarding their adoption in VR services, it should be remarked that the suggested presentation modes and visual guiding method are easy to implement, and can take advantage of automation techniques. _Always-visible_ subtitles are the easiest to implement, as they do not depend on the 3D VR scenes to which they refer, but are attached to the virtual camera. However, placeholders for the presentation of subtitles can be strategically added for enabling _Fixed-positioned_ and _Comic-style_ presentation modes. In addition, as mentioned in Section 3, the area for presenting the subtitles has a delimited size, and can be strategically presented to maximize readability and minimize collisions/occlusions. Although the results from this study may not be generalizable for all types of VR content and scenarios, particularly those using 6 DoF and in which actions take place in different places and depths, its findings provide valuable answers to RQ1 (what are the most appropriate subtitling presentation modes for 3D VR content? ), and also provided insights for further research on this topic. One example is the exploration of hybrid approaches, in which _Always-subtitles_ subtitles are enabled when the speakers are outside of the FoV, and this mode is switched to _Comic-style_ (or to some form of subtitles attached to the speaker) when the speaker is within the FoV. In addition, the conducted tests provided valuable feedback about the benefits of using visual guiding methods (RQ2). Although the use of a 3D arrow was well received, the hypothesis is that the results would have been even more positive in scenarios with 6 DoF and/or in scenarios in which the speakers and the users can freely and significantly move around the VR environment. In addition, although it was shown in [9] that the use of arrows was preferred to the use of a radar for VR360 video environments, a few users also suggested exploring the use of the radar as a guiding method, particularly in 3D VR environments with 6 DoF. Having determined that guiding methods are beneficial and well received, specific tests on comparing these two methods should be conducted in the future in 6 DoF scenarios to gain insights into the most appropriate one(s). In general, the conducted tests not only served to validate the appropriateness, benefits, and positive reception of the adopted solutions and variants to meet the key identified requirements for efficiently subtitling 3D VR content, but also to provide valuable feedback to fine-tune them, and even to identify further research opportunities. Finally, the tests were conducted with a reasonable number of hearing users, but with no particular recruitment filters, given the wide applicability of both subtitles and VR services, as highlighted in Section 1.