People judge what they can and cannot do all the time when acting in the physical world. Can I step over that fence or do I need to duck under it? Can I step off of that ledge or do I need to climb off of it? These qualities of the environment that people perceive that allow them to act are called affordances. This article compares people’s judgments of affordances on two tasks in both the real world and in virtual environments presented with head-mounted displays. The two tasks were stepping over or ducking under a pole, and stepping straight off of a ledge. Comparisons between the real world and virtual environments are important because they allow us to evaluate the fidelity of virtual environments. Another reason is that virtual environment technologies enable precise control of the myriad perceptual cues at work in the physical world and deepen our understanding of how people use vision to decide how to act. In the experiments presented here, the presence or absence of a self-avatar—an animated graphical representation of a person embedded in the virtual environment—was a central factor. Another important factor was the presence or absence of action, that is, whether people performed the task or reported that they could or could not perform the task. The results show that animated self-avatars provide critical information for people deciding what they can and cannot do in virtual environments, and that action is significant in people’s affordance judgments.

We explore whether a gender-matched, calibrated self-avatar affects the perception of the affordance of stepping off of a ledge, or visual cliff, in an immersive virtual environment. Visual cliffs form demonstrations in many immersive virtual environments because they create compelling environments. Understanding the role that self-avatars contribute to making such environments compelling is an important problem. We conducted an experiment to find the threshold at which subjects on a ledge in an immersive virtual environment would report that they could step gracefully off of the ledge without losing their balance, and compared the threshold height at which their decision changed under the condition of having and not having a self-avatar. The results show that people unrealistically say they can step off a ledge that is approximately 50% of their eyeheight without a self-avatar, and realistically about 25% of their eyeheight with a self-avatar.

The purpose of this study was to learn if self-avatars influence people's perception and action in virtual environments. People viewed two situations in a virtual environment through a head-mounted display and were asked to decide how they would act. In one situation their task was to imagine walking across a room which was divided by a horizontal bar. The bar's height was varied and the task was for people to say whether they would need to step over the bar or duck under it. In the other situation the task was to imagine walking through a doorway. The doorway's height was varied and the task was for people to say whether they could walk straight through the doorway or would need to duck to pass through. One-half the participants viewed the situations with a self-avatar and the others viewed it without an avatar. The height of the avatar was varied, so that it either equaled the participant's height or it was 15% taller. The results showed statistically significant effects of the avatar in the horizontal bar situation: their step-over or duck-under decision points were about 12% higher when the self-avatar was rendered taller. In the doorway situation the effect of the avatar was statistically non-significant. The step-over step-under task is a promising method to study perception and action in virtual environments.

This paper presents a mixed reality system for combining real robots, humans, and virtual robots. The system tracks and controls physical robots in local physical space, and inserts them into a virtual environment (VE). The system allows a human to locomote in a VE larger than the physically tracked space of the laboratory through a form of redirected walking. An evaluation assessed the conditions under which subjects found the system to be the most immersive.