Human–animal interaction in virtual reality has been explored for stress relief, yet balancing practical ease of use with natural haptic experience for relaxation remains a key challenge. We investigated whether mid-air ultrasound haptics, rendering breathing and fur stroking cues without wearable haptic devices, could enhance relaxation with a virtual cat. We first conducted a perceptual study to design a tactile cue for a cat’s breathing. By synchronizing expansion–contraction of the ultrasound focal region with intensity modulation, we demonstrated the realism and expressivity of the breathing cue. Next, we conducted an application study in which participants engaged in a short relaxation session with a virtual cat. Physiological and subjective measures showed that ultrasound haptics enhanced relaxation compared to both non-haptic interaction and controller-based vibrotactile feedback. These findings suggest that ultrasound haptics can extend VR-based human–animal interaction by combining accessibility with psychological benefits, opening new opportunities for well-being and therapeutic applications.

A prevailing assumption in Virtual Reality is that the perception of surface gloss attenuates with viewing distance due to the resolution limitations of head-mounted displays (HMDs). While prior work indicates that resolution loss can degrade cues such as highlight sharpness and binocular highlight consistency, the direct linkage between viewing distance and perceived gloss has not been systematically established in VR. This study systematically investigates this relationship, focusing on binocular highlight intensity asymmetry. Contrary to the common assumption, under physically based rendering, our results show no reliable decrease in perceived gloss with distance within the tested range, despite resolution limitations. Moreover, participants' gloss judgments appeared to be more strongly modulated by monocular cues (e.g., highlight luminance, contrast, and temporal information) than by the binocular asymmetry manipulation tested here under our tested conditions. Finally, we find that moderate departures from physically correct binocular highlight consistency did not, within a tested tolerance, undermine perceived realism. These findings provide a new basis for designing efficient rendering techniques that preserve gloss fidelity over distance in VR, suggesting that computational resources might be better allocated to preserving monocular cues.

Humans sometimes encounter dazzling light in everyday life, such as sunlight or high-beam headlights, which often evoke instinctive biological responses like blinking and afterimages. Accurately reproducing such phenomena is essential for enhancing realism in virtual reality (VR), especially in scenarios like training simulations or entertainment experiences. While conventional methods either rely on high-luminance displays or simulate isolated perceptual effects such as glare, few approaches have explored the combination of multiple physiological responses to intensify brightness perception without using physically intense light sources. This study addresses the gap by investigating how pseudo-blinking and afterimage presentation, in addition to glare effects, can enhance the dazzling sensation in VR. We developed a novel system that synchronizes screen darkening with skin-deformation-like vibration stimuli around the eyes to simulate a blink reflex, followed by gaze-dependent afterimage presentation that dynamically transitions to complementary colors in response to user blinking. Experimental results with 19 participants revealed that both pseudo-blinking and afterimage effects significantly enhanced the perceived dazzling sensation and realism. These findings suggest that simulating involuntary physiological reactions to light in VR can evoke strong perceptual impressions, enabling safe and cost-effective glare expression.

Impact sensation is vital for achieving high realism and immersion in virtual reality (VR) applications such as sports games. There has been substantial research focusing on the moment of impact, using methods like electrical muscle stimulation (EMS) and vibrotactile feedback. However, the size and complexity of these devices, along with concerns for user safety, limit their effectiveness in producing strong impact sensations. Additionally, less attention has been given to sensations experienced after a strong impact, like the tingling that follows a collision. This research focuses on an overlooked area: the aftereffects that emerge within the body following a physical impact. It specifically examines the tingling sensation that occurs after a strong hit, using a VR baseball bat-like device designed to deliver impulsive force, vibrotactile, and thermal feedback to the user’s hand. We conducted a user study (18 male, 6 female participants) to assess how these types of feedback affect the realism and intensity of impact sensations, as well as the tingling sensation perceived by users. The results revealed that both vibrotactile and thermal feedback as aftereffects significantly enhanced the impact sensation, confirming their ability to induce tingling sensations. Additionally, high-frequency vibrotactile stimuli particularly enhanced the tingling sensation and realism of impact. Although the sample had a gender imbalance, these findings highlight the potential for incorporating aftereffects feedback in VR systems to enhance impact sensations for entertainment and safety education purposes.

Paranormal visual effects, such as spirits and miracles, are frequently depicted in visual games and media design. However, current methods do not express paranormal experiences as aspects of the sixth sense. We propose utilizing binocular rivalry to provide a new visual presentation method by displaying different images in each eye. In this study, we conducted two experiments. Experiment 1 assessed paranormal sensation, color perception controllability, and visual discomfort caused by mismatched colors in each eye in relation to color difference. Experiment 2 assessed our proposed visual presentation method in three application scenarios. The results indicate that our proposed method improves the visual experience of more realistic paranormal phenomena. Moreover, the sensation of paranormal activity, color perception controllability, and visual discomfort increase as the color difference between the colors displayed in the two eyes increases.

In virtual environments, wind displays can reproduce the sensation of wind to enhance user experience such as presence. Enabling users to perceive strong winds can benefit several applications, such as disaster education and entertainment content. However, the large and bulky equipment required to blow strong winds across the entire body of the user limit its application. Although cross-modal effects are proposed to alter wind perceptions through multisensory stimuli, but methods to induce the perception of strong winds without generating a strong wind need further exploration. In this study, we propose a method to create an illusion of strong wind by providing tactile stimuli through clothes. We developed a compact and lightweight wearable device that vibrates the fabric by a motor to simulate its fluttering motion under a strong wi nd. Two user studies were conducted to investigate the effect of vibrating the clothes on the perceived wind velocity, realness of the wind, and presence. The results indicated that tactile stimuli provided by vibrating the clothes increased the perceived wind velocity to a similar level as the strong wind exceeding $10 \mathrm{~m} / \mathrm{s}$ while the parameters of the physical wind were unchanged. It was also revealed that the vibration of the clothes decreases the realness of the actual wind and a visual scene of the clothes of the avatar flutter increases presence. Thus, the proposed wearable device is useful for creating the experience of strong winds while keeping the wind displays compact.

The development of methods to simulate the sensation of wind that can promote relaxation and elicit positive emotional responses has become a topic of interest with the widespread adoption of virtual and augmented reality systems. Previous studies have simulated natural wind by varying wind speed in a controlled environment or moving a large flow of air through an area. In contrast to such approaches to modulate physical airflow, the use of multisensory stimuli to alter the impression and sense of comfort provided by a simulated wind has rarely been considered in previous research. If visual and auditory stimuli affect wind comfort, a multisensory design should be considered for relaxation systems that use wind effects. Therefore, we experimentally measured wind comfort and associated emotions when participants experienced outdoor and indoor virtual environments through immersive virtual reality to investigate whether cross-modal effects of variations in audio-visual stimuli would impact the relaxation effects associated with a virtual wind. The results show that the virtual environment of an outdoor meadow and the sound of natural wind significantly improved users' subjective experience of comfort and openness associated with the wind, as well as their emotional state. Simulated natural wind reduced mental stress compared to a condition without wind, as shown by questionnaires and biometric data. The results of this study indicate that multisensory stimuli conveying natural impressions and simulated natural wind are effective for wind-based relaxation.