Virtual reality (VR) is a mature technology, which has established itself as an important tool in many engineering applications, such as design review, inspection, and worker training. It was previously determined that VR 3D modelling (VR modelling) is suitable for design purposes [
1]. Moreover, some studies report that modelling in VR software is easier to learn, more natural and intuitive to use and enables faster modelling in comparison with traditional computer-aided design (CAD) desktop 3D modelling software [
2]. However, research regarding the use of VR in product design has been limited to the conceptualisation phase and design review. Moreover, previous design phase studies expressed doubt that VR tools can be used for mechanical design and engineering work as they lack the required accuracy and the capability to transfer the model into later stages of product development [
3].
This study aims to bridge this gap and investigate the usability of the VR tool in the product design stage and to research the possibility of converting and using the VR-created model in later phases such as detailing while ensuring an adequate level of accuracy. The study explores the possibilities the technology offers for the design of complex geometrical models. Given that VR supports easier navigation through the design environment (space), it should be simpler and faster for designers to create designs with complex curved geometries. It was investigated if objects created in VR can satisfy the required model quality and if they can be simply transferred to desktop applications, so that further detailing and editing of the model can be done seamlessly, quickly leading to simulation or manufacture and thus speeding up the development process. The aim was to extract the advantages and disadvantages of desktop CAD modelling and VR modelling in supporting the embodiment design starting from the product concept to its final form.
This work consists of the following parts: (1) Background and objectives introduce the topics and relevant contributions related to CAD modelling, VR technology and its different applications in engineering design and states the objectives of this research; (2) Methodology includes the description of methods and tools used in the study, which consists of a preliminary study aimed at identifying key steps and evaluation criteria in the 3D modelling process, and an experimental research study which explores the modelling capabilities in VR environment; (3) Results of the study; (4) Discussion of the results, and (5) Conclusion.
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]. Eschen 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. Delgado 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 Berg 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]. Berg and Vance [
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 Safadel and White [
19] it was concluded that VR visualisation had a positive compensating influence on participants with low spatial cognition abilities.
In the work of Wolfartsberger [
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. Another study showed that with using VR participants could better perceive the fit of user interface elements and estimate the model dimensions with a lower relative error than in desktop interface on PC screen [
15]. VR also offers advantages in fields such as programming of industrial robots [
21]. By immersing individuals in a virtual world where they may observe and interact with robots in 3D collaborative or distant locations, VR allows for more natural and intuitive interactions. This can improve situational awareness and make interaction simpler [
22]. Alongside the improved spatial perception of the objects, virtual environments can enhance the communication between the dislocated participants as they enable speech and gesturing while at the same time viewing the product in true scale 3D environment when compared to the regular video conferencing tools [
23]. Gong et al. [
24] investigated the application of VR collaboration in a globally distributed manufacturing company. They found that the greatest issue was the transfer of the models from CAD to VR environment. The interaction design of VR systems was highlighted as an important factor for manufacturing companies to widely adopt and benefit from the latest advancements of VR technologies. In addition, VR and AR technologies have high potential and play an important role in education and training of mechanical and design engineers. Researchers have discovered that studying with the support of MR technology can significantly improve the student’s abilities in geometric analysis and creativity [
25]. However, the learning theories on design are often not considered by developers of VR and AR applications, which makes it difficult to incorporate them in the study process [
26,
27].
Besides the application of VR for viewing and discussing proposed design solutions, this technology can also support earlier stages of design. According to Ulrich et al. [
28] the product development process consists of the following phases: planning and ideation, concept development, embodiment design, detail design, testing and refinement and production ramp-up. Engineers use various tools that can assist them with different tasks during development, with the aim to speed up the process. When the product concept is created, it is commonly represented in the form of sketches. These sketches serve as a starting point for the product embodiment, which can be formed as physical or virtual prototypes [
29]. With the rapid development of tools and technologies, virtual prototypes created using 3D modelling in CAD software have become the most common way for design representation [
30]. They enable engineers to easily share and modify their designs using dedicated desktop CAD tools. However, CAD on a screen cannot always meet all the requirements regarding the functional and ergonomic validations of complex 3D models [
20]. In recent years, CAD modelling tools were developed and adapted to support the use of VR headset technology. Berni and Borgianni [
31] classified design functions that can be supported by VR into early phases, co-design, 3D modelling, virtual assembly and prototyping, product evaluation and educational purposes. Balzerkiewitz and Stechert [
3] discussed the usability of VR tools and their capabilities for early design phases. They listed several challenges: for the detailed design phase the transfer from 3D VR to a CAD model has to be possible, the VR-created surface models must be automatically converted into solid bodies, collision detection has to be integrated to prevent overlapping of the objects and an automatic alignment of edges and axes must be enabled. In addition, they highlight that the software has to be intuitive and easy to use to enable wider adoption. As one of the main issues that hinder the use of this technology in engineering design, the authors name the reduced quality of imported models and the inability to edit them. The use of VR for creating design concepts was explored in several studies. Ye et al. [
2] researched how VR technologies can provide more natural and intuitive interaction between the designer and the CAD system using different sensory channels. It was found that VR can provide better support capabilities for conceptual design through its multiple interface integration and implementation, making the 3D sketching more intuitive and quicker, as there is no need to additionally reproduce the design in the CAD system. Van Goethem et al. [
1] tested the VR-supported conceptual design against traditional sketching on paper. The Gravity Sketch VR application with a virtual reality head-mounted display (HMD) was tested by a group of product development students where parameters like efficiency, ease of use and enjoyment were measured. Results have shown no significant difference between the quality of hand-made and VR-made sketches. A similar study conducted by Joundi et al. [
32] showed that the industrial design students find conceptual modelling using VR interesting and a positive experience, however, there are some issues to be considered, e.g., that the lack of surfaces produces inaccuracies in the model and that people draw better on a 2D surface than in 3D space directly. Nonetheless, the users were able to create the desired shapes and models in a rather limited time frame, showing that VR provides good support for quickly generating 3D concept models. Investigating sketching in different environments, Oti and Crilly [
33] stated that immersive 3D sketching is a unique tool that simultaneously supports behaviors that are commonly only found in paper-based sketching, CAD modeling and physical model making. In these studies, the VR-created concept models are built from and represented as a set of surfaces, but they lack an explanation of how the models can be used for further product development. In the next step, engineers have to transfer the surface model into a manufacturable model. This means that the geometry has to be fully enclosed (solid CAD model) and the transitions between the surfaces have to be well defined in order to be able to perform simulations and analyses on the models [
34], as well as to produce technical documentation and use it as input for manufacturing. The surface model can be transformed into a mesh model so that the VR generated geometry can be further manipulated. Misztal and Ginkel [
35] argue that the virtual mesh model can not provide a suitable mathematical surface quality, thus a CAD replica of the shape is also necessary. Zhong et al. [
36] took a different approach and proposed a methodology for direct solid modelling in VR. This reduces the need to replicate the design created in VR again in the CAD software. It is based on constraint-based geometry manipulation, which resembles Boolean operations in desktop CAD software. Even though this methodology is suitable for designing simple geometrical objects, it does not provide good support for complex freeform designs. Currently, available VR modelling applications and available features for solid geometry manipulation show that this approach has not gained significant traction.
To address these concerns, our research objective was to determine whether 3D modelling in VR can be used after the conceptual design phase to facilitate the embodiment from a product concept into its final form (3D model) following the engineering design process. If proven successful, this would reduce the need for switching between desktop CAD and VR environments during product development, thus reducing the time and the required designers’ efforts. To further explore the main research question, different parameters were considered including the possibility of converting a VR-created model into a sold CAD model and the usability of VR modelling tools in terms of speed, intuitiveness of the tools and the modelling process, as well as the output model quality. The metrics used was the modelling time, degree of task completion, overall usability and the quality of the final 3D model.