3/23/2005 © Dr. Zachary Wartell 1 3D Displays Overview Revision 1.3 Copyright 2006 Zachary Wartell...

3/23/2005 © Dr. Zachary Wartell 1

3D Displays Overview

Revision 1.3

Copyright 2006 Zachary WartellUniversity of North Carolina Charlotte


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.


Taxonomy

3D Displays

Volumetric 3D Displays

Surface 3D Displays

Holographic Stereoscopic


Ideal Surface Display

C

A B

D


unfocused

focused

Depth of Field

blur increases blur increases

unfocused

focused

Depth of Field

blur increases blur increases

Physical world creates natural blur


Ideal Surface Display creates natural blur

out of focus

in focus

Ideal Surface Display


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).


Stereoscopic Surface Display Wavefronts

Stereoscopic Display

both in focus


Accommodation and Vergence Link

physical box

eyes



physical box

fovea fixation point


physical box

foveafixation point



physical box

accommodation depth = vergence depth

foveafixation point



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


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


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


Fusion Metrics

Projection Plane

p

Eyes

Virtual Point hva

L R

A

-screen parallax, HVA, vergence difference


Screen Parallax Projection Plane

Eyes

B

B

Projection Plane

Eyes

A

C

Projection Plane

Eyes

C

D

p = -es

p=0

p = +es


Vergence Difference (-)

Projection Plane

Eyes

Virtual Point


Image Cross-talk/Ghosting

filters display

left

right


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.


Comparing Far Fusible Depth

maximum depth planes

screen

pmax1

pmax2dmaxA2dmaxA1

AB dmaxB2


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.


Nearest Portrayable Depth

maximum depth planes

screen

pmax1

pmax2dmaxA1dmaxA2

AB

dmaxB2


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.


View Frustums in Stereo

PRP

View Window

near clippingplane

far clipping plane

PRP

View Window

near clippingplane

far clipping plane

u

vn


View Frustum ≠ Eye Pupil and Retina

• Recall ideal surface display (slide 6) versus stereoscopic display (slide 8)

left

right

pupils!

retina


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


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


HMD

HeadsetDisplays(Internal)

Head Mounted Display (HMD)


HTD (Head-tracked Display)

3D Glasses

Head Tracker

Stationary Display

Desktop Stereo HTD


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


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


Small object closer by (=/≠) Large object far away

COP

Proj. Plane


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


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


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


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


Generate Fusible Imagery

• hardware:– need ideal surface display (hologram)– dynamic depth image plane– multi-planar display

• software: geometric scene manipulation to reduce screen parallax


Fusion Control

• heuristic limits on portrayed range of stereoscopic depth


Comfortable Near Fusion

LimitComfortable

Far Fusion LimitScreen


Fusion Control

Screen




LimitComfortable

Far Fusion Limit


Fusion Control

Screen




LimitComfortable

Far Fusion Limit


Frame cancellation/window violation

frustum virtual object

display frame


Frame cancellation/window violation

A B


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


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


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


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


near space

Induced Stereo Motion: Perpendicular-Far Space

modeledmodeled

=true

=displayed

true

far space

displayed

true

displayedtrue

x

z


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


Induced Stereo Motion: Shape

near space far space


Tracking ideally removes induction stereo motion


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


Tracking Latency Error


Calibration Error

• miss-measure eye separation or screen size


Fusion Adaptation Distortions

• assume no modeled→display distortion: ImageAdapted= T * ImageModeled

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3/23/2005 © Dr. Zachary Wartell 1 3D Displays Overview Revision 1.3 Copyright 2006 Zachary Wartell...

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