COMP4010 Lecture 4 - VR Technology - Visual and Haptic Displays. Lecture about VR visual and haptic display technology. Taught on August 16th 2016 by Mark Billinghurst from the University of South Australia
1. LECTURE 4: VR
TECHNOLOGY – VISUAL
AND HAPTIC DISPLAYS
COMP 4010 – Virtual Reality
Semester 5 - 2016
Mark Billinghurst, Bruce Thomas
University of South Australia
August 16th 2016
3. Using Technology to Stimulate Senses
• Simulate output
• E.g. simulate real scene
• Map output to devices
• Graphics to HMD
• Use devices to
stimulate the senses
• HMD stimulates eyes
Visual
Simulation
3D Graphics HMD Vision
System
Brain
Example: Visual Simulation
Human-Machine Interface
4. Key Technologies for VR Systems
• Visual Display
• Stimulate visual sense
• Audio/Tactile Display
• Stimulate hearing/touch
• Tracking
• Changing viewpoint
• User input
• Input Devices
• Supporting user interaction
10. Simple Magnifier HMD Design
p
q
Eyepiece
(one or more lenses) Display
(Image Source)
Eye f Image
1/p + 1/q = 1/f where
p = object distance (distance from image source to eyepiece)
q = image distance (distance of image from the lens)
f = focal length of the lens
12. Focal Length and Diopter
Focal Length - The
distance from the
surface of a lens at
which rays of light
converge.
Diopter - The power of
a lens. Equal to 1/
(focal length of the
lens measured in
meters)
13. Field of View
Monocular FOV is the angular subtense
(usually expressed in degrees) of the
displayed image as measured from the
pupil of one eye.
Total FOV is the total angular size of the displayed image
visible to both eyes.
Binocular(or stereoscopic) FOV refers to
the part of the displayed image visible to
both eyes.
FOV may be measured horizontally,
vertically or diagonally.
14. Ocularity
• Monocular - HMD
image goes to only
one eye.
• Bioccular - Same
HMD image to both
eyes.
• Binocular
(stereoscopic) -
Different but
matched images to
each eye.
15. Interpupillary Distance (IPD)
! IPD is the horizontal
distance between a
user's eyes.
! IPD is the distance
between the two
optical axes in a
binocular view system.
16. Vignetting and Eye Relief
Vignetting
• The blocking or
redirecting of light rays
as they pass through
the optical system.
Eye Relief Distance
• Distance from the last
optical surface in the
HMD optical system to
the front surface of the
eye.
17. LEEP Optics
• Large Expanse Extra
Perspective
• Very wide FOV for
stereoscopic images
• Higher resolution in
the middle of FOV
• Lower resolution on
the periphery
• Pincushion
distortion
19. Fresnel Lens
• A lens consisting of a
concentric series of simple
lens sections
• Result is a thin lens with a
short focal length and
large diameter
• More even resolution
distribution
• Less distortion
• from lanternroom.com
23. To Correct for Distortion
• Must predistort image
• This is a pixel-based
distortion
• Graphics rendering uses
linear interpolation!
• Too slow on most systems
• Use shader programming
24.
25. HMD Design Trade-offs
• Resolution vs field of view
• As FOV increases, resolution decreases for fixed pixels
• Eye box vs field of view
• Larger eye box limits field of view
• Size, Weight and Power vs everything else
vs.
26. The Perfect HMD
• “Oakley look” . i.e., thin & small optics
• Low cost & small image generators (OLED, LCOS, …)
• Wide field of view 30
o
to 110
o
full diagonal field
• Large eye box ~10 mm diameter, for eye ball movement
• Large eye relief > 20 mm, for lash clearance and glasses
• High resolution ~ SXGA (1280 x 1024) or higher
• Low distortion < 2%
• Bright hundreds of Cd/m2
• Artifact free; no “dirty windows” ; no raster; no sunlight scattering
• Low weight
• Other: eye tracking; battery life; connectivity….
35. Version 1.0 vs Version 2.0
• Version 1.0 – Android focused, magnetic switch, small phone
• Version 2.0 – Touch input, iOS/Android, fits many phones
41. Projection/Large Display Technologies
• Room Scale Projection
• CAVE, multi-wall environment
• Dome projection
• Hemisphere/spherical display
• Head/body inside
• Vehicle Simulator
• Simulated visual display in windows
42. CAVE
• Developed in 1992, EVL University of Illinois Chicago
• Multi-walled stereo projection environment
• Head tracked active stereo
Cruz-Neira, C., Sandin, D. J., DeFanti, T. A., Kenyon, R. V., & Hart, J. C. (1992). The CAVE: audio
visual experience automatic virtual environment. Communications of the ACM, 35(6), 64-73.
48. Multi-User CAVEs
• Limitation of CAVEs
• Stereo projection from only one user’s viewpoint
• Solution
• Higher frequency projectors and time slicing
Kulik, A., Kunert, A., Beck, S., Reichel, R., Blach, R., Zink, A., & Froehlich, B. (2011). C1x6: a
stereoscopic six-user display for co-located collaboration in shared virtual environments. ACM
Transactions on Graphics (TOG), 30(6), 188.
53. Allosphere
• Univ. California Santa Barbara
• One of a kind facility
• Immersive Spherical display
• 10 m diameter
• Inside 3 story anechoic cube
• Passive stereoscopic projection
• 26 projectors
• Visual tracking system for input
• See http://www.allosphere.ucsb.edu/
Kuchera-Morin, J., Wright, M., Wakefield, G., Roberts,
C., Adderton, D., Sajadi, B., ... & Majumder, A. (2014).
Immersive full-surround multi-user system
design. Computers & Graphics, 40, 10-21.
61. Haptic Feedback
• Greatly improves realism
• When is it needed?
• Other cues occluded/obstructed
• Required for task performance
• High bandwidth!
• Hands and wrist are most important
• High density of touch receptors
• Two kinds of feedback
• Touch Feedback
• information on texture, temperature, etc.
• Does not resist user contact
• Force Feedback
• information on weight, and inertia.
• Actively resists contact motion
62. Haptic Devices
• Pin arrays for the finger(s)
• Force-feedback "arms"
• "Pager" motors
• Particle brakes
• Passive haptics
• Many devices are application specific
• Like surgical devices
63. Active Haptics
• Actively resists contact motion
• Dimensions?
• Force resistance
• Frequency Response
• Degrees of Freedom
• Latency
• Intrusiveness
• Safety
• Comfort
• Portability
64. Force Feedback Joysticks
• WingMan Force 3D
• Inexpensive ($60)
• Actuators that can
move the joystick given
system commands
• Max 3.3 N of force
• Force feedback driving
wheel
70. Haptic Feedback in VR
• Virtual contact
• What should we do when we know that contact has been made
with a virtual object?
• The output of collision detection is the input to virtual contact
• Cues for understanding the nature of contact with objects are
typically over-simplified (e.g., sound)
• Training aids
• Can we convey additional information using the haptic channel?
77. Vibrotactile Cueing Devices
• Vibrotactile feedback has been incorporated into many
devices
• Can we use this technology to provide scalable, wearable
touch cues?
78. Tactile Mouse
• Logitch iFeel Mouse
• Electrical Actuator
• Shakes up and down (do
not disturb XY motion)
• Mouse over buttons
• Haptic Bump
• Rumble Pack
80. CyberTouch Glove
• Immersion Corporation
• Expensive - $15000
• Six Vibrotactile actuators
• Back of finger
• Palm
• Off-centered actuator motor
• Rotation speed=frequency of
vibration (0-125 Hz)
• When tracked virtual hand
intersects with virtual object,
send signal to glove to vibrate