2016 AR Summer School Lecture2
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The second lecture from the Augmented Reality Summer School talk by Mark Billinghurst at the University of South Australia, February 15th - 19th, 2016. This provides an overview of AR Technology.
![Augmented Reality Definition
• Defining Characteristics [Azuma 97]
• Combines Real andVirtual Images
• Both can be seen at the same time
• Interactive in real-time
• The virtual content can be interacted with
• Registered in 3D
• Virtual objects appear fixed in space
Azuma, R. T. (1997). A survey of augmented reality. Presence, 6(4), 355-385.](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
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2016 AR Summer School Lecture2
- 1. LECTURE 2: AUGMENTED REALITY TECHNOLOGY Mark Billinghurst AR Summer School February 15th – 19th 2016 University of South Australia
- 2. Augmented Reality Definition • Defining Characteristics [Azuma 97] • Combines Real andVirtual Images • Both can be seen at the same time • Interactive in real-time • The virtual content can be interacted with • Registered in 3D • Virtual objects appear fixed in space Azuma, R. T. (1997). A survey of augmented reality. Presence, 6(4), 355-385.
- 3. Augmented RealityTechnology ! Combining Real and Virtual Images • Display technologies ! Interactive in Real-Time • Input and interactive technologies ! Registered in 3D • Viewpoint tracking technologies Display Processing Input Tracking
- 4. AR Displays
- 5. AR Displays e.g. window reflections Virtual Images seen off windows e.g. Reach-In Projection CRT Display using beamsplitter Not Head-Mounted e.g. Shared Space Magic Book Liquid Crystal Displays LCDs Head-Mounted Display (HMD) Primarily Indoor Environments e.g. WLVA and IVRD Cathode Ray Tube (CRT) or Virtual Retinal Display (VRD) Many Military Applications & Assistive Technologies Head-Mounted Display (HMD) e.g. Head-Up Display (HUD) Projection Display Navigational Aids in Cars Military Airborne Applications Not Head Mounted (e.g. vehicle mounted) Primarily Outdoor (Daylight) Environments AR Visual Displays
- 6. Display Technologies ! Types (Bimber/Raskar 2003) ! Head attached • Head mounted display/projector ! Body attached • Handheld display/projector ! Spatial • Spatially aligned projector/monitor
- 9. Head Mounted Displays (HMD) • Display and Optics mounted on Head • May or may not fully occlude real world • Provide full-color images • Considerations • Cumbersome to wear • Brightness • Low power consumption • Resolution limited • Cost is high?
- 10. Key Properties of HMD • Field ofView • Human eye 95 degrees horizontal, 60/70 degrees vertical • Resolution • > 320x240 pixel • Refresh Rate • Focus • Fixed/manual • Power • Size
- 11. Types of Head Mounted Displays Occluded See-thru Multiplexed
- 12. ImmersiveVRArchitecture Head! Tracker Host! Processor Data Base! Model Rendering! Engine Frame! Buffer head position/orientation to network Display! Driver Non see- thru! Image source & optics virtual object Virtual World
- 13. See-thruARArchitecture Head! Tracker Host! Processor Data Base! Model Rendering! Engine Frame! Buffer head position/orientation to network Display! Driver see-thru! combiner Virtual Image superimpos ed! over real world object real world Image source
- 14. Optical see-through head-mounted display Virtual images from monitors Real World Optical Combiners
- 16. Epson Moverio BT-200 ▪ Stereo see-through display ($700) ▪ 960 x 540 pixels, 23 degree FOV, 60Hz, 88g ▪ Android Powered, separate controller ▪ VGA camera, GPS, gyro, accelerometer
- 17. ViewThrough Optical See-Through HMD
- 18. TheVirtual Retinal Display • Image scanned onto retina • Commercialized through Microvision • Nomad System - www.mvis.com
- 19. Strengths of optical see-throughAR • Simpler (cheaper) • Direct view of real world • Full resolution, no time delay (for real world) • Safety • Lower distortion • No eye displacement • but COASTAR video see-through avoids this
- 20. VideoARArchitecture Head! Tracker Host! Processor Graphics! renderer Digital! Mixer Frame! Buffer head position/orientation to network Display! Driver Non see- thru! Image source & optics Head- mounted camera aligned to display optics Video! Processor Video image of real world Virtual image inset into video of real world
- 23. Vuzix Wrap 1200DXAR ▪ Stereo video see-through display ($1500) ■ Twin 852 x 480 LCD displays, 35 deg. FOV ■ StereoVGA cameras ■ 3 DOF head tracking
- 24. ViewThrough aVideo See-Through HMD
- 25. Strengths ofVideo See-ThroughAR • True occlusion • Kiyokawa optical display that supports occlusion • Digitized image of real world • Flexibility in composition • Matchable time delays • More registration, calibration strategies • Wide FOV is easier to support
- 26. Optical vs.VideoAR Summary • Both have proponents • Video is more popular today? • Likely because lack of available optical products • Depends on application? • Manufacturing: optical is cheaper • Medical: video for calibration strategies
- 27. Eye multiplexedARArchitecture Head! Tracker Host! Processor Data Base! Model Rendering! Engine Frame! Buffer head position/orientation to network Display! Driver Virtual Image inset into! real world scene real world Opaque! Image source
- 28. Virtual Image‘inset’ into real
- 29. Google Glass
- 32. Vuzix M-100 ▪ Monocular multiplexed display ($1000) ■ 852 x 480 LCD display, 15 deg. FOV ■ 5 MP camera, HD video ■ GPS, gyro, accelerometer
- 33. DisplayTechnology • Curved Mirror • off-axis projection • curved mirrors in front of eye • high distortion, small eye-box • Waveguide • use internal reflection • unobstructed view of world • large eye-box
- 34. See-through thin displays • Waveguide techniques for thin see-through displays • Wider FOV, enable AR applications • Social acceptability Opinvent Ora Lumus DK40
- 36. SpatialAugmented Reality • Project onto irregular surfaces • Geometric Registration • Projector blending, High dynamic range • Book: Bimber, Rasker “Spatial Augmented Reality”
- 37. Projector-basedAR Examples: Raskar, MIT Media Lab Inami, Tachi Lab, U. Tokyo Projector Real objects with retroreflective covering User (possibly head-tracked)
- 38. Example of projector-basedAR Ramesh Raskar, UNC, MERL
- 39. Example of projector-basedAR Ramesh Raskar, UNC Chapel Hill
- 40. Head Mounted Projector • NVIS P-50 HMPD • 1280x1024/eye • Stereoscopic • 50 degree FOV • www.nvis.com
- 41. HMD vs.HMPD Head Mounted Display Head Mounted Projected Display
- 42. CastAR - http://technicalillusions.com/ • Stereo head worn projectors • Interactive wand • Rollable retro-reflective sheet
- 43. • Designed for shared interaction
- 44. Pico Projectors • Microvision - www.mvis.com • 3M, Samsung, Philips, etc
- 45. MIT Sixth Sense • Body worn camera and projector • http://www.pranavmistry.com/projects/sixthsense/
- 46. OtherAR Displays
- 47. Video MonitorAR Video cameras Monitor Graphics Combiner Video Stereo glasses
- 48. Examples
- 49. Virtual Showcase • Mirrors on a projection table • Head tracked stereo • Up to 4 users • Merges graphic and real objects • Exhibit/museum applications • Fraunhofer Institute (2001) • Bimber, Frohlich
- 50. Augmented Paleontology Bimber et. al. IEEE Computer Sept. 2002
- 51. Alternate Displays LCD Panel Laptop PDA
- 53. OtherTypes ofAR Display • Audio • spatial sound • ambient audio • Tactile • physical sensation • Haptic • virtual touch
- 54. Haptic Input • AR Haptic Workbench • CSIRO 2003 – Adcock et. al.
- 55. Phantom • Sensable Technologies (www.sensable.com) • 6 DOF Force Feedback Device
- 56. AR Haptic Interface • Phantom,ARToolKit, Magellan
- 58. Objects Registered in 3D • Registration • Positioning virtual object wrt real world • Tracking • Continually locating the users viewpoint • Position (x,y,z), Orientation (r,p,y)
- 59. Tracking Requirements • Augmented Reality Information Display • World Stabilized • Body Stabilized • Head Stabilized Increasing Tracking Requirements Head Stabilized Body Stabilized World Stabilized
- 60. 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)
- 62. MechanicalTracker • Idea: mechanical arms with joint sensors • ++: high accuracy, haptic feedback • -- : cumbersome, expensive Microscribe
- 63. MagneticTracker • Idea: difference between a magnetic transmitter and a receiver • ++: 6DOF, robust • -- : wired, sensible to metal, noisy, expensive Flock of Birds (Ascension)
- 65. Global Positioning System (GPS) • Created by US in 1978 • Currently 29 satellites • Satellites send position + time • GPS Receiver positioning • 4 satellites need to be visible • Differential time of arrival • Triangulation • Accuracy • 5-30m+, blocked by weather, buildings etc
- 66. InertialTracker • Idea: measuring linear and angular orientation rates (accelerometer/gyroscope) • ++: no transmitter, cheap, small, high frequency, wireless • -- : drift, hysteris only 3DOF IS300 (Intersense) Wii Remote
- 67. Mobile Sensors • Inertial compass • Earth’s magnetic field • Measures absolute orientation • Accelerometers • Measures acceleration about axis • Used for tilt, relative rotation • Can drift over time
- 68. OpticalTracking
- 69. OpticalTrackingTechnologies • Scalable active trackers • InterSense IS-900, 3rd Tech HiBall • Passive optical computer vision • Line of sight, may require landmarks • Can be brittle. • Computer vision is computationally-intensive 3rd Tech, Inc.
- 71. HiBallTracking System (3rd Tech) • Inside-Out Tracker • $50K USD • Scalable over large area • Fast update (2000Hz) • Latency Less than 1 ms. • Accurate • Position 0.4mm RMS • Orientation 0.02° RMS
- 73. Marker tracking • Available for more than 10 years • Several open source solutions exist • ARToolKit,ARTag,ATK+, etc • Fairly simple to implement • Standard computer vision methods • A rectangle provides 4 corner points • Enough for pose estimation!
- 74. Marker Based Tracking: ARToolKit http://artoolkit.sourceforge.net/
- 76. Tracking challenges inARToolKit False positives and inter-marker confusion (image by M. Fiala) Image noise (e.g. poor lens, block coding / compression, neon tube) Unfocused camera, motion blur Dark/unevenly lit scene, vignetting Jittering (Photoshop illustration) Occlusion (image by M. Fiala)
- 78. Markerless Tracking Magnetic Tracker Inertial Tracker Ultrasonic Tracker Optical Tracker Marker-Based Tracking Markerless Tracking Specialized Tracking Edge-Based Tracking Template-Based Tracking Interest Point Tracking • No more Markers! #Markerless Tracking Mechanical Tracker
- 79. 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
- 80. TextureTracking
- 81. Edge Based Tracking • RAPiD [Drummond et al. 02] • Initialization, Control Points, Pose Prediction (Global Method)
- 82. Line Based Tracking • Visual Servoing [Comport et al. 2004]
- 83. Model BasedTracking • OpenTL - www.opentl.org • General purpose library for model based visual tracking
- 84. Marker vs.natural feature tracking • Marker tracking • ++ Markers can be an eye-catcher • ++ Tracking is less demanding • -- The environment must be instrumented with markers • -- 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
- 85. Example: Outdoor Hybrid Tracking • Combines • computer vision • natural feature tracking • inertial gyroscope sensors • Both correct for each other • Inertial gyro - provides frame to frame prediction of camera orientation • Computer vision - correct for gyro drift
- 86. OutdoorARTracking System You, Neumann,Azuma outdoor AR system (1999)
- 87. Robust OutdoorTracking • Hybrid Tracking • ComputerVision, GPS, inertial • Going Out • Reitmayr & Drummond (Univ. Cambridge) Reitmayr, G., & Drummond, T. W. (2006). Going out: robust model-based tracking for outdoor augmented reaity. In Mixed and Augmented Reality, 2006. ISMAR 2006. IEEE/ACM International Symposium on (pp. 109-118). IEEE.
- 88. Handheld Display
- 89. Registration
- 91. The Registration Problem • Virtual and Real must stay properly aligned • If not: • Breaks the illusion that the two coexist • Prevents acceptance of many serious applications
- 92. Sources of registration errors • Static errors • Optical distortions • Mechanical misalignments • Tracker errors • Incorrect viewing parameters • Dynamic errors • System delays (largest source of error) • 1 ms delay = 1/3 mm registration error
- 93. Reducing static errors • Distortion compensation • Manual adjustments • View-based or direct measurements • Camera calibration (video)
- 94. View Based Calibration (Azuma 94)
- 95. Dynamic errors • Total Delay = 50 + 2 + 33 + 17 = 102 ms • 1 ms delay = 1/3 mm = 33mm error Tracking Calculate Viewpoint Simulation Render Scene Draw to Display x,y,z r,p,y Application Loop 20 Hz = 50ms 500 Hz = 2ms 30 Hz = 33ms 60 Hz = 17ms
- 96. Reducing dynamic errors (1) • Reduce system lag • Faster components/system modules • Reduce apparent lag • Image deflection • Image warping
- 97. Reducing System Lag Tracking Calculate Viewpoint Simulation Render Scene Draw to Display x,y,z r,p,y Application Loop Faster Tracker Faster CPU Faster GPU Faster Display
- 98. ReducingApparent Lag Tracking Update x,y,z r,p,y Virtual Display Physical Display (640x480) 1280 x 960 Last known position Virtual Display Physical Display (640x480) 1280 x 960 Latest position Tracking Calculate Viewpoint Simulation Render Scene Draw to Display x,y,z r,p,y Application Loop
- 99. Reducing dynamic errors (2) • Match input streams (video) • Delay video of real world to match system lag • Predictive Tracking • Inertial sensors helpful Azuma / Bishop 1994
- 100. PredictiveTracking Time Position Past Future Can predict up to 80 ms in future (Holloway) Now
- 102. Wrap-up • Tracking and Registration are key problems • Registration error • Measures against static error • Measures against dynamic error • AR typically requires multiple tracking technologies • Research Areas: • Hybrid Markerless Techniques, Deformable Surface, Mobile, Outdoors