Stereoscopy: from XY to Z3D Hints and Comfortable Stereoscopy

(2011/08/11)

OLM Digital, Inc.

Salvati Marc

Stereoscopy at OLM Digital, Inc

• Pokémon 3D Adventure 1&2– "Myū wo Sagase!” (2005)– "Pikachū no Kaitei Daibōken“ (2006)

• Drive Soul (2009)– Full CG stereoscopy test

• Inazuma Eleven The Movie (2010)– http://www.inazuma-movie.jp/– Japanese animation movie (1h30)– In house education – Development of production tools– Detailed depth– Safe Stereoscopy (for children!)

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Video

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P11_335-350

Overview

• 3D Hints

– Understanding depth perception

• Disparity range and comfort

• Display environment and comfort

• Confusing 3D

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3D HintsUnderstanding Depth Perception

(Stereopsis)

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3D Hints

• From our knowledge of the real world

– Size, position, shape

– Depth continuity

– Overlap, motion parallax

– Color, texture

• Usage

– When writing the storyboard

– When deciding parallax while converting 2D/3D

– When choosing candidate for impressive 3D

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Big/Small

• Big = close small = far

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Up/Down

• Upper = far, Lower = close

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Shape

• Shape of object changes with vanishing points

– Brain infers distance, size, angle information

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Depth Continuity

• Which one is closer?

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• More information makes it clear

– Depth continuity results in an easier depth resolution

Depth Continuity

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Overlap effect

• Overlapping info relates to distance

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Motion Parallax

• In the train, closer objects move faster

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Texture details

• Small details = far

• Rough details = close

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Color in open space

Blue channel

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Saturation

Brightness

Amplified contrast

Original

Decrease

Increase

Color in closed spase

• Darkness can increase with distance

– Well effect

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Conclusion

• Brain is great

– Used to real world

– Only with some hints, we get depth feeling

• Use and abuse 3D hints

– A scene with few 3D hints is a poor 3D scene

– Adding more disparity will not fix a poor 3D scene!

– Change camera angles, think the storyboard with 3D in mind!

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Disparity rangeand

Comfortable Stereoscopic Vision

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Comfortable Stereoscopic Vision

• Depth range control is necessary

– For impressive experience

– For comfortable experience

• Control depth within human limits

– Divergence limits

– Disparity range limits

• Concretely, how to do?

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Attention! Contradictory! Balance is critical!

Human Limits

• Divergence

– Human eyes usually do not diverge

– Inter-ocular distance

• Adult average: 6.35-6.5cm (up to more than 7cm)

• Children：5cm

• Disparity range limits (angle)

– Comfort limit: 0.5°～2-3°

– Disparity range sudden change

• Eye resolution

– Cannot see small details

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Divergence Limits

ＮＧ

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Disparity range definition

C A

Disparity range ＝ A － C

Accommodation

Convergence

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Disparity range definition

A C

Disparity range ＝ C － A

Accommodation

Convergence

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Disparity range definition

Far object Close object

C1

C2

Disparity range ＝｜C1 － C2｜

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Comfort limits

• Disparity range limits

Disparity range (degree)

Sensation

0～0.5 Comfortable

0.5～1 Small fatigue

1～2 Fatigue

2～3 Pain

3～ No stereoscopic fusion

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Sudden change in disparity range

• Forcing to change range can be painful

– Be aware of the cut effect

– The cut disparity range angle has to respect the limits

t

t+1

t t+1

ＯＫＮＧ

• Eye can not make the distinction with less than 0.016° between two objects

• More than 180m in theater

＜0.016°

Eye precision

?

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Concretely

• Avoid divergence

• Respect disparity range angle limit

– Forecast the resulting angle

• Display environment (cinema, TV, PC)

• Limit the depth budget accordingly

– Decide the limit of screen parallax

• Use depth script

– Manage eye fatigue

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Display Environment and Comfort

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Stereoscopic Display

• System to separate left and right image

– Color (anaglyph), light polarization (polarized glasses)

– Time (shutter glasses)

– Space (no glasses)

• Cross-talk problem

– Leak from one eye

to the other

– Ghost effect

• Comfort and Display

– Distance + Screen size ⇒ Disparity range

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Ghost

effect

Pro and Cons of Stereoscopic Display

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Display Pro Cons Application

Anaglyph + normal display

Can be seen withany kind of displaySimple to useCheap

Cross TalkColorizationTiredness

Individual preview during production

Polarized glass Light, cheap glassesNo batteryFew cross talk

Need specific,expensive display

CinemaEx: realD, IMAX

Shutter glasses CheapSimple to use with common projector, monitor

Expensive glassesNeed batterySynchronization is critical

Preview, cinemaEx: Xpand3D, nVidiaSony 3D tv…

No glasses No glasses ExpensiveFatigueImage qualityView angle

ExhibitionGadget?Ex: Nintendo 3ds

Television, personal computer

• Distance is related to the screen size

– Can predict

• Audience is at same distance

D

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D

Cinema

• People may be at really different distances

– Need to make compromise for everyone comfort

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Disparity Range Limits Example

• Screen resolution:1920x1080

• Inter-ocular distance = 0.05m (children limit)

• Distance to the screen

– Computer: 0.5m

– Cinema: 10m

• Screen size

– Computer: 0.75m

– Cinema: 7.5m

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Positive parallax(px)

Negative parallax

Computer(px)

Negative parallax

Cinema(px)

0 45 90

13 31 77

20 25 ×

45 0 ×

Parallax range (Pain)

Summary

• Predict and adapt– Display/projection environment(screen size, distance,

children..)– Respect disparity range angle limits– Avoid sudden disparity/parallax big changes– If exceeds comfort zone

• Progressively• For a short time

– Divergence• Positive parallax less than 5cm to avoid problem for all customers

• Don’t trust yourself– PC and cinema is different! Check in big environments– You’ll get used to fusion and have less and less pain!

Attention!Contradictory goal!

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Example of pain

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• Angle pattern

• Angle range: from 0.5° to 4° and more

– 5.5m distance, 11m distance and 22m distance

• Divergence: from 6cm to 48cm

• For adults: binocular distance=6.5cm

Disparity range angle limits (1m screen)

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Other Confusing Pictures

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Place relative to the screen

• 3D perception is deformed from the side

• Need to adapt theater layout?

Side Front

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• Cannot see what we should

From the side, unnatural feeling

Side front

confusion

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• More details in other course part

Breaking the stereoscopic window

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?

Other confusing images

• Vertical parallax

• LR inversion

• Pattern/checker like BG pattern (See other part)– Pattern size and parallax may conflict

• Pure black is always perceived in the screen– Don’t use pure black, add lights

• More contrast, more leak– Leak of light between eyes (cross talk)

– Strongly depends on projection environment

– Try to avoid too big contrast

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Other confusing images

• Motion sickness

– Rotation: faster than 30degrees/seconds=sickness

– Translation: cutting the screen in less than 1seconds = sickness

• No details is unnatural

– Stereoscopic fusion becomes difficult

– Try to always BG and details in the BG

– Flat colors are flat in stereoscopic images too

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Final Conclusion and Advices

• Safe parallax is necessary, but not enough

– Exploit 3D hints

– Manage viewer fatigue

– Manage floating window

– Avoid confusing pictures

• Parallax

– Divergence: 5~7cm

– Disparity angle range: < 2-3°

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