IVR Chapter 7 Motion tracking
Questions about the lecture 'Introduction to Virtual Reality' of the RWTH Aachen Chapter 7 Motion tracking
Questions about the lecture 'Introduction to Virtual Reality' of the RWTH Aachen Chapter 7 Motion tracking
Set of flashcards Details
| Flashcards | 21 |
|---|---|
| Language | English |
| Category | Computer Science |
| Level | University |
| Created / Updated | 03.02.2017 / 09.02.2017 |
| Weblink |
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What did Steve Bryson said?
[motion tracking]
“If I turn my head and nothing happens, it ain’t VR!”
What are the general criteria?
[motion tracking, 6]
1. Measures as position, orientation, angle, acceleration, distances
2. Dimensions // 3D for VR
3. Number of tracked segments
4. Data handling automatically or manually and in real time or not
5. Size of interaction volume (tradoff)
6. Ergonomics (intrusive or not)
What are the spatial criteria?
[motion tracking, 2]
1. Spatial accuracy (Grasping vs walking) // Hit around middle
2. Spatial precision // Hit exact anywhere
What are the temporal criteria?
[motion tracking, 2]
1. Temporal accuracy (Response time, latency, sample rate)
2. Temporal precision (Jitter)
What are the technologies?
motion tracking, 7]
1. Mechanical with the ultimate displayed
2. Electromagnetic
3. Instrumented gloves
4. Ultra sound
5. Intersense
6. Light
7. Satellite with global positioning system (GPS)
What are electromagnetic examples?
[technologies.motion tracking, 3]
1. Polhemus
2. Ascension
3. Used in military
What are the characteristics of electromagnetic?
[technologies.motion tracking, 5]
1. Good position and orientation
2. Sensitive to ferromagnetic materials in the environment
3. Accuracy decreases with growing distance
4. Large sensors (1-2cm)
5. Cabling
What are the tasks for instrumented gloves?
[technologies.motion tracking, 2]
1. Measures angles between finger segments
2. Difficult to measure thumb rotation for precision grip
What are the characteristics of instrumented gloves?
[technologies.motion tracking, 5]
1. Only makes sense with other trackers
2. Different qualities with flexion vs extension and adduction vs abduction
3. Error propagation
4. Discomfort
5. Calibration process necessary
What are the characteristics of intersense?
[technologies.motion tracking, 2]
1. Inertial and acoustic
2. Combination of accelerometers and gyroscopes
What are the technologies of light?
[technologies.motion tracking, 5]
1. Time of flight sensors
2. Structured light (e.g. Mircosoft Kinect)
3. Opto-electronical (e.g. A.R.T.)
4. HTC Vive with lighthouse
5. Oculus rift
What are the characteristics for time of flight sensors?
[light.technologies.motion tracking, 3]
1. Measure distance between camera and objects
2. 200x200pixels with 100Hz resolution
3. 1cm accuracy
What are tools for structured light?
[light.technologies.motion tracking, 3]
1. Pre-defined matrix of points by IR laser projector
2. Deformed point matrix captured by IR camera
3. Texture mapping by VGA camera
What are the characteristics for structured light?
[light.technologies.motion tracking, 2]
1. Use triangulation for 3D conversion
2. 640x480pixels with 30Hz resolution
What are tools for opto-electronical?
[light.technologies.motion tracking, 4]
1. 2 or more IR camers track 2D position of markers
2. Calculate 3D position via direct linear transformation (DLT)
3. Passive with IR light reflecting markers
4. Active with IR light emitting markers with cabling
What are the characteristics for opto-electronical?
[light.technologies.motion tracking, 3]
1. Selspot experiment of grasping real and virtual object
2. Good accuracy and latency sample rate
3. Occlusion possible
What are tools for HTC Vive?
[light.technologies.motion tracking, 3]
1. Two basis stations with IR LED lasers
2. IR light sensors on the HMD front
3. Time differences yield position and orientation
What is the characteristic for HTC Vive?
[light.technologies.motion tracking]
Also possible with one basis station with limited view angle
What are tools for oculus rift?
[light.technologies.motion tracking, 2]
1. Combination of gyrometer, accelerometer and magnetometer for R
2. IR LEDs attached to HMD and IR camera for p
What are we interested in for position and orientation of body segments?
[technologies.motion tracking]
Get xi with direct measure yi = Rxi + p and rotation R and translation p
What are formulas for position and orientation of body segments?
[technologies.motion tracking, 6]
1. xm = 1/n * Sumi=1n xm and ym = 1/n * Sumi=1n ym
2. X = [(x1-xm),…,(xn-xm)] and Y = [(y1-ym),…,(yn-ym)]
3. C = Y*XT the covariance matrix
4. C = U*W*VT with sigular value decomposition
5. R = U*(1,0,0;0,1,0;0,0,det(UVT))*VT
6. p = ym - Rxm
