Non-photorealistically rendered (NPR) immersive virtual environments (IVEs) can facilitate conceptual design in architecture by enabling preliminary design sketches to be previewed and experienced at full scale, from a first-person perspective. However, it is critical to ensure the accurate spatial perception of the represented information, and many studies have shown that people typically underestimate distances in most IVEs, regardless of rendering style. In previous work we have found that while people tend to judge distances more accurately in an IVE that is a high-fidelity replica of their concurrently occupied real environment than in an IVE that it is a photorealistic representation of a real place that they've never been to, significant distance estimation errors re-emerge when the replica environment is represented in a NPR style. We have also previously found that distance estimation accuracy can be improved, in photo-realistically rendered novel virtual environments, when people are given a fully tracked, high fidelity first person avatar self-embodiment. In this paper we report the results of an experiment that seeks to determine whether providing users with a high-fidelity avatar self-embodiment in a NPR virtual replica environment will enable them to perceive the 3D spatial layout of that environment more accurately. We find that users who are given a first person avatar in an NPR replica environment judge distances more accurately than do users who experience the NPR replica room without an embodiment, but not as accurately as users whose distance judgments are made in a photorealistically rendered virtual replica room. Our results provide a partial solution to the problem of facilitating accurate distance perception in NPR virtual environments, while supporting and expanding the scope of previous findings that giving people a realistic avatar self-embodiment in an IVE can help them to interpret what they see through an HMD in a way that is more similar to how they would interpret a corresponding visual stimulus in the real world.

Previous work has shown that giving a user a first-person virtual avatar can increase the accuracy of their egocentric distance judgments in an immersive virtual environment (IVE). This result provides one of the rare examples of a manipulation that can enable improved spatial task performance in a virtual environment without potentially compromising the ability for accurate information transfer to the real world. However, many open questions about the scope and limitations of the effectiveness of IVE avatar self-embodiment remain. In this paper, we report the results of a series of four experiments, involving a total of 40 participants, that explore the importance, to the desired outcome of enabling enhanced spatial perception accuracy, of providing a high level of geometric and motion fidelity in the avatar representation. In these studies, we assess participants' abilities to estimate egocentric distances in a novel virtual environment under four different conditions of avatar self-embodiment: a) no avatar; b) a fully tracked, custom-fitted, high fidelity avatar, represented using a textured triangle mesh; c) the same avatar as in b) but implemented with single point rather than full body tracking; and d) a fully tracked but simplified avatar, represented by a collection of small spheres at the raw tracking marker locations. The goal of these investigations is to attain insight into what specific characteristics of a virtual avatar representation are most important to facilitating accurate spatial perception, and what cost-saving measures in the avatar implementation might be possible. Our results indicate that each of the simplified avatar implementations we tested is significantly less effective than the full avatar in facilitating accurate distance estimation; in fact, the participants who were given the simplified avatar representations performed only marginally (but not significantly) more accurately than the participants who were given no avatar at all. These findings suggest that the beneficial impact of providing users with a high fidelity avatar self-representation may stem less directly from the low-level size and motion cues that the avatar embodiment makes available to them than from the cognitive sense of presence that the self-embodiment supports.

Previous research has shown that egocentric distance estimation suffers from compression in virtual environments when viewed through head mounted displays. Though many possible variables and factors have been investigated, the source of the compression is yet to be fully realized. Recent experiments have hinted in the direction of an unsatisfied feeling of presence being the cause. This paper investigates this presence hypothesis by exploring the benefit of providing self-embodiment to the user through the form of a virtual avatar, presenting an experiment comparing errors in egocentric distance perception through direct-blind walking between subjects with a virtual avatar and without. The result of this experiment finds a significant improvement with egocentric distance estimations for users equipped with a virtual avatar over those without.

Enabling veridical spatial perception in immersive virtual environments (IVEs) is an important yet elusive goal, as even the factors implicated in the often-reported phenomenon of apparent distance compression in HMD-based IVEs have yet to be satisfactorily elucidated. In recent experiments (Interrante et al., 2006), we have found that participants appear less prone to significantly underestimate egocentric distances in HMD-based IVEs, relative to in the real world, in the special case that they unambiguously know, through first-hand observation, that the presented virtual environment is a high fidelity 3D model of their concurrently occupied real environment. We had hypothesized that this increased veridicality might be due to participants having a stronger sensation of 'presence' in the IVE under these conditions of co-location, which state of mind leads them to act on their visual input in the IVE similarly as they would in the real world (the presence hypothesis). However, alternative hypotheses are also possible. Primary among these is the visual calibration hypothesis: participants could be relying on metric information gleaned from their exposure to the real environment to calibrate their judgments of sizes and distances in the matched virtual environment. It is important to disambiguate between the presence and visual calibration hypotheses because they suggest different directions for efforts to facilitate veridical distance perception in general (non-co-located) IVEs. In this paper, we present the results of an experiment that seeks novel insight into this question. Using a mixed within- and between-subjects design, we compare participants' relative ability to accurately estimate egocentric distances in three different virtual environment models: one that is an identical match to the occupied real environment; one in which each of the walls in our virtual room model has been surreptitiously moved ~10% inward towards the center of the room; and one in which each of the walls has been surreptitiously moved ~10% outwards from the center of the room. If the visual calibration hypothesis holds, then we should expect to see a degradation in the accuracy of peoples' distance judgments in the surreptitiously modified models, manifested as an underestimation of distances when the IVE is actually larger than the real room and as an overestimation of distances when the IVE is smaller. However, what we found is that distances were significantly underestimated in the virtual environment relative to in the real world in each of the surreptitiously modified room environments, while remaining reasonably accurate (consistent with our previous findings) in the case of the faithfully size-matched room environment. In a post-test survey, participants in each of the three room size conditions reported equivalent subjective levels of presence and did not indicate any overt awareness of the room size manipulation

Numerous previous studies have suggested that distances appear to be compressed in immersive virtual environments presented via head mounted display systems, relative to in the real world. However, the principal factors that are responsible for this phenomenon have remained largely unidentified. In this paper we shed some new light on this intriguing problem by reporting the results of two recent experiments in which we assess egocentric distance perception in a high fidelity, low latency, immersive virtual environment that represents an exact virtual replica of the participant’s concurrently occupied real environment. Under these novel conditions, we make the startling discovery that distance perception appears not to be significantly compressed in the immersive virtual environment, relative to in the real world.