COMP4076 / GV07 - Virtual Environments: Tracking and Interaction Wole Oyekoya Department of Computer Science University College London w.oyekoya@cs.ucl.ac.uk http://www.cs.ucl.ac.uk/teaching/VE
Outline • Introduction • Models of Interaction • Interaction Methods
Introduction • Introduction • Models of Interaction • Interaction Methods
Tracking and Interaction User Synthetic User Environment Computer Input Devices Tracking and Real interaction happens Environment here
Basic Components of an Interface • The input devices captures user actions • Transfer functions / control-display mappings / interaction techniques – Map the movement of the device into the movement of the controlled elements – Isomorphic: one-to-one mapping between motions in the physical and virtual worlds – Non-isomorphic: input is shifted, scaled, integrated, … • The display devices present the effects of the input to the user
What Are the Basic Interaction Tasks? • Locomotion or Travel – How to move through the space • Selection – How to indicate an object of interest • Manipulation – How to change properties of an object of interest • Symbolic – How to enter text and other parameters Won’t be • System control covered in this – How to change the way the system is behaving lecture
Challenges in Designing Metaphors? • Designing interaction metaphors for virtual environments is hard: – Six degrees of freedom • Lack of appropriate input devices – Isolated parts of body tracked – Boxing glove or fishing rod style of interaction metaphors • Divide and conquer the problem by identifying basic models of interaction
Models of Interaction • Introduction • Models of Interaction • Interaction Methods
Models of Interaction • Extended Desktop Model – The computer generates a 3D version of the familiar desktop – The user needs tools to do 3D tasks • Virtual Reality Model – The user’s body is an interface to the world – The system responds to everything they do or say
Extended Desktop Model • The desktop is now in 3D • It can extend beyond the boundaries of the computer screen itself • However, the user: – is not part of the scene – has a “God’s eye view”
Interaction in the Extended Desktop • Focus on analysing a task and creating devices that fit the task • Study ergonomics of the device and applicability/suitability for the role • Special-purpose devices can be developed to support interaction
2D Interaction in a 3D World: Google Earth
Modelling Package (3D Studio Max)
Types of Device to Enable 3D Interaction Polhemus Isotrak 3-Ball 3DConnexion Spacemouse 3DConnexion Spaceball Logitech 3D Mouse Inition 3DiStick Nintendo Wii Remote Ascension Wanda
GlobeFish and GlobeMouse
Limitations of the Extended Desktop Model • 3D tasks can be quite complicated to perform • Tasks can become very specialised – Counterintuitive – Requires a lot of user training Fakespace Cubic Mouse
Virtual Reality Model • Track the user as they move through a genuine 3D space • Need to track the user precisely and interpret what they do • Focus is on users exploring the environment
Interaction in the Virtual Reality Model • Tension between isomorphic and non-isomorphic movements – Isomorphic: one-to-one mapping between motions in the physical and virtual worlds – Non-isomorphic: input is shifted, scaled, integrated, … • Tension between mundane and magical responses of the environment – Mundane are where the dynamics are governed by the familiar laws of physics (Newtonian mechanics) – Magical are everything else (casting spells, automatic doors, etc…)
Body-Relative Interaction Technique based on Proprioception • 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)
Hand-Held Widgets • Hold controls in hands, rather than on objects • User relative motion of hands to effect widget changes Mine, Brooks Jr, Sequin
Gestural Actions • Head – butt zoom • Look – at Menus • Two – handed flying • Over – the – shoulder deletion Mine, Brooks Jr, Sequin
Limitations of the Virtual Reality Model • Can’t track user over very large areas – E.g. Some form of locomotion metaphor will be required for long distance travel (see later) • Physical constraints of systems • Limited precision and tracking points • Lack of physical force feedback
Overcoming Lack of Force Feedback • One way to overcome lack of force feedback is to use a haptic device – Will be discussed in another lecture • Another approach is to exploit visual dominance in the interpretation of cues • CyberForce CyberGrasp
Visual Dominance • The real hand is not constrained in space • The virtual hand can be constrained in virtual space • Can the user detect the difference? “The Hand is Slower than the Eye: A quantitative exploration of visual dominance over proprioception Burns, Whitton, Razzaque, McCallus, Panter, Brooks
Visual Dominance Task: playing Simon game Drift between virtual and real hand gradually introduced over time
Summary of Interaction Methods • The extended desktop model: – Desktop extends beyond physical screen – Interactions and devices on a case-by-case basis – Potentially more accurate, but counterintuitive and specialised interaction • The virtual reality model: – User’s body input to system – Potentially more intuitive but more general – Greater reliance on ability to have natural movement and ability to track – Partially resolved using visual dominance for HMDs
Interaction Methods • Introduction • Models of Interaction • Interaction Methods
Basic Interaction Tasks • Locomotion or Travel – How to effect movement through the space • Selection – How to indicate an object of interest Logically • Manipulation grouped together – How to move an object of interest • Symbolic – How to enter text and other parameters Won’t be • System control covered in this – Change mode of interaction or system state lecture
Locomotion • Introduction • Models of Interaction • Interaction Methods – Locomotion or Travel Techniques – Selection and Manipulation
Purpose of Locomotion • Change the pose of the viewpoint (both position and attitude) from some start location A to some end location B • This is the most fundamental task for a virtual environment – Arguably if the user can’t change the pose of the viewpoint, it’s not really a virtual environment at all
Types of Travel Techniques • There are two fundamentally different types: • Virtual techniques: – The user’s body remains stationary even through the viewpoint moves • Physical techniques: – The user’s physical motion is used to transport the user through the virtual world
Virtual Locomotion Techniques • The user remains stationary even though the viewpoint moves • Techniques must be used to specify – Direction – Speed
Taxonomy of Virtual Locomotion Techniques Bowman, Koller and Hodges
Taxonomy of Virtual Locomotion Techniques Bowman, Koller and Hodges
Controlling Direction by Steering • Continuous specification of direction of motion • Direction can be specified by many means: – Gaze-directed – Pointing – Physical device (steering wheel, flight stick)
Steering Techniques • Gaze-based: – Actually uses head orientation – Cognitively simple – Cannot look around whilst travelling • Pointing-based: – Actually uses on hand orientation – Cognitively more complicated – Makes it possible to look in one direction whilst travelling in another – However, you can’t hold other objects or manipulate them whilst travelling
Target-Based Steering • Specify discrete target or goal • Multiple ways to specify the goal: – Point at object – Choose from list – Enter coordinates • Once specified, travel to the target is passive • Convenient way to get from A to B, but inflexible
Route-Based Steering • Generalisation of the target-based metaphor • User specifies multiple waypoints on a map • The system generates a path and passively moves the user along the path • Placement of waypoints controls granularity of movement
Taxonomy of Virtual Locomotion Techniques Bowman, Koller and Hodges
Two-Handed Velocity / Acceleration Selection • Line between hands defines direction of travel • Distance between hands specifies constant speed • Pinch glove gestures provide “nudges” Mine, Brooks Jr, Sequin
“Grabbing the Air” • Use hand gestures to move through the world • Metaphor is pulling a rope • Often implemented using pinch gloves • Physically occupies hands • Slow • Fatiguing
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