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Rutgers University - Virtual Reality Technology Input Devices: Trackers, Navigation and Gesture Interfaces.

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Presentation on theme: "Rutgers University - Virtual Reality Technology Input Devices: Trackers, Navigation and Gesture Interfaces."— Presentation transcript:

1 Rutgers University - Virtual Reality Technology Input Devices: Trackers, Navigation and Gesture Interfaces

2 Rutgers University - Virtual Reality Technology What is Virtual Reality? “A high-end user interface that involves real-time simulation and interaction through multiple sensorial channels.” (vision, sound, touch, smell, taste) Input Devices

3 Rutgers University - Virtual Reality Technology 3-D System of coordinates of a VR object Virtual objects have 6 degrees of freedom (D.O.Fs): -three translations; -three rotations. Input Devices

4 Rutgers University - Virtual Reality Technology Trackers measure the motion of “objects” such as user’s wrist or his head vs. a fixed system of coordinates. Technologies to perform this task: Magnetic trackers (prevalent); Ultrasonic trackers (less used); Mechanical trackers (special cases); Inertial/ultrasonic trackers (new). Input Devices

5 Rutgers University - Virtual Reality Technology Input Devices

6 Rutgers University - Virtual Reality Technology Tracker characteristics: Tracker characteristics: Measurement rate – Readings/sec; Sensing latency; Sensor noise and drift; Measurement accuracy (errors); Measurement repeatability; Tethered or wireless; Work envelope; Sensing degradation. Input Devices

7 Rutgers University - Virtual Reality Technology Tracker characteristics: Tracker characteristics: Real object position Accuracy Resolution Tracker position measurements Input Devices

8 Rutgers University - Virtual Reality Technology Tracker characteristics: Tracker characteristics: Real object fixed position Signal noise Time Tracker data Input Devices

9 Rutgers University - Virtual Reality Technology Tracker characteristics: Tracker characteristics: Real object fixed position Sensor drift Time Tracker data Input Devices

10 Rutgers University - Virtual Reality Technology Tracker characteristics: Tracker characteristics: Real object position Sensor latency Time Tracker data Input Devices

11 Rutgers University - Virtual Reality Technology Tracker characteristics: Tracker characteristics: Tracker Update Rate Input Devices

12 Rutgers University - Virtual Reality Technology Mechanical Trackers Definition: A mechanical tracker consists of a serial or parallel kinematic structure composed of links interconnected by sensorized joints. Input Devices

13 Rutgers University - Virtual Reality Technology Mechanical Trackers Use sensors imbedded in exoskeletons to measure position; Have extremely low latencies; Are immune to interference from magnetic fields; But limit the user’s freedom of motion; Can be heavy is worn on the body Input Devices

14 Rutgers University - Virtual Reality Technology Input Devices

15 Rutgers University - Virtual Reality Technology Exoskeleton structure Interface With computer Input Devices

16 Rutgers University - Virtual Reality Technology Magnetic Trackers Definition: A magnetic tracker is a non-contact position measurement device that uses a magnetic field produced by a stationary TRANSMITTER to determine the real-time position of a moving RECEIVER element Input Devices

17 Rutgers University - Virtual Reality Technology Magnetic Trackers Use low-frequency magnetic fields to measure position; Fields are produced by a fixed source; Size of source grows with the tracker work envelope; The receiver is attached to the tracked object and has three perpendicular antennas; Distance is inferred from the voltages induced in the antennas – needs calibration… Input Devices

18 Rutgers University - Virtual Reality Technology Magnetic tracker with Data Glove Input Devices

19 Rutgers University - Virtual Reality Technology Fastrack magnetic tracker system Stylus Source Receiver Electronic interface Input Devices

20 Rutgers University - Virtual Reality Technology Long Ranger source for the tracker system Source Input Devices

21 Rutgers University - Virtual Reality Technology Fastrack magnetic tracker electronics Source Receivers Input Devices

22 Rutgers University - Virtual Reality Technology Polhemus Long Ranger tracking errors (Rutgers) Input Devices

23 Rutgers University - Virtual Reality Technology Tracking error as a function of tripod height

24 Rutgers University - Virtual Reality Technology DC Magnetic Tracker Block Diagram Input Devices

25 Rutgers University - Virtual Reality Technology Flock of Birds magnetic tracker (Ascension Co.) Input Devices

26 Rutgers University - Virtual Reality Technology Motion Star wireless tracker (courtesy of Ascension Technology) Input Devices

27 Rutgers University - Virtual Reality Technology Wireless suit (Ascension Technology) Sensors: 20/suit 100 updates/sec 3 meters range from base unit Resolution<2 mm and <.2 degrees Electronic unit (2 hours battery life) Input Devices

28 Rutgers University - Virtual Reality Technology Motion Star block diagram Input Devices

29 Rutgers University - Virtual Reality Technology Magnetic Tracker Calibration Use mechanical measurements to reduce errors; Sensor noise – variation in measurement with no real object motion – solved by over-sampling; Size of errors grow from source outwards; Errors both in position and orientation. Input Devices

30 Rutgers University - Virtual Reality Technology Magnetic tracker accuracy degradation Input Devices

31 Rutgers University - Virtual Reality Technology Magnetic Tracker Errors due to ambient noise: e ambient = K n (d transmitter-receiver ) 4 due to metal: K r (d transmitter-receiver ) 4 e metal = (d transmitter-metal ) 3 x (d metal-receiver ) 3 Input Devices

32 Rutgers University - Virtual Reality Technology Comparison of AC and DC magnetic trackers DC trackers are immune to non-ferromagnetic metals (brass, aluminum and stainless steel) Both DC and AC trackers are affected by the presence of Ferromagnetic metals (mild steel and ferrite). Both are affected by copper; AC trackers have better resolution and accuracy. AC trackers have slightly shorter range Input Devices

33 Rutgers University - Virtual Reality Technology Input Devices

34 Rutgers University - Virtual Reality Technology Ultrasonic Trackers Definition: A non-contact position measurement device that uses an ultrasonic signal produced by a stationary transmitter to determine the real-time position/orientation of a moving receiver. Input Devices

35 Rutgers University - Virtual Reality Technology Ultrasonic Trackers Use low-frequency ultrasound to measure position; Sound produced by a fixed triangular source (speakers); Number of sources grows with the tracker work envelope; The receiver is triangular and attached to the tracked object and has three microphones; Distance is inferred from the sound time of flight; Sensitive to air temperature and other noise sources; Requires “direct line of sight”; Slower than magnetic trackers (max 50 updates/sec). Input Devices

36 Rutgers University - Virtual Reality Technology Ultrasonic tracker (Logitech) Input Devices

37 Rutgers University - Virtual Reality Technology Large-volume ultrasonic tracker (Logitech) Input Devices

38 Rutgers University - Virtual Reality Technology Optical Trackers Definition: A non-contact position measurement device that uses optical sensing to determine the real-time position/orientation of an object Input Devices

39 Rutgers University - Virtual Reality Technology Optical trackers: a) outside-looking-in; b) inside-looking-out Input Devices

40 Rutgers University - Virtual Reality Technology Inside-out optical tracker advantages The best accuracy is close to the work envelope. Very large tracking surface and resistance to visual occlusions (line of sight). Input Devices

41 Rutgers University - Virtual Reality Technology Outside-looking-in LaserBIRD optical tracker Input Devices

42 Rutgers University - Virtual Reality Technology Inside-looking-out LaserBIRD optical tracker Input Devices

43 Rutgers University - Virtual Reality Technology HiBall 3000 wide area tracker HiBall 3000 wide area tracker (courtesy of 3rdTech Inc.) 6 optical lenses HiBall Optical Sensor HiBall Optical Sensor interior Signal conditioning electronics electronics 6 photodiodes The sensor advantages are:  High sampling rate (2000 Hz);  High accuracy (0.5 mm, 0.03°) and high resolution (0.2 mm, 0.03°)  Impervious to metallic or ultrasonic interference;  Very large tracking area (up to 40 ft x 40 ft), small weight (8 oz).

44 Rutgers University - Virtual Reality Technology HiBall 3000 tracker HiBall 3000 tracker on an HMD on an HMD Lateral effect photo diodes

45 Rutgers University - Virtual Reality Technology Types of VR Applications Types of VR Applications Beacon array modules (6 strips with 8 LED/strip)

46 Rutgers University - Virtual Reality Technology Hybrid Ultrasonic/Inertial Trackers No interference from metallic objects; No interference from magnetic fields; Large-volume tracking; “Source-less” orientation tracking; Full-room tracking; A newer technology. Input Devices

47 Rutgers University - Virtual Reality Technology But… Accelerometer errors  a lead to decreased accuracy since  x=  a t 2 2 Errors grow geometrically in time! Gyroscope errors compound position errors; Needs independent position estimation to reduce “drift”; Input Devices

48 Rutgers University - Virtual Reality Technology Tracker components (InterSense Co.) Base unit Sonic Strips I-cube

49 Rutgers University - Virtual Reality Technology Tracker components (courtesy of Intersense Co.) Degrees of freedom: 6 Resolution: 1.5 mm RMS Angular: 0.05 o RMS Update rate: 180 sets/s max – one station Down to 90 updates/sec - for four stations. Latency 4–10 ms Max tracking area: 900 meters 2 (300 strips, 24 hubs)

50 Rutgers University - Virtual Reality Technology InterSense Stereo Glasses tracker (courtesy of Intersense Co.) I-Cube Accel./gyro Ultrasonic emitter

51 Rutgers University - Virtual Reality Technology InterSense Stereo stylus tracker (courtesy of Intersense Co.) Accelerometer Ultrasonic emitter

52 Rutgers University - Virtual Reality Technology IS 900 block diagram IS 900 block diagram Input Devices

53 Rutgers University - Virtual Reality Technology IS 900 software block diagram IS 900 software block diagram

54 Rutgers University - Virtual Reality Technology Link to VC 2.1 on book CD

55 Rutgers University - Virtual Reality Technology Input Devices

56 Rutgers University - Virtual Reality Technology Navigation and Gesture Input Devices Navigation interfaces allow relative position control of virtual objects; Gesture interfaces allow dextrous control of virtual objects and interaction through gesture recognition. Input Devices

57 Rutgers University - Virtual Reality Technology Navigation Input Devices Are the Cubic Mouse, the trackball and the 3-D probe; Perform relative position/velocity control of virtual objects; Allow “fly-by” application by controlling a virtual camera. Input Devices

58 Rutgers University - Virtual Reality Technology The Cubic Mouse Input Devices

59 Rutgers University - Virtual Reality Technology Link to VC 2.2 on book CD

60 Rutgers University - Virtual Reality Technology Trackballs Input Devices

61 Rutgers University - Virtual Reality Technology The Microscribe (Immersion Co.) Input Devices

62 Rutgers University - Virtual Reality Technology Gesture Input Devices Are sensing gloves such as: - Fakespace “Pinch Glove” - 5DT Data Glove; - The DidjiGlove - Immersion “CyberGlove” Have larger work envelope than trackballs/3-D probes; Need calibration for user’s hand. Input Devices

63 Rutgers University - Virtual Reality Technology Finger Degrees of Freedom Input Devices

64 Rutgers University - Virtual Reality Technology Hand work envelope vs. interface type Input Devices

65 Rutgers University - Virtual Reality Technology The Pinch Glove (Fakespace Co.) - no joint measures, but contact detection

66 Rutgers University - Virtual Reality Technology The Pinch Glove (Fakespace Co.)

67 Rutgers University - Virtual Reality Technology The glove interface: a) five-sensor version; b) 16-sensor version A) One optical fiber/finger Roll/pitch sensing Two sensors/finger plus abduction sensors 5DT Data Glove 100 datasets/sec, 12 bit A/D flexion resolution, wireless version transmits data at 30 m, needs calibration

68 Rutgers University - Virtual Reality Technology 5DT Data Glove

69 Rutgers University - Virtual Reality Technology The coupling of intermediate and distal finger joints 5DT Data Glove Glove has less sensors than hand joints … Needs to infer distal joint flexion angle

70 Rutgers University - Virtual Reality Technology 5DT Data Glove Input Devices

71 Rutgers University - Virtual Reality Technology Linear calibration method 5DT Data Glove Input Devices

72 Rutgers University - Virtual Reality Technology Inexpensive wired glove for computer animation; Uses capacitive sensors (two per finger) and a 10-bit A/D converter (1,024 points); Can do 70 hand configuration reads/sec.; Communicates with the host over an RS232 (19.2 k) The Didgiglove

73 Rutgers University - Virtual Reality Technology The CyberGlove Uses linear sensors – electrical strain gauges; Angles are obtained by measuring voltages on a Wheastone bridge; 112 gestures/sec “filtered”. Sensor resolution 0.5 degrees, but errors accumulate to the fingertip (open kinematic chain); Sensor repeatability 1 degree Needs calibration when put on the hand; Is expensive (about $10,000)

74 Rutgers University - Virtual Reality Technology The CyberGlove (Vertex Co.)

75 Rutgers University - Virtual Reality Technology Link to VC 2.3 on book CD

76 Rutgers University - Virtual Reality Technology


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