Matching actual treadmill walking speed and visually perceived walking speed in a projection virtual environment

When developing our Immersive Virtual Environment Rehabilitation Treadmill (IVERT) system (Figure 1), we observed the well known phenomenon of visuals feeling "too slow" compared to walking speed (Durgin 2005). The work reported here was motivated by needing a factor, the optical flow multiplier (OFM), to multiply by the treadmill speed to generate a viewpoint/visual speed that "felt right" to the IVERT users. Our most frequent use case will be the therapist setting the treadmill speed and then the program multiplying treadmill speed by the OFM to generate the viewpoint speed.