# VR as a 3D Modelling Tool in Engineering Design Applications
## 1 Introduction
### Background and Objectives  
In recent years, immersive technologies are developing rapidly [4] and are gaining greater recognition in engineering. Augmented reality (AR) and virtual reality (VR) are a part of a wider field of mixed reality (MR), a group of technologies that tend to overlay and anchor virtual objects to the real world so that the users can interact with them [5]. AR is better used in cases where more interaction is required between the users, when the real-world background is important and where the environment or the tasks are not suitable for using headset equipment. For such reasons, in the mechanical engineering domain, AR is e.g., widely used as assistance for maintenance, inspection [6; 7], collaborative design [8] and assembly [9]. [PERSON] et al. [9] suggest that the interaction time between the user and the virtual model can be used as a measure of the utility of a certain MR technology. VR technology is well suited for activities in the earlier stages of the product development process, where the product's form hasn't been finally decided and it is still under development and testing, but also for the design overview and inspection. [PERSON] et al. [10] defined 6 usage categories for AR and VR in architecture, engineering and construction domains: (a) AR and VR for stakeholder engagement, (b) AR and VR for design, (c) AR and VR for design review, (d) AR and VR for construction, (e) AR and VR for operations, and (f) AR and VR for training. As one of the main challenges of VR technology, they outlined the hardship of archiving AR and VR outputs for later review or to record the experiences that the user had in AR and VR environments. With a focus on VR technology, in the paper by [PERSON] et al. [11], the authors made a survey amongst 25 industrial companies on the use of VR in their processes. They listed different use cases where VR technology was used in practice: visibility/viewability [12; 13], ergonomics/reachability [14], packaging, aesthetic quality/craftsmanship (visual inspection), storytelling, abstract data visualization (e.g., airflow simulations) and for communication across disciplines. In the engineering design domain, several authors have investigated the potential of using VR technology for stakeholder engagement and design review. To measure the influence of VR on the users, the researchers considered different tangible aspects of the review process, e.g., time, the number of identified issues or design faults and analysis of human factors such as spatial perception [15]. [PERSON] and [PERSON] [16] conducted a study with design and manufacturing engineers who participated in design reviews in an immersive VR environment. They found that with the true scale geometry representation in VR participants gained a better understanding of the spatial relationships between product components as well as the interactions required to assemble the product. Also, the environment encouraged engagement and improved the design discussions between the members. Collaboration in dislocated, virtual teams, where team members have never met in person is common in the modern product design process [17]. Novel ICT technologies [18] including VR are proving to be vital in such workflows. Research reveals that people have different spatial cognition capabilities. It was also recognised that these capabilities influence the success in STEM fields, where the inability in mental visualization can have a negative effect on performing tasks involving spatial skills. In a study by [PERSON] and [PERSON] [19] it was concluded that VR visualisation had a positive compensating influence on participants with low spatial cognition abilities. In the work of [PERSON] [20] a VR engineering design review approach was compared to a traditional approach using CAD software on a screen. The study showed that a VR-supported design review allowed users to find more faults in a 3D model than in a CAD software-based approach on a PC screen.