As virtual reality (VR) headsets become more comfortable and accessible, their growing use in high-stakes, time-critical settings raises concerns about fatigue. Fatigue impairs perceptual and cognitive functioning. It reduces oculomotor accuracy and visual focus, and can lead to an early decline in depth estimation performance. By augmenting the visual presentation with depth information cues, adaptive designs can reduce fatigue-related depth perception errors, enhancing safety and task effectiveness. Explicit cues present depth information directly through text or color, while subtle cues adjust scene properties, such as depth-dependent blur, to convey depth information implicitly without drawing overt attention. We examined how fatigue interacts with different cues in a 27-hour within-subject protocol. Across six overnight sessions (20:00– 07:00), twenty-three participants completed a VR depth perception task at varying fatigue levels and under four cue conditions: no cue (baseline), text, color, and blur. Over the night, vigilance declined, sleepiness and mental effort increased, and simulator sickness rose before stabilizing, independent of cue condition. All augmented cues reduced depth estimation error relative to baseline. Text yielded the largest and most consistent accuracy gains, especially for farther targets and later sessions. At peak fatigue, response probability dipped for text but remained stable for blur and color, indicating an accuracy versus responsiveness trade-off. These results support mixed adaptive designs that default to subtle cues to preserve responsiveness at low alertness and introduce explicit overlays when precise metric information is needed.

Understanding an environment relies on human sensory systems, with visual perception as the primary source for defining spatial relationships and estimating distances. The visual system uses natural cues, each offering partial information that can lead to bias and conflicts, especially when ambiguous. Virtual Reality (VR) environments challenge these natural depth cues with discrepancies in perspective and variations in light and shadow depiction, leading to potential confusion in depth perception. However, VR also allows for the isolation and study of these cues. This paper introduces artificial subtle cues (texture blur) to enhance natural depth information in VR. Our results show that augmenting natural depth cues with artificial ones improves depth prediction accuracy and spatial relationship awareness. Subtle blur cues enhance depth estimation without participants’ subjective awareness of the augmentation, suggesting that such subtle cueing can effectively enhance depth perception.