## 4 Immersive Virtual Reality: Hardware and Software Perspectives
### Overview of Immersive Virtual Reality Hardware
For example, some devices provide optimized haptic feedback to the torso, enhancing tactile sensations during VR use [109]. For precise body tracking, accessories are available to monitor facial expressions and eye movement [110], hand tracking [111; 112], tracking of orientation and rotation of the legs for control of locomotion [113] and even full body tracking [88; 114; 115]. Muscle-movement detectors such as _FirstVR_[116], feature optical sensors that detect arm and hand movements while providing vibration feedback. All-in-one solutions like the _Tesla Suit_ integrate multiple functionalities, offering comprehensive body tracking with haptic feedback, motion capture, and biometric monitoring [117]. Some external sensors, require the installation of base stations to monitor sensor movements, a process known as outside-in tracking [118]. Others use built-in cameras for self-contained tracking, referred to as inside-out tracking, which provides greater mobility [88]. There are also products that enable motion tracking without the use of wearable sensors, utilizing motion-tracking cameras instead. _Orbbec_ offers such solutions, like the _Femto Bolt_[119], which serves a similar purpose to the former _Kinect_. Some accessories are particularly useful in healthcare settings, such as facial interface with silicone facial pad, designed for easier sanitation [120], or UV-C disinfection cabinet for mobile headsets [121]. Limited physical space for VR use can be mitigated with devices like VR walkers, which enable locomotion within a confined area, allowing users to walk, run, or engage in movement-based actions without physically moving through the real-world environment [122]. Accessory compatibility varies--some are exclusive to headsets from the same manufacturer [114], while others are third-party compatible, functioning across multiple brands [123]. These various accessories allow users to tailor their VR setup to their specific needs, enhancing realism and interaction in virtual environments, whether for gaming, professional applications, or therapeutic use. Currently, VR hardware appears to be fairly accessible for general consumers, with entry-level headsets available at relatively affordable prices. More affordable options include the _DPVR P1 Personal_ for USD 198, _Meta Quest 3S_ starting at approximately USD 300, _HTC Vive Focus Plus_ at USD 450, _Sony's PlayStation VR2_ at USD 550, and _Steam's Valve Index_ at USD 540, making these devices feasible options for many users interested in experiencing VR. However, the cost spectrum varies widely, with some mid- and high-tier models priced at thousands of euros. For instance, the _Pimax Crystal_ series ranges from $860 to $1200, _Lenovo's ThinkReality VRX_ is offered at USD 1300, _DPVR PRO-4K_ at USD 1099, _VR TierOne_'s at USD 1800, _Apple's Vison Pro_ at USD 3500, and _HTC Vive's Focus Vision_ and _Focus 3_ models are priced at USD 1000 and USD 1300, respectively. At the high end, _Varjo_ stands out as an enterprise-grade option, with models such as the _XR-4_ starting around USD 5990 or _XR-4 Focal Edition_, starting at USD 9990. Unlike consumer-focused companies like _Meta_ and _Sony_, which primarily target the entertainment sector, _Varjo_ caters to professional fields, including healthcare, aerospace, marine and heavy industry, and government defense. Its key strength lies in its photorealistic image quality, making it exceptionally suited for developing VR environments that closely replicate real-world scenarios. This wide price range of immersive VR hardware allows VR to reach both casual users and those needing advanced, industry-specific features. Tables 1 and 2 present a summary of the review of hardware equipment for immersive VR.