3/23/2005 © dr. zachary wartell 1 3d displays overview revision 1.3 copyright 2006 zachary wartell...
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3/23/2005 © Dr. Zachary Wartell 1
3D Displays Overview
Revision 1.3
Copyright 2006 Zachary WartellUniversity of North Carolina Charlotte
3/23/2005 © Dr. Zachary Wartell 2
3D Displays : Basic Properties
• (1) “retinal disparity”- (also called stereo parallax) display presents a left eye perspective view of a virtual scene to the left eye and different right eye perspective view to the right eye. The retinal disparities in the left and right retinal images induce a perceived 3D image of the scene. Implicitly the user experiences ocular vergence as she fixates on objects at different stereo depths.
• (2) “multi-viewpoint”- (also called motion parallax) image pair presented to the user’s eyes is dependent on the user’s head position; moving or walking around the display; the user perceives the virtual objects from different vantage points. “Multi-viewpoint” means continuous and correct changes to the perceived images as the head moves in any direction.
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Taxonomy
3D Displays
Volumetric 3D Displays
Surface 3D Displays
Holographic Stereoscopic
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Ideal Surface Display
C
A B
D
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unfocused
focused
Depth of Field
blur increases blur increases
unfocused
focused
Depth of Field
blur increases blur increases
Physical world creates natural blur
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Ideal Surface Display creates natural blur
out of focus
in focus
Ideal Surface Display
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Stereoscopic Surface Display
• cannot create the wavefronts of the synthetic 3D• multi-viewpoint property: a stereoscopic display must :
– determine the user’s head position– render a left and right eye image specifically
computed for that head position; – channel each of the two images to the appropriate
eye.
(while at a given moment a full holographic display outputs an image for every possible eye position, a typical stereoscopic display outputs an image for only the two current eye positions).
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Stereoscopic Surface Display Wavefronts
Stereoscopic Display
both in focus
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Accommodation and Vergence Link
physical box
eyes
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Accommodation and Vergence Link
physical box
fovea fixation point
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physical box
foveafixation point
Accommodation and Vergence Link
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physical box
accommodation depth = vergence depth
foveafixation point
Accommodation and Vergence Link
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blur increases
A) Physical
no blur!
B) Virtual
display
O=C=A
OC < A
blur increases
A) Physical
no blur!
B) Virtual
display
O=C=A
OC < A
Stereoscopic Display versus Physical World
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Fixate on farther object
blur increases
A) Physical
no blur!
B) Virtual
OC > A
O=C=A
display
blur increases
A) Physical
no blur!
B) Virtual
OC > A
O=C=A
display
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Fixate on even farther objects
blur increases
A) Physical
no blur!
B) Virtual
display
?
O=C=A
O, C=? >> A
blur increases
A) Physical
no blur!
B) Virtual
display
??
O=C=A
O, C=? >> A
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Fusion Metrics
Projection Plane
p
Eyes
Virtual Point hva
L R
A
-screen parallax, HVA, vergence difference
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Screen Parallax Projection Plane
Eyes
B
B
Projection Plane
Eyes
A
C
Projection Plane
Eyes
C
D
p = -es
p=0
p = +es
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Vergence Difference (-)
Projection Plane
Eyes
Virtual Point
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Image Cross-talk/Ghosting
filters display
left
right
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Experimental Limits in Stereo Display
• Valyus [Valy66] gives a vergence difference range of +/- 1.6 degrees.
• Yeh and Silverstein [Yeh90] – find a fusible HVA range of -4.93 to 1.57 degrees for
viewing durations that allow ocular vergence (2 s) – a HVA range of -27 min arc to 24 min arc for viewing
durations that don’t allow ocular vergence (200ms). They recommend keeping applications to the smaller of these ranges.
• William’s and Parrish’s experiments suggest a viewing volume of –25% through +60% of the head-to-screen distance.
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Comparing Far Fusible Depth
maximum depth planes
screen
pmax1
pmax2dmaxA2dmaxA1
AB dmaxB2
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Far Depth Limits
Head to Screen Distance (m)
A B
Far
Dep
th L
imit
(m)
Solid line – Valyus’s+1.6 vergence difference; Dash line – Yeh’s +1.57 HVA; Dash-dot - Valyus’s max parallax approximation; Circles – William and Parrish limits.
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Nearest Portrayable Depth
maximum depth planes
screen
pmax1
pmax2dmaxA1dmaxA2
AB
dmaxB2
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Limitations of Fusibility Limits
• varies with display technology• varies with contrast of given image• scenes have arbitrary distribution of depth –
experiments usually use single stimuli • individual differences, etc.
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View Frustums in Stereo
PRP
View Window
near clippingplane
far clipping plane
PRP
View Window
near clippingplane
far clipping plane
u
vn
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View Frustum ≠ Eye Pupil and Retina
• Recall ideal surface display (slide 6) versus stereoscopic display (slide 8)
left
right
pupils!
retina
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View Frustum = Eye Pupil and Physical Pixels
• graphics pipeline (frustum) knows nothing of retina’s shape, that is the brains problem!
left
right
physicalpixels!
pupils!
retina
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View Frustum = Eye Pupil and Physical Pixels
• Recall ideal surface display (slide 6) versus stereoscopic display (slide 8)
pupils! projection =physicalplane pixels
near clippingplanes
far clippingplanes
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HMD
HeadsetDisplays(Internal)
Head Mounted Display (HMD)
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HTD (Head-tracked Display)
3D Glasses
Head Tracker
Stationary Display
Desktop Stereo HTD
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View Coordinate Hierarchy (Simplified)
Platform
Tracker
Head-Sensor
Eyes
Projection Plane
? A Generic
Display-Sensor
Platform
Tracker
Head-Sensor
Eyes
Projection Plane
Platform
Tracker
Eyes Projection Plane
Head-Sensor
Platform
Tracker
Eyes Projection Plane
Head-Sensor
B HTD C HMD D “Free” HTD
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View Coordinate Hierarchy
• platform-to-world – position/orientation/scale – UI manipulates
• tracker-to-platform – fixed by physical display arrangement
• headSensor-to-tracker – dynamically determined by tracker hardware
• eyes-to-headSensor – fixed by physical display arrangement
• projectionPlane-to-(headSensor/platform) - fixed by physical display arrangement
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Small object closer by (=/≠) Large object far away
COP
Proj. Plane
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Platform Scale DOF
Object zoomed-out location Eye
Display Surface
Head Displacement
Projected Points
Eyes
Object start location
Unfusible Screen Parallax
Object zoomed-in location
A
B
Object zoomed-out location
Eye
Object start location
Frustum
C
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Four Eye Separations
Physical Virtual (Physical * Platform Scale)
True
True Physical Eye Separation (subject’s interocular)
True Virtual Eye Separation
Modeled
Modeled Physical Eye Separation (software value)
Modeled Virtual Eye Separation
Physical Virtual (Physical * 106)
True
True Physical Eye Separation 6.0 cm
True Virtual Eye Separation 60km
Modeled
Modeled Physical Eye Separation 3.0 cm
Modeled Virtual Eye Separation 30 km
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Proj. Window 5 x 5m (phys)
(virtual)12km
(physical)5m
Platform
Tracker
Head-Sensor
Eyes
Projection Plane
SW←Plat=SParent(Plat)←Plat=2400
y
xz
Plat.
physical: 1m virtual: 2400m
y
x
z
Eyes
HTD Example
modeled e.s. phy: 3.0cm
vir: 72m
true e.s. phy: 6.5cm
vir: 156m
S W←?=2400
S Parent(?)←?=1
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Goals for 3D Display
• generating fusible stereoscopic imagery• generating accurate stereoscopic imagery• maximizing the added value of stereoscopic
depth images • minimizing frame cancellation • bringing manipulated stereoscopic imagery
within arms’ reach to improve direct manipulation
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Generate Fusible Imagery
• hardware:– need ideal surface display (hologram)– dynamic depth image plane– multi-planar display
• software: geometric scene manipulation to reduce screen parallax
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Fusion Control
• heuristic limits on portrayed range of stereoscopic depth
• heuristic limits on portrayed range of stereoscopic depth
Comfortable Near Fusion
LimitComfortable
Far Fusion LimitScreen
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Fusion Control
Screen
• heuristic limits on portrayed range of stereoscopic depth
• heuristic limits on portrayed range of stereoscopic depth
Comfortable Near Fusion
LimitComfortable
Far Fusion Limit
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Fusion Control
Screen
• heuristic limits on portrayed range of stereoscopic depth
• heuristic limits on portrayed range of stereoscopic depth
Comfortable Near Fusion
LimitComfortable
Far Fusion Limit
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Frame cancellation/window violation
frustum virtual object
display frame
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Frame cancellation/window violation
A B
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Spatial Distortion
Virtual Modeled Adapted
Perceived
-perceptual matching-magnitude estimation-category estimation-mapping
-registration exp. -subjective magnitude
viewscale factor
fusioncontrol
technique
individual differences
& procedureeffect and
error
anaytic/geometricanalysis
experimentalanalysis
Displayed
calibrationerrors
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Displayed Distortion
• assume no modeled→adaptation distortion:
ImageDisplay= T * ImageModeled
• sources:– stereo-no tracking– stereo with eye pair offset error– stereo with tracking latency error– stereo with tracking & calibration error
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near space
Stereo-No Tracking: Induced Stereo Motion
• assume projection window is correctly measured and model eye separation = true eye sep.!
modeledmodeled
=true
=displayed
displayed
true
true
displayed
near space far spacex
z
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modeled
Induced Stereo Motion: Lateral-Near Space
=true
true
displayed
true
displayed
near space far space
Near Space Far Space
with head motion
opposite head motion
x
z
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near space
Induced Stereo Motion: Perpendicular-Far Space
modeledmodeled
=true
=displayed
true
far space
displayed
true
displayedtrue
x
z
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modeled
near space
Induced Stereo Motion: Perpendicular/Near Space
modeledtrue
far space
=true
true true Near Spc Far Spc
Hd Forw. forward backHd Back back forward
x
z
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Induced Stereo Motion: Shape
near space far space
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Tracking ideally removes induction stereo motion
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Eye Pair Offset Error
• modeled eye location pair is at constant translation offset true eye locaiton pair– constrant translational tracking error– translational mis-calibration between
coordinate systems in view hierarchy
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Tracking Latency Error
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Calibration Error
• miss-measure eye separation or screen size
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Fusion Adaptation Distortions
• assume no modeled→display distortion: ImageAdapted= T * ImageModeled