Virtual Environments Week 9 Seminar Presence Presence Presence
- Slides: 33
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 90 m-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 Variable( Tree 1 /s) (low) Tree 2 (high) Task Level 1 (simple) Task Level 2 (complex) Pitch Mean=3. 4 sd=1. 4 Mean =3. 3 sd =1. 4 Mean= 3. 7, sd = Mean = 5. 1 Sd = 1. 1 0. 9 Yaw Mean=12. 3 Mean=10. 1 Mean=9. 4 Sd=3. 7 Sd=3. 5 Sd=3. 3 Mean=13. 0 Sd=3. 1 Roll Mean=13. 5 Mean=11. 2 Mean=2. 6 Sd = 4. 1 Sd=3. 7 Sd=0. 7 Mean=4. 0 Sd=1. 7 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 10 m x 4 m with millimeter precision – Two optical sensors view infrared LED’s on ceiling. – Tracked Position & Orientation updated every 1. 5 k. Hz – Tracker latency of 25 ms, total latency 100 mm • 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
How does the world look like?
The Experiment • Technology – Silicon, Onyx 2 with 1 graphic pipeline, two raster managers. – Four 195 Mhz R 10000 processors, 2 GB main memory. – Scene Rendered using Open. GL, frame rate 30 Hz stereo – Viewing by V 8 Head Mounted Display with VGA resolution (640 x 3) x 480 – Display consists of two 1. 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 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 match between sensors and displays Content factor User characteristics
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. • Social elements, such as the acknowledgement of the user through the reactions of other actors, virtual or real, will be important for establishing a sense of social presence 15 agents) exhibit a range of autonomous behaviors
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
Relationship between presence factors
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