A foot-level motion remapping framework for inclined stair walking in virtual reality

This paper proposes a foot-level motion remapping framework that enables users to experience inclined stair walking in virtual reality (VR) while physically walking on flat ground. Existing stair-walking and motion remapping approaches often focus on discrete step-height changes, root-level avatar correction, or hardware-assisted interaction, and therefore have limited ability to represent the continuous geometric variation and asymmetric foot-contact behavior that occur on inclined stair-like surfaces. To address this limitation, the proposed method models the foot using separate toe and heel components and decomposes the gait cycle into Lift, Contact, and Release states. For each gait state, toe and heel contributions are adaptively weighted according to the virtual inclination angle using an anchor-based continuous weighting scheme. The resulting foot motion is temporally stabilized and hierarchically propagated to the waist and head to reduce excessive visual oscillation. The framework was implemented in a real-time Unity-based VR system and evaluated under flat, intermediate, and steep inclination conditions. The evaluation additionally includes a non-anchor inclination condition, sequence-level trajectory-fidelity measures, and comparison with a prior stair-remapping method. The results show that the proposed method reduces frame-wise height jitter, improves motion stability, and maintains real-time performance compared with baseline remapping variants. These findings support foot-level state-based remapping as a practical approach for generating trajectory-stable inclined locomotion in VR without requiring a physical stair apparatus.