## 3 Results  
### Showcasing the Results through User Experience  
To demonstrate the applicability of using NeRF-based 3D models for training activities, the industrial metaverse described in Section 2.2 is utilized, enabling the simultaneous connection of two users. Meta Quest 2 VR hardware devices are employed, equipped with hand tracking that allows users to interact with virtual objects naturally and keep their hands free of devices. Additionally, this environment enables voice communication, allowing operators to communicate during their training as they would in a real space. It is worth mentioning that the industrial metaverse developed for this work offers two forms of user movement: natural translation, involving movement through the real space, and teleportation-based translation, enabling users to move even in confined real-world spaces. These two forms of movement are common in virtual spaces because, on the one hand, for true immersion in the virtual world, users should experience it similarly to how they would in the real world. On the other hand, due to real-world space limitations, teleportation is necessary to navigate through the entire virtual space. The target objects for training can be seen in Figure 11: spiral pneumatic tube, Figure 11a; pneumatic motor for surface treatment operations with robots, Figure 11b; industrial gripper for robots, Figure 11c; vision system for studying surface defects using deflectometry, Figure 11d. These objects have been chosen for their industrial relevance and the challenge in obtaining a visually realistic model, particularly the vision system due to light reflections. The results of the models viewed from the metaverse are depicted in Figure 12.  
Figure 10: Inspector window with shared object components. Figure 11: Real objects to be scanned and recreated using NeRFs. (**a**) Spiral pneumatic tube. (**b**) Driller. (**c**) Industrial clamp. (**d**) Vision system. Figure 12: Results of the 3D models in NeRFs viewed from the industrial metaverse. (**a**) NeRF spring. (**b**) NeRF driller. (**c**) NeRF industrial clamp. (**d**) NeRF vision system. To showcase the solution's results, a demonstration was conducted where two users entered the industrial metaverse developed (see [[https://media.upv.es/player/?id=18668260-613b-11](https://media.upv.es/player/?id=18668260-613b-11) ee-8548-1 bcf94a5 ee62]([https://media.upv.es/player/?id=18668260-613b-11](https://media.upv.es/player/?id=18668260-613b-11) ee-8548-1 bcf94a5 ee62)) (accessed on 19 February 2024). This aimed to validate the outcomes and verify its proper functionality in real time. The demonstration provided a tangible view of the capabilities and possibilities offered by the industrial metaverse, emphasizing its real-time performance. Figure 13 shows several captured moments from the user experience for various actions within the metaverse. In particular, Figure 13a depicts the hand gesture required for spatial navigation within the virtual environment. This not only broadens the age range of users but also grants complete freedom for natural interaction with virtual objects and avatars. In Figure 13b, one of the 6D models distributed across the industrial metaverse is showcased. Each model is positioned on a tray atop a pedestal, with the trays featuring grip points for user interaction. Figure 13c displays the available options panel within the metaverse, triggered when the user places both hands in front of their field of view. Pressing the green button activates a mobile device, allowing users to take photos to save images of the training session for later use. The red button allows users to exit the virtual space. Figure 13d,e illustrate user interaction with elements within the space: the first one shows user-to-user interaction, passing a model from one user to another, whereas the second one depicts a user comparing two 6D models, manipulating both simultaneously.