Interactions with the physical environment, such as passive haptic feedback, have been previously shown to provide richer and more immersive virtual reality experiences. A strict correspondence between the virtual and real world coordinate systems is a staple requirement for physical interaction. However, many of the commonly employed VR locomotion techniques allow for, or even require, this relationship to change as the experience progresses. The outcome is that experience designers frequently have to choose between flexible locomotion or physical interactivity, as the two are often mutually exclusive. To address this limitation, this paper introduces reactive environmental alignment, a novel framework that leverages redirected walking techniques to achieve a desired configuration of the virtual and real world coordinate systems. This approach can transition the system from a misaligned state to an aligned state, thereby enabling the user to interact with physical proxy objects or passive haptic surfaces. Simulation-based experiments demonstrate the effectiveness of reactive alignment and provide insight into the mechanics and potential applications of the proposed algorithm. In the future, reactive environmental alignment can enhance the interactivity of virtual reality systems and inform new research vectors that combine redirected walking and passive haptics.
