# Comparative Evaluation of Different following Mechanisms in VR Guided Tour: A Preliminary Study
## 1 Introduction  
Given virtual reality's (VR) popularity, VR already impacts various applications such as education [1; 2; 3] and tourism [4]. Nowadays, due to the COVID-19 pandemic, tourism has temporarily halted, and traveling around the world is nearly impossible [5; 6]. In such difficult times, the VR tour is not only a useful tool to maintain the attractiveness of destinations [7] but also a substitute [8; 9] and rehearsal for real-world tourism. However, experience in VR is quite different from in real life [10]. A common situation in education and tourism is that the user might have to follow a specific target such as the teacher or the tour guide and listen to audio narrations about the environment. While touring in real life, it is easy to follow the tour guide without strain. We can use all our human senses to observe a tour guide's movement, listen to sounds to judge position, or look at where the crowds are heading. However, while touring in virtual reality, we do not have all the clues from our sense organs. The visual system is the primary means of interaction in a virtual world. Thus, it is much more challenging to concentrate on the tour guide's movement while looking around in the virtual environment.  
Furthermore, the experience in VR-guided tours is also related to the locomotion allowed in the VR environment. [PERSON] et al. [11] discovered that giving users a larger space to walk around offers benefits over general virtual travel techniques. However, current consumer-level VR solutions are usually space-limited, and the available physical spaces may contain several obstacles. Thus, users may experience spatial discontinuity or dangers while using VR devices. Generally, a video-based virtual tour is a pre-recorded video following a fixed guide path. The video content may be captured by 360 degreevideos recorded in the real world [10] or pre-computing from synthetic virtual 3D scenes. In this case, the viewers do not have to move or make an effort to follow the tour guide; they can only slightly change their head orientation but cannot freely change their positions. On the other hand, 3D virtual tours create a complete 3D environment and give users more freedom to explore the virtual world; viewers can go to any place they want in the virtual world and observe the scene they are interested in. However, it is easy to get lost from tracking the tour guide. As mentioned earlier, while experiencing a virtual tour, we usually have limited space, so the users have to use different locomotion techniques to move around [12]. Meanwhile, users need to make much more effort to follow the virtual tour guide, which results in missing points of interest, decreasing immersion, and frustrated users. Therefore, it is crucial to balance how much freedom users can have regarding locomotion and movement when following a virtual tour guide.  
In this paper, we focus on the learning effect of different following mechanisms in VR-guided tours and try to find the best one that helps users pay attention to their surroundings and the audio narrations. In a virtual scene replicated from Barcelona, we compare the performance of three following mechanisms: limited (which restricts the user's ability to move), semi-limited (which constrains the user's range of activity), and not-limited (user's movement is not constrained). Our hypothesis is that: in a VR-guided tour, the following mechanisms may affect the participants' learning efficiency and user experience. We evaluated the effect with questionnaires including user experience in VR, gaming experience, and how many details the user remembered in the VR tour. We found that the semi-limited mechanism is superior to the others. As the experiment shows, the semi-limited mechanism minimizes the frustration from the physical space limitation and lets users concentrate on the guided tour and the virtual environment.