# A Comparative Study of Design Evaluation with Virtual Prototypes Versus a Physical Product
## 1 Introduction  
Design evaluation is an essential phase in the product development process. This is particularly true when a company plans to develop and release a new product. In the conventional approach, physical prototypes are produced for the purpose of verifying the design functions and collecting user feedback. In different stages of the design process, the prototypes' level of realism may vary depending on use. The lifecycle of current consumer products is relatively short. Using physical models to verify the product design may no longer be an effective solution, considering the cost, time, and effort required to produce physical prototypes [1]. Advances in computer technologies allow for a more realistic simulation, i.e., developing virtual prototypes of the final product. Although a visual virtual prototype has various obvious limitations in terms of design evaluation, e.g., haptic or textile feedback is difficult to realize with current rendering technologies, it can still adequately simulate the visual aspects of a product [2]. Design features, such as colors or textures, can be replaced and assessed visually, and require a short amount of rendering time. This may explain why most previous studies focused on the visual aspects of design evaluation by using virtual prototypes [3]. Early researchers such as [4] argued that a good product could fulfil the user's needs at the functional, usability, and emotional levels. They suggested that more comprehensive approaches,such as those including emotional aspects, should be introduced in the design evaluation stage. [PERSON] [5] investigated how sketches, physical models, and virtual media contribute to the evaluation of card designs. It was found that the familiarity of the product influenced the evaluation result, even though the physical models were still perceived to be more realistic. [PERSON] and [PERSON] [6] found that hand sketches could communicate the design concepts more intuitively. They reported that computer aided media impose somewhat of a constraint to the designer's creativity: They compared 2D virtual prototypes with the actual products and found the former to be effective with regard to evaluation of simple design features. [PERSON] et al. [7] proposed two different experimental implementations for the real-time integration of virtual and physical prototyping based on computer aided design (CAD) techniques and rapid prototyping. A digital mock-up (DMU) was developed for use in an experiment that compared simulated assembly tasks in both real and virtual environments [8]. The subjective evaluation results of the real (RE), virtual (VE), and virtual with force feedback (VEF) environments indicated a real sensory and difficulty gap between the RE and VEF, while a smaller difference was observed between the RE and the VE. [PERSON] et al. [9] analyzed user impressions of a product using virtual prototyping. They characterized the relationship between user impressions and design elements of automobile interior through experiments. Experimental data validated that virtual prototyping can help analyze user impressions of design alternatives at the early stage of the design process. [PERSON] and [PERSON] [10] conducted an experimental study for comparing augmented reality (AR) and virtual environment (VE) prototypes of a rock crushing machine. The experimental result indicated that the VE system was more suitable to support the assessment of visibility, reach, and the use of tools than the AR system. The previous study [11] emphasized the importance of working prototypes in product development and the importance of obtaining the users' reactions upon interacting with such prototypes. They demonstrated how virtual reality (VR) prototypes do not only represent a valid alternative to physical prototypes, but also take a step forward owing to the possibility of simulating multisensory and real-time modifiable interactions between the user and the prototypes. [PERSON] et al.