Hit-Stop in VR: Combination of Pseudo-haptics and Vibration Enhances Impact Sensation

Impact sensation is essential for high immersion and enjoyment in virtual-reality (VR) applications (e.g., sports games). Current off-the-shelf VR controllers have vibrotactile actuators that present impact sensations using only vibrations. If dedicated devices for impact feedback (e.g., solenoids) can be also used, a more robust impact sensation can be presented. However, current off-the-shelf controllers generally do not have such impact feedback devices. To present impact sensations using these controllers, this paper proposes the incorporation of a hit-stop effect into VR, which pauses movement or displays a slow-motion animation at the moment of impact. This effect enhances the sense of impact alongside vibrotactile feedback. A user study showed that the impact force sense can be presented with a hit-stop visualization effect even without vibration. In contrast, because a long hit-stop duration increases the mismatch between actual and virtual body motions, it sometimes causes users to feel a reduced sense of agency. Ultimately, we found that the combination of vibrations and hit-stops can maintain this sense while enhancing the impact sensation.