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Virtual Environments. Week 9 Seminar. Presence. . Presence. Presence: Refers to ‘Being in an environment Degree of presence in one environment relative to another Subjective presence Response to questions about being there Verbal and conscious Evaluation of an experience
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Virtual Environments Week 9 Seminar Presence \
Presence • Presence: • Refers to ‘Being in an environment • Degree of presence in one environment relative to another • Subjective presence • Response to questions about being there • Verbal and conscious • Evaluation of an experience • Behavioural Presence • Observable responses to stimuli • Responses to the events in the environment in question • May be measured by subjective means or through observation
Bodily Movement and Presence • Main Hypothesis: • “ The environment relative to which major body movements are made has a higher probability of being the dominant presence environment, other things being equal” • Examine influence of two factors • Extent of body movement • Complexity of task • Major interest on body movement • Motivated by two factors • “aha” type of experience • Construct interactive techniques • Null Hypothesis • Scores are attributed randomly and independently • Measured with questionnaires with six questions each on scale of 1 to 7
Factorial Design • Assess the extent to which body movement influences presence, particularly bending and head movement • Scenario devised that would naturally induce subjects to use bending and head movements • Field of unusual plants or trees with large leaves distributed at random through the field • Half subjects put into field where heights varied, other half where heights were constant • Asked to move around field and count number of diseased plants • More complex task also given
Design Virtual field Virtual lab
Design(2) • 20 subjects in total, between factorial design used within 5 subjects in each condition • 15 male subjects, no subject had involvement in research or knowledge of purpose • 150 trees in each scene, randomly distributed in a garden of dimension 90m-75 • Each tree had 16 leaves • A healthy one • One bad leaf • 4 bad leaves
Procedure • When initially put HMD on subjects were placed in virtual lab • Carried out initial training tasks “in the lab” • Instructed to turn head, bend down, e.t.c to realise these actions were possible • Then went through door into field of plants and told to carry out tasks • 3 minutes time limit stated beforehand • Then returned to lab, removed HMD and questionnaires administered
Explanatory Variables • Background information: gender and occupation • Pitch in degrees/sec • Yaw in degrees/sec • Roll in degrees/sec • Mean and standard deviation of hand height above ground level
Results • Body movement • Variation of body height (bending and standing) • Degree of head colation • ‘Tree height’ main source of variation for body movement, whereas task main source of variation for head colation • Low variation tree field - no bending down but considerable head movement. • Average head movement not significant between 2 tree groups – major difference was overall body movement • Body movement measured by hand height
Results 2 Note: The differences within each pair of Task means are significant on a t test at 5% on 18 df),
Analysis • Task not as significant as interaction between gender and task • Significant relationship between presence and body movement variables • Positively associated with yaw • Negatively associated with vertical variation
Conclusion • Presence likely to be positively associated with amount of body movement • Results of impact of type of task inconclusive
Walking>Walking in-Place>Flying in Virtual Environment • Previous Study: • Slater et.al 1995 • Walking-in-Place Vs push button flying • Virtual treadmill • Neural Networks to analyze the tracked head motion • Gains: • Virtual Walking has higher subjective sense of presence than push button flying.
Current Project Hypothesis: Real walking results in higher sense of presence • Current Study: • Add Real Walking • Use Wide area tracker • Enhanced Graphics & Avatar representation • Objectives: • Do Results of previous study hold true given more recent technology? • To compare Virtual walking, Real Walking & flying with respect to ease of Locomotion & subjective presence.
Terminologies • Flying: • Flying is done in the direction of gaze to make the Flyer & Virtual walker groups match. • Virtual Walking: • Participants reproduce the physical head motion generated during actual walking, but without physical locomotion • Real Walking: • Participants are free to walk around in the entire Virtual scene as in real.
Real Walking Implemented • Implementing Virtual Walking: • Track user’s head & one hand using a custom optical tracker • Track over a range of 10m x 4m with millimeter precision • Two optical sensors view infrared LED’s on ceiling. • Tracked Position & Orientation updated every 1.5kHz • Tracker latency of 25ms, total latency 100mm • Problems: • Watch the cables!!
How does the world look like? • The Virtual World • Divide tracked place into a training & experimental area. (room with the virtual pit) • Modern Graphics Engine, 40000 polygons • More Detailed Avatar, 11000 polygons • Radiosity lighting & texture for almost half the polygons • Subjects looking down can see their virtual body, feet, untracked left hand & tracked right hand.
The task • In the training room: • Instructions given to • Travel to a certain point along the corridor • Grasp virtual objects • In the experiment room • Walk to the chair
The Experiment • Technology • Silicon, Onyx2 with 1 graphic pipeline, two raster managers. • Four 195Mhz R10000 processors, 2GB main memory. • Scene Rendered using OpenGL, frame rate 30Hz stereo • Viewing by V8 Head Mounted Display with VGA resolution (640x3) x 480 • Display consists of two1.3 inch active LCD
Experiment 2 • Input • Joystick with four buttons, two were used in experiment, tracked by ceiling tracker. • Participants • 33 ‘naive’ subjects, grouped into virtual walkers, real walkers, flyers. 5 women, 6 men. & 11 ‘expert ’ subjects, 10 men, 1 woman • Questionnaires • Simulation sickness questionnaires • Presence questionnaires • Oral sessions
Conclusions & Results • Conclusions • Confirm that presence is highly correlated with degree of association with virtual body. • Presence is higher for real walkers than for virtual walkers & flyers. • Locomotion
Results 2 • Subjective Presence • No significance difference in all groups • Association with virtual body, directly related to rating of presence • Females have higher sense of presence than males (play less video games) • For flyers & virtual walkers higher discomfort is created by less sense of present but not the case for real walkers
Improvements • Cables are unsatisfactory, currently working on wireless • Real walkers are best for human scale space but not cheap • Replace flying with virtual walking, when presence is important, & inexpensive to implement • Avatar realism, worth investing on • Clothing identification very important for some • Investigate voice location e.g. give instructions through HMD.
The concept of Presence “Perceptual illusion of non-mediation” Lombard and Ditton The extent to which the person fails to perceive or acknowledge the existence of a medium during a technologically mediated experience.
Presence “when the individual fails to perceive the medium throughout a technologically mediated experience..”
Types of Presence The sense of presence has been studied as some Type of Presence: Physical: Feeling of been located somewhere (else). Social: Feeling of been (and communicate) together.
Determinants of presence • The extent and fidelity of sensory information. • The match between sensors and displays • Content factor • User characteristics In order to improve the sense of presence we analyze the Factors that encourage or discourage the feeling of “being there”
The extent and fidelity of sensory information • the ability of a technology to produce a sensorially rich mediated environment. • the amount of useful and salient sensory information presented in a consistent manner to the appropriate senses of the user.
The match between sensors and displays Refers to the sensory-motor contingencies, i.e. the mapping between the user’s actions and the perceptible spatio-temporal effects of those actions. For example, using head tracking, a turn of the user’s head should result in a corresponding real-timeupdate of the visual and auditory display.
Content factor Our ability to interact with the content and to modify it • objects, actors, and events represented by the medium • the user’s representation or virtual body in the VE • autonomy of the environment, i.e.the extent to which objects and actors (e.g. agents) exhibit a range of autonomous behaviors • Social elements, such as the acknowledgement of the user through thereactions of other actors, virtual or real, will be important for establishing a sense of social presence15
User characteristics • the user’s perceptual, cognitive and motor abilities (e.g. stereoscopic acuity, susceptibility to motion sickness, concentration) • prior experience with and expectations towards mediated experiences • willingness to suspend disbelief • various mental health conditions, like depression, anxiety, or psychotic disorders, are also likely to affect an individuals sense of presence
