The Effects of Head Pitch on Translation Gain in Virtual Reality Environments

Redirected Walking (RDW) in virtual reality relies on carefully calibrated translation gain to maintain a natural mapping between physical and virtual spaces. However, most existing gain strategies assume the user maintains a horizontal viewing direction, ignoring the potential effects of head pitch angle. This oversight can lead to perceptual bias and reduce redirection quality. In this paper, we investigate how the user’s Point of Subjective Equality (PSE) and perceived threshold ( \(\sigma \) ) for virtual speed changes vary with head pitch. Using a psychophysical approach, we guided users through a speed discrimination task and collected speed perception judgments and subjective discomfort scores across seven pitch angles. Results showed that users tended to underestimate speed when looking upward (with significantly higher PSE), while speed was overestimated and \(\sigma \) decreased in downward conditions, indicating increased speed sensitivity. This trend held across scenes, though exact values varied. SSQ assessments further showed that upward views were more likely to induce motion sickness, whereas horizontal and mildly upward views were more comfortable. These findings reveal the impact of head pitch on speed perception and user experience, providing an empirical basis for adaptive gain control in VR.