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A Full-Body Avatar Improves Egocentric Distance Judgments in an Immersive Virtual Environment. Betty J. Mohler † , Heinrich H. Bülthoff † , William B. Thompson* & Sarah H. Creem-Regehr +. † Max Planck Institute for Biological Cybernetics, Germany,

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introduction and background

A Full-Body Avatar Improves Egocentric Distance Judgments in an Immersive Virtual Environment

Betty J. Mohler†, Heinrich H. Bülthoff†, William B. Thompson* & Sarah H. Creem-Regehr+

†Max Planck Institute for Biological Cybernetics, Germany,

*University of Utah, School of Computing, +University of Utah, Psychology Department



  • Participants were in one of 2 five minute exploration conditions
  • For both exploration conditions, participants were instructed to look down and explore the space where their body was located.
  • Independent t-test confirmed a significant difference between the percent distance walked in the two conditions (t= 4.261, p<0.01)
  • Distance judgments are compressed in head-mounted display (HMD)-based virtual environments (e.g., [Loomis and Knapp 2003]).
  • A user’s own body is almost never rendered in HMD-based VEs.
  • In the real world, a view of one’s body is not necessary in order to make accurate egocentric distance judgments [Creem-Regehr et al. 2005].
  • The visibility of a user’s body may affect the perceptual fidelity of virtual environments in the following ways:
  • Visual and/or proprioceptive feedback associated with an awareness of one’s body could provide a metric for scaling of absolute dimensions of space.
  • Presence of the body in the VE could serve to ground or situate the user in the VE, acting as a frame of reference.
  • Draper [1995] demonstrated that rendering parts of a user’s body in an HMD affects space perception, with equivocal results.
  • Beyond this work, the influence of the body on space perception within the context of virtual environments has been largely unexplored.
  • Experimental hypothesis:
  • The lack of a fully-articulated self-avatar may contribute to the perceptual distortions in HMD-based VEs.

Without Avatar

  • Pre-exploration without self-avatar (76.9%) results in more compression in egocentric distance judgments in a HMD-based VE as compared to pre-exploration with a full body self-avatar (89.3%)

For both conditions participants wore an eMagin HMD and a tight suit with 37 markers tracking their body movements in real-time.

With Fully-Articulated Avatar



  • If participants are able to explore a fully-articulated avatar of themselves within the immersive VE they will make less errors in their subsequent egocentric distance judgments.
  • Future research will explore the impact of non-articulated avatars and non-co-located avatars on egocentric distance judgments in a virtual environment.

Participants could see their legs, arms, feet and hands freely moving in the space, these motions were consistent with their actual movement captured with Vicon. Each body segment of the avatar was scaled to match the dimensions of each participant. No line was placed on the floor in this condition.




  • LOOMIS, J. M., AND KNAPP, J. 2003. Visual perception of egocentric distance in real and virtual environments. In Virtual and Adaptive Environments, L. J. Hettinger and M. W. Haas, Eds. Erlbaum, Mahwah, NJ, ch. 2, 21–46.
  • CREEM-REGEHR, S. H., WILLEMSEN, P., GOOCH, A. A., AND THOMPSON, W. B. 2005. The influence of restricted viewing conditions on egocentric distance perception: Implications for real and virtual environments. Perception 34, 2, 191–204.
  • DRAPER, M. 1995. Exploring the Influence of a Virtual Body on Spatial Awareness. Master’s thesis, Seattle, WA 98195, USA.
  • Resources
  • Tracking space with 12 Vicon Cameras (6x7 meters in size, 26-60 ms latency)
  • eMagin HMD (40 degree diagonal FOV)
  • Procedure:
  • Experiment was a between-subject design
  • Independent Variable: Exploration condition, with or without a fully-articulated self-avatar
  • Dependent Variable: Egocentric distance judgment: direct blind-walking
  • 12 paid volunteers (6 for each condition)

Direct Blind Walking in a Different Virtual World

  • Direct blind-walking task in a different virtual world than was used for the exploration phase
  • Without the view of the avatar

Acknowledgements: This work was supported in part by NSF grant IIS-0745131.

Special thanks to Michael Weyel and Martin Breidt for technical assistance, Naima Laharnar and Ekaterina Volkova for help with data collection, and Jenny Campos , Victoria Interrante, and William Warren for interesting discussions.