Effective collaboration in Virtual Reality depends on users' ability to accurately perceive the affordances of others within a shared space. This paper presents the first empirical investigation of how people judge others' reaching capabilities in Immersive Virtual Environments (IVEs). We examined whether observers can reliably estimate the maximum horizontal reach distance of virtual actors, how different actor representations influence these perceptual judgments, and whether calibration feedback can improve estimation accuracy. Participants (N=35) judged the reachability of objects for virtual actors across three visual fidelity conditions: high-fidelity, low-fidelity, and end-effector-only representations. Results demonstrate that users can successfully estimate others' horizontal reachability in IVEs, though with overestimation. Calibration through action feedback significantly improved estimation accuracy, with overestimation decreasing across trials. Visual fidelity showed no main effect on initial reachability judgments but significantly affected postcalibration performance, with low-fidelity representations demonstrating significantly better calibration outcomes compared to high-fidelity avatars, while end-effector-only representations showed no significant difference from either condition. The findings contribute to the social perception literature in Virtual Reality (VR) and to provide design guidelines for avatar systems in collaborative virtual environments, where spatial coordination and shared action planning are critical.

Immersive Virtual Environments (IVEs) incorporating tangible graspable objects are becoming more accessible for training and other applications. Visual and proprioceptive information has been shown to be important for accurate distance and size perception. However, previous research has shown that users overestimate the size of tangible objects in IVEs. To address this issue, researchers have demonstrated the use of calibration to alter users' perceptions. In this study, we examined the carryover effects of calibration on the perceived size of graspable dials in IVEs. Participants wore head-mounted displays and experienced two calibration perturbations: Divergent Plus (physical dials 10% larger than virtual) and Divergent Minus (physical dials smaller than virtual). These were compared to the baseline Convergent condition (equal diameters). The results showed significant effects of the calibration on the accuracy of diameter estimates. Overall, a higher overestimation of dial sizes for the haptics-only condition was observed as compared to the vision-only condition. Additionally, participants' estimations worsened when haptic information was added to the vision during calibration but improved when vision information was added to the haptics-only condition during calibration. These findings highlight the importance of calibration in improving the accuracy of size perception in IVEs and contribute to our understanding of how tangible graspable objects are perceived in immersive virtual environments.

Direct perception, as part of the ecological approach to perception, defines a relationship between an organism and their environment that is specified by lawful information.Researchers can apply the ecological approach to eXtended Reality (XR) work to obtain a richer understanding of users' perception-action coordination in novel virtual settings.To encourage widespread adoption of this theoretical framework, this methodological paper introduces four major concepts from the ecological approach that are highly relevant to XR applications.We also provide an overview of existing literature to illustrate how those concepts may be used to inform and test their designs.These elements include the study of calibration and attunement, affordances, action based responses, and intrinsic scaling for measurements.The goal of this work is to increase awareness of the value of the ecological approach, and to provide a practical, evidence-based reference for researchers interested in applying these techniques in XR research.

This empirical evaluation aimed to investigate how size perception differs between OST AR and the real world, focusing on two judgment methods: verbal reports and physical judgments. Using a within-subjects experimental design, participants viewed target objects in different sizes in both AR and real-world conditions and estimated their sizes using verbal and physical judgment methods across multiple trials. The study addressed two key hypotheses: (H1) that size perception in AR would differ from the Real World, potentially due to rendering limitations in OST-HMDs, and (H2) that verbal reports and physical judgments would yield different levels of accuracy due to distinct cognitive and perceptual processes involved in each method. Our findings supported these hypotheses, revealing key differences in size perception between the two judgment methods and viewing conditions. Participants consistently underestimated object sizes when using verbal reports in both AR and real-world conditions, with more pronounced errors in AR. In contrast, physical judgments yielded more accurate size estimates under both viewing conditions. Notably, the accuracy of verbal reports decreased as target sizes increased, a trend that was particularly evident in AR. These results underscore the perceptual challenges associated with verbal size judgments in AR and their potential limitations in applications requiring precise size estimations. By highlighting the differences in accuracy and consistency between verbal and physical judgment methods, this study contributes to a deeper understanding of size perception in OST AR and real-world contexts.

Interpupillary distance (IPD) is the most important parameter for creating a user-specific stereo parallax, which in turn is crucial for correct depth perception. This is why contemporary Head-Mounted Displays (HMDs) offer adjustable lenses to adapt to users’ individual IPDs. However, today’s Video See-Through Augmented Reality (VST AR) HMDs use fixed camera placements to reconstruct the stereoscopic view of a user’s environment. This leads to a potential mismatch between individual IPD settings and the fixed Inter-Camera Distances (ICD), which can lead to perceptual incongruencies, limiting the usability and, potentially, the applicability of VST AR in depth-sensitive use cases. To investigate this incongruency between IPD and ICD, we conducted a 2 × 3 mixed-factor design user study using a near-field, open-loop reaching task comparing distance judgments of Virtual Reality (VR) and VST AR. We also investigated changes in reaching performance via perceptual calibration by incorporating a feedback phase between pre- and post-phase conditions, with a particular focus on the influence of IPD-ICD differences. Our Linear Mixed Model (LMM) analysis showed a significant difference between VR and VST AR, an effect of IPD-ICD mismatch, and a combined effect of both factors. However, subjective measures showed no effect underlining the subconscious nature of the perception of VST AR. This novel insight and its consequences are discussed specifically for depth perception tasks in AR, eXtended Reality (XR), and potential use cases.

In immersive virtual environments (IVEs), accurate size perception is critical, especially in training simulations designed to mimic real-world tasks, such as, nuclear power plant control room or medical procedures. These simulations have dials or instruments of varying sizes. Visual information of the objects alone, often fails to capture subtle size differences in virtual reality (VR). However, integrating haptic and hand-avatars may potentially improve accuracy and performance. This improvement could be especially beneficial for real-world scenarios where hand(s) are intermittently visible or obscured. To investigate how this intermittent presence or absence of body-scaled hand-avatars affects size perception when integrated with haptic information, we conducted 2x2 mixed-factorial experiment design using a near-field, size-estimation task in VR. The experiment conditions compared size estimations with or without virtual hand visibility in the perception and reporting phases. The task involved 16 graspable objects of varying sizes and randomly repeated 3 times across 48 trials per participant (total 80 participants). We employed Linear Mixed Models (LMMs) analysis to objective measures: perceived size, residual error and proportional errors. Results revealed that as the tangible-graspable size increases, overestimation reduces if the hand-avatars are visible in the reporting phase. Also, overestimation reduces as the number of trials increases, if the hand-avatars are visible in the reporting phase. Thus, the presence of hand-avatars facilitated perceptual calibration. This novel study, with different combinations of hand-avatar visibility, taking perception and reporting of size as two separate phases, could open future research directions in more complex scenarios for refined integration of sensory modalities and consequently enhance real-world application performance.

Many AR applications require users to perceive, estimate and calibrate to the size of objects presented in the scene. Distortions in size perception in AR could potentially influence the effectiveness of skills transferred from the AR to the real world. We investigated the after-effects or carry-over effects of calibration of size perception in AR to the real world (RW), by providing feedback and an opportunity for participants to correct their judgments in AR. In an empirical evaluation, we employed a three-phase experiment design. In the pretest phase, participants made size estimations to target objects concurrently using both verbal reports and physical judgment in RW as a baseline. Then, they estimated the size of targets, and then were provided with feedback and subsequently corrected their judgments in a calibration phase. Followed by which, participants made size estimates to target objects in the real world. Our findings revealed that the carryover effects of calibration successfully transferred from AR to RW in both verbal reports and physical judgment methods.

Spatial perception in virtual reality (VR) has been a hot research topic for years. Most of the studies on this topic have focused on visual perception and distance perception. Fewer have examined auditory perception and room size perception, although these aspects are important for improving VR experiences. Recently, a number of studies have shown that perception can be calibrated to information that is relevant to the successful completion of everyday tasks in VR (such as distance estimation and spatial perception). Also, some recent studies have examined calibration of auditory perception as a way to compensate for the classic distance compression problem in VR. In this paper, we present a calibration method for both visual and auditory room size perception. We conducted experiments to investigate how people perceive the size of a virtual room and how the accuracy of their size perception can be calibrated by manipulating perceptible auditory and visual information in VR. The results show that people were more accurate in perceiving room size by means of vision than in audition, but that they could still use audition to perceive room size. The results also show that during calibration, auditory room size perception exhibits learning effects and its accuracy was greatly improved after calibration.

Various experiments have led to a better understanding of how the surrounding environment influences long-term memory and spatial cognition, including those indicating how environmental context is encoded. However, specific external environment characteristics that may impact cognitive memory and performance remain unclear. Using an immersive Virtual Reality (VR) environment, we investigated the effects of color congruency on object placement accuracy, recall speed, and recognition.

The perception of distance is a complex process that often involves sensory information beyond that of just vision. In this work, we investigated if depth perception based on auditory information can be calibrated, a process by which perceptual accuracy of depth judgments can be improved by providing feedback and then performing corrective actions. We further investigated if perceptual learning through carryover effects of calibration occurs in different levels of a virtual environment’s visibility based on different levels of virtual lighting. Users performed an auditory depth judgment task over several trials in which they walked where they perceived an aural sound to be, yielding absolute estimates of perceived distance. This task was performed in three sequential phases: pretest, calibration, posttest. Feedback on the perceptual accuracy of distance estimates was only provided in the calibration phase, allowing to study the calibration of auditory depth perception. We employed a 2 (Visibility of virtual environment) $\times 3$ (Phase) $\times 5$ (Target Distance) multi-factorial design, manipulating the phase and target distance as within-subjects factors, and the visibility of the virtual environment as a between-subjects factor. Our results revealed that users generally tend to underestimate aurally perceived distances in VR similar to the distance compression effects that commonly occur in visual distance perception in VR. We found that auditory depth estimates, obtained using an absolute measure, can be calibrated to become more accurate through feedback and corrective action. In terms of environment visibility, we find that environments visible enough to reveal their extent may contain visual information that users attune to in scaling aurally perceived depth.

Mixed reality (MR) interactions feature users interacting with a combination of virtual and physical components. Inspired by research investigating aspects associated with near-field interactions in augmented and virtual reality (AR & VR), we investigated how avatarization, the physicality of the interacting components, and the interaction technique used to manipulate a virtual object affected performance and perceptions of user experience in a mixed reality fundamentals of laparoscopic peg-transfer task wherein users had to transfer a virtual ring from one peg to another for a number of trials. We employed a 3 (Physicality of pegs) X 3 (Augmented Avatar Representation) X 2 (Interaction Technique) multi-factorial design, manipulating the physicality of the pegs as a between-subjects factor, the type of augmented self-avatar representation, and the type of interaction technique used for object-manipulation as within-subjects factors. Results indicated that users were significantly more accurate when the pegs were virtual rather than physical because of the increased salience of the task-relevant visual information. From an avatar perspective, providing users with a reach envelope-extending representation, though useful, was found to worsen performance, while co-located avatarization significantly improved performance. Choosing an interaction technique to manipulate objects depends on whether accuracy or efficiency is a priority. Finally, the relationship between the avatar representation and interaction technique dictates just how usable mixed reality interactions are deemed to be.

As virtual reality (VR) technology sees more use in various fields, there is a greater need to understand how to effectively design dynamic virtual environments. As of now, there is still uncertainty in how well users of a VR system are capable of tracking moving targets in a virtual space. In this work, we examined the influence of sensory modality and visual feedback on the accuracy of head-gaze moving target tracking. To this end, a between subjects study was conducted wherein participants would receive targets that were visual, auditory, or audiovisual. Each participant performed two blocks of experimental trials, with a calibration block in between. Results indicate that audiovisual targets promoted greater improvement in tracking performance over single-modality targets, and that audio-only targets are more difficult to track than those of other modalities.

Over the past two decades self-avatars have been shown to affect the perception of both oneself and of environmental properties including the sizes and distances of elements in immersive virtual environments. However, virtual avatars that accurately match the body proportions of their users remain inaccessible to the general public. As such, most virtual experiences that represent the user have a generic avatar that does not fit the proportions of the users' body. This can negatively affect judgments involving affordances, such as passability and maneuverability, which pertain to the relationship between the properties of environmental elements relative to the properties of the user providing information about actions that can be enacted. This is especially true when the task requires the user to maneuver around moving objects like in games. Therefore, it is necessary to understand how different sized self-avatars affect the perception of affordances in dynamic virtual environments. To better understand this, we conducted an experiment investigating how a self-avatar that is either the same size, 20% shorter, or 20% taller, than the user's own body affects passability judgments in a dynamic virtual environment. Our results suggest that the presence of self-avatars results in better regulatory and safer road crossing behavior, and helps participants synchronize self-motion to external stimuli quicker than in the absence of self-avatars.

With the popularity of Virtual Reality (VR) on the rise, creators from a variety of fields are building increasingly complex experiences that allow users to express themselves more naturally. Self-avatars and object interaction in virtual worlds are at the heart of these experiences. However, these give rise to several perception based challenges that have been the focus of research in recent years. One area that garners most interest is understanding the effects of self-avatars and object interaction on action capabilities or affordances in VR. Affordances have been shown to be influenced by the anthropometric and anthropomorphic properties of the self-avatar embodied. However, self-avatars cannot fully represent real world interaction and fail to provide information about the dynamic properties of surfaces in the environment. For example, pressing against a board to feel its rigidity. This lack of accurate dynamic information can be further amplified when interacting with virtual handheld objects as the weight and inertial feedback associated with them is often mismatched. To investigate this phenomenon, we looked at how the absence of dynamic surface properties affect lateral passability judgments when carrying virtual handheld objects in the presence or absence of gender matched body-scaled self-avatars. Results suggest that participants can calibrate to the missing dynamic information in the presence of self-avatars to make lateral passability judgments, but rely on their internal body schema of a compressed physical body depth in the absence of self-avatars.

User representations are critical to the virtual experience, and involve both the input device used to support interactions as well as how the user is virtually represented in the scene. Inspired by previous work that has shown effects of user representations on the perceptions of relatively static affordances, we attempt to investigate how end-effector representations affect the perceptions of affordances that dynamically change over time. Towards this end, we empirically evaluated how different virtual hand representations affect users' perceptions of dynamic affordances in an object retrieval task wherein users were tasked with retrieving a target from a box for a number of trials while avoiding collisions with its moving doors. We employed a 3 (virtual end-effector representation) X 13 (frequency of moving doors) X 2 (target object size) multi-factorial design, manipulating the input modality and its concomitant virtual end-effector representation as a between-subjects factor across three experimental conditions: (1) Controller (using a controller represented as a virtual controller); (2) Controller-hand (using a controller represented as a virtual hand); (3) Glove (using a hand tracked hi-fidelity glove represented as a virtual hand). Results indicated that the controller-hand condition produced lower levels of performance than both the other conditions. Furthermore, users in this condition exhibited a diminished ability to calibrate their performance over trials. Overall, we find that representing the end-effector as a hand tends to increase embodiment but can also come at the cost of performance, or an increased workload due to a discordant mapping between the virtual representation and the input modality used. It follows that VR system designers should carefully consider the priorities and target requirements of the application being developed when choosing the type of end-effector representation for users to embody in immersive virtual experiences.

Inspired by previous works showing promise for AR self-avatarization - providing users with an augmented self avatar, we investigated whether avatarizing users' end-effectors (hands) improved their interaction performance on a near-field, obstacle avoidance, object retrieval task wherein users were tasked with retrieving a target object from a field of non-target obstacles for a number of trials. We employed a 3 (Augmented hand representation) X 2 (density of obstacles) X 2 (size of obstacles) X 2 (virtual light intensity) multi-factorial design, manipulating the presence/absence and anthropomorphic fidelity of augmented self-avatars overlaid on the user's real hands, as a between subjects factor across three experimental conditions: (1) No-Augmented Avatar (using only real hands); (2) Iconic-Augmented Avatar; (3) Realistic Augmented Avatar. Results indicated that self-avatarization improved interaction performance and was perceived as more usable regardless of the anthropomorphic fidelity of avatar. We also found that the virtual light intensity used in illuminating holograms affects how visible one's real hands are. Overall, our findings seem to indicate that interaction performance may improve when users are provided with a visual representation of the AR system's interacting layer in the form of an augmented self-avatar.

Virtual Reality (VR) is well-known for its use in interdisciplinary applications and research. The visual representation of these applications could vary depending in their purpose and hardware limitation, and in those situations could require an accurate perception of size for task performance. However, the relationship between size perception and visual realism in VR has not yet been explored. In this contribution, we conducted an empirical evaluation using a between-subject design over four conditions of visual realism, namely Realistic, Local Lighting, Cartoon, and Sketch on size perception of target objects in the same virtual environment. Additionally, we gathered participants' size estimates in the real world via a within-subject session. We measured size perception using concurrent verbal reports and physical judgments. Our result showed that although participants' size perception was accurate in the realistic condition, surprisingly they could still tune into the invariant but meaningful information in the environment to accurately estimate the size of targets in the non-photorealistic conditions as well. We additionally found that size estimates in verbal and physical responses were generally different in real world and VR viewing and were moderated by trial presentation over time and target object widths.

Distance compression, which refers to the underestimation of ego-centric distance to objects, is a common problem in immersive virtual environments. Besides visually compensating the compressed distance, several studies have shown that auditory information can be an alternative solution for this problem. In particular, reverberation time (RT) has been proven to be an effective method to compensate distance compression. To further explore the feasibility of applying audio information to improve distance perception, we investigate whether users’ egocentric distance perception can be calibrated, and whether the calibrated effect can be carried over and even sustain for a longer duration. We conducted a study to understand the perceptual learning and carryover effects by using RT as stimuli for users to perceive distance in IVEs. The results show that the carryover effect exists after calibration, which indicates people can learn to perceive distances by attuning reverberation time, and the accuracy even remains a constant level after 6 months. Our findings could potentially be utilized to improve the distance perception in VR systems as the calibration of auditory distance perception in VR could sustain for several months. This could eventually avoid the burden of frequent training regimens.

The availability of new and improved display, tracking and input devices for Virtual Reality experiences has facilitated the use of partial and full body self-avatars in interaction with virtual objects in the environment. However, scaling the avatar to match the user's body dimensions remains to be a cumbersome process. Moreover, the effect of body-scaled self-avatars on size perception of virtual handheld objects and related action capabilities has been relatively unexplored. To this end, we present an empirical evaluation investigating the effect of the presence or absence of body-scaled self-avatars and visuo-motor calibration on frontal passability affordance judgments when interacting with virtual handheld objects. The self-avatar's dimensions were scaled to match the participant's eyeheight, arms length, shoulder width and body depth along the mid section. The results indicate that the presence of body-scaled self-avatars produce more realistic judgments of passability and aid the calibration process when interacting with virtual objects. Also, participants rely on the visual size of virtual objects to make judgments even though the kinesthetic and proprioceptive feedback of the object is missing or mismatched.

Prior research in depth perception and perceptuo-motor calibration have primarily focused on participants completing experiments in single sessions and therefore do not empirically evaluate changes over time. Further, these studies do not typically take into account the amount of experience that the participants have in virtual reality (VR) prior to participation, the role of experience during participation, or calibration that may occur throughout the experiment session. In this contribution, we conducted a novel empirical evaluation of how calibration affects perception-action coordination over time. We recruited novice VR users and they completed eight sessions of a depth perception reaching experiment over the course of 12 weeks. During these experiments, we examined how participants' ability to estimate depth in a virtual environment changed as they gradually gained experience. While previous literature has shown that participants tend to underestimate distances, we found that this underestimation diminished over time as they gained experience in the virtual environment. Our study highlights the need for carrying out VR studies over time and the influence that longitudinal calibration can have on spatial perception in long-term VR experiences.

Immersive Virtual Environments (IVEs) incorporating tangibles are becoming more accessible. The success of applications combining 3D printed tangibles and VR often depends on how accurately size is perceived. Research has shown that visuo-haptic perceptual information is important in the perception of size. However, it is unclear how these sensory-perceptual channels are affected by immersive virtual environments that incorporate tangible objects. Towards understanding the effects of different sensory information channels in the near field size perception of tangibles of graspable sizes in IVEs, we conducted a between-subjects study evaluating the accuracy of size perception across three experimental conditions (Vision-only, Haptics-only, Vision and Haptics). We found that overall, participants consistently over-estimated the size of the dials regardless of the type of perceptual information that was presented. Participants in the haptics only condition overestimated diameters to a larger degree as compared to other conditions. Participants were most accurate in the vision only condition and least accurate in the haptics only condition. Our results also revealed that increased efficiency in reporting size over time was most pronounced in the visuo- haptic condition.

As Virtual Reality (VR) devices become more accessible, a multitude of VR applications engage users in highly immersive virtual environments that feature realistic graphics, real-life scenarios, and self-avatars. Many of these simulations require users to make spontaneous affordance judgments such as stepping over obstacles, passing through gaps, etc. which are shown to be affected by the nature of our self-representation in the virtual world. As the technology for creating self-avatars becomes more widely available, it is important to explore how various affordance judgments are affected by the presence of self-avatars. In this work, we investigate the effects of body-scaled self-avatars on the affordance of passability in a natural setting. We implemented a gender-matched body-scaled self-avatar using HTC Vive trackers and evaluated how passability judgments for a sliding doorway in VR, with and without an avatar, compared to the real world judgments. The results suggest that passability judgments are more conservative in VR as compared to the real world. However, the presence of a self-avatar does not significantly affect passability judgments made in VR. This does not align with previous findings which show that having a self-avatar improves judgments and estimates.

The commercialization of Virtual Reality (VR) devices has made it easier for everyday users to experience VR from the comfort of their living rooms. This recent uptake in VR has also increased reported incidents of cybersickness. Cybersickness refers to the discomfort experienced by an individual while experiencing virtual environments. The symptoms are similar to those of motion sickness but are more disorienting in nature resulting in dizziness, blurred vision, etc. Cybersickness is currently one of the biggest hurdles to the widespread adoption of VR, and it is therefore critical to explore the factors that influence its onset. Towards this end, we present a proof of concept simulation to study cybersickness in highly realistic immersive virtual environments.

Research has shown that self-avatars (life-size representations of the user in Virtual Reality (VR)) can affect how people perceive virtual environments. In this paper, we investigated whether the visual fidelity of a self-avatar affects reach boundary perception, as assessed through two variables: 1) action taken (or verbal response) and 2) correct judgment. Participants were randomly assigned to one of four conditions: i) high-fidelity self-avatar, ii) low-fidelity self-avatar, iii) no avatar (end-effector), and iv) real-world as reference task group. Results indicate that all three VR viewing conditions were significantly different from real world in regards to correctly judging the reachability of the target. However, based on verbal responses, only the "no avatar" condition had a non-trivial difference with real world condition. Taken together with reachability data, participants in "no avatar" condition were less likely to correctly reach to the reachable targets. Overall, participant performance improved after completing a calibration phase with feedback, such that correct judgments increased and participants reached to fewer unreachable targets.

Every task we perform in our day-to-day lives requires us to make judgements about size, distance, depth, etc. The same is true for tasks in an immersive virtual environments (IVE). Increasingly, Virtual Reality (VR) applications are being developed for training and entertainment, many of which require the user to determining whether s/he can pass through an opening. Typically, people determine their ability to pass through an aperture by comparing the width of their shoulders to the width of the opening. Thus, judgments of size and distance in an IVE are necessary for accurate judgments of passability. In this experiment, we empirically evaluate how passability judgments in an IVE, viewed through a Head-Mounted Display (HMD), compare to judgments made in the real world. An exact to scale virtual replica of the room and apparatus was used for the VR condition. Results indicate that the accuracy of passability judgments seem to be comparable to the real world.

Immersive Virtual Environments (IVEs) are becoming more accessible and more widely utilized for training. Previous research has shown that the matching of visual and proprioceptive information is important for calibration. While research has demonstrated that self-avatars can enhance ones' sense of presence and improve distance perception, the effects of self-avatar fidelity on near field distance estimations has yet to be investigated. This study tested the effect of avatar fidelity on the accuracy of distance estimations in the near-field. Performance with a virtual avatar was also compared to real-world performance. Three levels of fidelity were tested; 1) an immersive self-avatar with realistic limbs, 2) a low-fidelity self-avatar showing only joint locations, and 3) end-effector only. The results suggest that reach estimations become more accurate as the visual fidelity of the avatar increases, with accuracy for high fidelity avatars approaching real-world performance as compared to low-fidelity and end-effector conditions. In all conditions reach estimations became more accurate after receiving feedback during a calibration phase.

No abstract available.

In an initial study, we characterized the properties of human reach motion in the presence or absence of visuo-haptic feedback in real and Immersive Virtual Environments (IVEs) or virtual reality within a participant’s maximum arm reach. Our goal is to understand how physical reaching actions to the perceived location of targets in the presence or absence of visuo-haptic feedback are different between real and virtual viewing conditions. Typically, participants reach to the perceived location of objects in the three-dimensional (3D) environment to perform selection and manipulation actions during 3D interaction in applications such as virtual assembly or rehabilitation. In these tasks, participants typically have distorted perceptual information in the IVE as compared to the real world, in part due to technological limitations such as minimal visual field of view, resolution, latency, and jitter. In an empirical evaluation, we asked the following questions: (i) how do the perceptual differences between virtual and real world affect our ability to accurately reach to the locations of 3D objects, and (ii) how do the motor responses of participants differ between the presence or absence of visual and haptic feedback? We examined factors such as velocity and distance of physical reaching behavior between the real world and IVE, both in the presence or absence of visuo-haptic information. The results suggest that physical reach responses vary systematically between real and virtual environments, especially in situations involving the presence or absence of visuo-haptic feedback. The implications of our study provide a methodological framework for the analysis of reaching motions for selection and manipulation with novel 3D interaction metaphors and to successfully characterize visuo-haptic versus non-visuo-haptic physical reaches in virtual and real-world situations.

We report the results of an empirical evaluation to examine the carryover effects of calibrations to one of three perturbations of visual and proprioceptive feedback: i) Minus condition (-20% gain) in which a visual stylus appeared at 80% of the distance of a physical stylus, ii) Neutral condition (0% gain) in which a visual stylus was co-located with a physical stylus, and iii) Plus condition (+20% gain) in which the visual stylus appeared at 120% of the distance of the physical stylus. Feedback was shown to calibrate distance judgments quickly within an IVE, with estimates being farthest after calibrating to visual information appearing nearer (Minus condition), and nearest after calibrating to visual information appearing further (Plus condition).

Research in visuo-motor coupling has shown that the matching of visual and proprioceptive information is important for calibrating movement. Many state-of-the art virtual reality (VR) systems, commonly known as immersive virtual environments (IVE), are created for training users in tasks that require accurate manual dexterity. Unfortunately, these systems can suffer from technical limitations that may force de-coupling of visual and proprioceptive information due to interference, latency, and tracking error. We present an empirical evaluation of how visually distorted movements affects users' reach to near field targets using a closed-loop physical reach task in an IVE. We specifically examined the recalibration of movements when the visually reached distance is scaled differently than the physically reached distance. Subjects were randomly assigned to one of three visual feedback conditions during which they reached to target while holding a tracked stylus: i) Condition 1 (-20% gain condition) in which the visual stylus appeared at 80% of the distance of the physical stylus, ii) Condition 2 (0% or no gain condition) in which the visual stylus was co-located with the physical stylus, and iii) Condition 3 (+20% gain condition) in which the visual stylus appeared at 120% of the distance of the physical stylus. In all conditions, there is evidence of visuo-motor calibration in that users' accuracy in physically reaching to the target locations improved over trials. During closed-loop physical reach responses, participants generally tended to physically reach farther in condition 1 and closer in condition 3 to the perceived location of the targets, as compared to condition 2 in which participants' physical reach was more accurate to the perceived location of the target.

Distances are regularly underestimated in immersive virtual environments (IVEs) [Witmer and Kline 1998; Loomis and Knapp 2003]. Few experiments, however, have examined the ability of calibration to overcome distortions of depth perception in IVEs. This experiment is designed to examine the effect of calibration via haptic and visual feedback on distance estimates in an IVE. Participants provided verbal and physical reach responses to target distances presented during three sessions; a baseline measure without feedback, a calibration session with visual and haptic feedback, and finally a post-calibration session without feedback. Feedback was shown to calibrate distance estimates within an IVE. Discussion focused on the possibility that costly solutions and research endeavors seeking to remedy the compression of distances may become less necessary if users are simply given the opportunity to use manual activity to calibrate to the IVE.

An experiment was conducted to examine the effects of immersion on a spatial updating task in a virtual panoramic environment (VPE). A virtual panorama, such as Google Streetview, is an environment that is comprised of 3D (spherical) images taken at regular intervals in a real world setting. Participants in this experiment navigated the National Mall area of Washington DC in Google Streetview using either a keyboard and mouse or a head-mounted display (HMD) with a head orientation tracker.

Few experiments have been performed to investigate near-field egocentric distance estimation in an Immersive Virtual Environment (IVE) as compared to the Real World (RW). This article investigates near-field distance estimation in IVEs and RW conditions using physical reach and verbal report measures, by using an apparatus similar to that used by Bingham and Pagano [1998]. Analysis of our experiment shows distance compression in both the IVE and RW conditions in participants' perceptual judgments to targets. This is consistent with previous research in both action space in an IVE and reach space with Augmented Reality (AR). Analysis of verbal responses from participants revealed that participants underestimated significantly less in the virtual world as compared to the RW. We also found that verbal reports and reaches provided different results in both IVEs and RW environments.