Displays - CAIG Lab

caig.cs.nctu.edu.tw

Displays - CAIG Lab

Human Computer Interaction

8. 3D User Interfaces (A)

Display and devices

Course no. ILE5013

National Chiao Tung Univ, Taiwan

By: I-Chen Lin, Assistant Professor


Objectives

• Display interfaces in addition to PC monitors.

• Devices conforming to users’ perceptual

abilities.

• The applications of advances display.

Ref:

• D.A. Bowman, E. Kruijff, J.J. LaViola, I. Poupyrev, 3D User Interfaces: Theory and

Practice, Addison Wesley Professional, 2005.

• Course notes, “3D User Interfaces”, CS, Columbia Univ..


Displays

Displays, aka output devices, present information to

human senses.

• For a single user or multiple users.

• Scene representations are rendered or composed

into a form that can be presented by a display.

• Computer graphics and image processing tech.

• Properties

• Sampling

• Resolution

• ……


Visual Perception

• Range

• 400~700 nm

http://www.yorku.ca/eye/spectru.htm


Visual Perception (cont.)

• Red, green, blue cones

http://www.normankoren.com


Spatial Resolution

• ~1 arc minute (1/60 of a degree)

• Visual acuity (VA) in Snellen notation

• VA = D'/D

• D' is the standard viewing distance

(usually 6 meters)

• D is the distance at which each

letter of this line subtends 5

minutes of arc (each stroke of the

letter subtending 1 minute)

• MAR: minimum angle of resolution

Snellen Notation

Metric Imperial

MAR logMAR Decimal

6/60 20/200 10 1.0 0.10

6/48 20/160 8.0 0.9 0.13

6/38 20/125 6.3 0.8 0.16

6/30 20/100 5.0 0.7 0.20

6/24 20/80 4.0 0.6 0.25

6/19 20/60 3.2 0.5 0.32

6/15 20/50 2.5 0.4 0.40

6/12 20/40 2.0 0.3 0.50

6/9.5 20/30 1.6 0.2 0.63

E

6 meter distance

5 arc minute

6/7.5 20/25 1.25 0.1 0.80

6/6 20/20 1.00 0.0 1.00

6/4.8 20/16 0.80 -0.1 1.25

6/3.8 20/12.5 0.63 -0.2 1.58

6/3.0 20/10 0.50 -0.3 2.00


Visual Perception (cont.)

• Temporal resolution

• ~ 25–60 Hz (and higher): flicker fusion frequency

• Dependent on brightness, location on the retina

• higher for a fatigued observer

• Field of view

• Both eyes: ~ 200° horizontal, 120° stereo overlap

• One eye: ~ 60° toward nose, 90° toward side, 50° up,

70° down


Visual Cues

• E.g. depth cues, helping us understand the depth of

objects

• Monocular, static (pictorial)

• Monocular, dynamic

• Binocular


Monocular, Static Cues

• Relative size

• Occlusion

• Perspective

• Linear

• Aerial


Monocular, Static Cues

• Lighting

• Shadow

• Texture gradients


Monocular, Dynamic Cues

• Motion parallax


Binocular Cues

http://www.yorku.ca/eye/disparit.htm

http://www.csus.edu/indiv/w/

wickelgren/psyc110/Stereopsis.jpg


3D Displays

• Conforming to #visual properties dependent on goals,

budgets, requirement of realism, etc.

www.fakespace.com

www.elumens.com


3D Displays (cont.)

www.ait.nrl.navy.mil/vrlab/projects/Workbench

www.evl.uic.edu

www.fakespace.com/curv.shtml


Visual Display Characteristics

• Resolution

• Absolute: Pixels per linear inch

• Relative: Pixels per degree

• May vary across display

• Absolute variance caused by unequal distribution

• E.g., Higher pixel density at center of display

• Relative variance caused by user position

• E.g., Higher pixel density at periphery

Absolute variance

Relative variance


Visual Display Characteristics

• Field of Regard (FOR)

• Degrees of visual angle within which imagery can be

presented by a display

• Often measured in horizontal, vertical (or diagonal)

degrees

• Depends on location of user relative to display

• Field of View (FOV)

• Portion of the FOR that can be seen by a user at a given

point in time


Stereoscopic Viewing

• Spatial multiplexing

• Stereoscope

• Presents each eye with its

own view

• Viewing in virtual

environment

• Changing views according

to head poses.

users.telenet.be/thomasweynants

/stereoscope.html

www.microvision.com


Boom Displays

• High-resolution stereo display

• Mounted on a counterbalanced arm

• Serves as a mechanical tracker

• Makes it easy to manipulate massive display

NASA Ames Virtual Wind Tunnel


Stereoscopic Viewing

• Temporal multiplexing

• Liquid crystal shutter eyewear

• Right/left lenses alternatively

opacify in synchrony with display

of left/right views

• Synchronized to infrared emitter

http://www.stereographics.com

http://ccrs.nrcan.gc.ca/resource/tutor/stereo


Stereoscopic Viewing

• Spectral multiplexing

• “Red–blue” anaglyph stereo

• Display overlapped left/right images in red/blue.

• Can process only edges to retain color in object interior

mars.jpl.nasa.gov/MPF/mpf/anaglyph-arc.htm


Stereoscopic Viewing

• Polarization multiplexing

• Linear (horizontal/vertical): limited head

tilting

• Circular (lefthanded/right-handed)

• Screen must preserve polarization (metallized)

http://www.stereoscopy.com

http://www.barco.com


Geometry of Large display

• Surface geometry

• Planar

• Curved

• Hemispheric

• Multiple surfaces

www.fakespace.com

www.fakespace.com/curv.shtml

www.elumens.com


CAVE (Cave Automatic Virtual Environment)

www.evl.uic.edu


Autostereoscopic Viewing

• Spatial multiplexing

• Parallax barrier methods

• Parallax stereogram

• by interleaving the columns from two images

http://local.wasp.uwa.edu.au/~pbourke/stereographics/lenticular/


Autostereoscopic Viewing

• Spatial multiplexing

• Parallax barrier methods

• Parallax panoramagram

• Can use physically moving mechanical or virtually moving

liquid crystal barrier to create active display for a tracked

user


Autostereoscopic Viewing

• Spatial multiplexing

• Lenticular approach

• Array of cylindrical lenses

• Brighter than barrier

http://www.holografika.com/

http://local.wasp.uwa.edu.au/~pbourke/stereographics/lenticular/


Optical See-Through Displays

• optics: “mirror beam splitter” = “combiner”

• Real world is full resolution/FOV, but

• virtual world cannot block real world

• virtual/real worlds at ∆ distances

Synthetic graphics/

Augmented info.

Saab AddVisor 150


Video See-Through Displays

• Videomixing

• Real world is low resolution/FOV, but

• virtual world can block real world

• virtual/real worlds at same distance

• problems with camera mounting/optics

Camera

Synthetic graphics

Mixed Reality Systems Lab COASTAR

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