VR Introduction (for web3d) Jyun-Ming Chen Fall 2001

Contents VR Definitions VR Paradigms VR Devices

VR Definitions... making systems that fool human senses... a new media for getting your hands on information... The difference between VR and multimedia is that VR is about creation... The question... [is] whether the created world is real enough for you to suspend your disbelief for a period of time...

VR Definitions (cont) a human-computer interface computer creates a sensory-immersing environment, which interactively responds to and is controlled by the behavior of the user 3 I ’ s of VR interactive, immersive, imaginative

Variations of VR Generally speaking, they do achieve certain levels of 3 “ I ” s. Yet, they don ’ t look the same (and cost differently) projected reality augmented reality HUD (head-up display) tele-presence desktop VR

6 Immersive VR an immersive experience in which participants: wear tracked head- mounted displays view stereoscopic images listen to 3-D sounds free to explore and interact within a 3-D world

Desktop & Projective VR

Augmented VR & Telepresence

Web3D and VR You can think of Web3D as an inexpensive means to realize desktop VR Characteristics: Platform: the WWW browser Graphics performance: restricted by browser and/or plug-in Cost: none Language/software: open-source and some proprietary

VR Devices

System Architecture reality engine generate desired output from the cues of input sensors for example input: pos/orient of head output: scene to HMD

Position Sensors 6DOF (x,y,z, r,p,y) contact vs. non-contact potentiometer magnetic, ultrasound, radar absolute vs. relative

Sensor Parameters update rate measurement per sec. latency time delay between action & result accuracy difference between actual & measured resolution minimal detectable change modes of operation streaming: sensor send data continuously one-shot: data sent when requested working envelope data property noise, interference, limitations,...

Magnetic Sensors 3 stationary orthogonal antenna, producing a low freq. field receiver: another set of ortho. antennas signals of receiver to determine pos/orient hook up receiver to moving objects

Magnetic Sensors (cont) Sensor noise conditioning circuitry increase near the limit of envelope accuracy degrades near metallic objects [calibration method] Multiple receiver/transmitter large envelope moving objectS data transmission speed up

Ultrasound Sensors from 9 distance between speaker- microphone, compute the pos/orient c = ( T)m/s each speaker activates in cycles

Ultrasound (cont) pros cheaper not subject to metallic interference cons line-of-sight constraint lower update rate (than magnetic ones) background noise (bounced off surfaces) multiple spkr/mic possible

Data Glove most intuitive way to interface with virtual world gesture: human hands has a much richer vocabulary (than the 6 DOF) original goal Zimmerman, interested in computer music, wondered whether there ’ s a way to make music by playing air guitar 1987: optical fiber + Lycra glove + Polhemus Isotrack

most gloves handle angle flexion only Hand DOF

Joint-Angle Measurement technology determines the price and accuracy optical fiber strain gauge conductive ink sensor mechanical devices

HMD basic components optics: focus; increase fov screen: CRT or LCD enclosure: hold components; provide occlusion design concerns ergonomics (wt. comfort) image quality tracking

Stereo Glasses group viewing cannot afford to give everyone an HMD technology shutter glasses r/b glasses spatial multiplexing image (SMI) responsive workbench

3D Sound important for immersive experience Stereo sound vs. 3D sound [cp. DirectSound]

Human Hearing Model Cues for sound localization ITD (interaural time difference) IID (interaural intensity difference) no info of front & back –head, torso, pinna scattering

Measuring HRTF HTRF (head related transfer function) some data commercially available

Using HTRF virtual sound position should be changed according to head position Foster estimates MIPS for each sound source even more expensive for reflected sounds convolvotron source position + corresponding HRTF [convolution] D/A, then headphone commercial cards Acoustetron, Beachtron no. of sound sources, reverberation allowed, Doppler effects,...