## 2 Background Information
### Virtual Reality  
VR technology can be used to improve a wide range of production processes in the digital factory, including design and prototyping. VR technology can be used to create virtual prototypes of products and production processes. This allows designers and engineers to test different design options and identify potential problems before they are physically built, which can save time and money in the production process. Virtual Reality (VR) can be classified in various ways, depending on the context and perspective of the classification. Here are a few common ways to classify virtual reality. Firstly, based on the level of immersion. VR can be classified into fully immersive, semi-immersive, and non-immersive VR. Fully immersive VR offers the highest level of immersion, where the user is completely immersed in a virtual world, often using a VR headset and hand-held controllers. Semi-immersive VR provides a partially immersive experience, where the user interacts with a virtual environment using a screen or projection. Non-immersive VR involves the use of a computer screen or mobile device to display a virtual environment [29]. Secondly, VR can be classified based on the type of hardware used, such as head-mounted displays (HMDs), haptic devices, and motion tracking systems. Thirdly, VR can be classified based on its application, such as gaming, training and simulation, education, healthcare, and entertainment. Lastly, VR can be classified based on the degree of interactivity, such as passive, interactive, and immersive. Passive VR involves the user observing a virtual environment without interacting with it. Interactive VR allows the user to interact with the virtual environment using input devices such as controllers or touchscreens. Immersive VR provides a high level of interactivity, where the user can fully engage with the virtual environment and interact with it in a more natural way. In VR-based process simulation, as shown in Figure 1, there are two classifications of categories, which have their specific characteristics in this process. The first classification is the types of human-machine interfaces, which are visual, acoustic, and touch interfaces. The visual interface is classified as head-mounted and not head-mounted. Touch interface should be defined as tactile feedback and proprioceptive feedback. Modelling and simulation are used with methods managing virtual objects and interactive feedback. Managing virtual objects are known to be based on rules and knowledge and on a physical basis. Interactive feedback uses such methods as visualization, sonification and touch rendering [30; 31; 32]. VR technology has the potential to improve a wide range of production processes in the digital factory, from training and design to quality control and maintenance. By providing workers with a more immersive and interactive experience, VR can help digital  
Figure 1: VR Process Simulation classifications. factories to operate more efficiently, ultimately leading to cost savings, improved product quality, and increased customer satisfaction. VR technology has shown promising results in improving production processes in the digital factory, and it has several advantages over traditional methods of training, design, and maintenance. Compared to traditional methods, VR technology offers a more immersive and interactive experience, allowing workers to gain hands-on experience in a safe and controlled environment. This can reduce the risk of accidents and injuries and increase worker confidence and skill levels. Additionally, VR simulations can be repeated multiple times, allowing workers to practice and refine their skills until they are confident in their ability to perform tasks in the real world. This can improve productivity and reduce the likelihood of errors or quality issues. VR technology can also be used to create virtual prototypes of products and production processes, allowing designers and engineers to test different design options and identify potential problems before they are physically built.