Bevegelsessporing. fourms. University of Oslo. MUS Musikk og bevegelse. 6mars2014. Music, Mind, Motion, Machines

Transcription

1 Bevegelsessporing MUS6 - Musikk og bevegelse 6mars4

2 Analog! Digital: Sampling Bevegelsessporingssystem Digitalt bilde av bevegelsen, består av en rekke snapshots bevegelse: - analog - skjer hele tiden Sampling I I virkeligheten skjer en bevegelse hele tiden I En datamaskin kan ikke forholde seg til analoge data, og må sample den analoge bevegelsen et visst antall ganger per sekund.

3 Det er viktig at samplingsraten er høy nok sine tone: H z sampled at Hz sampled at Hz sampled at.5 Hz... too low!! ALIASING: The reconstructed signal is no longer a Hz sine tone

4 Det er viktig at oppløsningen er høy nok I Vi kan for eksempel ikke studere hoftebevegelsene til en sambadanser med et GPS system som har en oppløsning på ca 3 meter. I Danseren kan bevege seg.5 meter til hver side uten at vi ser noe forskjell i dataene. I Hvis du vil bruke et videokamera til å studere danseren, er det viktig at kameraet enten har god oppløsning, eller står nærme nok til å fange bevegelsene skikkelig. (helst begge deler)

5 Body motion: Tracking technologies Magnetic Mechanical Avg. motion image Original image Pre-processed Inertial acoustic Motion history image Motion image Vertical motion Motiongram Time Optical markerless Optical marker-based

6 Body motion: Tracking technologies Inertial/ magnetic Mechanical Electromagnetic Optical (visual) Optic (infrared) Physiological + - flexible - small - flexible - small - flexible - resolution - no cables - identification - no markers - absolute - accessible - speed - resolution - # markers - indirect motion sensing - - relative - relative - cable - short range - D - markers - speed - calibration - resolution - identification - identification - indirect motion sensing Fra Jensenius, Nymoen, Godøy (8)

7 Motion Capture / Bevegelsessporing I Sensing the motion I Processing the the sensor data I Storing the data Motion Tracking Motion Capture sensor data motion data Sensing Processing Storing

8 Sensing

9 Body motion: Sensing technologies I Mechanical sensing I Force sensing I Acoustic sensing I Inertial sensing I Electromagnetic sensing I Physiological sensing I Optical sensing We ll go into a bit more detail on a few of these

10 Mechanical sensing: Potentiometers and sliders Potentiometer / potmeter Slider Concept: Electricity in! Scaling! Scaled electricity out

11 STOP Inertial sensing: Accelerometers and Gyroscopes Tiny chips found in every smart phone these days: Accelerometer: measures acceleration, including: I Gravity I Change in speed I Change in direction Conceptual example: Car standing still, or driving straight at steady speed Going downhill Gyroscope: measures rotation, meaning: I Change in direction More difficult to illustrate, but you may know the concept from some everyday objects: Car breaking: Car accelerating: Driving direction Driving direction

12 Optical sensing: Video Illustration by Alexander Refsum Jensenius

13 Optical sensing: Video Illustration by Alexander Refsum Jensenius

14 Optical sensing: Video Illustration by Alexander Refsum Jensenius

15 Tracking

16 Optical tracking: Blob detection Example task: Find the red ball: Red plane

17 Optical tracking: Blob detection Example task: Find the red ball: Green plane

18 Optical tracking: Blob detection Example task: Find the red ball: Blue plane

19 Optical tracking: Blob detection Example task: Find the red ball: Red plane

20 Optical tracking: From position to trajectory

21 Optical tracking: From position to trajectory

22 Optical tracking: From position to trajectory

23 Optical tracking: From position to trajectory

24 Optical tracking: From position to trajectory

25 Optical tracking: From position to trajectory

26 Optical Marker-Based Motion Capture

27 Optical Marker-Based Motion Capture a) The cameras see a marker in their field of view Camera Camera Camera 3 b) Each camera shows a corresponding image, where the marker position is given in two dimensions Camera Camera Camera 3 c) Since the position and orientation of each camera is known, as well as its field of view, a 3D vector where the dot must be locted can be determined. d) The marker is found in the intersection between the 3D vectors Camera Camera Camera Camera 3

28 Optical Marker-Based Motion Capture Systems available at UiO: Qualisys OptiTrack

29 Markers Rigid bodies Kinematic chains

30 Markers Rigid bodies Kinematic chains

31 Markers Rigid bodies Kinematic chains Marker Rigid object Kinematic chain

32 Processing motion data

33 All data contains noise!

34 Drift in inertial systems Horisontal position of the captured Xsens data (meters) 5 4 position norm (m) Magnitude of position, velocity and acceleration Qualisys ipod ipod (filtered) 3 Starting point velocity norm (m/s) 3 End point acceleration norm (m/s ) time (s)

35 Preprocessing: Gap-filling

36 Preprocessing: Smoothing

37 Visualization: Typical plot of XYZ data of one marker. Not so intuitive...

38 Visualization: Another option: Putting X, Y and Z on different axes, and let colour denote time

39 Visualization: Plotting many (4) xyz marker positions can get really messy position (mm) time (s)

40 Visualization: Another option is to use colour coding: Mocapgrams marker name LBHD RBHD LFHD RFHD LSHO LELB LWRI RHAO RHAI LHAO LHAI RSHO RELB RWRI C7 T CLAV STRN LPSI RPSI LSBL RSBL RTOE LTOE time (s)

41 Position Hastighet Akselerasjon Figure from: R.I.Godøy. Quantal Elements in Musical Experience in R. Bader(ed.), Sound Perception Performance, Current Research in Systematic Musicology, Springer 3.

42 MoCap Toolbox Demo

43 Først litt annen info: I Oppgave : Frist i morgen I Oppgave 3: Frist 7 april. Legges ut snart, følg med på kurssiden I Semesteroppgave: Finne tema I Presentasjon av tema april I Åpen dag: 3 mars. Ikke forelesning. Mocap toolbox til Matlab (skal være installert på midi-rommet). I MATLAB: Mocap toolbox, from University of Jyväskylä. materials/mocaptoolbox