# Subtitling 3D VR Content with Limited 6 DoF: Presentation Modes and Guiding Methods
## 2 Related Work
### 3D VR Content Subtitling  
Recent works have reported on relevant issues related to the integration and presentation of subtitles in 3D environments. The study in [21] notes the necessity to further research means to appropriately subtitle 3D VR content. That study claims that appropriate subtitling solutions are necessary, not just to contribute to the narrative and maximize the user's engagement and immersion, but critically to avoid the occurrence of ghosting effects that may hinder readability, and cause eyestrain and simulation sickness. These conclusions were reached after reviewing and analyzing, based on a descriptive approach, a variety of 3D-subtitled movies, using both stereoscopic video and computer-generated 3D content as the production formats. For instance, it was remarked that a non-curated super-imposition of traditional 2D subtitles on top of the 3D content can destroy the viewing experience, having an impact on the depth estimation, and causing ghosting, shadowing, and dizziness effects. An appropriate implementation can, however, minimize the impact of these issues, e.g., by positioning the subtitles close to the rendering plane, and applying appropriate lighting, shades, and colors [22].  
From the analyzed corpus in [21], interesting insights were provided. Most of 3D movies place the subtitles in the perspective closest to the viewer, but are not really integrated with the movie dynamics and effects. Some of these adjust the depth of subtitles according to the scene and speaker's location; however guidelines were not provided, and concrete patterns were not identified, for these adjustments. Interestingly, one of the analyzed movies (_Avatar, Director: [PERSON]_, 2010) adopts a dynamic subtitling strategy based on changing the subtitles' position depending on the location of the speaker on the screen and the type of scene, to facilitate reading and improve the tracking of the action. In essence, the study in [21] presents the need for better subtitling solutions for 3D content, exploring requirements and appropriate alternatives. The goal must be to ensure accessibility and content comprehension, but without having a negative impact on the user experience.  
Similarly, an exploratory study concerning the usage of subtitles in video games was conducted in [23]. It was found that subtitles are not yet efficiently provided in the game industry. That study also highlights the need for appropriate solutions, standards, and recommendations for subtitling this relevant medium, given its interactive and immersive nature, and high dynamism. This would not only enhance game accessibility, but also improve the gaming experience for all players, in a variety of application contexts (e.g., entertainment, training, and therapy). Consistent with this, the study in [24] claimed that the appropriate subtitling solutions for VR _\"have the potential to make the overall viewing experience less disjointed and more immersive\"_.  
These two last studies [21; 23] have served as a motivation for conducting the research presented in the current work, which goes even one-step beyond considering 3D movies, but interactive 3D VR content with limited 6 DoF, thus moving closer to the gaming sector.  
In particular, our work departs from the lessons learned in [9] regarding the use and benefits of presentation modes and guiding methods for VR360 video. Our aim was to examine their adoption and improvement for 3D VR, for which accessibility solutions (including subtitling) are yet nonexistent, despite their relevance.