Human-centric virtual lighting: Effects of color temperature and daylight simulation in virtual environments

As virtual environments and metaverse platforms transform human interaction, understanding how lighting influences perception and behavior in digital spaces is critical. This study investigates the effects of correlated color temperature (CCT) and virtual daylight on human evaluations of virtual environments across two complementary experiments: one conducted in an uncontrolled real-world setting and the other in a controlled laboratory environment. Building on principles of human-centric lighting (HCL), we propose a framework for human-centric virtual lighting (HCVL) to optimize user experience in immersive digital spaces. In Experiment 1, participants evaluated 12 renderings of virtual exhibition stands and meeting spaces under varied lighting conditions, using Flynn et al.'s semantic differential scale. The real-world setting prioritized ecological validity, with participants using personal devices (with, for example, heterogeneous brightness and resolution) and representing diverse demographics (22 nationalities, ages 20-58). Experiment 2 replicated the design in a controlled laboratory condition, utilizing standardized monitors, and a homogeneous participant group (German undergraduate students, ages 18-26). Both experiments assessed perceptions of warmth, brightness, spaciousness, and preference, with statistical analyses comparing warm vs. cool CCT and daylight vs. room lighting effects. Key findings revealed large effects of CCT on perceived brightness and medium effects on stimulation and spaciousness, aligning with physical lighting research. Virtual daylight elicited robust preferences, rated as brighter, more private and aesthetically appealing, reflecting innate human biases toward daylight. Crucially, the laboratory results confirmed the real-world findings but with greater consistency, underscoring the impact of device variability and demographic diversity on the result from real-world setting. This study makes three primary contributions: (1) Empirical validation of HCVL principles, demonstrating that the effects of CCT and daylight transcend environmental modality (physical vs. virtual); (2) A methodological framework for balancing ecological validity and experimental control in virtual lighting research; (3) Practical insights for virtual space designers, emphasizing the integration of user expectations (e.g., "conceptual lighting") and adaptive daylight simulations. These results bridge the gap between physical and virtual lighting research, offering actionable guidelines for creating immersive, well-being-oriented digital spaces. Future work should explore cultural and ambient moderators of HCVL to support inclusive virtual spaces design.