## 2 Development of a Prototype of Industrial Metaverse for Teaching/Learning Activities
### Development of Realistic Industrial Objects Based on NeRFs  
In Figure 4, a detailed workflow is presented for creating immersive industrial metaverses in Unity using NeRFs. This groundbreaking methodology enables the generation of realistic 3D models from captured images, offering a novel approach to virtual representation. To achieve a seamless integration of physical models into the virtual space, the workflow has been structured into _six steps_ as detailed below, each crucial for the overall success of the process. 1. [label=(S0)]
2. Capture of model images: Record a video around the object from different perspectives, followed by the extraction of the individual images for use in the NeRF model generation process. 3. NeRF Generation: Create a folder structure in Instant NeRF [20] and generate JSON file based on captured images for 3D reconstruction. This step culminates in generating the NeRF 3D model. Figure 3: Methodology proposed for designing an industrial metaverse. * Exporting NeRF to Unity: Transfer the NeRF model from Instant NeRF to Unity. During this process, resolution is configured to ensure a visually adequate representation of the model in the Unity environment. * Creation of 3D texture: Assemble a mosaic of model images. This mosaic is imported into Unity as a 2D texture, which is then transformed into a 3D texture to be applied to the NeRF object. * Incorporating NeRF Object into Unity Scene: Create a material based on the 3D texture and apply the 3D texture to the NeRF object. A GameObject is configured to effectively represent the NeRF model within the virtual scene created in Unity. * Metaverse integration: Develop scripts that allow real-time interactions with the NeRF model. Specific components are configured to share the object in a metaverse, utilizing Photon PUN2 to synchronize and enable interaction among different users in the virtual environment. This comprehensive workflow offers a step-by-step guide for seamlessly transitioning physical models into immersive industrial metaverse. It is important to note that the NeRF representation within Unity serves as a virtual copy, meticulously capturing the form of the real NeRF based on the acquired images. Leveraging this NeRF technology opens new possibilities for virtual representation, collaboration, and exploration in industrial environments. Case Study: Obtaining a NeRF in Unity  
This case study provides a practical demonstration of the step-by-step process outlined earlier for obtaining a NeRF in Unity. By following the detailed steps discussed, this case study offers a hands-on example that illustrates the seamless integration of NeRF into the Unity development environment. In the initial phase of this case study, the process began with the capture of model images (S1). A video was recorded around the object from various perspectives and then individual images were extracted from the video. As shown in Figure 5, the images are placed in the \"images\" folder, which should be created within a directory where Instant NeRF is located. Transitioning to the next phase (S2), the process involves obtaining a JSON file containing camera parameter values for each captured image. Colmap [21] is used in this work to generate this file. The subsequent step unfolds as Instant NeRF takes center stage, utilizing the acquired JSON file to adeptly reconstruct the NeRF model within a matter of seconds, as showcased in Figure 6.  
Proceeding to the next step (S3), the subsequent phase involves acquiring the 3D texture for a Unity-ready representation of the obtained NeRF. In the Instant NeRF tools window, a pivotal option labeled \"save PNG sequence\" is available. This option facilitates the exportation of NeRF slices, which are cross-sectional views of the 3D volume. Prior to extraction, modifications can be made to tailor the NeRF to specific requirements, including  
Figure 4: Workflow for creating a NeRF-based industrial metaverse. volume trimming and resolution adjustments to meet the desired specifications for integration into Unity.