Ownership and Copyright © Springer-Verlag London Ltd Virtual Reality (2002) 6:75–85 Simulating Self-Motion I: Cues for the Perception of Motion L. R. Harris 2,3,4 , M. R. Jenkin 1,4 , D. Zikovitz 3,4 , F. Redlick 3,4 , P. Jaekl 2,4 , U. T. Jasiobedzka 1,4 , H. L. Jenkin 2,4 , R. S. Allison 1,4 Centre for Vision Research, 1 Department of Computer Science, 2 Department of Psychology and 3 Department of Biology, York University; 4 Centre for Research in Earth and Space Technology, Toronto, Ontario, Canada Abstract: When people move there are many visual and non-visual cues that can inform them about their movement. Simulating self-motion in a virtual reality environment thus needs to take these non-visual cues into account in addition to the normal high-quality visual display. Here we examine the contribution of visual and non-visual cues to our perception of self-motion. The perceived distance of self-motion can be estimated from the visual flow field, physical forces or the act of moving. On its own, passive visual motion is a very effective cue to self-motion, and evokes a perception of self-motion that is related to the actual motion in a way that varies with acceleration. Passive physical motion turns out to be a particularly potent self-motion cue: not only does it evoke an exaggerated sensation of motion, but it also tends to dominate other cues. Keywords: Proprioception; Self-motion; Visual and non-visual cues to motion Introduction A fundamental goal of virtual reality is to provide a user with a compelling sensation of an alternate environ- ment. The process of simulating the changing visual view that observers would see if they were really mov- ing around the simulated environment has tended to dominate virtual reality research, while other cues associated with self-motion are often ignored – though some haptic self-motion cue systems have been con- structed (e.g. [1,2]), and auditory self-motion cues have been studied as well (see [3]). It is, however, a tribute to the flexibility of the human sensory system that provid- ing only visual information in a virtual reality stimulation works as well as it does. Indeed, even just moving the user’s view from one point to another without the user actually selecting where to go, or physically moving at all, can provide a compelling sense of self-motion. There are two basic aspects to simulating motion in a virtual reality system. Firstly, how do viewers inform the virtual reality generator where they are and where they would like to move to in the environment? Secondly, how are viewers’ movements within the environment actually simulated so as to provide them with a convincing and accurate sensation that they really have moved? These problems are inter-related, since how viewers control the simulation contributes to their experience. If the user just sits in a chair and controls their motion around the virtual world with a joystick, then almost all of the cues to motion need to be simulated. At the other end of the spectrum, if viewers inform the gen- erator about their movements by actually making com- plete and natural movements, then many of the natural non-visual cues to motion will be present, and there will be no need to simulate them. Even in this case, 75