According to several studies, introducing a static frame of reference (independent visual background) may reduce simulation sickness. A technique called Nasum Virtualis shows a virtual nose as a fixed frame of reference for VR headsets.Whittinghill, D. M., Ziegler, B., Moore, J., & Case, T. (2015). Nasum Virtualis: A Simple Technique for Reducing Simulator Sickness in Head Mounted VR. In Game Developers Conference. San Francisco.
