CLASS ASSIGNMENTS

1
CLASS ASSIGNMENTS

• Project
• 40 persons ? 7 groups of 5/6
• Own project

2
Project (groups of 5/6)

• Initial report 1 page
• List of group
• Which techniques
• How evaluation
• Final report 15 pages
• Problem
• VR concepts
• Implementation and Results
• Conclusion
• Class presentation

3
Projects

• 1. Mapping 6DoF to 2DoF
• 2. Primary Depth Cues Evaluation
• 3. Secondary Depth Cues Evaluation
• 4. Point Location Task Evaluation
• 5. Space Ball Device Evaluation
• 6. Gyration Device Evaluation
• 7.

4
Own project (groups of min 3)

• Initial report 1 page
• List of group
• Problem
• Approach and Evaluation
• Final report 10 pages
• Problem
• VR concepts
• Implementation and Results
• Conclusion
• Class presentation

5
Nine Lectures

• Introduction
• Human factors
• Interaction 1 (basic interaction)
• Interaction 2 (two handed interaction)
• Tracking
• Haptics and Auditory Systems
• Distributed / Collaborative / Telepresence
• Augmented Reality
• Usability

6
Introduction

• Models of interaction
• Constraints
• Types of interaction
• Types of device
• Basic Interaction
• Locomotion
• Body-Centred Interaction Proprioception
• Selection Manipulation

7
1. Models of Interaction

• Virtual Reality Model
• The user is using their body as an interface to
  the world
• The system responds to everything they do or say
• Extended Desktop Model
• The user needs tools to do 3D tasks

8
Virtual Reality Model

• Need to track the user precisely and interpret
  what they do
• Focus is on users exploring the environment
• Tension between realistic and non-realistic
  responses of the environment
• Mundane are where the world responds as if it was
  controlled by laws of physics
• Magical are everything else (automatic doors,
  objects in vacuum, etc)

9
Limits of VR Model

• Cant track user over very large areas
• e.g. Some form of locomotion metaphor will be
  required for long distance travel
• Physical constraints of systems
• Limited precision and tracking points
• Lack of physical force feedback

10
Extended Desktop Model

• Focus on analysing a task and creating devices
  that fit the task
• Study ergonomics of the device and
  applicability/suitability for the role

11
Limits of ED Model

• 3D tasks are quite complicated to perform
• Tasks can become very specialised
• Leads to a proliferation of physical (and
  virtual) devices

Fakespace Cubic Mouse
12
Types of Physical Devices
3DConnexion Spacemouse
Polhemus Isotrak 3-Ball
Logitech 3D Mouse
Ascension Wanda
3DConnexion Spaceball
Inition 3DiStick
13
Types of Physical Devices

• Wands with 6 DoF sensor
• 3-4 buttons
• 2D joystick

14
Input Devices

• 6DOF position tracking systems
• Head tracking
• Hand(s) tracking

15
Logical Input Types

• Continuous functions
• Wand joystick (x -1, 1, y -1, 1)
• Tracked position (x, y, z)
• Tracked orientation (h, p, r)

• Discrete events
• Wand buttons (on off)

16
Virtual Devices
17
The Problem

• How does one map a particular input device into a
  particular virtual device?
• How to start/stop the interaction
• How to drive the interaction

Inputdevices
Virtual devices
f - ?
18
Basic interaction tasks
User
Object
Translate
Rotate
Scale
19
Basic Math

• Coordinate systems
• nodes
• Transformations between coordinate systems
• Links
• Notation
• PW TWO PO
• TRW TWO TRO

20
Basic Math Grabbing

• Object-hand transform
• TOWTWRTRTTTH

21
2. Basic Interaction Tasks

• Locomotion
• How to effect movement through the space
• Selection
• How to indicate an object of interest
• Manipulation
• How to move an object of interest

22
Locomotion

• User points (somehow) in the direction of motion
• User presses a button

23
Selection and Manipulation

• User points at object with their hand
• User selects by pressing a button
• User grabs by pressing 2nd button
• Object is rigidly attached to hand coordinate
  system

24
Selection Only

• Occlusion selection
• Similar to selection with a mouse
• Put hand over object (occlude it) to select it

25
3. Locomotion

• Travel in Immersive Virtual Environments An
  Evaluation of Viewpoint Motion Control
  Techniques, Bowman, Koller and Hodges
• One of the first rigorous studies of some of the
  trade-offs between different travel techniques

26
Taxonomy of Travel
Bowman, Koller and Hodges
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Quality Factors

• 1. Speed (appropriate velocity)
• 2. Accuracy (proximity to the desired target)
• 3. Spatial Awareness (the users implicit
  knowledge of his position and orientation within
  the environment during and after travel)
• 4. Ease of Learning (the ability of a novice user
  to use the technique)
• 5. Ease of Use (the complexity or cognitive load
  of the technique from the users point of view)
• 6. Information Gathering (the users ability to
  actively obtain information from the environment
  during travel)
• 7. Presence (the users sense of immersion or
  being within the environment)

28
Experiment 1

• Absolute motion task
• Gaze v. Point AND constrained v. unconstrained
• Bowman claimed expected gaze to be better
• Neck muscles are more stable
• More immediate feedback
• Eight subjects, each doing four times 80 trials
  (five times 4 distances to target, four target
  sizes)

29
Experiment 1

• No difference between techniques
• Significant factors were target distance and size

30
Experiment 1

• No difference between techniques
• Significant factors were target distance and size

31
Experiment 2

• Relative motion task
• No prior expectation
• Need forward and reverse direction
• Nine subjects, four sets of 20 trials

32
Experiment 2

• Obvious difference
• Cant point at target and look departure point
  simultaneously

Bowman, Koller and Hodges
33
Summary of 1st Two Experiments
34
Experiment 3

• Testing spatial awareness based on four travel
  variations
• Constant speed (slow)
• Constant speed (fast)
• Variable speed (smooth acceleration)
• Jump (instant translation)
• Concern is that jumps and other fast transitions
  confuse users

35
Experiment 3

• However, there was no main effect
• What does this tell us?

36
4. Body-Centred Interaction

• Proprioception is defined by Oliver Sacks as "...
  that continuous but unconscious sensory flow from
  the movable parts of our body (muscles, tendons,
  joints), by which their position and tone and
  motion is continually monitored and adjusted, but
  in a way which is hidden from us because it is
  automatic and unconscious
• Proprioception is a resource for us to exploit in
  designing virtual reality interfaces

37
Body-Centred Interaction

• Participants can use their own body
• Can estimate distances
• Can perform actions without looking
• If we render that body (or other sufficient
  feedback), then user can identify the interaction
  metaphors with their own body

38
BCI Examples

• Walking on the spot
• Head motion has a characteristic motion when the
  user walk on the spot
• Physically closer to the real action
• Self-scaling
• Using gestures to scale ones own body as a way
  of re-scaling the world

39
5. Selection and Manipulation

• Moving Objects In Space Exploiting
  Proprioception In Virtual-Environment
  Interaction, Mine, Brooks Jr. and Sequin
• One of the first papers to discuss a range of
  selection and manipulation tasks

40
Body-Relative Interaction

• Provides
• Physical frame of reference in which to work
• More direct and precise sense of control
• Eyes off interaction
• Enables
• Direct object manipulation (for sense of position
  of object)
• Physical Mnemonics (objects fixed relative to
  body)
• Gestural Actions (invoking commands)

41
Working within Arms Reach

• Provides more direct mapping between hand motion
  and object motion
• Provides finer angular precision of motion
• Automatic scaling mechanism developed, so user
  can interact with objects lying at any distance
  as though in arms reach
• user doesnt always notice scaling

42
Scaled-World Grab for Manipulation

• Automatically scale world, so that selected
  object is within arms reach
• Near and far objects easily moved

43
Mine, Brooks Jr, Sequin
44
Previous Techniques

• Ray-Based
• Ray is centred on users hand
• All manipulations are relative to hand motion
• Translation in beam direction is hard
• Rotation in local object coordinates is nearly
  impossible

Mark Mine, http//www.cs.unc.edu/mine/isaac.html
45
Previous Techniques

• Object-Centred
• Select with ray as before
• Local movements of hand are copied to object
  local coordinates

Mark Mine, http//www.cs.unc.edu/mine/isaac.html
46
Scaled-World Grab for Locomotion

• User transports himself by grabbing an object in
  the desired travel direction and pulling himself
  towards it
• User can view the point of interest from all
  sides very simply
• For exploration of nearby objects, virtual
  walking is more suitable while going much
  further, invoking a separate scaling operation or
  switch to an alternate movement mode is better

47
Physical Mnemonics

• Storing of virtual objects and controls relative
  to users body
• Pull-down menus
• Hand-held widgets
• Field of View-Relative mode switching

48
Pull-Down Menus

• Problems with virtual menus
• Heads-up are difficult to manage
• Fixed in world often get lost
• Could enable menu with ..
• Virtual button (too small)
• Physical button (low acceptability)
• Instead hide menus around the body, e.g. above
  FOV

49
Hand-Held Widgets

• Hold controls in hands, rather than on objects
• User relative motion of hands to effect widget
  changes

50
FOV-Relative Mode Switching

• Change behaviour depending on whether a limb is
  visible
• Hand visible, use occlusion selection
• Hand not visible, use ray selection

51
Gestural Actions

• Head butt zoom
• Look at Menus
• Two handed flying
• Over the shoulder deletion

52
Experiment 1

• Align docking cube with target cube as quickly as
  possible
• Comparing three manipulation techniques
• Object in hand
• Object at fixed distance
• Object at variable distance (scaled by arm
  extension)

53
Experiment 1

• 18 subjects
• In hand was significantly faster

Mine, Brooks Jr, Sequin
54
Experiment 2

• Virtual widget comparison
• Comparing
• Widget in hand
• Widget fixed in space
• 18 subjects (as before)
• Performance measured by accuracy not time

55
Experiment 2

• Widget in hand was significantly better

Mine, Brooks Jr, Sequin
56
Other Work

• Still an active field
• Shadow cone
• Shadow-based interaction
• Worlds in miniature
• Voodoo dolls
• Etc

57
Summary

• A lot of work has been done and is being done in
  3D interaction
• Covered locomotion and selection manipulation
• However it is still quite tedious to use most 3D
  user interfaces
• Lack of precision is probably main problem
• However, people are able to interact

58
Two-Handed Input

• Exploits the relationship between dominant and
  non-dominant hands

Cooperative Bimanual Action, Hinckley et al., CHI
1997
Personal Interaction Panel, Vienna University of
Technology