Extended reality (XR) refers to technologies that either extend the physical environment with digital content or fully replace it with virtual environment (VE), enabling users to perceive and interact with virtual objects within a spatial context. Immersion is one of the key characteristics of XR systems. It relates to sensory fidelity and influences users’ perception of presence within XR. Beyond presenting predefined content, immersive environments are increasingly expected to respond to users’ behaviors, preferences, and contexts. Previous studies on personalized smart immersive XR (PSI-XR) show that personalization can be supported through explicit input, implicit behavior information, sensing technologies, recommendation mechanisms, and user modeling. These developments have motivated the integration of XR technologies and smart techniques to create user-centered environments that adapt to users’ requirements, enhancing immersive experiences. 

This licentiate thesis investigates PSI-XR from two connected perspectives: the design perspective and the perceptual perspective. From the design perspective, the thesis first systematically reviews the application areas, enabling technologies, smart and personalized techniques, and key challenges of PSI-XR to understand how such environments can be realized. Building on this review, the thesis proposes a conceptual design of a personalized virtual reality (VR) system as a PSI-XR application, using furniture arrangement as an illustrative context and combining head-mounted display (HMD)-based VR, multimodal interaction, hand and eye tracking, and generative artificial intelligence (GenAI). From the perceptual perspective, the thesis examines whether PSI-XR can provide perceptually credible visual experiences for users. One perceptual study compares visual realism and visual acuity between real world and VR, showing that VR can achieve a high level of visual realism and convey basic visual information about virtual objects while still presenting limitations in visual acuity. Since perceptual credibility also depends on how virtual objects are digitally represented and rendered, the second perceptual study compares 3D Gaussian Splatting (3DGS) with mesh-based rendering in VR, showing that 3DGS can be perceptually comparable to mesh under distant static observation but performs less robustly under proximal viewing, free movement, and multi-object conditions. 

Overall, this thesis suggests that an important potential value of PSI-XR lies not simply in increasing immersion or intelligence, but in how effectively immersive technologies, smart personalization techniques, and perceptual credibility work together to support a user-centered environment.