Locomotion is a fundamental interaction technique that allows free navigation in virtual scenes. A large body of literature has demonstrated that natural locomotion experience can significantly improve the sense of presence and help users achieve better performance in tasks such as searching and training. In the upcoming metaverse era, locomotion will play a critical role in the success of large-scale interactive applications. Perception and redirection are two tightly connected problems in virtual locomotion. Given a limited physical condition and a target virtual scene, how to make the perceived locomotion as natural as possible, and further unknowingly redirect the user in the physical world is an open question. In this special issue, we have selected five papers that provide their latest updates for research problems of view control, virtual jumping, climbing, and searching.
Existing redirected walking controllers are effective in the horizontal direction; however, they cannot help participants experience immersive walking along an upslope. Wang et al. developed a virtual climbing system that uses the tactile feedback provided by the sponges to simulate the tactile sense during climbing. Their research revealed that to a certain extent, when the thickness of the flexible material increases, the user's upslope experience will be enhanced. Moreover, by setting the collision avoidance priority, the virtual climbing system can enhance users' immersive experience of upslope walking. The proposed system expanded the application scenario of current redirected walking techniques.
Redirected jumping is a novel interaction technique that allows VR users to insensibly enhance the virtual jumping performance by applying jumping gains. To investigate the effect of environment and self-representation in the virtual environment on redirected jumping, Li et al. conducted a user study that considered invisible, feet visible and full-body visible illustrations of self-representation in low- and high- visual richness virtual scenes. They concluded that both virtual environment and self-representation influence users' perception and performance in redirected jumping, and must be considered when designing locomotion techniques. Liu et al. investigated the influence of alley width on the detection threshold of virtual jumping, and summarized the relationship between the occlusion distance and manipulation range of the distance, height and rotation gains in a complex environment.
Efficient navigation techniques can help VR users better understand the virtual environment and lead them to the target destination more easily. However, previous auxiliary tools such as top view maps or trails become less efficient when the user is searching for dynamic targets in the environment with complex occlusions. To solve this problem, Zhao et al. designed a virtual camera priority-based assistance which can generate an instant optimized path from a set of fixed virtual cameras. This path can guide users to the place where they are more likely to find the target. A user study revealed their proposed method was more efficient than the conventional navigation methods in finding dynamic targets.
Head-mounted displays are usually used to offer VR users accurate motion tracking for immersive VR interaction with the scene. However, users may sometimes perform actions unrelated to the VR scene such as adjusting the head position to avoid neck pain or reacting to the distraction from the real-world, which will lead to the situation that head tracking is not desirable and may break the user's sense of presence. Fan et al. became the first to conduct the study to address the problem. They trained a classifier to detect scene-irrelevant motions using temporal eye-head-coordinated information sequences and their method will suspend motion tracking where scene-irrelevant motions are detected, which can improve user continuity without increasing sickness or breaking immersion.
We would like to thank Virtual Reality Intelligent Hardware for their assistance in the publication of this special issue, and all the contributors and the reviewers for their hard work in making the publication a success. We hope this special issue will provide useful references and insights for readers engaged in the related research.