# Comparative Evaluation of Different following Mechanisms in VR Guided Tour: A Preliminary Study
## 3 Material and Methods
### User Study  
In the experiment, participants begin the tour in the virtual world we built based on the street view in Barcelona, Spain. The tour guide will lead them along the prerecorded route, past three of the landmarks discussed earlier. As soon as the tour guide reaches each historical site, the guide will stop moving and present the surroundings and history, which is also prerecorded. Participants can resume the tour by pressing a button. In addition, the tour includes some unique objects and events to explore; the guide will also introduce them. The tour takes about 25 min to complete. In the limited following mechanism, participants are always located eight meters behind the tour guide. Participants cannot move around on their own; they can only change the orientation of the viewpoint by rotating their heads. In the semi-limited mechanism, the participants can move freely only in a range of eight meters centered at the tour guide. Whenever the participants move away from the tour guide by more than eight meters and the time after the last reposition is more than 10 s, they will be transmitted to a new position behind the tour guide, and the distance is half the range. To minimize the possibility of feeling disoriented, the participant's viewing orientation will be kept after the repositioning. Last, in the not-limited mechanism, the participants can move anywhere and even ignore the guide completely. A total of 29 participants (18 male, 11 female) recruited from our campus consented and were paid for participating in a one-hour experiment. All of them had no or less (have played only one or two times before) VR experience. Most of them were undergraduates, and only six participants were graduate students. Their ages ranged from 19 to 22. The participants were divided into four groups randomly, as shown in Table 1.  
Figure 3: The experiment’s virtual environment and attractions. **Up**: The La Sagrada Familia in the virtual guided tour. **Down**: The user’s view during the guided tour. The setup for the VR tour experience consisted of an HTC VIVE headset and an in-ear headphone. The HTC VIVE's two screens each have a 110 degrees field of view, and each screen's resolution is 1080 \(\times\) 1200 with a 90 Hz refresh rate. Because of a safety perspective, we asked the user to sit on an office chair with wheels. The free space he/she can move is around 3 m \(\times\) 1.5 m. However, in most cases, users use the controller and teleport to move in the virtual environment. The experiment consisted of the following steps, as seen in Figure 4:  
1. Participants were randomly assigned to one of the following mechanisms initially. 2. (5 min) Participants were given a general introduction telling them what they would experience in the guided tour in VR, followed by instructions on using the controller to move around and interact with the virtual environment. 3. (5 min) After a short break, they put on the VR headset and roamed around to become familiar with the environment. 4. (25 min) Afterwards, they started the main guided tour with prerecorded narration. The whole tour takes about 20-25 min to finish. 5. Finally, participants filled out a 4-part questionnaire. The experiment took roughly 50 min in total. As mentioned before, we used questionnaires to measure the opinions and attitudes of the users. All questionnaire questions were Likert-scale questions or open-ended questions; for the Likert-scale questions, we used a scale from 1 to 5. Precisely, the questionnaire can be divided into four sub-questionnaires:  
* Game Experience: The Game Experience Questionnaire (GEQ) [32] is a questionnaire widely applied in games research, assessing the experience on seven aspects: immersion, flow, competence, positive and negative affect, tension, and challenge. GEQ provides a measure of the gaming experience for the virtual guided tour. In this paper, we applied a concise version called the in-game GEQ. It consists of 14 Likert questions. By applying GEQ, we can assess how much the virtual tour entertains the users.