Output Devices - I

Universidade de Aveiro Departamento de Electrónica, Telecomunicações e Informática

Realidade Virtual e Aumentada 2017/2018 Beatriz Sousa Santos

What is Virtual Reality?

“A high-end user interface that involves real-time simulation and interaction through multiple sensorial channels.” (vision, sound, touch, smell, taste) (Burdea and Coiffet., 2003)

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Output Devices: Graphics, 3-D Sound, and Haptic Displays

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(Burdea and Coiffet., 2003)

The human senses need specialized interfaces

• Graphics displays for visual feedback

• 3-D audio hardware for localized sound

• Haptic interfaces for force and touch feedback

Only a few examples of experimental devices providing smell olfactory and taste feedback

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The ultimate display?

"The ultimate display would, of course, be a room within which the computer can control the existence of matter. A chair displayed in such a room would be good enough to sit in. Handcuffs displayed in such a room would be confining, and a bullet displayed in such a room would be fatal.” (Ivan Sutherland, 1965)

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Visual Displays

“A graphics display is a computer interface that presents synthetic world images to one or several users interacting with the virtual world.”

(Burdea and Coiffet., 2003)

• Personal displays: Main technologies:

- HMDs (VR/AR)

- Binoculars LEDs/OLEDs

- Monitor-based displays/active glasses LCDs

- Autostereoscopic displays lenticular/barrier

• Large volume displays:

–Workbenches

– Caves projectors

– Walls, domes

– Surface … …

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Human Visual System

And depth perception

• Vision is the dominant sensorial channel

• Depth perception in mono images is based:

- on occlusion (one object blocks another from view)

- shadows

- textures

- motion parallax

(closer images appear to move more than distant ones)

(Burdea and Coiffet., 2003)

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• Depth perception in stereo is based on stereopsis

(when the brain registers and fuses two images)

• Image parallax means that the two eyes register different images

(horizontal shift)

• The amount of shift depends on the “inter-pupillary distance”

(IPD) (varies for each person in the range of 53-73 mm)

• Works in the near field (to a few meters from the eye)

• 3-5% of people are stereoblind

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(Jerald., 2016)

• Many of the perceptual cues we use to visualize 3D structures are available in 2D projections

• Such cues include: – occlusion (one object partially covering another) – perspective (point of view) – familiar size (we know the real-world sizes of many objects) – atmospheric haze (objects further away look more washed out)

• Four cues are missing from 2D media:

– stereo parallax—seeing a different image with each eye – movement parallax—seeing different images when we move the head – accommodation—the eyes’ lenses focus on the object of interest – convergence—both eyes converge on the object of interest

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• All 3D display technologies (stereoscopic displays) provide at least stereo parallax

• Autostereoscopic displays provide the 3D image without needing any eyewear

• Volume displays provide a “real” 3D image

• VR systems use the first type (stereoscopic displays)

10 https://voxon.co/stl-rendering-voxon-vx1-3d-volumetric-display

Stereopsis

Stereo ="solid" or "three-dimensional“

opsis = appearance or sight

'binocular vision‘ , 'binocular depth perception' , 'stereoscopic depth perception'

• Stereopsis is the impression of depth that is perceived when a scene is viewed with both eyes by someone with normal binocular vision

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• Binocular disparity is due to the different position of our two eyes

Projection plane

eyes

object

Right eye image Left eye image

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Projection plane

eyes

object (Hearn and Baker, 2002)

• Need to present two images of the same scene

• The two images can be presented:

• at the same time on two displays (HMD)

• time-sequenced on one display (active glasses)

• spatially-sequenced on one display (auto-stereoscopic displays)

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Implications for Stereo Viewing devices

Left eye, right eye images

(Burdea and Coiffet., 2003)

Common ways to produce a 3D sensation

• Anaglyphs: two colored images and color coded glasses (red/cyan(green))

• Two images with different light polarization and polarizing glasses

– Linear and circular

• Double frame-rate displays combined with LCD shutter glasses

• Autostereoscopic displays

– Parallax barrier and lenticular lens

• Head Mounted Displays (HMDs)

and “exotic displays”

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• All show the right image to the right eye and the left image to the left eye!

• All these technologies provide:

• stereo parallax

• When combined with head tracking,

they can provide

• movement parallax

for a single viewer

• In Virtual Reality the technologies used are:

- Different light polarization and polarizing glasses

- Double frame-rate displays combined with LCD shutter glasses

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Polarized light stereoscopy

• 3D movies have used polarized technology since the 1930s

• Two images are projected on the same screen through different polarizing filters

• Gray linear-polarizing filters are easily manufactured, thus correct color rendition is possible

• Two types of polarization can be used: • Linear • Circular

Vertical polarizer

Circular polarized light

http://en.wikipedia.org/ wiki/Polarized_3D_glasses

Verical polarization of light

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• Advantages of polarized glasses:

– are generally inexpensive

– don't require any power

– don't require synchronization with the display

– do not suffer from flicker

• Disadvantages:

– The images for polarized glasses may have to share the screen simultaneously, and therefore cannot have full resolution

– There are incompatible polarized systems (circular or linear polarized)

– The head should not be tilted to maintain the 3D effect with linear polarization

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https://www.inition.co.uk/extraordinary-technology/stereoscopic-3d-displays/

Shutter glasses for stereoscopic displays

• Active-shutter glasses are small LCD screens that alternately dim the left and right "lenses" in succession

• They are synchronized with the display usually through IR or radio signals

• Each eye can see the image intended for it

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• Can be bought for < 100€

• Need a battery

Passive (polarized) versus active (shutter)?

• Active

– Better image quality

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• Passive

– cheaper

– lighter

– batteryless

– syncless glasses

Visual Displays in Virtual Reality

“A graphics display is a computer interface that presents synthetic world images to one or several users interacting with the virtual world.”

(Burdea and Coiffet., 2003)

• Personal displays: Main technologies:

- HMDs (VR/AR)

- Binoculars/hand held LEDs/OLEDs

- Monitor-based displays/active glasses LCDs

- Autostereoscopic displays lenticular/barrier

• Large volume displays:

–Workbenches

– Caves projectors

– Walls, domes

– Surface … …

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Main Properties of Visual Displays

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Visual presentation properties:

• Color

• Spatial resolution

• Contrast

• Number of display channels

• Focal distance

• Opacity

• Masking

• Field of view (FOV)

• Field of regard (FOR)

• Head position information

• Graphics latency tolerance

• Temporal resolution

Logistic Properties:

• User mobility

• Interface with tracking

• Environment requirements

• Associability with other sense displays

• Portability

• Throughput

• Encumbrance

• Safety

• Cost

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Focal distance

Focal distance is the measurement between the participant's eyes and the virtual image. (A) projection display - distance to the display screen. (B) HMDs create a virtual image at some distance beyond the physical display

Field of view (FOV) and Field of regard (FOR)

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(Sherman and Craig, 2003)

FOR is a measure of the amount of coverage a given display provides when head motion and other factors are considered. (A) Head-based displays can easily provide a loo% FOR, (B) stationary displays are limited to the area of the screens

FOV is the amount of the viewer's visual field covered by a display. Head-based displays (A) tend to have smaller, fixed FOV angles compared with those possible in projection- based displays

Visual Displays: a possible taxonomy (Burdea and Coiffet, 2003)

• Personal displays:

- HMDs (VR/AR)

- Binoculars

- Monitor-based displays/active glasses

- Autostereoscopic displays

• Large volume displays:

– Workbenches

– Caves

– Walls, domes

– Surface … …

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Visual Displays: another taxonomy (Sherman and Craig, 2003)

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• Head-based (occlusive)

• Non-occlusive head-based

• Handheld

• Monitor- based (Fishtank)

• Projection Displays Stationary displays

Personal Displays

A Visual display that outputs a virtual scene destined to be viewed by a single user. Such image may be monoscopic or stereoscopic, monocular (for a single eye) or binocular (displayed on both eyes).

• Head Mounted Displays (HMDs)

• 3-D Binoculars (hand supported)

• Auto-stereoscopic displays

(desk supported)

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HMD integration in a VR system

simple HMD

More professional HMD

(Burdea and Coiffet., 2003) 28

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- Bright, crisp, high-contrast OLED display

- Stereo

- High resolution full-color SXGA 1280×1024 pixels

- 60º field of view

- Integrated yaw/pitch/roll tracker

- Self contained, lightweight (450 g)

- Integrated high-quality stereo audio and microphone

- Price ~$13000

Example of a “professional” HMD zSight™ OLED HMD (Sensics)

http://sensics.com/portfolio-posts/zsight/

The low cost Head-Mounted Displays: Oculus Rift

http://www.oculusvr.com/

2014, DK2: - low persistence OLED display to eliminate

motion blur and judder (two of the biggest contributors to simulator sickness)

- It also makes the scene appear more visually stable, increasing the potential for presence

- 960×1080 pixels per-eye display improves clarity, color, and contrast.

Price: ~~$400

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Oculus Rift and human factors in VR

http://www.youtube.com/watch?v=iACAS_RAneE

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Oculus Rift vs PlayStation VR: What is the best VR gaming headset?

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https://www.wareable.com/vr/oculus-rift-vs-playstation-vr

HTC Vive

https://www.vive.com/eu/

Price: ~~$700

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Headsets using Smartphones: Google Cardboard

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https://en.wikipedia.org/wiki/Google_Cardboard

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https://techcrunch.com/2016/11/10/googles-daydream-view-made-me-a-believer-again-in-consumer-vr/

Popular Augmented Reality Headsets: Google Glass (2013)

http://www.youtube.com/watch?v=JSnB06um5r4

https://www.google.com/glass/start/

https://www.wired.com/story/google-glass-2-is-here/

Display - reflects light into the wearer's eye Camera – photos and video Touchpad – on the side Micro – voice control 1500 $

Google glass (2015)

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http://www.pcadvisor.co.uk/feature/gadget/google-glass-release-date-uk-price-specs-3436249/

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Google glass (2017?)

https://www.wired.com/story/google-glass-2-is-here/

Meta Glasses

• 3D See Through Display

- Resolution: 960 x 540 pixels per eye

- FOV : 35 degree field of view

• Cameras

- 3D Time-of-flight depth camera

- Color (RGB) Camera

• Head Tracking

- 360 degree tracking

- Accelerometer, gyroscope and compass

• Audio

- Dolby 3D audio

- Two built-in microphones

• Now there is a new version: Meta2

40 https://www.metavision.com/

Hololens Microsoft AR glasses

https://www.microsoft.com/en-us/hololens/

Developement edition: 3000 $ Thyssenkrupp – a new vision to elevator maintenance: Preparing the visit: On site:

https://www.youtube.com/watch?v=8OWhGiyR4Ns

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Hand Held devices

- Binoculars (older and more expensive) - Tablets/ smartphones (more and more used for AR)

(Jerald, 2016)

Virtual Binoculars

(Burdea and Coiffet., 2003) 43

• Handheld, interactive, immersive displays

• combine high-resolution microdisplays with adjustable, wide field-of-view optics

• Have a familiar form (pair of binoculars)

• May have a tracker as accessory

Examples:

Virtual Binocular SX

Virtual Binocular SV

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Virtual Binocular SX

Price: $7,900

Virtual Binocular SV

Price: $20,900

• Two technologies:

lenticular

barrier

• Do not require use of special glasses

• Allow several vantage points

Passive - do not track user’s head (restrict user’s position)

Active - track the head motion (give more freedom)

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Auto-stereoscopic displays

Lenticular:

– an array of cylindrical lenslets is placed in front of the pixel raster

– lenslets direct the light from adjacent pixel columns to different viewing slots at the ideal viewing distance

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Each of the viewer’s eyes sees light from only every second pixel column

Commercial examples: - 45”; 1920 x 1080 pixels; 8 view points - 84”; 3840 x 2160 pixels; 16 view points http://www.alioscopy.com/en/3Ddisplays.php

Parallax barrier:

– a barrier mask is placed in front of the pixel raster

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Each of the viewer’s eyes sees light from only every second pixel column

Holographic displays

• The image source is based on standard flat panel technology of which the image is seen upon glass panel with several optical layers

• Objects appear to float in space

• For the maximum 3D effect, the background seen through the display should be several feet behind the display and dark in color

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http://www.eonreality.com/eon-holographic-i

Large Volume Displays • Allow several co-located users to view a monoscopic or stereoscopic view of

the virtual world

- monitor-based large volume displays

- projector-based large volume displays

• Allow more freedom of motion vs. personal displays.

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Projector based Large-volume displays

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• CAVE type displays

• Wall-type displays

• Domes

• Workbanch-type displays

CAVE 3-D large volume display (Fakespace Co.)

(Plato’s allegory of the cave, where a philosopher contemplates reality and illusion ...)

CRT Projector

Mirror

Screen

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CAVEs

http://www.mechdyne.com/cave.aspx

Enter the CAVE

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Examples of several CAVE configurations and prices

http://www.visbox.com/products/cave/

http://www.mechdyne.com/cave2.aspx

CAVE 2TM

“near-seamless, 320-degree,

panoramic 2D/3D virtual

environment that matches

human visual acuity . . .

The CAVE2™ is a revolutionary

system that supports

information-rich analysis with

stunning immersive visuals

and intuitive interaction tools”

• Accommodate several users

• A single projector on a large wall means small image resolution

• Tiled displays place smaller images side-by-side so they need multiple projectors

• Images need to have overlap, to assure continuity

• However overlap from two projectors means intensity discontinuity (brighter

images in the overlap areas) • Projectors need to modulate intensities to dim their light for overlap pixels

Wall-type displays

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http://www.mechdyne.com/portable-3d-display.aspx

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• Widely installed immersive reconfigurable visual environment

• Adequate for applications that will benefit from more than one display configuration (there is a mobile version)

• Walls can be moved independently to create new formats (7.5' x 10' )

• Has three walls and one floor screen • In < 5 min can become: - A flat wall display - An angled theater,

- An L-shape - A CAVE-like immersive room

FLEX TM - Reconfigurable immersive display

http://www.mechdyne.com/flex.aspx http://www.mechdyne.com/plex.aspx

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Wall-type displays

Typical uses:

• Multi-disciplinary research

• Product design reviews

• Large audience presentations

• Computational fluid dynamics

• Geophysical exploration and training

• Terrain mapping and situational awareness

• Any application where multiple display modes would be beneficial …

Issue: Tiled composite image from four projectors

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Tiled composite image from four projectors after adjustment

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Dome-type display Immersadome

http://inition.co.uk/3D-Technologies/immersive-display-immersadome-range

- 3D immersive visual environment

- Up to 20 people (depending on dome size)

- Resolution: 1400 x 1050

- 180°horizontal x 135°vertical (distortion

free projection)

- Multiple control options (mouse, keyboard, joystick, tracker-ball, haptic)

- Applications:

- museums, - group training - flight or driver simulation…

Advantages: • Accommodate many users (tens to hundreds)

• Give users more freedom of motion

Disadvantages: • Large cost (up to millions of dollars)

• Even with several displays resolution is low (larger area)

Dome-type displays

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http://pacificdomes.com/immersive-virtual-reality-dome-environments/

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Dome type displays

VisionDome 5(m); 2 to 20 users; price > $85,000.00

http://www.vrealities.com/products/vr-domes/visiondome-5

Visual Displays: another taxonomy (Sherman and Craig, 2003)

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• Head-based (occlusive)

• Non-occlusive head-based

• Handheld

• Monitor- based (Fishtank)

• Projection Displays Stationary displays

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Benefits of Stationary Displays (monitor and projection based)

• Higher resolution (than most HMDs)

• Wider field of view

• Longer user endurance (i.e., can stay immersed for longer periods)

• Higher tolerance for display latency

• Greater user mobility (fewer cables)

• Less encumbering

• Lower safety risk

• Better for group viewing

• Better throughput

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Benefits of Head-based Displays (Occlusive and Non-occlusive)

• Lower cost (for lower resolution models)

• Complete field of regard

• Greater portability

• Can be used for augmenting reality

• Can occlude the real world

• Less physical space required

• Less concern for room lighting and other environmental factors

Benefits of Hand-based Displays

• Greater user mobility

• Greater portability

• Can be combined with stationary VR displays

Main bibliography

- G. Burdea and P. Coiffet, Virtual Reality Technology, 2nd ed. Jonh Wiley and Sons, 2003

- Craig, A., Sherman, W., Will, J., Developing Virtual Reality Applications: Foundations of Effective Design, Morgan Kaufmann, 2009

- Jerald, J., The VR Book: Human-Centered Design for Virtual Reality, ACM and Morgan & Claypool, 2016

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