## 2 Methods  
The methodology used in this study was organised into two phases related to each specific objective of the study (Figure 1): (1) market research; (2) case study. In the first phase, market research was conducted to perform a commercial analysis of devices and applications that implement immersive technologies (VR, AR, and MR) in the product design process. The study was divided into two scopes: (1) hardware, which included a comparative technical analysis, differentiating between wired and wireless solutions and using the variables of connection mode, type of compatible immersive technology, resolution, graphic quality and accuracy, latency and tracking capability, compatibility with design software, user mobility, ease of transport and installation, release date, and cost; (2) immersive software for 3D sketching and sculpting, 3D modelling, simulation, and visualisation, taking into account the compatibility with VR, AR and MR, with different types of immersive hardware, with other compatible software, and with the possibility of team collaboration. This analysis allowed us to establish an updated map of immersive solutions applicable to industrial design. In the second phase of the study, the usability of immersive technologies applied to the design of industrial products was evaluated. A methodological design based on a single case study with embedded units of analysis and an exploratory approach was adopted. This type of design is suitable for empirical studies that aim to describe and interpret complex phenomena in depth, integrating qualitative and quantitative methods [66]. The main case focused on a professional designer as the sole participant, which allowed for a controlled observation of the learning curve and gradual adaptation to the use of immersive technologies. The embedded units of analysis corresponded to seven products designed by the participant: (1) ring, (2) candle holder, (3) vehicle, (4) mouse, (5) outdoor armchair, (6) reading armchair, (7) high stool. The selection of Design Units was focused on covering a representative range of types of industrial products. Diversity was prioritised in terms of  
Figure 1: Phases of research methodology. scale and geometric complexity, functionality and use, context of use, and applicability to different industrial sectors. In addition, all products cover different stages of the design process, from sketching and conceptual design to visualisation and validation. In each Design Unit, the main design techniques were analysed: sketching, immersive modelling and rendering with VR, and validation in a real context of use with AR. The case study was conducted in a controlled design environment, using VR headsets (Meta Quest 3) and immersive modelling software (Gravity Sketch) as the technological setup, with an industrial designer with initial inexperience in virtual reality. The participant signed an informed consent form before the start of the study. Given the continued use of immersive environments, basic measures were adopted to mitigate potential adverse effects, such as cybersickness, including limited session durations, frequent breaks, and personalised calibration of the visualisation device. Each Design Unit was developed through two sequential times. First, a traditional sketching stage was conducted in which the participant created hand-drawn concept sketches to explore initial ideas and define the basic structure of each product. These sketches served as the foundation for the second stage, in which the same design concepts were further developed using an immersive design workflow with 'Meta Quest 3' headsets (Meta Platforms, Inc., Menlo Park, CA, USA) [67] and 'Gravity Sketch 6.4' (Gravity Sketch Ltd., London, UK) [68]. This sequential approach reflects a common progression in industrial design practice and allowed the study to observe how immersive tools contribute to design development following early ideation.