Tracking Gkhan Tekkaya Grkan Vural Can Eroul Outline

Tracking Gökhan Tekkaya Gürkan Vural Can Eroğul

Outline • Tracking – Overview – Head Tracking – Eye Tracking – Finger/Hand Tracking • Demos

Tracking - Purpose • To update the visual display based on the viewers head position and orientation. • Instead of tracking the viewer's eyes directly, we track the position and orientation of the user's head. From this we determine the position and orientation of the two eyes.

Tracking - Overview • We may also be tracking the user's hand(s), fingers, legs or other interface devices. • Want tracking to be as 'invisible' as possible to the user. • Want the user to be able to move freely with few encumberances

Tracking - Overview • Want to be able to have multiple 'guests' nearby • Want to track as many objects as necessary • Want to have minimal delay between movement of an object and the detection of the objects new position / orientation (< 50 msec total) • Want tracking to be accurate (1 mm and 1 degree)

Tracking Devices - Electromagnetic • large transmitter and one or more small sensors. • transmitter emits an electromagnetic field. • sensors report the strength of that field at their location to a computer • sensors can be polled specifically by the computer or transmit continuously.

Tracking Devices - Electromagnetic • uses: – projection based systems, HMDs • advantages are: – – large tracking volume (approx 10 feet / 3 meters) no line-of-sight restriction sensors are small and light technology has been around for a while • disadvantages are: – – affected by metal in the nearby area latency can be high (0. 1 seconds) accuracy is low in large volumes somewhat expensive

Tracking Devices - Electromagnetic • Polhemus: – Motion Tracking: • • • LIBERTY LATUS LIBERTY PATRIOT FASTRAK MINUTEMAN – Scanning: • Fast. SCAN – Eye Tracking: • Vision. Trak

Tracking Devices - Electromagnetic

Tracking Devices - Mechanical • rigid structures with multiple joints • one end is fixed, the other is the object being tracked • could be tracking users head, or their hand • physically measure the rotation about joints in the armature to compute position and orientation • structure is counter-weighted - movements are slow and smooth • Knowing the length of each joint and the rotation at each joint, location and orientation of the end point is easy to compute.

Tracking Devices - Mechanical

Tracking Devices - Mechanical • uses: – BOOMs, Phantom • advantages are: – – low latency high accuracy sensors are small and light technology has been around for a while • disadvantages are: – small volume – only track one object at a time

Tracking Devices - Acoustic • small transmitter and one medium sized sensor • each transmitter emits ultrasonic pulses which are received by microphones on the sensor (usually arranged in a triangle) • as the pulses will reach the different microphones at slightly different times, the position and orientation of the transmitter can be determined

Tracking Devices - Acoustic • Logitech: – 6 degrees of freedom – 3 D and 2 D modes – Ultrasonic Technology – High level of ruggedness – PC and Unix compatibility – 250 dpi resolution/ 3 D mode – 400 dpi resolution/ 2 D mode

Tracking Devices - Acoustic

Tracking Devices - Optical • LEDs or reflective materials are placed on the object to be tracked • video cameras at fixed locations capture the scene • image processing techniques are used to locate the object • With fast enough processing you can also use computer vision techniques to isolate a head in the image and then use the head to find the position of the eyes

Tracking Devices - Optical • A. R. T. system from Germany:

Tracking Devices - Inertial • self-contained • gyroscopes / accelerometers used • knowing where the object was and its change in position / orientation the device and 'know' where it now is • tend to work for limited periods of time then drift.

Tracking Devices - Combinations • self-contained • gyroscopes / accelerometers used • knowing where the object was and its change in position / orientation the device and 'know' where it now is • tend to work for limited periods of time then drift.

Tracking Devices - Combinations • Intersense uses a combination on Acoustic and Inertial can deal with fast movements and acoustic keeps the inertial from drifting