The Effects of Head-Mounted Display Mechanics on Distance Judgments in Virtual Environments

Cynthia S. Sahm, Sarah H Creem-Regehr, William B. Thompson and Peter Willemsen

Department of Psychology and School of Computing

University of Utah

Outline Introduction Throwing vs. Walking The Problem Method Results Conclusion

Introduction Our distance perception in virtual

immersive environments is compressed

This paper attempts to give some insight into why that is

The study in this paper deals with absolute egocentric distance judgments in action space

Throwing vs. Walking as Indicators of Distance Perception Standard blind walking

Locomotion Egocentric updating of environment

with ones movement Can this influence the response

measure

Blind throwing View a target on the ground Attempt to throw a bean bag at

target while blindfolded

Been shown to be accurate in real world conditions

Experiment Subjects judge distances using

both throwing and blind walking in a virtual and a real environment

Distances 3, 4, 5 and 6 meters

Result

Conclusion Both methods show similar results

in both a real and a virtual environment

This suggests that distance compression is not caused by the specific response measure

Problem Distance judgments in virtually

immersive environments are compressed.

The quality of the rendered graphics does not explain this, Thompson et al.

Limited field of view does not explain this, Knapp and Loomis

Does the mechanical aspects of wearing a HMD explain this phenomenon?

Problem cont. How can a HMD affect distance

judgments? Mass

Weight Distribution

Moment of inertia Angle of declination

Method Three viewing conditions

Virtual world using a HMD Real world using a mock HMD Real world condition

Tested both direct and triangular walking

Method cont. 83 students (42 male, 41 female) Each subject experienced one of

six possible conditions Triangulated walking 5m, 10m, 15m Direct walking 4m, 6m, 8m

Each subject performed 15 trials (3 practice

Direct and Triangulated walking

Distance To target

Direction to target

Direction to apparent target

target

≈ 2.5m≈70º

target

Mock HMD Replica shell of nVisor SX HMD Mass of mock HMD was adjusted

using small weights

Mock HMD Location of center of mass

Point of balance when suspended from a string

Moments of inertia of the mock HMD Period of oscillation when attached to a

pendulum

Environments

Real World Virtual World

Procedure The authors did not address specific

instructions given to the subjects. Previous experiment instructions

Given written instructions Given a demonstration of the task in space

smaller than the actual experiment spatial layout Allowed to practice blind walking prior to

experiment Instructed to get a good image Allowed to rotate their head about their neck Not allowed to move their head from side to side

Result, direct walking

Result, triangulated walking

Mock HMD vs High Quality CG

High quality CG

Conclusion Mechanical aspects of wearing a

HMD does account for some of the distance compression experienced in virtual environments

HMD does not solely explain the compression

Questions?