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VR Output

VR Output. VR Output. 人類 (Human) 電腦 (Computer) 視覺 (See) 視訊 (Video,Image), 文字 (Text) 聽 覺 (Hear) 音訊 (Audio) 觸 覺 (Touch) 力回饋 (Force feedback) 味 覺 (Taste) 嗅 覺 (Smell). 角膜. Human eye. 虹膜. 瞳孔. 睫狀肌. 水晶體. Understanding the human visual system is necessary to design or select a graphics

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VR Output

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  1. VR Output

  2. VR Output • 人類(Human) 電腦(Computer) • 視覺(See) 視訊(Video,Image), 文字(Text) • 聽覺(Hear)音訊(Audio) • 觸覺(Touch)力回饋(Force feedback) • 味覺(Taste) • 嗅覺(Smell)

  3. 角膜 Human eye 虹膜 瞳孔 睫狀肌 水晶體 Understanding the human visual system is necessary to design or select a graphics display 玻璃液 視網膜 鞏膜 中央凹 脈胳膜 神經節細胞(100萬個)

  4. Cones & Rods圓錐細胞 & 圓柱細胞( day & night)(夜盲 vs. 色盲)

  5. The Human Visual System • More than 126 million photoreceptors that are unevenly distributed over the retina • Fovea • The central area of the retina • Several degrees around the eye’s viewing axis • High resolution and color perception • Focus area • Areas that surround the fovea • Low-resolution • Motion perception photoreceptors • We do not know what portion of the display is viewed by the fovea – The whole scene needs to be rendered at high resolution – A waste of graphics processing – The eye tracking technology is at present too bulky to be integrated with personal displays

  6. Field of view • One eye • Approximately 150o horizontally and 120o vertically • Both eyes • Approximately 180o horizontally and 120o vertically • Central portion of the viewing volume • The area of stereopsis • Both eyes register the same image • Approximately 120o horizontally • The brain measures depth

  7. Each eye sees a different field of view

  8. Stereoscopic vision • The convergence angle • The angle between the viewing axis and the line to the fixation point • The angle depends also on the interpupillary distance (IPD) • Interpupillary distance (IPD) • The distance between the pupils of the right and left eyes • Varies among male and female adults within a range of 53-73 mm • The baseline from which a person interprets distances to objects • The larger the IPD, the larger is the convergence angle

  9. Stereoscopic vision • Image parallax • The fixation point appears shifted horizontally between the right and left eyes • The different position in relation to the two eyes • Must be replicated to help the brain interpret depth in the simulated world created by VR graphics and stereo viewing hardware • Stereoscopic displays • Need to output two slightly shifted images • Two displays (e.g., HMD): present its image to the corresponding eye • Single display: time-sequenced or spatially sequenced

  10. Depth perception • Stereopsis is depends on distances to objects • Good for short distances, where the image parallax is substantial • As objects get further away from the viewer, their horizontal shift gets smaller • Accuracy is degraded substantially at 10m from the user • Based on cue inherent in the image • Linear perspective, shadows, occlusions, surface texture, object detail, and motion parallax

  11. Personal Graphics Displays • A graphics display that outputs a virtual scene destined to be viewed by a single user • Types: monoscopic or stereoscopic • Category – Head-mounted displays (HMD) – Hand-supported displays (HSD) – Floor-supported displays – Autostereoscopic monitors

  12. Head-Mounted Displays (HMD) • Project an image floating some 1-5 m in front of the user • The lower the HMD resolution and the higher the FOV  The greater is the number of arc-minutes of eye view corresponding to each pixel • Consumer-grade HMDs • Usually LCD displays • TV programs and video games: NTSC/PAL monoscopic video input • VR system: Require the conversion of the graphics output signal RGB format to NTSC/PAL • Professional-grade HMDs • Usually CRT displays • Specifically for VR: Accept RGB video input

  13. Head Mounted Displays • Can display either stereo or mono images • Stereo images (binocular disparity) • Same image twice (binocular concordance) • Single image (uniocular) • May be totally immersive or semi-immersive (see-through) • May include a built-in head-tracker • May have built-in stereo headphones

  14. VPL Eyephone & Olympus Eye-trek • The VPL EyePhone in early 1990s – The first LCD-based HMD – Resolution of 360 x 240 – FOV of 100o horizontally and 60o vertically – 2.4 kg – Induce user fatigue • The Olympus EyeTrek in 2000 – Resolution of 267 x 225 (FMD200) – 30o horizontally and 22.7o vertically – 100 grams

  15. Dayang Cy-visor DH-4400VP • Liquid-crystal-on-silicon (LCOS) display • Higher electrode densities (e.g., display resolution) • Reduced power consumption • Reduced volume • Reduced manufacturing costs • SVGA-resolution (800 x 600) • 60o horizontal x 43o vertical FOV • 160 grams

  16. ProView XL35 • The professional grade LCD-based HMD • High-resolution AMLCD displays • The support allows for the placement of a tracker close to the top of the head • 28o horizontal x 21o vertical stereo: 100% overlap • XGA resolution (1024 x 768 x 3 pixels) • Very low virtual image granularity: 1.6 arc-minutes/color pixel • Adjustable IPD (55-75 mm) • Allow eyeglasses to be worn together • 992 grams, $19,500

  17. Datavisor HiRes • Two monochrome miniature CRTs • 1280 x 1024 resolutions • 78o horizontal x 39o vertical FOV • IPD (58-73 mm) • Focal distance (from 0.25 m to infinity) • 1.9 arc-minutes/color pixel • 1587 grans, $35,000

  18. Virtual Retinal Display (VRD) • by Microvision • Image is projected directly onto the retina

  19. Video see-through AR • the computer graphics are overlaid on video of the real world • TriVisio ARvision-3D • Optical see-through AR • the virtual images are overlaid directly on the real world • MicroOptical HMV-V2

  20. HMD of the future? • Built by Toshiba in 2006 • 120° horizontally • 70° vertically • 40 centimetre dome-shaped screen • 3 Kg • Looking more like the helmet from Armstrong's space suit than the must-have product of tomorrow

  21. Hand-Supported Displays (HSD) • Personal graphics displays that the user holds in one or both hands in order to periodically view a synthetic scene • The user can go in and out of the simulation as required by the application • Hardware • – Similar to HMDs • – Push buttons used to interact with the virtual scene

  22. Virtual Binocular SX • Virtual Binocular SX by NVIS Inc. • Constructed to resemble the look and feel of regular binoculars • Allows variable distance focusing as well as zooming on the scene • Two miniature LCOS displays • A tracker to measure the user’s viewing direction • High-resolution image (1280 x 1024) • Low granularity (1.6 arc-minutes/pixel) • Large weight (about 1 kg, without the tracker) • High unit cost ($19,900)

  23. Floor-Supported Displays • HMDs and HSDs could cause simulation sickness from large time delay between corresponding head and image motions • The use of mechanical tracker: Almost instantaneous response to the user’s head motion • Characteristics of floor-supported displays • An articulated mechanical arm to offload the weight of the graphics display from the user • Integrate sensors directly in the mechanical support structure holding the display • Offer larger FOV and superior graphics resolution than HMDs or HSDs

  24. BOOM (Binocular Omni-Orientation Monitor) • By Fakespace • Uses a CRT to provide high-resolution display • It is comfortable to use, since it does not have to be worn • Has fast, accurate, built-in tracking

  25. BOOM3C • Fakespace Labs • A position resolution of 0.1o • The latency is negligible (0.2 msec) • Allows intermittent use of computer keyboards • Less freedom of motion due to a dead zone created by the supporting pole • Work envelope: A hollow cylinder of 1.8 m diameter and 0.8 m height • Graphics resolution: 1280 x 1024 • Considerably larger FOV than that of the Datavisor HMD

  26. Window VR • By Virtual Research Systems • A high-resolution LCD flat panel display: 21 in. diagonal, 1600 x 1200 pixels • Rely on third-party 3D trackers (InterSense 300 inertial trackers) that inherits the problems associated with latencies and tracker noise • Only monoscopic graphics can be displayed • Two handles with pushbuttons and switches • The weight is supported by cables connected to an overhead counterbalanced arm • The simplicity of the device and the lack of complex optics make it intuitive to use: The feeling is that of viewing the simulation through a window • No restrictive space inside the work envelope: The supporting arm is off-axis

  27. Desk-Supported Displays • HMDs and HSDs • Excessive display weight causes fatigue to users (e.g., neck and arm pain) • Floor-supported displays • Excessive weight increases inertia when the display is rotated • Can cause unwanted pendulum oscillations • Desk-supported displays • Fixed and designed to be viewed while the user is sitting: Weight is not an issue • The user’s freedom of motion is limited when compared to HMDs or HSDs

  28. Autostereoscopic displays • Produce a stereo image while viewed with unaided eyes • Do not wear any vision apparatus • “column-interlaced” image format • Alternates individual columns assigned to the left-eye view and the right-eye view • Reduced horizontal image resolution • Increased system complexity and increased cost • Two types: Passive & Active

  29. Passive autostereoscopic display • Do not track the user’s head • Restrict the user’s eyes to be within a small area for the stereo perception to be realized • The relation between the backlighting distance d and the distance to the user D determines a stereo viewing cone • DTI 2018XL Virtual Window & Sharp LL-151D

  30. Active autostereoscopic display • Tracking the user’s head and performing a real-time adaptation of the column interlaced image • Alleviate the problem of limited viewing volume in passive autostereoscopic display • Allows changes in viewing angle as large as ±25o to be accommodated when the user is 65 cm from the display • Apply mechanical means to adapt the column-interlaced image to the user’s head position • Ecomo4D display by Elsa

  31. Major drawbacks of personal graphics displays • Hard to justify the high price of professional grade products for one viewer • There are cases when more than one user has to look at the same image • Share ideas • Work collaboratively

  32. Large-Volume Displays • Graphics displays that allow several users located in close proximity to simultaneously view an image of the virtual world • Improves users’ freedom of motion and natural • interaction capability compared to personal displays • Classifications • Monitor-based (single or side-by-side CRTs) • Projector-based: Workbenches, CAVEs, display walls, and domes

  33. Monitor-Based Large-Volume Displays • Use the stereo-ready monitor • Capable of refreshing the screen at double the normal screen rate: 120-140 scans/sec • Each user wears a set of shutter glasses • An infrared (IR) emitter located on top of the CRT display controls the active glasses • Close and occlude one eye or the other alternately • A head tracker can be added to the system • Change the image according to the user’s viewing direction • Placed on top of the monitor

  34. Characteristics of Monitor-Based Large-Volume Displays • The image is much shaper than that of LCD-based HMDs • Not tiring even for long simulation times • The image is less luminous than on a normal screen • Require the direct line of sight between the IR emitter and the IR received • Only one person can control over the virtual scene • Work as a window to the virtual world • Limited working envelope • The user’s FOV grows with the reduction in the distance to the monitor and with the size of the screen

  35. Liquid Crystal Shutter (LCS) • Display shows left and right images alternately, switching at high speed between images • CRT monitor is required with double the normal scan rate • Infrared (IR) emitter can be used to synchronize the active glasses in a wireless mode • Typical 'Fishtank VR' • Particularly good for large audiences in a theatre

  36. Panoram • PV290 display by Panoram Technologies • Three TFT panels, each with a resolution of 1280 x 1024 pixels • Compound image with 3840 x 1024 pixels: Require proper synchronization

  37. Projector-Based Displays • Allow many closely located users to participate in a VR simulation • CRT projectors to produce the stereo-pair image • More recently digital projectors replaced CRT projectors • Frame sequential mode • The projector splits the number of scan lines in two • The user wearing active glasses sees a stereo image • Drawbacks • Inability to project bright images • Cost

  38. Workbench & V-Desk • Workbench by Fakespace in 1998 • The first projector-based large-volume displays • Project 3D scene on a large horizontal table-size display • V-Desk 6 by Trimension in 2001

  39. Stereo viewing cone of Workbench • Several viewers wearing active glasses can simultaneously see 3D objects floating on top of the workbench in a stereo viewing cone. • This cone depends on the position of the user and the degree of tilting of the workbench surface. • If the workbench is horizontal, tall 3D objects will be clipped at the side opposite the user • The stereo collapsed effect • Modern workbenches allow the user to control the workbench angle based on application needs • L-shaped workbench

  40. Projector arrays • A large-volume display formed of a number of functionally identical projectors calibrated to display a tiled composite image of the virtual scene • Used to simultaneously satisfy the requirements of large image size, image brightness, and high resolution for wall-size displays • Requirements: Synchronization, Color uniformity and brightness • Example: PanoWall and Workwall

  41. Blending the array images • Very important for the image quality • Approximately 25% of adjacent images are overlapped • Increases luminosity in the overlapping zones • Images coming from the multiple graphics computer is preprocessed

  42. CAVE • CAVE by Electronic Visualization Lab, Univ. of Illinois at Chicago, 1993 • Consists of 10-ft (~ 3m) cubical structure • Four CRT projectors: The front, the left, the right sides, and the floor • The projectors are synchronized to reduce flicker • About 12 users wearing active glasses see a very convincing 3D scene

  43. Domes • Large, spherical displays that produce a 360o FOV surroundings • As large as 400-500 viewers • Rely on multiple projectors arranged radially around a semispherical rear-projection screen • The number of projectors depends on the application and the dome dimensions • Require special optics to pre-distort the image prior to projection on the curved screen • V-Domes are used in high-tech theaters cost about 2 million dollars

  44. Passive polarized stereo projector • Differently polarizing filters are placed in front of each projector lens • Users wear polarizing glasses where each lens only admits the light from the corresponding projector

  45. Passive polarized stereo projector • Use pairs of polarized projectors • Use inexpensive polarized glasses: About $1 each • “Passive” stereo glasses have lenses polarized differently for the right and left eyes • Each eye sees the image component of the stereo pair with matching polarization • The brain integrates the two images for the stereo effect • Less expensive solution for large groups of people looking at a stereo image than using active glasses

  46. Sound Displays • Computer interfaces that provide synthetic sound feedback to users interacting with the virtual world • The sound can be monaural (both ears hear the same sound) or binaural (each ear hears a different sound) • Play an important role in increasing the simulation realism by complementing the visual feedback provided by the graphics displays • When sound is added, the user’s interactivity, immersion, and perceived image quality increase

  47. Importance of Sound • Important to create a sense of atmosphere • Can greatly enhance feeling of presence • Can be used to provide valuable depth cues, aiding navigation • Enables the user to perceive events that occur outside the immediate field of view • Highly immersive virtual reality simulationsshould have 3D sound in addition to graphicsfeedback • A virtual ball bouncing in a virtual room that isdisplayed on a CRT monitor: Simple monaural sound is sufficient • A virtual ball bouncing in a virtual room that isdisplayed on a HMD: The simulation needs a device that provides binauralsound in order to localize the sound in 3D spacerelative to the user

  48. Stereo vs. 3D sound • Stereo sound on headphone • Seems to emanate inside the user’s head • Nor externalized as real sounds are • Sound source will follow the user’s head motion • 3D sound on headphones or on speakers • Contain significant psychoacoustic information to alter the user’s perception in believing that the recorded sound is actually coming from the user’s surroundings • Sound source is localized in space • Direct sound from the source + sound bounced off the walls, the floor, and the ceiling

  49. The Human Auditory System • Human perceive sound through vibrations arriving at the brain via the skeletal system or via the ear canal • Elements used by the brain to measure the source location • – Intensity, frequency, and temporal cues present in the sound perceived by the left and right ears

  50. The Vertical-Polar Coordinate System • Measure the sound source location: determined by three variables, azimuth, elevation, and range • Azimuth angle • The angle between the nose and a plane containing the source and the vertical axis z • -180o ≤ θ ≤ 180o • Elevation angle • The angle between the horizontal plane by a line passing through the source and the center of the head • -90o ≤ ψ ≤ 90o • Range • The distance to the source measured along this line

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