VR/AR in Design & Production Processes of Innovative Biomedical Products

Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 1 BIOMEDIX Erasmus+ strategic partnership for Higher Education BIOMEDICAL INNOVATIONS THROUGH DIGITAL TRANSFORMATION Chapter 3: VR/AR in Design & Production Processes of Innovative Biomedical Products Project Title Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange KA220-HED-AA8A896B Output Development and Publication of an e-Book on Biomedical Innovations through Digital Transformation Module Chapter 3 VR/AR in Design & Production Processes of Innovative Biomedical Products Date of Delivery 27.10.2025 Authors Filip GÓRSKI, Nikola VITKOVIĆ, Jakub GAPSA, Emilia SMOLAREK, Dolores OJADOS Version V1 This chapter is accompanied with a number of Virtual Reality and Mixed Reality applications, for standalone and PC VR devices (headsets). Use the QR codes in Appendix 1 to download these apps. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 2 Contents 1 Introduction ............................................................................................................................. 3 2 XR in Biomedical Product Design ............................................................................................. 4 2.1 Principles and basic definitions ................................................................................... 4 2.2 XR in Visualization of Anatomic Data .......................................................................... 7 2.3 XR in Simulation and Prototyping of Biomedical Products ....................................... 15 2.4 Customization and Patient-Specific Solutions ........................................................... 19 3 XR in Production and Maintenance Workflows .................................................................... 22 3.1 Training and Skill Development ................................................................................. 22 3.2 Production Workflow and Quality Control ................................................................ 29 4 Tools and Techniques ............................................................................................................ 33 4.1 XR Systems Hardware ................................................................................................ 33 System classes ....................................................................................................... 33 VR projection devices ........................................................................................... 35 MR and AR devices ............................................................................................... 38 Tracking systems and interaction devices ............................................................ 42 4.2 Software for VR/AR Solutions ................................................................................... 45 Application Development Environments .............................................................. 45 VR and MR Software Packages ............................................................................. 47 AR Software Packages ........................................................................................... 52 4.3 Methodology of Building XR Applications for Biomedical Products ......................... 56 4.4 Case Examples ........................................................................................................... 60 Holographic Try-On of Surgical Guides for Lower Jaw Implantation .................... 60 Training of 3D Printing Processes of Orthopedic Products ................................... 63 Implant Design in VR/MR ...................................................................................... 66 5 Conclusions ............................................................................................................................ 70 References ...................................................................................................................................... 72 Appendix 1 ...................................................................................................................................... 77 Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 3 1 Introduction This chapter explores the transformative role of Virtual Reality (VR), Augmented Reality (AR), and Mixed Reality (MR) in the design and production of innovative biomedical products. The focus is on leveraging immersive technologies for designing patient-specific solutions such as prostheses, implants, and orthoses, as well as their applications in training and production workflows. The trio of above-mentioned Extended Reality techniques encompass an idea to create an unreal world, populated with imaginary objects, allowing feeling and interacting with them to learn new insights [1]. This helps simulating, repeating and testing various phenomena, procedures and hypotheses, which is especially crucial in medicine and biomedical engineering. Various immersive technologies can support the whole lifecycle of development of biomedical devices and their use in medicine, both by doctors (including students and young doctors) and patients themselves, ensuring complete safety – by working on virtual twins of anatomical devices and body parts – with a considerable level of perceived realness, enabling to gain considerable new insights, improving certain processes both from the medical and the engineering point of view. Usefulness of VR, AR and MR in modern healthcare is indisputable. That is why it is crucial for biomedical engineering learners to gain as much knowledge about capabilities of these technologies as possible. This chapter aims at providing basic, up-to-date knowledge regarding how these technologies work in principle, how can they support development of biomedical products (especially anatomically customized, as presented in the other chapters) and what processes can be improved by use of digital simulations. The chapter also aims at highlighting specific examples of applications (on par with contents of the other chapters) and discuss certain challenges and opportunities for adoption of the technology in the biomedical domain. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 4 2 XR in Biomedical Product Design 2.1 Principles and basic definitions The acronym XR, standing for Extended Reality, is a collective term encompassing three major interactive three-dimensional (3D) technologies: Virtual Reality (VR), Augmented Reality (AR), and Mixed Reality (MR). These technologies form a continuum of immersion and digital integration, ranging from full immersion (virtuality) to completely physical reality, without any augmentations. Within this continuum, different systems provide varying degrees of sensory stimulation and interaction between the real and digital worlds. Extended Reality (XR) is an umbrella term that includes Virtual Reality (VR), Augmented Reality (AR), and Mixed Reality (MR), differing mainly in how much of the real world is replaced or augmented by digital content. At one end lies the Virtual Reality (VR) – a fully digital, computer-generated 3D environment that replaces the user’s sensory perception of the real world with an artificial, simulated environment. The user is entirely immersed in this virtual world and interacts with it through motion-tracked devices such as controllers or gloves. In VR, the physical surroundings are excluded, and all sensory input (mainly visual and auditory) originates from the system. Augmented Reality (AR), on the other hand, superimposes virtual objects onto the real environment, enabling users to perceive both simultaneously. AR enriches the real world by overlaying digital elements that are contextually related to physical objects or spaces. As defined by Ronald Azuma (1997) [2], AR combines real and virtual imagery, allows real-time interaction, and spatially anchors digital content in the real world. Typical AR systems include smartphoneor tablet-based applications using cameras and motion sensors, or wearable smart glasses with semi-transparent displays (a class of devices pioneered by Google with their 2013 Google Glass device). Mixed Reality (MR) merges and dynamically integrates both realms, allowing digital objects to coexist and interact with the physical environment. MR systems track user and environmental motion in real time, often without markers, providing spatially consistent visualizations known as “holograms.” The user can manipulate these virtual objects as if they were part of the physical scene. Examples include Microsoft HoloLens or Meta Quest Pro systems (formerly known as Oculus, legacy naming used prior to 2021). MR represents the midpoint of the XR continuum, offering the flexibility of AR with the interactivity and spatial awareness of VR. Together, VR, AR, and MR define the XR continuum, in which the ratio between digital and physical perception varies depending on the degree of immersion and interaction. Modern Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 5 applications frequently blend these approaches, creating hybrid solutions that adapt to specific industrial, medical, and educational tasks. The continuum is shown in Figure 2.1. Fig. 2.1. Extended Reality technologies continuum, based on Milgram [3] and Górski [1] Fundamental to understanding XR are three core concepts, often represented as the I³ Triangle [4] (Burdea & Coiffet, 2003): Interaction, Immersion, and Imagination. These three pillars define the experiential and functional dimensions of XR. Interaction refers to the real-time reciprocal relationship between the user and the digital environment. It encompasses all input and output processes that allow the user to affect the virtual scene, selecting, moving, or transforming objects, activating simulations, or navigating through space. Advanced interaction techniques rely on tracking technologies that monitor the position and orientation of the user’s head, hands, and body segments. Devices include optical sensors, infrared cameras, or inertial measurement units (IMUs). High-quality interaction enhances realism and supports intuitive control. Immersion is the psychological sensation of “being present” in a non-physical environment. It depends not only on display quality but also on field of view, frame rate, latency, and congruence between sensory stimuli and physical motion. Immersion may be partial (e.g., on desktop VR systems) or total (as in head-mounted displays or CAVE systems). Interestingly, as highlighted in the lecture materials, immersion does not rely exclusively on the graphical fidelity of visuals, fluency and sensory consistency play more decisive roles. Imagination represents the cognitive complement of immersion. Even the most sophisticated hardware cannot replace the user’s interpretative ability to perceive the digital world as real. A fully “ideal” VR system, capable of complete sensory substitution, remains unattainable in a foreseeable future. As such, effective XR experiences rely on a balance between technological fidelity and the user’s imagination. Imagination also stands in for “good will” of the user – if the users are enforced to use XR, its efficiency will probably be lower, as they won’t be fully engaged. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 6 Among technical phenomena accompanying XR, one of the most studied is cyber sickness (also VR sickness, simulator sickness), caused by conflicts between visual, vestibular, and proprioceptive cues. Symptoms include nausea, dizziness, and headaches, often resulting from latency, motion mismatches, or low-quality optics. For safe and comfortable long-term XR usage, it is crucial to properly lay out the experiences in the immersive space, both from the software and hardware point of view, to reduce the potential of this unwanted phenomenon to the least extent possible. Other important technical notions include: • holograms – spatially anchored digital objects, typically seen in MR environments. Although not true holography in the optical sense, the term refers to 3D-rendered entities perceived as existing in the user’s surroundings, • markers – physical patterns (fiducial codes) used in AR to define spatial references for overlaying digital models, • tracking – real-time measurement of the user’s or object’s position and orientation, indispensable for maintaining correct spatial perception, • latency – the delay between user motion and corresponding visual update; critical for immersion and comfort, • Field of View (FoV) – the angular extent of the observable scene; wider FoV enhances realism and reduces disorientation, • cyber sickness – an unpleasant phenomenon caused by incompatibility of perceived and simulated reality, resulting in a set of symptoms from the nervous and digestive system, lowering quality of immersive experience or enforcing users to cease it entirely [41]. An XR system comprises two essential layers: hardware and software. The hardware provides the sensory interface (input/output), while the software defines the logic, visual content, and interaction mechanisms. Both layers must be seamlessly integrated to deliver a coherent user experience. Hardware architectures vary depending on the XR modality and level of immersion. They can range from fully stationary – PC-based immersive VR systems – high-performance computers coupled with head-mounted displays (HMDs) such as HTC Vive, Varjo or Meta Quest devices connected to PCs, offering precise motion tracking and full spatial immersion – to wearable AR/MR devices – smart glasses or headsets (e.g., HoloLens, Magic Leap, Quest Pro) enabling markerless spatial mapping and natural, gesture-based interaction, with complete freedom of mobility and locomotion. Common to all these systems is the necessity of real-time tracking, achieved by combining inertial, optical, and sometimes depth sensors (e.g., LiDAR). Input devices include motion controllers, gloves, or haptic interfaces, while output components deliver stereoscopic Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 7 imagery, 3D audio, and, increasingly, tactile feedback. The classes and components of these systems are more widely described in section 4.1 of this chapter. Software in XR systems serves multiple roles: rendering 3D content, managing interactivity, synchronizing tracking data, and providing the graphical user interface. Most applications are developed using game engines such as Unity or Unreal Engine, which integrate 3D visualization, physics simulation, and scripting tools. Specialized toolkits like the Microsoft Mixed Reality Toolkit (MRTK) support hardware interoperability and spatial interaction logic. More on XR software can be found in section 4.2 of this chapter. Although XR technologies are widely associated with entertainment and gaming, their industrial applications have become increasingly strategic. The automotive, aerospace, and machinery sectors were among the earliest adopters. Companies such as Boeing, Volkswagen, and MAN have used immersive simulations for design validation, assembly training, and production line optimization. These implementations demonstrated substantial reductions in training time, prototyping costs, and design iteration cycles [5]. In Europe, Volvo has extensively used Mixed Reality for virtual test drives and design evaluation, demonstrating industrial-grade XR adoption in automotive development. In the automotive industry, VR enables engineers to visualize full-scale digital prototypes, assess ergonomics, and simulate assembly operations before any physical component is produced. AR assists maintenance personnel by projecting instructions directly onto machinery, reducing human error. MR, in turn, facilitates collaborative engineering by merging real components with virtual prototypes, supporting hybrid work between design offices and production floors. Similar transformations occur in the aerospace and space exploration sectors, where XR supports the planning of complex assembly sequences, astronaut training, and mission simulations. The manufacturing industry employs XR for process optimization, factory layout planning, and operator training under the Industry 4.0 paradigm, integrating digital twins and cyber-physical systems. Beyond production, XR is rapidly expanding into healthcare, education, and biomedical engineering, enabling virtual prototyping of medical devices, visualization of anatomical data, and immersive surgical planning. Its interdisciplinary versatility confirms XR as a core enabling technology for innovation, bridging physical and digital domains. 2.2 XR in Visualization of Anatomic Data In the not-so-distant past anatomy was dependent on dissection to study complex structures of the human body and their interaction [6]. Now, with the rapid development of computers, 3D models of human body parts (also referred to as digital anatomy) have been introduced to medical practice [6]. Although XR was not primarily developed for biomedical Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 8 applications, as is the case with most engineering technologies, it has quickly been adopted as an important tool in medicine. The primary use of XR in biomedical applications has been tied to the visualization of medical data for education, pre-operative planning, mid-surgery models, immersive implant and surgical guide designers, etc. This has been achieved through the incorporation of the already widespread medical imaging technologies such as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) with VR, AR, and MR, thus allowing for realistic representations of complex anatomical structures, as well as implants and surgical procedures. This section of the book will further elaborate how the XR technologies are used to enhance the understanding of complex anatomical structures, how the integration of medical imaging (CT and MRI) with XR is done, and where XR is applied in medicine. Up to the introduction of XR, anatomy was primarily taught using traditional (textbooks and cadavers) and modern tools (tangible models and digital anatomy tools). These approaches have proven effective for educational purposes, but how well do they adapt to specific patient cases, preoperative planning and surgery simulation? The answer is that these tools can with certain limitations be used for these purposes, but that a greater amount of personalization and flexibility is possible with the introduction of VR, AR and MR as an educational and preoperative planning/simulation tool. As previously mentioned, these methodologies are commonly referred to under the umbrella term XR and are based on the integration of medical imaging (3D organ representations) in digital space. One major drawback of XR in medicine is that it cannot give full tactile experience which is achievable with traditional cadaver dissection. [7] This is why XR should not be considered strictly as a substitute for traditional methods, but as a complementary methodology which is exceptionally adapted for specific use cases and has the advantage of not requiring cadavers which require special considerations. [7] XR application requires high-quality virtual 3D models of the human body. These models are created based on 3D blocks created from 2D slices of the human body. Based on these 3D blocks, segmentation is performed manually or using algorithms which identify different types of tissue to extract the desired region of interest (ROI). Then medical practitioners can evaluate the 3D models on 2D screens. Most CT and MRI scans were performed, so medical experts could diagnose specific patient cases, due to this there exist a lack of isotropic high resolution medical images which are required as datasets in order to develop XR applications. Additionally for AR, image registration algorithms and depth indicators are needed to align the digital anatomy to specific surfaces and provide room for appropriate interaction with the models. To clarify this, in AR the models of organs need to be presented in proper projections and positions in respect to the observer position and viewing angle using the AR application. This is achieved using markers or recognition methodologies which can be used to overlay the digital anatomy over real life body parts. To use AR for surgery guidance, in addition to digital Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 9 anatomy representation and positioning, these applications need to be able to follow the positioning of relevant instruments and tools which will be used in surgery. Also, it is important to consider that during surgical operations, the organs do not remain in the same positions as those that are observed from still medical imaging, in order to account for these deformation finite element method may be employed to provide model deformation estimates and geometric representations. This is where the main difference between AR and VR in digital anatomy applications can be seen, as VR is used predominantly for education, and primarily needs to provide 3D organ representations in the digital world, while AR is meant for cases which require interactions between the digital anatomy and real-world cases. [8] The basic principle of XR in digital anatomy is to display a part of the real-world anatomy in the digital world. For an XR application to be developed, digital anatomy must be extracted from medical images. During the CT or MR scan, parts of the body are digitized into the acquired volume, this raw data is then codified in DICOM format. This format can be read by medical imaging software, but in order for it to be converted into specific organs, various volume rendering techniques (VRT) are applied to create a rendered volume (RV). There are multiple approaches to creating digital anatomy based on DICOM files and they can be categorized into three groups: • automatic reconstruction methods, • semi-automatic reconstruction methods and • manual reconstruction methods. [9] In the automatic reconstruction method, an algorithm (software preset: bones, soft tissue, etc.) is used consisting of certain parameters in order to reveal the desired part of the geometry based on the imported data. This is a fast way to visualize geometry, but it comes with drawbacks, as it is fully automatic it is up to the predefined settings to distinguish between various tissue types and different anatomical structures which can lead to connecting parts of the anatomy which should not be connected or having residual structures which were not wanted but due to the selection threshold are displayed either way. On the other hand, this methodology gives the most exact results, as it is a direct translation from the scan and is not prone to human error. For semi-automatic reconstruction method the operator is able to change the parameters in order to influence the result, which allows for correcting the previously stated problems, but requires a greater knowledge of anatomy in order to avoid human error. [9] XR applications have already been developed which allow the direct visualization of medical imaging scans, such as: DICOM VR, Imaging Reality, Specto VR, etc. With the manual reconstruction method, the whole volume derived from the medical imaging is displayed to the operator. [9] Based on this volume, the operator first crops the desired ROI out of the entire volume rendering, this is done using 2D projections and the 3D view, during which good knowledge of anatomy is important in order to achieve the desired Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 16 usability problems and safety concerns virtually rather than through multiple physical revisions – thereby shortening their development cycle. Likewise, product developers at Kaleidoscope Innovation found that collaborative VR “walk-arounds” of a 3D model helped their team spot and fix design flaws in real time, avoiding costly late-stage changes. These cases underscore how XR is revolutionizing virtual prototyping in the biomedical domain by making design evaluation more efficient, immersive, and insightful. 1. Virtual Prototyping for Testing Design Concepts Designers can import CAD models of a medical device into a VR or MR system and simulate its form and function under various scenarios. For instance, a catheter or surgical instrument design can be visualized inside a virtual patient model to assess its navigation path through anatomy, all before any physical prototype is fabricated. The literature indicates that integrating virtual prototypes into the early design stage improves design validation by exposing more device behaviors to analysis and simulation than was previously possible. Mejía-Gutiérrez et al. (2017) describe a systems-engineering-based virtual prototyping approach that links device requirements to a sequence of simulations, demonstrating that many performance and safety checks can be completed on a virtual model [20]. By the time a design reaches physical prototyping, most obvious issues have already been resolved in VR. As a result, developers experience fewer design-build-test cycles overall. Using VR models can cut the number of physical prototype iterations roughly in half for a new medical device, since engineers are able to iteratively refine the design virtually and only commit to a physical prototype once the VR simulations were satisfactory. These advantages are attributed to the realism and interactivity of modern XR simulations – designers and stakeholders can manipulate a virtual device as if it were real, probing its features and responding to its behavior. Studies have documented that users find this immersive 3D interaction more intuitive and informative than reviewing abstract drawings or screen-based CAD models. In a multi-user VR design review, for example, Truong et al. (2021) observed that teams achieved better planning accuracy and design decisions compared to 2D workflows, thanks to the ability to experience the prototype at true scale with natural spatial context [19]. Overall, virtual prototyping with XR not only accelerates design cycles but also enhances the quality of early-stage design evaluations, leading to more robust biomedical products. Beyond general device development, XR prototyping is proving especially valuable for patient-specific biomedical products. Custom implants and prostheses traditionally require meticulous tailoring to an individual’s anatomy, often involving repeated fittings. XR allows this customization to be done virtually upfront. For example, in dental implantology, researchers have used VR to simulate implant placement in a patient’s jaw model, optimizing the implant’s position and angle in a risk-free virtual setting before surgery. Monaghesh et al. (2023) report that such VR-based planning can improve precision and confidence in dental implant procedures, effectively serving as a virtual prototyping of the implant’s integration into the patient’s anatomy [22]. Similarly, in prosthetics design, Mixed Reality can overlay a 3D prosthetic limb model onto a patient to evaluate fit and alignment in situ. Designers at Poznań University of Technology Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 17 (part of BIOMEDIX project consortium) developed an MR “try-on” system where an amputee and clinician can see a virtual prosthetic socket attached to the patient’s residual limb, check the fit from all sides, and even adjust parameters on the fly (Fig. 2.6). This kind of virtual fitting helps identify comfort and sizing issues early [1]. Virtual try-ons significantly reduced the number of physical test sockets needed for custom prosthetic limbs, since many adjustments (length, width, angulation) were resolved in the XR model beforehand [23]. In general, virtual prototyping in XR provides a powerful means to test design concepts under conditions that closely mimic real-world use. Fig. 2.6. Mixed Reality fitting of a prosthesis to a stump By doing so entirely in software, teams can explore more design alternatives with minimal cost. This encourages experimentation and innovation in biomedical design, as even unconventional ideas can be prototyped virtually and fail fast if needed, without the usual expense of physical iteration. Researchers emphasize that this flexibility of XR prototyping drives a more user-centered design process for medical products, ultimately yielding devices that are better optimized for their end-users and clinical environments. 2. Evaluating Fit, Function, and Ergonomics in XR A critical aspect of biomedical product development is ensuring that a new device not only functions as intended, but also fits the human body and can be used comfortably and safely. XR technologies offer unique tools to evaluate fit, function, and ergonomics during prototyping. In a virtual or mixed reality environment, developers can combine digital device models with realistic human models to examine interactions that would be difficult to assess on a computer screen alone. Recent studies underline the benefit of integrating Virtual Reality and Digital Human Modeling for early ergonomics assessment. For example, da Silva et al. (2022) review how VR coupled with human avatar simulations allows engineers to perform physical ergonomics analyses (reach, posture, visibility, etc.) during the design phase of industrial and medical products [24]. Instead of relying solely on expert intuition or later user testing, one can deploy a virtual human in VR to test how a surgeon would hold a new instrument or how a patient might interact with a medical device’s interface. XR also supports functional testing of a device’s operation via simulation. High-fidelity VR prototypes can include basic physics and haptic feedback, enabling approximate trials of Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 18 device function. For instance, in a VR simulation of a new laparoscopic tool, the resistance of tissue can be modeled and fed back through a haptic controller, allowing designers to feel whether the tool’s handle provides sufficient leverage. While not a perfect substitute for real materials, these simulations can highlight functional shortcomings (like insufficient range of motion or too much required force) in the design concept. For example, an AR headset can project a full-scale model of a new dialysis machine into a hospital ward to check if it fits beside a hospital bed and if nurses can reach all its controls when other equipment is present. Such AR/MR-supported analyses are particularly useful for environment integration tests – e.g. ensuring a new operating room device does not obstruct staff movement or verifying that a surgical robot can be positioned optimally. Researchers in human factors engineering are increasingly advocating for VR/MR inclusion in the medical device design toolkit, seeing it as a way to inject rigorous human-centric evaluation into early design stages [24]. As XR hardware becomes more accessible (e.g. standalone VR headsets and AR glasses), we can expect virtual ergonomic testing to become a standard practice in biomedical product development. 3. Collaborative Design in Virtual Spaces XR is not only useful for individual simulations, but also enables collaborative design processes in ways that conventional tools cannot. In the biomedical field, device development often requires input from multidisciplinary teams – mechanical engineers, biomedical scientists, clinicians, end-users, and other stakeholders – who may be located in different places. Virtual Reality and Mixed Reality platforms provide a shared immersive space where these participants can engage with the prototype together in real time, enhancing communication and collaboration across distances. In a collaborative XR design review, team members each wear VR headsets (or use AR devices) and see the same life-size virtual prototype in a shared environment. They can point out features, suggest modifications, and even annotate or edit the design, all while conversing naturally as avatars around the virtual object. This real-time collaboration in virtual space removes the barriers of 2D teleconferencing where a single person shares a screen. Instead, everyone in the XR meeting experiences the prototype as if in the same room, leading to a more mutual understanding of design intent. This can lead to Metaverse-like workflows, where specialists from various geographical locations connect in order to perform treatment of a difficult health condition for a specific patient, potentially saving lives. Studies have begun to quantify the benefits of collaborative VR design sessions. Truong et al. (2021) conducted a case study with remote engineering teams using a multi-user VR system for a complex design task (planning an elevator machine room) and found that the VRcollaborative approach improved planning accuracy and team communication compared to traditional workflows [19]. These findings are highly relevant to medical device design, where spatial ergonomics and human interactions are critical. We can envision, for example, a collaborative VR review where a surgeon, an industrial designer, and an ergonomist jointly evaluate a new operating room device: the surgeon’s avatar can demonstrate how they would operate the device, the designer can adjust elements on the fly, and the ergonomist can Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 19 observe and flag any awkward motions – all in one session, despite each expert being in a different physical location. Collaborative XR is also proving valuable for design education and communication in biomedical engineering. In design reviews, complex data (like 3D scan data of anatomy, or simulation results) can be visualized for all participants in XR, ensuring everyone sees the same picture. This shared understanding reduces miscommunication. Choi et al. (2015) noted that in manufacturing, VR/AR collaboration tools helped different departments to communicate design changes more effectively by providing a common 3D reference frame [25]. Similarly, in medical device design, regulatory and management stakeholders can join an XR review to better grasp a device’s features and usage context, which might accelerate design approval cycles. By walking a regulatory expert through a virtual usage scenario of a device (e.g. a surgeon performing a procedure with it in VR), the development team can more clearly demonstrate compliance with requirements or address concerns interactively. It should be noted that successful XR collaboration requires careful implementation – aspects like network synchronization, user embodiment, and intuitive controls affect how well teams can work together. However, as we recently found during the COVID-19 pandemic, the utility of remote VR collaboration when travel was restricted was unparallel – rare cases of companies that had XR design infrastructure in place were able to continue their device development with minimal disruption, as engineers and clinicians could meet in VR to evaluate prototypes. 2.4 Customization and Patient-Specific Solutions Interactive VR/AR product configurators have been shown to enhance the design process for medical devices. For example, Lin and Lee [26] developed a VR-based prosthetic design platform where patients co-created their prosthesis appearance alongside designers; this cocreative VR approach improved design efficiency and user involvement. Similarly, in previous work of some authors of this book [27] integrated extended reality into the prosthetic design workflow – including an AR-based configurator for selecting prosthesis modules – and demonstrated that such XR tools can effectively support engineering design stages. These studies support the claim that VR/AR configurators can make medical product design more effective by enabling immersive visualization and real-time customization. Effective deployment of VR/AR in this domain requires integration with CAD/CAM tools. Research shows that virtual design environments can interface with CAD models and digital fabrication. For instance, Hauschild et al. [28] created a VR system for prosthetic limb design that incorporated realistic musculoskeletal models; this allowed engineers to design and simulate prosthetic components in VR and then transfer the designs to physical prototypes, bridging the gap to CAD/CAM production. Modern workflows like the AutoMedPrint system, also created and researched by some authors of this book use 3D scans and automated CAD algorithms to generate prosthesis Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 20 designs, and then employ AR/VR modules to assist in customizing these designs with the patient before fabrication, as illustrated in an example of a prosthetic VR configurator (Fig. 2.7) [1,29] and AR virtual mirror for orthoses [30]. In the case depicted at Fig. 2.7, although VR controllers usually are not suitable for the people with upper limb disability, the design of Meta Quest 2 controllers was actually beneficial – the controller simulates a physical prosthesis and the user can actually operate it as such, greatly benefitting realism and getting familiar with the device before it’s even constructed. Fig. 2.7. VR configuration of prosthesis in two modes, described in [1,29] One key benefit of applying VR/AR and scanning technologies is enhanced patient engagement. Studies in prosthetics have found that when patients are involved in design choices (even just cosmetic decisions), their satisfaction with the device increases significantly. Lee et al. [31] reported that amputees who were offered options in the look of their prosthesis (through an interactive design process) felt more empowered and had higher overall satisfaction than those who were not involved, underscoring the positive impact of patient participation in design. VR-based co-design further boosts engagement – patients in Lin and Lee’s VR configurator study actively took part in shaping their prosthesis and this was beneficial for both the users and the designers. In addition, VR/AR visualization can speed up decision-making – designers and patients can quickly try out different configurations in a virtual space, avoiding the need for multiple physical prototypes. Another benefit is enhanced customization accuracy and fit. Highresolution 3D scans ensure that the device geometry matches the patient’s anatomy within millimeter precision. For example, the custom neck brace by Sabyrov et al. [32] achieved a very exact fit; the authors note the final 3D-printed orthosis “possesses high accuracy in terms of the neck shape of the patient” due to the precise digital scan and modeling process Likewise, using VR to adjust and visualize a prosthesis can help catch design issues early, potentially improving the final fit and comfort, as demonstrated by using VR for fitting a prosthesis automatically generated in the AutoMedPrint system [23] (Fig. 2.8), as mentioned briefly in the previous subchapter. Overall, these technologies contribute to faster design cycles, better-fitting products, and more satisfied patients. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 21 Fig. 2.8. Digital fitting of a prosthesis in VR and final result – reality, as described in [23] Despite the promise of VR/AR in custom medical design, there are challenges and barriers to consider. Technical limitations remain a concern: for example, fully immersive VR can deliver high detail and realism, but current systems often suffer from resolution limits, cumbersome hardware, and a learning curve for new users. In previous work [27] we observed that while VR was extremely powerful for training and simulation, it required significant user familiarization due to technical complexities, whereas AR/MR were easier to jump into but not yet as mature in performance. This indicates that each technology has trade-offs – VR offers immersion but can be costly and complex, and AR/MR have usability advantages but need further development to reach the same effectiveness. Another challenge is integration into existing workflows. Hospitals and clinics may have established CAD/CAM processes, and introducing VR/AR tools or new scanning systems requires compatibility and training. Ensuring that data flows smoothly (for instance, exporting a patient-specific design from a VR configurator into a CAD model ready for 3D printing) can be non-trivial. Researchers stress the importance of developing standard procedures so that XR technologies become a seamless part of product development, rather than a standalone novelty Cost and accessibility are also potential barriers. High-end VR headsets, AR glasses, 3D scanners, and software licenses can represent a significant investment for healthcare providers. While these costs are decreasing over time, budget constraints and the need for technical support can slow adoption in smaller clinics. Moreover, the benefit of these technologies must justify the expense – for widespread acceptance, VR/AR solutions need to prove that they save time or improve outcomes enough to offset implementation costs [33]. Finally, there may be human factors challenges such as resistance to change or the training required for clinicians to effectively use VR/AR systems. Ongoing research and pilot programs are addressing these issues, and as the technology matures (and success stories accumulate), many of these barriers are expected to diminish. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 22 3 XR in Production and Maintenance Workflows 3.1 Training and Skill Development Virtual Reality (VR) has emerged as a transformative tool for industrial training, significantly enhancing the preparation of production and maintenance personnel to handle complex equipment. VR environments simulate realistic operational scenarios, enabling staff to gain essential experience in a controlled, safe, and repeatable setting, which is particularly beneficial for industries involving high-risk or high-cost operations. One of the primary strengths of VR training is its immersive quality, which has been widely recognized to improve learning outcomes. Immersive experiences has been known for decades to facilitate better retention of procedures and allow trainees to practice repetitively without risk to personal safety or equipment [34]. For example, personnel training to manage complex machinery or hazardous materials can safely rehearse emergency response procedures, thus increasing confidence and competence in real-life scenarios. Virtual training of a vehicle operation (Fig. 3.1) can help to learn how to avoid obstacles and maneuver in tight spaces, with no risk of damaging the equipment or harming anyone [35]. Fig. 3.1 Virtual forklift training at Poznan University of Technology, as described in [35] Research demonstrates that VR significantly enhances the effectiveness of industrial training compared to traditional methods [5,34,36]. Trainees exposed to immersive VR show quicker acquisition of skills and better knowledge retention, resulting in improved operational efficiency. The interactive nature of VR training ensures that users remain actively engaged, further boosting learning effectiveness through hands-on practice and immediate feedback. Training workers in production is often a highly complex process. To train a skilled worker, companies must invest significant resources, including time, money, equipment, and personnel responsible for conducting the training, lecturers or trainers. As a result, training new workers is a demanding task. Additionally, it is common for employees to leave the company for better salaries, improved working conditions, or other opportunities, even after Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 23 completing training and working for several months. This leads to a situation where worker training can be inefficient in terms of the resources invested compared to the productive output gained. For this reason, companies increasingly resort to either "poaching" already trained and experienced workers or reducing the resources allocated to worker training. Resource reduction can be achieved through various optimizations, but over the years, with the development of Industry 4.0, one of its key pillars has proven to be a highly valuable tool in this regard – VR technology. Numerous studies on this topic confirm its effectiveness. VR technology offers numerous advantages in training workers across different job positions, such as: • Safe learning environment – Employees can practice dangerous or complex tasks (e.g., surgery, machinery operation) without real-world risks. • Hands-on experience – Interactive simulations help reinforce learning better than traditional methods. • Cost-effective – Reduces the need for expensive physical setups, travel, and materials. • Repeatable and scalable – Employees can train as many times as needed, ensuring consistent skill development. • Higher engagement – Immersive learning increases focus and retention compared to passive training methods. • Remote accessibility – Staff can train from anywhere, reducing logistical challenges. • Real-time feedback and analytics – Trainers can track performance and tailor learning experiences. • Faster skill acquisition – Accelerates learning curves through active participation. A well-designed VR training scene should include the following key components to ensure an effective learning experience: 1. Realistic Environment - the virtual setting should closely replicate the actual workplace or training scenario (e.g., a hospital, factory, laboratory (Figure 3.2), in addition to having highquality 3D models and textures enhance immersion (Figure 3.3). Fig. 3.2 Realistic VR scenario of material testing laboratory Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 24 Fig. 3.3 Virtual representation of the CNC machine from the real world 2. Interactive Elements - users should be able to manipulate objects, press buttons (Figure 3.4), operate machines, or interact with virtual characters (Figure 3.5). This encourages handson learning rather than passive observation. Figure 3.4 Interactive buttons (VR Robotics Simulator) Figure 3.5 Avatar collaboration and communication in VR (Horizon Workrooms) 3. Step-by-Step Guidance (Figure 3.6) - instructions should be provided through voiceovers, text prompts (Figure 3.7), or visual markers (e.g., arrows, highlights). This helps users learn tasks gradually. Figure 3.6 Step by step guides Figure 3.7 Highlighting object of interest with arrows and text (Box Organizer VR and MR Application) 4. Scenario-Based Learning - the VR scene should simulate real-life situations (e.g., responding to an emergency, assembling a machine, handling customers). Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 25 Figure 3.8 Real life scenario of welding robot (VR robotics simulator) 5. Performance Feedback and Assessment - real-time feedback via pop-ups, scoring systems, or progress tracking helps users improve. Mistakes should trigger corrections or explanations. 6. Repetition and Skill Reinforcement - users should have the ability to repeat tasks multiple times for skill mastery. Adjustable difficulty levels can cater to different skill levels. 7. Safety and Error Handling - simulations should include safety guidelines and consequences of mistakes (e.g., showing what happens if a worker misuses equipment). Many industrial entities have successfully implemented VR training systems, achieving notable improvements in their workforce training programs. For instance, ExxonMobil's 3D Training Environment uses immersive VR to instruct operators and engineers in the maintenance of gas pipelines and drilling platforms. Utilizing advanced CAVE (Cave Automatic Virtual Environment) systems, ExxonMobil offers realistic, large-scale simulations allowing natural physical interaction and collaborative scenarios [37]. Operators learn and repeatedly perform essential maintenance tasks such as valve inspections and operations under realistic virtual conditions. Similarly, Baker Hughes developed a VR training solution for turbine maintenance using HTC Vive hardware and the Unity3D platform. Trainees interactively perform procedures, including detailed visual inspections and maintenance protocols, significantly increasing proficiency and reducing risks associated with training on actual highvalue turbines [38]. In electrical energy sectors, companies such as Digital Engineering and Enea Operator (Fig. 3.9) have implemented VR-based training platforms to educate technicians and operators about high-voltage substations and distribution equipment. Interactive scenarios effectively familiarize trainees with critical components and maintenance procedures, significantly reducing operational risks and costs associated with physical training [39]. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 32 for inspection data – operators see deviations exactly where they occur on the part, rather than looking back-and-forth between the part and a separate screen. Studies report that overlaying measurement results onto parts in AR helps catch dimensional issues much earlier, minimizing scrap and rework. Especially for one-off, patient-matched devices, this virtual inspection approach ensures each unique product meets accuracy and conformance requirements (fit, alignment, surface quality) before it ever reaches the patient. In summary, AR and VR tools in quality control enable near zero-defect manufacturing for medical products by making inspections more intuitive, data-rich, and closely tied to the digital design intent. Fig. 3.14 Polyrix stationary AR for deviation visualization [49] Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 33 4 Tools and Techniques 4.1 XR Systems Hardware System classes A structured classification of XR technologies helps understand their varying functionalities, applications, and interaction modalities. VR systems can be broadly categorized into three primary classes: Desktop VR, Projective VR, and Immersive VR, as presented in Fig. 4.1, based on previous work [5]. Figure 4.1. Classification of VR system types Desktop VR represents the most basic form of virtual reality systems. In this setup, the user typically remains stationary, interacting with virtual environments via a desktop computer. The visual output is usually provided through single-person projection devices such as specialized 3D monitors or VR goggles. Interaction within desktop VR systems primarily relies on haptic devices or handheld controllers, enabling users to manipulate virtual objects and navigate virtual spaces effectively. Projective VR, on the other hand, elevates user interaction by utilizing larger projection surfaces, such as PowerWalls. This VR class supports collaborative experiences by accommodating multiple users simultaneously. Unlike desktop VR, users interact with virtual environments in a standing position, using gestures or handheld controllers. The larger visual display enhances spatial awareness and facilitates more natural, intuitive group interactions, ideal for collaborative tasks and shared virtual environments. Immersive VR systems offer the highest level of immersion among VR categories. Users experience complete immersion in virtual worlds, enabled by advanced hardware such as Head-Mounted Displays (HMDs) or CAVE (Cave Automatic Virtual Environment) systems, Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 34 allowing room-scale movement. Interaction in immersive VR is particularly advanced, utilizing precise motion tracking technology. This tracking capability provides a realistic user experience, significantly enhancing engagement and effectiveness, especially in training simulations and complex spatial applications. Parallel to VR, AR/MR systems enhance physical reality by overlaying virtual elements onto real-world views. These systems also fall into three distinctive classes: Stationary AR/MR, Handheld AR/MR, and Immersive AR/MR (Fig. 4.2). Figure 4.2. Classification of AR/MR system types Stationary AR/MR setups are characterized by fixed-position displays such as televisions, projectors, or stationary HMDs. These systems employ advanced motion tracking coupled with object recognition capabilities. Although they offer highly precise augmentation, stationary AR/MR systems restrict interaction to a defined, limited working area, making them ideal for precise tasks requiring accuracy and stable environmental conditions. Handheld AR/MR systems utilize commonly available devices such as smartphones or tablets. These affordable, widely accessible systems incorporate internal measurement units (IMU) and camera-based marker recognition and tracking. Despite their lower cost and portability, interaction capabilities and immersion levels remain relatively limited compared to stationary or immersive setups. Immersive AR/MR systems represent the pinnacle of augmented reality experiences. They incorporate smart glasses or sophisticated headsets equipped with advanced motion tracking technologies including infrared sensors, cameras, and other specialized sensors. These highcost solutions provide substantial mobility and intuitive interaction, facilitating rich, dynamic experiences that seamlessly blend digital content with the physical world. Their versatility makes them highly suitable for applications requiring both freedom of movement and high interaction fidelity, such as in industrial maintenance, medical procedures, or complex training scenarios. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 35 VR projection devices The projection subsystem is the foundation of every Virtual Reality (VR) installation. It serves as the interface between the digital environment and human perception, determining the degree of immersion, realism, and comfort achievable by the user. Although VR systems may vary widely in their purpose and complexity, all of them rely on stereoscopic visualization - the generation of two slightly different images for the left and right eyes, which are fused by the human visual system into a single perception of spatial depth. Modern VR projection technologies can be divided into two principal categories: personal systems, designed for individual immersion, and multi-user systems, designed for collaborative experiences. The most widespread form of immersive visualization is the Head-Mounted Display (HMD), also known as VR goggles. This category has evolved rapidly since the mid-2010s, when consumer-level devices such as Oculus Rift and HTC Vive initiated the modern era of accessible virtual reality [50]. An HMD (Fig. 4.3) integrates stereoscopic displays, optical lenses, motion tracking sensors, and audio systems into a compact, wearable device that completely replaces the user’s visual input from the physical world with a digitally generated scene. Each eye is presented with a dedicated image generated by small high-resolution OLED or LCD panels, often exceeding 2000×2000 pixels per eye and operating at refresh rates above 90 Hz to minimize latency and motion blur. The lenses within the headset are responsible for focusing and slightly distorting the image so that it covers a large portion of the user’s field of view (FoV), typically between 90° and 120°, thereby enhancing the sense of presence. Advanced systems, such as the Varjo XR-4, implement aspherical or pancake optics to improve clarity across the visual field and reduce chromatic aberrations. Figure 4.3. Head-Mounted Display example – HTC Vive Pro goggles – with examples of controllers To achieve coherence between head movement and visual update, HMDs employ 6-DoF (degrees of freedom) tracking using inertial measurement units (IMUs) and optical sensors. There are two dominant approaches: outside-in tracking, in which external base stations or Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 36 cameras monitor the headset’s position (as in early Vive or Oculus systems), and inside-out tracking, where cameras integrated in the headset analyze the surrounding environment to determine motion in real time. The latter has become standard, providing higher portability and ease of setup [51]. Tracking precision below one millimeter and latency under 20 ms are today’s typical performance targets, essential to maintaining immersion and avoiding cyber sickness. A crucial aspect of personal VR projection is interactivity. HMDs are often accompanied by motion controllers, hand-tracking sensors, or haptic gloves, allowing users to reach, grab, and manipulate virtual objects intuitively (as presented in Fig. 4.3). High-end systems may include eye-tracking modules for foveated rendering, where image resolution dynamically follows the user’s gaze, optimizing computational load. Some research-grade devices combine facial expression tracking and electromyography to capture user reactions for medical or psychological applications. The compact, mobile form of HMDs has made them the standard tool for biomedical visualization, virtual prototyping, and training. They allow clinicians and engineers to enter a shared digital space without requiring dedicated infrastructure. However, they remain individual experiences by nature, each user perceives their own rendered scene through their own headset. For collaborative sessions, synchronization among multiple HMDs is necessary, yet the physical sense of co-presence is limited. In scenarios where collective viewing, spatial gestures, or natural face-to-face communication are essential, multi-user projection systems offer more suitable solutions. Multi-user projection systems create immersive experiences within shared physical spaces, where several participants can view and interact with the same virtual environment simultaneously. These systems emerged earlier than modern HMDs and have retained importance in industrial, scientific, and educational contexts, particularly where collaboration, natural body movement, and high visual fidelity are required [5,52]. The simplest multi-user configuration is the PowerWall, a large high-resolution stereoscopic screen (flat or slightly curved) typically exceeding 3 × 2 m in size. Users wear active or passive 3D glasses that filter the stereoscopic image projected onto the surface. A tracking system follows the position of at least one “leading” viewer — often the main operator — adjusting the rendered perspective so that depth perception remains geometrically correct. PowerWalls are popular in design review and medical visualization labs, offering immersive depth while retaining awareness of the physical surroundings. Their open structure makes them ideal for demonstrations and discussions among groups. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 37 Figure 4.4. CAVE system by Barco [54] A more advanced architecture is the CAVE (Cave Automatic Virtual Environment) system, first developed at the University of Illinois in the early 1990s (Fig. 4.4). As opposed to a onesided PowerWall, CAVE is a conceptional upgrade: it consists of multiple projection surfaces, usually three to six walls, including the floor and sometimes the ceiling, forming a cube or partial enclosure. Each wall displays a synchronized stereoscopic image, creating a continuous 3D environment surrounding the user. Multiple projectors, arranged per surface, are controlled by a cluster of rendering computers ensuring precise image blending and synchronization [53]. Inside a CAVE, users wear lightweight shutter glasses and motion-tracking markers that define the point of view. The sense of presence achieved is substantial, often comparable to high-end HMDs (purely subjective – some users prefer HMDs, some are more keen to use CAVEs and CAVE-like systems), but with added advantages: free physical movement, eye contact between participants, and real-world contextual cues such as real instruments or mock-up objects that can be integrated into the simulation. For biomedical applications, CAVE systems are particularly valuable in surgical training (e.g. hospital visualization), anatomical visualization, and collaborative implant design, where multiple specialists may simultaneously observe and discuss anatomical models or procedural sequences. It is noteworthy that CAVE systems are notoriously difficult in purchase and installation, requiring much more investment, logistics and organization to make them happen, plus they are also immobile. That is why in recent years, more flexible and very cheap modern HMDs have taken the floor. Further advancements have introduced hybrid systems, such as multi-surface curved projection domes, rear-projected augmented theaters, and mixed-reality rooms combining physical props with dynamic digital content. These installations often employ laser projectors, 4K or 8K resolution per wall, and refresh rates up to 120 Hz, delivering exceptional image sharpness and color depth. The increasing accessibility of compact laser projectors and highbandwidth graphics pipelines has lowered the cost barrier, making CAVE-like experiences feasible for universities, research laboratories, and large hospitals, but surely not for small and medium enterprises, yet alone single users. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 38 While multi-user systems provide superior group immersion and visual communication, they also require careful calibration and maintenance. Projection alignment, ambient lighting control, and synchronization between multiple computers are essential for accurate depth perception. Consequently, their installation and operation are more complex than personal HMD systems and usually require teams of qualified engineers. Nevertheless, for high-value collaborative applications, such as multi-surgeon procedure planning, team-based rehabilitation research, or engineering education, these systems offer unmatched experiential quality and shared understanding. In biomedical engineering, both categories of devices find complementary use: HMDs facilitate individual design and training tasks, while multi-surface projection systems provide the stage for collaborative simulation, surgical planning, and education. Their continued convergence, driven by improvements in resolution, tracking precision, and mixed-reality integration, points toward the emergence of hybrid immersive laboratories, where digital models of human anatomy and biomedical devices coexist seamlessly with the real world, offering unprecedented opportunities for innovation, safety, and understanding. MR and AR devices Depending on their architecture and visualization method, AR/MR projection devices can be divided into three main categories: smart glasses, optical see-through headsets, and video see-through mixed reality systems. Each of these classes offers a distinct approach to the integration of digital imagery with human vision, tailored to specific application domains. The simplest and most lightweight class of AR devices are smart glasses (Fig. 4.5), designed primarily to deliver context-aware information rather than fully spatial holograms. Their characteristic feature is the use of small projection modules that display semi-transparent images onto one or both lenses, allowing the user to perceive the real environment almost unobstructed. These systems are often monocular, meaning that only one eye receives the digital overlay, ensuring comfort during long-term wear but limiting depth perception. Figure 4.5. Wearing smart glasses with hand controller system Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 39 Early commercial examples include Google Glass [55], which used a miniature prism to project a virtual image appearing as a small floating screen in the upper corner of the user’s vision. Although its consumer market attempt was short-lived, the concept evolved into successful enterprise solutions for logistics, maintenance, and telemedicine. Other manufacturers, such as Vuzix (Blade, M400 series) and Epson (Moverio BTseries), adopted similar optical principles — combining transparent waveguides with compact micro-displays to show text, icons, and video feeds within the user’s natural view. Smart glasses rely on limited tracking capabilities, typically using inertial sensors and frontfacing cameras for basic head orientation recognition. They are lightweight (40–100 g) and energy-efficient, often running on Android-based operating systems and connecting to smartphones or cloud services via Wi-Fi or Bluetooth. In biomedical applications, they serve mainly as assistance and visualization tools: displaying live patient data during surgery, showing instructions during rehabilitation, or guiding medical technicians through assembly and calibration tasks. The advantage of smart glasses lies in their mobility and unobtrusiveness, which enable use in sterile or dynamic environments. A more advanced form of AR visualization is provided by optical see-through (OST) goggles, which deliver true three-dimensional, spatially registered virtual content. These systems employ semi-transparent waveguides or combiners that allow real-world light to pass through while reflecting projected digital imagery directly into the user’s eyes. Unlike smart glasses, optical see-through headsets provide binocular stereoscopic vision, producing a convincing illusion of depth and physical presence of holograms anchored to real-world objects. The most recognized representative of this category is Microsoft HoloLens (Fig. 4.6), which popularized the term Mixed Reality [56]. The device integrates a high-resolution projection module with an array of environmental sensors, depth cameras, and inertial units that continuously scan the user’s surroundings. Using real-time spatial mapping, the system reconstructs a digital 3D model of the environment, allowing holograms to be placed on surfaces, respond to occlusions, and maintain spatial stability as the user moves. This capability distinguishes MR from simpler AR, where virtual objects often “float” without physical context. Figure 4.6. HoloLens 2 – state-of-the-art optical see through goggles Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 40 Other notable devices include Magic Leap 2, Epson Moverio AR headsets, and emerging industrial OST systems by Lenovo, Rokid, and RealWear. These devices support gesture and voice-based interaction, enabling the user to manipulate virtual content naturally — for instance, rotating a 3D model of a bone structure with hand movements or selecting interface elements through gaze tracking. Optical see-through headsets typically feature limited field of view (FoV) compared to VR headsets, ranging between 40° and 60°, and their brightness must compete with ambient light. Nonetheless, their ability to integrate virtual models into the real workspace makes them ideal for surgical planning, clinical training, and collaborative design of medical devices. Holographic visualization of patient anatomy or prosthetic prototypes allows doctors and engineers to examine complex spatial relationships in real scale, fostering understanding and reducing errors. The third category, increasingly prevalent in both professional and consumer markets, comprises video see-through (VST) mixed reality systems. These devices use conventional VR headsets equipped with front-facing cameras, which capture the user’s physical surroundings and blend them in real time with rendered virtual content (Fig. 4.7). Instead of looking through transparent optics, the user perceives the real world via the digital feed from cameras, enabling perfect alignment between real and virtual imagery. The Meta Quest Pro and Quest 3 represent this class, offering high-resolution color passthrough and inside-out tracking. The integration of stereoscopic cameras and depth sensors allows accurate environmental reconstruction, supporting occlusion, lighting estimation, and dynamic object tracking. Other examples include Varjo XR-4, which achieves near-photorealistic mixed reality by combining ultra-high-resolution micro-OLED panels with video passthrough exceeding 20 megapixels per eye, or more modern Apple Vision Pro. Figure 4.7. Video-see-through goggles with finger tracking – Apple Vision Pro Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 41 The main advantage of VST systems lies in their flexibility and full control of the image pipeline. Because the user views a purely digital composition, software can easily adjust brightness, depth cues, and blending modes. Moreover, unlike optical systems, they can fully block real-world light when necessary, instantly switching between immersive VR and contextual MR modes. This dual capability makes them particularly suited for research, simulation, and design review, where both isolated virtual immersion and environmental awareness are needed. Their limitations include camera latency, potential color distortion, and lower transparency fidelity compared to direct optical vision, though recent advances in high-speed imaging have greatly mitigated these issues. Beyond dedicated headsets, AR and MR experiences can be delivered through a variety of auxiliary devices. The most accessible are mobile devices, smartphones and tablets (Fig. 4.8), which use their integrated cameras to overlay virtual elements onto live video streams. Popularized by applications such as Pokémon Go or medical AR visualization software, this approach offers an inexpensive entry into augmented reality, suitable for education, marketing, and telemedicine demonstrations. Despite limited immersion, the convenience and ubiquity of these devices make them valuable for field operations and patient engagement. Figure 4.8. Augmented Reality application presented on a screen of a tablet Large-format stationary AR projection systems are also gaining relevance. They employ projectors combined with motion tracking to cast interactive images directly onto physical surfaces, anatomical models, or operating tables. Such systems, sometimes referred to as Spatial Augmented Reality (SAR), are useful for teaching anatomy, planning surgical approaches, or guiding medical procedures without wearable hardware. Emerging technologies include light field and holographic displays, capable of generating volumetric images visible to the naked eye without glasses. Although still experimental and expensive, they represent a promising direction toward true three-dimensional visualization that could eventually supersede current AR paradigms. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 48 2. MRTK (Mixed Reality Toolkit). This tool is great for Microsoft platforms like HoloLens, but also for MR-capable devices, offering wide device support but requiring more configuration effort. 3. SteamVR Plugin. This software is essential for PC-based VR, supporting devices like HTC Vive, but has issues like black screens in certain modes. 4. Meta XR All-in-One SDK. Present in Unity since first Oculus goggles, now managed through Unity’s XR Plugin system, it’s specific to Meta hardware but requires a Facebook account, with divided examples causing some confusion. 5. XRTK.io. A third party plugin, lightweight and extensible, suitable for advanced users, but complex for beginners with few sample scenes. The XR Interaction Toolkit (Fig. 4.13) supports VR, Augmented Reality (AR), and Mixed Reality (MR). It is compatible with cross-platform devices such as Oculus, SteamVR, HP Reverb, Pico, Varjo, and Vive. It utilizes OpenXR, Physics, Locomotion, and Hand Tracking APIs, enabling a wide range of interactions. It’s easy to implement with pre-configured files for basic interactions like Select, Grab, and Hover. Scalable for larger projects, well-documented, and supported by a large community. It remains free for Unity Personal users, making it accessible for students. However, it’s difficult to add custom features due to reliance on Unity's Input System, which can limit flexibility. It lacks specific, complex samples for UI or hand interactions, potentially requiring additional development effort. Its use can be regarded as easy, particularly for beginners, due to pre-configured samples and straightforward setup. Recommended for those new to VR development in Unity. It would seem ideal for multi-platform VR games and applications where ease of use and scalability are priorities. It has extensive documentation (Unity XR Interaction Toolkit Documentation) [64]. Figure 4.13. Unity XR Interaction Toolkit – example scene Mixed Reality Toolkit (MRTK) by Microsoft (Fig. 4.14) is focused on VR and AR, with crossplatform support for Meta, SteamVR, ARCore, ARKit, Magic Leap, HoloLens, and Windows MR. Utilizes OpenXR, Physics, and Hand Tracking, offering robust interaction capabilities. It has Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 49 wide device support, particularly strong for Microsoft ecosystems like HoloLens. There is robust support from Microsoft and the package remains open-source. It includes excellent sample scenes for quick prototyping. Modular architecture allows for flexibility in development. In terms of its weaknesses, it differs from standard Unity conventions, which can confuse developers unfamiliar with its structure. The toolkit is also configuration-heavy, with potential for errors during setup and update between versions of the toolkit itself and Unity engine. Partial multi-platform support due to evolving XR standards, which may limit compatibility. The difficulty of use can be regarded as medium – it requires familiarity with Unity and some configuration effort. Suitable for intermediate developers or those targeting Microsoft platforms. However, in the case of having a pre-configured project ready for use as a template, it is possible to streamline the effort and quickly get the interactions working. without too much coding. It is recommended for non-gaming VR/AR applications, especially those targeting HoloLens or other Mixed Reality devices. It has extensive documentation (Mixed Reality Toolkit Overview) [65]. Figure 4.14. Mixed Reality Toolkit – example scene SteamVR Plugin (Fig. 4.15) provides OpenVR rendering for Unity XR, supporting many PCVR devices like HTC Vive, Oculus Rift, Meta Quest (via Link), Windows Mixed Reality, and Valve Index. Access to controllers and input requires the beta version of SteamVR Unity Plugin (v2.6.0b4), ensuring compatibility with SteamVR hardware. It offers a unified interface for major VR devices, simplifying development for PC-based VR. Includes pre-built DLLs for ease of access and supports npm installer for easy upgrades via Unity Package Manager. Provides a QuickStart guide for installation and setup, aiding beginners. However, some devices may have inaccurate or incomplete features, particularly non-major SteamVR hardware. Known issues include black screens in OpenVR Mirror View Mode and performance spikes with runtime changes to RenderScale and ViewPortScale, which can affect user experience. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 50 It is moderately difficult to use, involving downloading the installer, importing into Unity, and configuring XR Management UI. However, in the case of pre-configured projects (which require some effort), adding interactions is relatively simple and usually does not require writing additional scripts for basic scenarios. It is regarded as essential for VR applications targeting SteamVR-compatible hardware, particularly for PC-based VR development. Further information is available at SteamVR Unity XR Plugin GitHub [66]. Figure 4.15. SteamVR plugin – example scene Meta XR All-in-One SDK Toolkit is focused on VR for Oculus/Meta hardware, supporting OpenXR, Hand Tracking, and Passthrough. Frequent updates (e.g., v37 is the latest) ensure compatibility with Meta devices like Quest 2, 3 and Pro. Direct access to Meta's advanced features, such as hand tracking and avatars, enhances immersion capabilities. It is widely used for Meta-specific development, with frequent updates to address bugs and add features. However, it is limited to the Meta/Oculus hardware, restricting cross-platform development. Requires a Facebook account for development, which may be a barrier, especially for corporate implementations. Examples are divided (pre/post Interaction SDK), causing confusion for new users. It has smaller community compared to other tools, limiting support resources. It is moderately difficult to implement, due to the need for Oculus-specific setup and divided examples, which can add complexity for beginners. It is ideal for VR/MR applications targeting \Meta devices only, especially when leveraging Meta's unique features, not considering use of any other hardware brand. Details are available at Unity Oculus XR Plugin [67]. XRTK.io is an external, third party tool (differing from the above mentioned by not being official, i.e. developed by hardware/software providers). It supports VR and AR, with crossplatform compatibility for Meta, SteamVR, ARCore, ARKit, Magic Leap, HoloLens, and Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 51 Windows MR. Utilizes OpenXR, Physics, and Hand Tracking, offering a lightweight and extensible framework. It is lightweight and has efficient architecture, familiar to users of MRTK, making it easier for those with prior experience. Flexible and extensible, suitable for advanced use cases requiring customization. However, it offers only a few sample scenes, which can make it harder for beginners to get started. Architecture can be difficult for those without prior experience, requiring a steeper learning curve. Slower development and support due to being community-driven, potentially delaying updates. It can be regarded as medium or hard to use it, as it is efficient but complex for beginners, requiring advanced Unity knowledge for full utilization. It is recommended for advanced developers seeking a lightweight, extensible framework for multi-platform VR/AR, particularly for non-standard interactions. Table 4.1. VR software tools for Unity engine – summary, created on the basis of own experiences and [62,63] Tool Capabilities Strengths Weaknesses Difficulty of Use Unity XR Interaction Toolkit VR, AR, MR; Cross-platform; OpenXR, Physics, Locomotion, Hand Tracking API Easy implementation, scalable, good documentation, big community, free (Unity personal) Difficult to add custom features, no UI/1-2 hand interaction samples Easy MRTK VR, AR; Crossplatform; OpenXR, Physics, Hand Tracking Wide device support, robust Microsoft support, open source, excellent sample scenes, modular Differs from Unity conventions, configuration errors possible, partial multi-platform support Medium / easy SteamVR Plugin VR; OpenVR rendering; Supports HTC Vive, Oculus Rift, etc., requires beta for input Unified interface, prebuilt DLLs, easy upgrades via npm installer Some devices incomplete, black screens in Mirror View Mode, performance spikes Medium / easy Meta XR All-in-One SDK VR; Meta-specific; OpenXR, Hand Tracking, Passthrough, frequent updates Access to Meta's advanced features, frequent updates, widely used platform Confined to Meta/Oculus, requires Facebook account, examples divided, small community Medium XRTK.io VR, AR; Crossplatform; OpenXR, Physics, Hand Tracking Lightweight, efficient, familiar to MRTK users, flexible/extensible, multi-platform Few sample scenes, architecture difficult for beginners, slower support Medium to hard Below, basic recommendations and considerations are presented regarding selection and use of the above-mentioned tools: Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 52 • for beginners: start with the Unity XR Interaction Toolkit for its ease of use and comprehensive documentation. It is ideal for multi-platform VR development and free for Unity Personal users, making it accessible for students. • for more advanced users: consider MRTK for its wide device support and modularity, or XRTK.io for a lightweight, extensible framework, particularly for non-standard interactions. • for Meta-Specific Development: use the Meta XR All-in-One SDK for access to Meta's advanced features, noting the requirement for a Facebook account and potential example confusion. • for SteamVR hardware and PC VR in general: the SteamVR Plugin is essential for PC-based VR development targeting SteamVR-compatible devices and it is not difficult to learn and use, but be aware of known issues. When choosing a tool, consider the target platform, project complexity, and developer experience level. For instance, XR Interaction Toolkit is recommended for multi-platform VR games, while MRTK and XRTK.io are better suited for non-gaming purposes, especially on Microsoft platforms. AR Software Packages AR development in Unity, similarly as in the case of VR and MR, involves leveraging specialized tools to interact with AR hardware, manage user inputs, and ensure cross-platform compatibility. Given the rapid evolution of XR technologies, selecting the right SDK or plugin is crucial for creating immersive and functional AR experiences. For building augmented reality (AR) applications in Unity, several Software Development Kits (SDKs), APIs, and plugins are available, each with unique strengths for programming interactions. These tools help engineering students create immersive AR experiences by integrating digital content with the real world, supporting features like image tracking, plane detection, and hand interactions. The analysis presented below is based on official Unity documentation [68] and comparisons and comparative studies realized by community and experts [69-71]. The key tools and their capabilities are as below: 1. Unity AR Foundation. This is Unity's official cross-platform solution, supporting both iOS (via ARKit) and Android (via ARCore). It offers plane detection, raycasting, light estimation, face tracking, and body tracking, making it versatile for various AR projects [72]. 2. Vuforia. It is third-party a solution known for advanced image and object tracking, including model targets, Vuforia is suitable for complex AR experiences on multiple platforms like iOS and Android [73]. 3. EasyAR. This tool provides image, 3D, and face tracking, with a free tier for noncommercial use, making it accessible for students starting out [74]. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 53 4. Mixed Reality Toolkit (MRTK). Primarily for mixed reality, MRTK also supports AR, offering spatial mapping and hand tracking, especially useful for Microsoft devices like HoloLens [65]. Unity AR Foundation is an “official” solution and it contains cross-platform support for iOS (via ARKit) and Android (via ARCore), including plane detection, raycasting, light estimation, face tracking, and body tracking. Utilizes OpenXR and provides a unified API for AR development. As it is an official Unity solution, it means it is also free for all users, wellintegrated with Unity's ecosystem, has extensive documentation, and a large community. Regular updates ensure compatibility with the latest Unity versions and AR platforms. Supports multiple AR features out of the box, making it ideal for multi-platform AR apps. However, it is limited to the features provided by ARKit and ARCore, which may vary by device. Might not support all AR-capable devices, especially older models, and can be less flexible for custom features compared to native SDKs. This toolkit is moderately difficult, as it requires familiarity with Unity and some understanding of AR concepts. However, the availability of samples and tutorials, such as those found at Unity AR Foundation Documentation, makes it accessible for beginners. It is recommended for multi-platform AR games and applications where ease of use and scalability are priorities, especially for students new to AR development. Vuforia is focused on AR (Fig. 4.16), with support for image tracking, object tracking, and model targets across platforms like iOS, Android, and others. It includes advanced features like extended tracking (e.g. 3D solids used as markers) and device tracking, suitable for complex AR experiences. It is a mature SDK with over a decade of development, having a robust feature set for marker-based and markerless AR, extensive documentation, and good integration with Unity. It supports a variety of optical and video see-through displays, including HoloLens and Magic Leap, as detailed at Vuforia Unity Documentation. It requires licensing fees for commercial use, which can be a barrier for students or small projects. May be more complex for beginners due to its advanced features and setup, but for simple AR applications (using image target markers for displaying 3D content) it is very easy. Currently, the developers are not focused on new developments, potentially limiting future updates. The software is moderately difficult, depending on the features used. Setup involves importing the Unity package and configuring prefabs, which can be challenging without prior experience, as noted in various tutorials. It is ideal for AR applications requiring advanced image or object recognition, particularly for commercial projects where budget allows for licensing fees, but is still usable in simple, educational projects due to its versatility. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 54 Figure 4.16. Programming AR visualization with Vuforia in Unity EasyAR is a toolkit that supports image tracking, 3D tracking, and face tracking, with integration for Unity. Offers a free tier for non-commercial use, covering iOS and Android platforms. Recent updates, such as version 4.6.5 released in December 2024, ensure compatibility with Unity 6+ and AR Foundation 5/6+, as seen at EasyAR Documentation. It is quite easy to integrate with Unity, with a thin wrapper exposing features, good documentation, and a free tier for non-commercial projects. Open-source code for the Unity plugin enhances community contributions. The toolkit supports multiple platforms, making it versatile for student projects. Comparing to the other solutions, such as Vuforia, it might lack advanced features. It is also less known in the AR community, potentially limiting support resources. Recent updates focus on compatibility, but advanced features may require paid upgrades. EasyAR is considered as being of easy to moderate difficulty, designed for user-friendliness with prefabs and samples, suitable for beginners with basic Unity knowledge. It would be recommended for non-commercial AR projects, especially for students starting out, due to its free tier and ease of use. The MRTK was described properly in the previous section. Its use for pure AR solutions is questionable, however it is a good solution when building AR applications for Microsoft devices (HoloLens). It requires familiarity with Unity and some configuration effort, especially for AR-specific features. It is best for intermediate to advanced developers targeting Microsoft platforms. Beyond the above SDKs and plugins, Unity provides several supporting tools essential for AR development: • XR Core Utilities for other XR plugins, with version 2.3 installed as a dependency for many XR tools. Enhances functionality for developers using multiple XR systems. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 55 • XR Hands Package - hand tracking support, including a hand data model, API, XR Hand Skeleton Driver, XR Hand Mesh Controller, and HandVisualizer sample (version 1.2). Crucial for AR applications requiring hand interaction. • Input System, essential for handling AR controller input, tracking data, and haptics, with version 1.8 required for XR Interaction Toolkit and OpenXR. Ensures smooth integration of user inputs. The tools are summarized in the table 4.2 below. Table 4.2. AR software tools for Unity engine – summary, created on the basis of own experiences and [69-71] Tool Capabilities Strengths Weaknesses Difficulty of Use Unity AR Foundation Cross-platform (iOS, Android), plane detection, raycasting, light estimation, face/body tracking Official Unity solution, free, wellintegrated, large community Limited to ARKit/ARCore features, device support limitations Medium Vuforia Image/object tracking, model targets, multiple platforms Long history, robust features, good for complex AR Licensing fees, complexity, less new development focus Medium EasyAR Image/3D/face tracking, Unity support, free noncommercial Easy Unity integration, good documentation, free tier Limited advanced features, less known Easy to Medium MRTK MR/AR/VR support, spatial mapping, hand tracking, crossplatform Open-source, welldocumented, modular, good for Microsoft ecosystems Complex for beginners, Microsoft focus Medium to Hard Below, basic recommendations and considerations are presented regarding selection and use of the above-mentioned tools: • for beginners – start with Unity AR Foundation for its ease of use and comprehensive documentation. It is free and scalable, making it accessible for students. EasyAR is also a good choice for non-commercial projects due to its free tier and user-friendly design. • for intermediate and advanced users – consider Vuforia for its robust feature set, especially for projects requiring advanced image or object recognition, though be mindful of licensing costs. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 56 • for non-commercial projects – EasyAR stands out with its free tier, suitable for student projects without budget constraints, while Unity AR Foundation remains a strong free option. • for Microsoft ecosystems - MRTK would be a good choice, especially if targeting HoloLens or other Microsoft MR devices, offering extensive support and features for AR development; it could be interconnected with other toolkits (e.g. Vuforia), especially when AR and MR capabilities are to be utilized within a single application. When choosing a tool, consider the target platform, project complexity, and developer experience level. For instance, Unity AR Foundation is recommended for multi-platform AR games, while MRTK is better suited for non-gaming AR applications on Microsoft platforms. 4.3 Methodology of Building XR Applications for Biomedical Products The methodology presented in this chapter is based on previous work on building open, VR applications with use of Knowledge Engineering techniques, notably MOKA methodology. The methodology is universal and it speeds up the process of getting the applications built, while lowering the bar for skills and knowledge necessary for starting the development process. Details can be found, among other sources, in the publications [5,75,76]. Here, a short version will be presented. Disclaimer: XR applications described in this section (as well as case study examples in other sections) may constitute medical devices only if they comply with applicable regulatory frameworks (EU MDR, FDA, ISO 13485 and others). Otherwise, they should be considered educational, training, or wellness tools. Also, the methodology focus more on the technical side of things, rather than the regulatory ones. If the goal is full-product development, it should be expanded with stages such as requirements engineering, regulatory validation (MDR/FDA), verification & validation (V&V), risk management (ISO 14971), usability engineering (IEC 62366), and post-market surveillance. The main methodological assumptions are as following [5,75,76]. 1. The VR applications should be classified to one of three basic levels, according to knowledge contained within them (Fig. 4.7). 2. Each knowledge level has specific requirements regarding knowledge sources necessary for use in the development process (Table 4.3). 3. Each knowledge level has specific technical requirements, manifesting in scope of programming tools and VR hardware necessary for use in the final application. 4. Main stages of building an application are compatible with existing methodologies of building knowledge-based applications, such as the MOKA. 5. The methodology allows making decisions regarding potential of building a given VR system and its key parameters on a very early development stage, thanks to the stages of identification and justification. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 57 6. The key stage of development of an open VR system is the second phase, which is the third and the fourth stage – acquisition and formalization of knowledge, on the basis of which the VR application will be built. 7. Actual programming work and selection of software and hardware are realized only in the last phase of development, that is stage five and six of the methodology. Each professional XR application – including the medical ones – contains a determined knowledge amount, available for the user. Amount of this knowledge and its types determine a level of complexity of the problem of building the system that supplies that knowledge, that is why it is a key information during formulation of technical requirements and realization of work related to building the system. It is proposed, based on previous work (Fig. 4.17), to divide the applications into the three basic levels: 1. General knowledge: general information about a given product/process/object: appearance (visualization, animation), structure, basic variability. 2. Procedural knowledge: a sequence, an algorithm to apply in a given case, potentially concerning a way of conduct with a given technical or biological object or basic process methodology (e.g. stages of assembly). 3. Practical skills, applied knowledge: manual activities, such as machine operation, maintenance activities, manufacturing process activities, surgical or diagnostic procedure activities. In some cases, muscle memory can be gained. Figure 4.17. Levels of knowledge – medical XR applications [76] Considering general recommendations regarding building an industrial VR system, first stage of the work – the identification – may be started. The identification consists in answering the three key questions: 1. Who will be recipient of the application? 2. What is the main problem of the recipient? 3. What value will the VR application bring to the recipient? The identification is therefore a stage, in which the target group of recipients of XR application is determined – in the case of medical applications, it will usually be doctors, Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 64 • reducing the financial barriers associated with hands-on training by eliminating material costs and equipment risks, • providing realistic scenarios with interactive elements that closely mimic real-world operations, thereby enhancing the transferability of skills from the virtual environment to actual practice. The VR application simulates the complete operational cycle involved in manufacturing orthopedic orthoses. It includes detailed virtual representations of a commonly used 3D printer (Flashforge Creator Pro) and associated tools, interactive interfaces for printer preparation, print parameter selection, filament handling, and post-processing tasks. Users are guided through these procedures by real-time narration available in multiple languages, which is integrated with immersive visual and tactile feedback mechanisms such as precise hand tracking, gaze detection, and interactive animations. Participants can repetitively and safely execute standard procedures, master operational sequences, and gain hands-on experience that closely mirrors actual 3D printing processes in clinical and technical environments. The development of the VR application was executed using the Unity 3D game engine, combined with SteamVR, ensuring compatibility with widely-used virtual reality headsets, including Meta Quest 2 and Meta Quest 3. The design aimed at achieving realism and immersive user interactions reflective of real-world operations. A critical phase of implementation was creation of 3D models, primarily focused on accurately representing the printer, tools and filaments. They were modeled after physical measurements, using Autodesk Inventor, followed by UV mapping and texture application in Autodesk 3ds Max and Unity, respectively. The VR interface incorporates several advanced interaction techniques, such as raycasting for gaze detection, precise hand tracking for realistic object manipulation, and animated sequences to simulate operational tasks accurately. For instance, the filament loading mechanism utilizes the Obi Rope plugin for dynamic cable simulation, providing a lifelike interactive experience. To enhance usability, a teleportation system was implemented to enable effortless navigation within the virtual workspace, accommodating various training scenarios without the need for extensive physical movement. The training application features scenarios that realistically replicate tasks from printer preparation through to final post-processing of the printed orthoses. These include selecting the appropriate filament type and color, configuring print parameters on a simulated laptop, loading filament, initiating printing operations, and conducting final quality checks. Users are supported throughout these processes by bilingual narration and visual prompts, effectively guiding them through each step and highlighting potential errors for immediate corrective feedback. The application – seen from the perspective of a user – is presented in Fig. 4.22. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 65 Fig. 4.22. Virtual training of orthotic 3D printing The evaluation methodology involved two distinct participant groups: young engineers and experienced 3D printing specialists. The primary goal was to assess the usability, realism, and educational impact of the VR application. Practical tests were conducted using Meta Quest VR headsets (Meta Quest 3 for young engineers and Meta Quest 2 for experts). Participants completed randomly assigned scenarios involving different orthosis components, materials, and colors to simulate varied real-world conditions. The young engineers (10 participants, aged 20-30, inexperienced with VR and 3D printing) and experts (5 specialists with over 10 years of experience in medical 3D printing and 2 years in VR) engaged in practical sessions lasting approximately 20–30 minutes (Fig. 4.23). Task completion times and accuracy were monitored and recorded. Fig. 4.23. Evaluation of virtual training procedure Results indicated a high success rate, with a 90% accuracy in correctly completing the virtual orthosis printing procedures. The average completion time was around 9 minutes. Errors were mainly related to filament selection, nozzle cleaning procedures, and post- Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 66 processing steps. Both groups positively rated the realism, procedural accuracy, and operational safety of the application. Young engineers were impressed with realism of the process and the models. Experts, on the other hand, emphasized the application's value in standardizing procedures and improving their ability to analyze operational workflows. Survey feedback reinforced these impressions, indicating approval regarding realism, ease of use, safety, and educational benefit. However, users also pointed out some issues, such as occasional confusion while navigating the VR interface and uncertainties during specific tasks, particularly among less experienced participants. The experts recommended enhancements to interface intuitiveness and material differentiation. The VR application successfully demonstrated substantial potential as an effective, realistic, and safe training tool for additive manufacturing processes in orthopedic device production. The findings of this study underscore the significant advantages of employing VR as a training tool for additive manufacturing in the orthopedic sector. The high ratings received in procedural realism, operational safety, and overall educational value validate VR's efficacy as an alternative to traditional training methods. VR’s capability to offer repeatable, standardized training while minimizing risks associated with actual equipment and material handling is particularly beneficial. However, despite these strengths, several areas for improvement were identified. Challenges faced by users, especially novices, regarding interface navigation and task execution indicate the necessity for refining user interfaces and interaction mechanisms. Enhanced onboarding processes and clearer visual guidance would likely reduce initial barriers, making the technology more accessible and intuitive. Future developments will focus on expanding the complexity and diversity of training scenarios, providing adaptive learning pathways tailored to user expertise. Moreover, subsequent research should involve medical professionals actively engaged in point-of-care manufacturing to further validate the VR approach's practicality and effectiveness. Comparative studies with traditional hands-on training will offer additional insights into VR's long-term viability and impact on skill retention and operational efficiency. In conclusion, virtual reality represents a promising, innovative approach for training in the rapidly evolving field of orthopedic additive manufacturing, offering potential for widespread implementation across medical and engineering domains [78]. Implant Design in VR/MR Utilization of Virtual Reality (VR) and Mixed Reality (MR) technology in implant design is transforming the medical and dental process by a considerable margin in the accuracy, personalization, and convenience of the procedure. The technologies allow the engineer and surgeon to design patient-specific implants using medical imaging and advanced 3D modeling software. 1. Workflow of Implant Designing in VR/MR: Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 67 Implant designing in VR/MR is a workflow: Medical Imaging Acquisition; CT or MRI scans provide patient-specific anatomy data on which the implant is calculated; Segmentation and 3D Reconstruction; Mimics or 3D Slicer software reconstructs DICOM images in three dimensions. The models accurately define the patient's anatomy. • VR/MR Integration - The 3D model is imported into a VR/MR platform where designers re-model and model the implant interactively. There can be prolonged real-time interaction with Unity, Unreal Engine, or medical VR software. • Customization and Simulation - Surgeons and engineers model the behavior of the implant prior to surgery within the patient anatomy, and the implant shape, size, and fit are custom-dressed using VR/MR. It is pre-manufacture optimized. • Manufacturing and Validation - The final implant design is then translated as an STL file to be 3D printed or CNC machined to yield a biocompatible and accurate implant. 2. Benefits of VR/MR in Implant Design: • Higher Accuracy and Personalization. VR/MR facilitates real-time interaction in 3D with anatomical models instantly, unlike traditional methods, to facilitate accurate customization of the implant to anatomy of the patient [17]. • Improved Preoperative Planning and Outcomes - VR/MR permits the surgeons to offer pre-op visualization on which the surgeons can preoperatively plan the different forms of the implant ahead of surgery. VR/MR reduces surgery time, complication rate, and post-op revision (15). • Shortened Design and Manufacturing Cycle - It takes less time to manufacture implants by using 3D modeling and VR/MR, hence fewer production hours and prototyping are needed. It is also convenient when trauma injuries occur and a patient-specific or customized implant is needed to be developed in the shortest possible manner. • Enhanced Collaborative and Training - VR/MR enables remote collaboration, i.e., surgeons, prosthetists, and engineers can work remotely in a shared environment remotely. VR/MR enables simulation training of surgeons and implanters for surgery and implantation [16]. 3. Implant Positioning Applications of VR/MR: • Cranial and Maxillofacial Implants - VR/MR enables planning for a customized titanium or PEEK implant for skull or facial reconstruction with improved postoperative cosmetics and function. • Orthopaedics Implants - Patient-specific implants for spines, hips, and knees ensure improved alignment, comfort, and function. • Dental Implants - Accuracy of dental jaw implants, prosthetics, and bridges to the patient's advantage and benefit is improved with VR/MR. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 68 • 3D-Printed Biocompatible Implants - Through virtual modeling, it is possible to create bioengineered implants from titanium, ceramic, or degradable plastic and give birth to a new regenerative medicine field [17]. 4. Future Applications of VR/MR in Implantology With the emergence of artificial intelligence (AI) and machine learning, VR/MR implant design would be under objective and precise design. AI-segmentation will prevent human mistakes, and instantaneous real-time feedback in VR space will enhance processes. VR/MR telemedicine technologies will also enable worldwide collaboration, and patient-specific implant solutions would be accessible anywhere in the world. MR and VR are transforming implant design with interactive, patient-specific personalization of surgical outcomes. Where high-end manufacturing, 3D imaging, and realtime communication converge, VR/MR is making the vision of more efficient, more precise, and more customized implant solutions a reality. With changing technology, its use in dental and medical implantology will keep on becoming more the norm, leading to better outcome of the patient as well as success rate of the procedure. In the Figure 4.24 and 4.25, the process of integration of the obj models of the human humerus and cloverleaf plate are shown. This application enables virtual positioning of the plate 3D model on the humerus bone in VR. Figure 4.24. The Cloverleaf plate and humerus bone in Unity Software Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 69 Figure 4.25. Positioning the plate in VR Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 70 5 Conclusions XR, encompassing VR, AR, and MR, represents an evolving spectrum of technologies that extend human perception and interaction with digital environments. Defined by immersion, interaction, and imagination, XR systems combine hardware precision with software intelligence to simulate or augment reality. Their classification spans from mobile AR on handheld devices to fully immersive VR and hybrid MR headsets capable of real-time environmental mapping. Having matured from research prototypes to practical industrial tools, XR technologies today serve as key instruments in modern product development processes, enhancing design communication, reducing prototyping costs, and fostering user-centered innovation. As such, XR is no longer a futuristic concept but an integral component of digital transformation across engineering and biomedical domains. The integration of XR technologies into the design and production workflows of biomedical products marks a fundamental transformation in how innovation is conceived, tested, and delivered in healthcare. Through immersive visualization, spatial interaction, and real-time simulation, XR tools offer biomedical engineers, designers, and clinicians new ways to explore complex ideas, collaborate across distances, and ultimately create more personalized, functional, and effective solutions for patients. This chapter has examined the role of XR in multiple stages of product development: from early prototyping, fit evaluation, and surgical simulation, to factory planning, virtual inspection, and quality inspection on the production floor. The ability to design and iterate without the constraints of physical materials, and to collaborate within shared virtual environments, has shown tangible benefits in speed, accuracy, and flexibility. For anatomically customized medical devices in particular, XR enables a seamless transition from digital model to clinical implementation. This is especially relevant in the context of additive manufacturing and personalized medicine. However, challenges remain. Technical barriers, such as the cost of high-performance hardware and difficulties integrating XR systems with existing software and manufacturing infrastructure, can slow down implementation. On the user side, learning curves remain steep, especially for non-technical medical staff. Some users experience physical discomfort, such as cyber sickness or fatigue during prolonged headset use, and ergonomic mismatches between device interfaces and clinical settings are still being addressed. Moreover, as XR systems often handle sensitive patient data, robust data security and privacy safeguards must be a central concern in any deployment. Looking forward, the convergence of XR with artificial intelligence and software automation offers exciting new capabilities. AI-driven XR environments can adapt to users' actions, predict behavior, and generate optimized scenarios in real time, opening new Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 71 opportunities in surgical rehearsal, medical education, and even automated design of prosthetics (as mentioned in chapter 2 of this e-book). Emerging hardware innovations are also expected to reduce headset weight, improve visual comfort, and increase spatial resolution, further enhancing user experience and widening accessibility. At the same time, XR applications are branching into new medical domains: Mixed Reality is beginning to support molecular modeling, biostructure visualization, and drug formulation, domains where spatial intuition and precision are crucial. The notion of a "medical metaverse" – one of the central themes of the BIOMEDIX project – is also no longer just a conceptual exercise. Virtual laboratories, remote multidisciplinary design reviews, and shared surgical planning environments are being developed that may redefine how healthcare professionals collaborate, especially in globally distributed or resource-limited contexts. XR technologies could help decentralize innovation, making highend design and diagnostics accessible beyond traditional institutions. In conclusion, XR is more than a set of visualization tools. It really helps to enable and accelerate innovation in biomedical product development focused on additive manufacturing. For organizations seeking to adopt these technologies, a phased integration approach is recommended: starting with visualization and design, then expanding into production and clinical applications, supported by ongoing training and ethical data practices. As immersive technologies mature, they hold great promise not only for improving the tools we can create, but also for reshaping the way we think, collaborate, and care in the biomedical domain. Biomedical Innovations through Digital Transformation of Additive Technologies and Knowledge Exchange - ERASMUS KA 220 BIOMEDIX This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Page | 72 References 1. 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