2022 COMP4010 Lecture4: AR Interaction
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Lecture 4 in the 2022 COMP 4010 lecture series on AR/VR. This lecture is about AR Interaction techniques. This was taught by Mark Billinghurst at the University of South Australia in 2022.
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2022 COMP4010 Lecture4: AR Interaction
- 1. AR INTERACTION COMP 4010 Lecture Four Mark Billinghurst August 18th 2022 mark.billinghurst@unisa.edu.au
- 2. REVIEW
- 3. AR RequiresTracking and Registration • Registration • Positioning virtual object wrt real world • Fixing virtual object on real object when view is fixed • Calibration • Offline measurements • Measure camera relative to head mounted display • Tracking • Continually locating the user’s viewpoint when view moving • Position (x,y,z), Orientation (r,p,y)
- 4. Sources of Registration Errors •Static errors • Optical distortions (in HMD) • Mechanical misalignments • Tracker errors • Incorrect viewing parameters •Dynamic errors • System delays (largest source of error) • 1 ms delay = 1/3 mm registration error
- 5. Reducing Static Errors •Distortion compensation • For lens or display distortions •Manual adjustments • Have user manually alighn AR andVR content •View-based or direct measurements • Have user measure eye position •Camera calibration (video AR) • Measuring camera properties
- 6. Reducing dynamic errors (1) •Reduce system lag •Faster components/system modules •Reduce apparent lag •Image deflection •Image warping
- 7. TRACKING
- 8. Frames of Reference • Word-stabilized • E.g., billboard or signpost • Body-stabilized • E.g., virtual tool-belt • Screen-stabilized • Heads-up display
- 9. Tracking Requirements • Augmented Reality Information Display • World Stabilized • Body Stabilized • Head Stabilized Increasing Tracking Requirements Head Stabilized Body Stabilized World Stabilized
- 10. Tracking Technologies § Active • Mechanical, Magnetic, Ultrasonic • GPS, Wifi, cell location § Passive • Inertial sensors (compass, accelerometer, gyro) • Computer Vision • Marker based, Natural feature tracking § Hybrid Tracking • Combined sensors (eg Vision + Inertial)
- 12. Why Optical Tracking for AR? • Many AR devices have cameras • Mobile phone/tablet, Video see-through display • Provides precise alignment between video and AR overlay • Using features in video to generate pixel perfect alignment • Real world has many visual features that can be tracked from • Computer Vision well established discipline • Over 40 years of research to draw on • Old non real time algorithms can be run in real time on todays devices
- 13. Common AR Optical Tracking Types • Marker Tracking • Tracking known artificial markers/images • e.g. ARToolKit square markers • Markerless Tracking • Tracking from known features in real world • e.g. Vuforia image tracking • Unprepared Tracking • Tracking in unknown environment • e.g. SLAM tracking
- 14. Marker Based Tracking: ARToolKit http://www.artoolkit.org
- 15. Natural Feature Tracking • Use Natural Cues of Real Elements • Edges • Surface Texture • Interest Points • Model or Model-Free • No visual pollution Contours Features Points Surfaces
- 16. Detection and Tracking Detection Incremental tracking Tracking target detected Tracking target lost Tracking target not detected Incremental tracking ok Start + Recognize target type + Detect target + Initialize camera pose + Fast + Robust to blur, lighting changes + Robust to tilt Tracking and detection are complementary approaches. After successful detection, the target is tracked incrementally. If the target is lost, the detection is activated again
- 17. Marker vs.Natural FeatureTracking • Marker tracking • Usually requires no database to be stored • Markers can be an eye-catcher • Tracking is less demanding • The environment must be instrumented • Markers usually work only when fully in view • Natural feature tracking • A database of keypoints must be stored/downloaded • Natural feature targets might catch the attention less • Natural feature targets are potentially everywhere • Natural feature targets work also if partially in view
- 18. Model BasedTracking • Tracking from 3D object shape • Example: OpenTL - www.opentl.org • General purpose library for model based visual tracking
- 19. Tracking from an Unknown Environment • What to do when you don’t know any features? • Very important problem in mobile robotics - Where am I? • SLAM • Simultaneously Localize And Map the environment • Goal: to recover both camera pose and map structure while initially knowing neither. • Mapping: • Building a map of the environment which the robot is in • Localisation: • Navigating this environment using the map while keeping track of the robot’s relative position and orientation
- 20. Parallel Tracking and Mapping Tracking Mapping New keyframes Map updates + Estimate camera pose + For every frame + Extend map + Improve map + Slow updates rate Parallel tracking and mapping uses two concurrent threads, one for tracking and one for mapping, which run at different speeds
- 21. Parallel Tracking and Mapping Video stream New frames Map updates Tracking Mapping Tracked local pose FAST SLOW Simultaneous localization and mapping (SLAM) in small workspaces Klein/Drummond, U. Cambridge
- 22. Visual SLAM • Early SLAM systems (1986 - ) • Computer visions and sensors (e.g. IMU, laser, etc.) • One of the most important algorithms in Robotics • Visual SLAM • Using cameras only, such as stereo view • MonoSLAM (single camera) developed in 2007 (Davidson)
- 23. Combining Sensors andVision • Sensors • Produces noisy output (= jittering augmentations) • Are not sufficiently accurate (= wrongly placed augmentations) • Gives us first information on where we are in the world, and what we are looking at • Vision • Is more accurate (= stable and correct augmentations) • Requires choosing the correct keypoint database to track from • Requires registering our local coordinate frame (online- generated model) to the global one (world)
- 24. ARKit – Visual Inertial Odometry • Uses both computer vision + inertial sensing • Tracking position twice • Computer Vision – feature tracking, 2D plane tracking • Inertial sensing – using the phone IMU • Output combined via Kalman filter • Determine which output is most accurate • Pass pose to ARKit SDK • Each system compliments the other • Computer vision – needs visual features • IMU - drifts over time, doesn’t need features
- 25. ARKit –Visual Inertial Odometry • Slow camera • Fast IMU • If camera drops out IMU takes over • Camera corrects IMU errors
- 26. Conclusions • Tracking and Registration are key problems • Registration error • Measures against static error • Measures against dynamic error • AR typically requires multiple tracking technologies • Computer vision most popular • Research Areas: • SLAM systems, Deformable models, Mobile outdoor tracking
- 28. Augmented Reality technology • Combines Real and Virtual Images • Needs: Display technology • Interactive in real-time • Needs: Input and interaction technology • Registered in 3D • Needs: Viewpoint tracking technology
- 29. How Do You Design an Interface for This?
- 30. AR Interaction • Designing AR Systems = Interface Design • Using different input and output technologies • Objective is a high quality of user experience • Ease of use and learning • Performance and satisfaction
- 31. Typical Interface Design Path 1/ Prototype Demonstration 2/ Adoption of Interaction Techniques from other interface metaphors 3/ Development of new interface metaphors appropriate to the medium 4/ Development of formal theoretical models for predicting and modeling user actions Desktop WIMP Virtual Reality Augmented Reality
- 32. Interacting with AR Content • You can see spatially registered AR.. how can you interact with it?
- 33. Different Types of AR Interaction • Browsing Interfaces • simple (conceptually!), unobtrusive • 3D AR Interfaces • expressive, creative, require attention • Tangible Interfaces • Embedded into conventional environments • Tangible AR • Combines TUI input + AR display
- 34. AR Interfaces as Data Browsers • 2D/3D virtual objects are registered in 3D • “VR in Real World” • Interaction • 2D/3D virtual viewpoint control • Applications • Visualization, training
- 35. AR Information Browsers • Information is registered to real-world context • Hand held AR displays • Interaction • Manipulation of a window into information space • Applications • Context-aware information displays Rekimoto, et al. 1997
- 38. Current AR Information Browsers • Mobile AR • GPS + compass • Many Applications • Wikitude • Yelp • Google maps • …
- 39. Example: Google Maps AR Mode • AR Navigation Aid • GPS + compass, 2D/3D object placement
- 41. Advantages and Disadvantages • Important class of AR interfaces • Wearable computers • AR simulation, training • Limited interactivity • Modification of virtual content is difficult Rekimoto, et al. 1997
- 42. 3D AR Interfaces • Virtual objects displayed in 3D physical space and manipulated • HMDs and 6DOF head-tracking • 6DOF hand trackers for input • Interaction • Viewpoint control • Traditional 3D user interface interaction: manipulation, selection, etc. Kiyokawa, et al. 2000
- 43. AR 3D Interaction (2000)
- 46. Advantages and Disadvantages • Important class of AR interfaces • Entertainment, design, training • Advantages • User can interact with 3D virtual object everywhere in space • Natural, familiar interaction • Disadvantages • Usually no tactile feedback • User has to use different devices for virtual and physical objects Oshima, et al. 2000
- 47. 3. Augmented Surfaces and Tangible Interfaces • Basic principles • Virtual images are projected on a surface • Physical objects are used as controls for virtual objects • Support for collaboration Wellner, P. (1993). Interacting with paper on the DigitalDesk. Communications of the ACM, 36(7), 87-96.
- 48. Augmented Surfaces • Rekimoto, et al. 1999 • Front projection • Marker-based tracking • Multiple projection surfaces • Object interaction Rekimoto, J., & Saitoh, M. (1999, May). Augmented surfaces: a spatially continuous work space for hybrid computing environments. In Proceedings of the SIGCHI conference on Human Factors in Computing Systems (pp. 378-385).
- 49. Augmented Surfaces Demo (1999) https://www.youtube.com/watch?v=r4g_fvnjVCA
- 50. Tangible User Interfaces (Ishii 97) • Create digital shadows for physical objects • Foreground • graspable UI • Background • ambient interfaces
- 51. Tangible Interfaces - Ambient • Dangling String • Jeremijenko 1995 • Ambient ethernet monitor • Relies on peripheral cues • Ambient Fixtures • Dahley, Wisneski, Ishii 1998 • Use natural material qualities for information display
- 52. Tangible Interface: ARgroove • Collaborative Instrument • Exploring Physically Based Interaction • Map physical actions to Midi output • Translation, rotation • Tilt, shake
- 54. ARgroove in Use
- 55. Visual Feedback •Continuous Visual Feedback is Key •Single Virtual Image Provides: • Rotation • Tilt • Height
- 56. i/O Brush (Ryokai, Marti, Ishii) - 2004 Ryokai, K., Marti, S., & Ishii, H. (2004, April). I/O brush: drawing with everyday objects as ink. In Proceedings of the SIGCHI conference on Human factors in computing systems (pp. 303-310).
- 57. i/O Brush Demo (2005) https://www.youtube.com/watch?v=04v_v1gnyO8
- 58. Many Other Examples • Triangles (Gorbert 1998) • Triangular based story telling • ActiveCube (Kitamura 2000-) • Cubes with sensors • Reactable (2007- ) • Cube based music interface
- 59. Lessons from Tangible Interfaces • Physical objects make us smart • Norman’s “Things that Make Us Smart” • encode affordances, constraints • Objects aid collaboration • establish shared meaning • Objects increase understanding • serve as cognitive artifacts
- 60. But There are TUI Limitations • Difficult to change object properties • can’t tell state of digital data • Limited display capabilities • projection screen = 2D • dependent on physical display surface • Separation between object and display • ARgroove – Interact on table, look at screen
- 61. Advantages and Disadvantages •Advantages • Natural - user’s hands are used for interacting with both virtual and real objects. • No need for special purpose input devices •Disadvantages • Interaction is limited only to 2D surface • Full 3D interaction and manipulation is difficult
- 62. Orthogonal Nature of Interfaces 3D AR interfaces Tangible Interfaces Spatial Gap No – Interaction is Everywhere Yes – Interaction is only on 2D surfaces Interaction Gap Yes – separate devices for physical and virtual objects No – same devices for physical and virtual objects
- 63. Orthogonal Nature of Interfaces 3D AR interfaces Tangible Interfaces Spatial Gap No – Interaction is Everywhere Yes – Interaction is only on 2D surfaces Interaction Gap Yes – separate devices for physical and virtual objects No – same devices for physical and virtual objects
- 64. 4. Tangible AR: Back to the Real World • AR overcomes display limitation of TUIs • enhance display possibilities • merge task/display space • provide public and private views • TUI + AR = Tangible AR • Apply TUI methods to AR interface design Billinghurst, M., Kato, H., & Poupyrev, I. (2008). Tangible augmented reality. ACM Siggraph Asia, 7(2), 1-10.
- 65. Space vs. Time - Multiplexed • Space-multiplexed • Many devices each with one function • Quicker to use, more intuitive, clutter • Real Toolbox • Time-multiplexed • One device with many functions • Space efficient • mouse
- 66. Tangible AR: Tiles (Space Multiplexed) • Tiles semantics • data tiles • operation tiles • Operation on tiles • proximity • spatial arrangements • space-multiplexed Poupyrev, I., Tan, D. S., Billinghurst, M., Kato, H., Regenbrecht, H., & Tetsutani, N. (2001, July). Tiles: A Mixed Reality Authoring Interface. In Interact (Vol. 1, pp. 334-341).
- 67. Space-multiplexed Interface Data authoring in Tiles
- 70. Tangible AR: Time-multiplexed Interaction • Use of natural physical object manipulations to control virtual objects • VOMAR Demo • Catalog book: • Turn over the page • Paddle operation: • Push, shake, incline, hit, scoop Kato, H., Billinghurst, M., Poupyrev, I., Imamoto, K., & Tachibana, K. (2000, October). Virtual object manipulation on a table-top AR environment. In Proceedings IEEE and ACM International Symposium on Augmented Reality (ISAR 2000) (pp. 111-119). IEEE.
- 71. VOMAR Interface
- 73. Advantages and Disadvantages •Advantages • Natural interaction with virtual and physical tools • No need for special purpose input devices • Spatial interaction with virtual objects • 3D manipulation with virtual objects anywhere in space •Disadvantages • Requires Head Mounted Display
- 74. 5. Natural AR Interfaces • Goal: • Interact with AR content the same way we interact in the real world • Using natural user input • Body motion • Gesture • Gaze • Speech • Input recognition • Nature gestures, gaze • Multimodal input FingARtips (2004) Tinmith (2001)
- 75. External Fixed Cameras • Overhead depth sensing camera • Capture real time hand model • Create point cloud model • Overlay graphics on AR view • Perform gesture interaction Billinghurst, M., Piumsomboon, T., & Bai, H. (2014). Hands in space: Gesture interaction with augmented-reality interfaces. IEEE computer graphics and applications, 34(1), 77-80.
- 77. Head Mounted Cameras • Attach cameras/depth sensor to HMD • Connect to high end PC • Computer vision capture/processing on PC • Perform tracking/gesture recognition on PC • Use custom tracking hardware • Leap Motion (Structured IR) • Intel RealSense (Stereo depth) Project NorthStar (2018) Meta2 (2016)
- 78. Project NorthStar Hand Interaction
- 79. Self Contained Systems • Sensors and processors on device • Fully mobile • Customized hardware/software • Example: Hololens 2 (2019) • 3D hand tracking • 21 points/hand tracked • Gesture driven interface • Constrained set of gestures • Multimodal input (gesture, gaze, speech)
- 80. Hololens 2 Gesture Input Demo (MRTK) https://www.youtube.com/watch?v=qfONlUCSWdg
- 81. Speech Input • Reliable speech recognition • Windows speech, Watson, etc. • Indirect input with AR content • No need for gesture • Match with gaze/head pointing • Look to select target • Good for Quantitative input • Numbers, text, etc. • Keyword trigger • “select”, ”hey cortana”, etc https://www.youtube.com/watch?v=eHMkOpNUtR8
- 82. Eye Tracking Interfaces • Use IR light to find gaze direction • IR sources + cameras in HMD • Support implicit input • Always look before interact • Natural pointing input • Multimodal Input • Combine with gesture/speech Camera IR light IR view Processed image Hololens 2
- 84. Evolution of AR Interfaces Tangible AR Tangible input AR overlay Direct interaction Natural AR Freehand gesture Speech, gaze Tangible UI Augmented surfaces Object interaction Familiar controllers Indirect interaction 3D AR 3D UI Dedicated controllers Custom devices Browsing Simple input Viewpoint control Expressiveness, Intuitiveness
- 86. Interaction Design “Designing interactive products to support people in their everyday and working lives” Preece, J., (2002). Interaction Design • Design of User Experience with Technology
- 87. Bill Verplank on Interaction Design https://www.youtube.com/watch?v=Gk6XAmALOWI
- 88. •Interaction Design involves answering three questions: •What do you do? - How do you affect the world? •What do you feel? – What do you sense of the world? •What do you know? – What do you learn? Bill Verplank
- 89. Typical Interaction Design Cycle Develop alternative prototypes/concepts and compare them, And iterate, iterate, iterate....
- 90. PROTOTYPING
- 91. How Do You Prototype This?
- 93. View Through Google Glass
- 101. Tom Chi’s Prototyping Rules 1. Find the quickest path to experience 2. Doing is the best kind of thinking 3. Use materials that move at the speed of thought to maximize your rate of learning
- 102. How can we quickly prototype XR experiences with little or no coding?
- 103. Prototyping in Interaction Design Key Prototyping Steps
- 104. ● Quick visual design ● Capture key interactions ● Focus on user experience ● Communicate design ideas ● “Learn by doing/experiencing” Why Prototype?