Input and Output Devices - Virtual Reality Input and Output...

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Virtual Reality Input and Output Devices
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Basic Components
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Input Devices Concerns with interfaces for: tracking users and users navigating through the virtual environment and interacting with the virtual objects
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Trackers Three-Dimensional Position Trackers Types of trackers: Mechanical trackers Ultrasonic trackers Optical trackers Inertial trackers etc.
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6DOF Trackers Consider the following important properties of 6DOF (degrees of freedom) trackers for choosing the right device for the given applications: 1. Update rate – how many measurements per second (Hz); higher rate smoother tracking of movements 2. Latency – the delay between the change of the position and orientation of the target being tracked and the report of change to the computer; greater than 50 ms, user will notice and can cause nausea 3. Accuracy – the measure of error in the reported position and orientation; smaller values better accuracy 4. Resolution – smallest changes in position and orientation that can be detected by the tracker; smaller values better performance 5. Range – working volume within which the tracker can measure position and orientation with its specified accuracy and resolution. 6. Others – ease of use, size, weight etc. of the device.
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Mechanical Trackers similar to a robot arm consists of a jointed structure with rigid links, a supporting base, and an active end active end is attached to the body part being tracked
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Mechanical Trackers Fast, accurate, and is not susceptible to jitter But tends to encumber the movement of the user, has a restricted area of operation, and the technical problem of tracking the head and two hands at the same time is still difficult
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Electromagnetic Trackers Often used in immersive applications Consists of: An emitter/source (static part) Receivers/detectors/sensors (a number of movable parts A control station
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Electromagnetic Trackers Allows several body parts to be tracked simultaneously The emitter produces three electromagnetic fields each of which is perpendicular to the others The detector/sensor on the user's body then measures field attenuation and sends its measurements to the control unit The control unit calculates the position and orientation of the given sensor relative to the three electromagnetic fields produced by the source
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Electromagnetic Trackers Advantages Sensors are small, light and handy Relatively high updates rates and low latency Others? Disadvantages: Magnitude of the magnetic field decreases with distance from the emitter, resolution worse as the emitter-receiver distance is growing Magnetic field is subject to distortion lead to inaccurate measurements (the detector must be within a restricted range from the source as a result user has a limited working volume)
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Ultrasonic Trackers Use ultrasonic waves (above 20kHz) for determining the position and orientation of object in space. The device consist of three high frequency sound
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This note was uploaded on 02/06/2012 for the course FACULTY OF WXGE6320 taught by Professor Noraini during the Winter '09 term at University of Malaya.

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Input and Output Devices - Virtual Reality Input and Output...

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