Stereoscopy: from XY to Z
3D 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!)2VideoP11_335-350

3Overview• 3D Hints– Understanding depth perception• Disparity range and comfort• Display environment and comfort• Confusing 3D4

3D Hints
Understanding 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 = far7

Up/Down• Upper = far, Lower = close8

Shape• Shape of object changes with vanishing points– Brain infers distance, size, angle information9

Depth Continuity• Which one is closer?

10Depth Continuity• More information makes it clear– Depth continuity results in an easier depthresolution

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Overlap effect• Overlapping info relates to distance12Motion Parallax• In the train, closer objects move faster13

Texture details• Small details = far• Rough details = close

14Color in open space
Saturation

Amplified contrast

Decrease

OriginalBrightness

Blue channel

Increase15

Color in closed spase• Darkness can increase with distance– Well effect16

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 with3D in mind!
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Disparity range
andComfortable Stereoscopic Vision18

Comfortable Stereoscopic Vision• Depth range control is necessary– For impressive experience– For comfortable experience

Attention! Contradictory!
Balance is critical!

• Control depth within human limits– Divergence limits– Disparity range limits• Concretely, how to do?

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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
20Divergence Limits

ＮＧ21

Disparity range definition
Disparity range ＝ A － CConvergence

CAAccommodation

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Disparity range definitionDisparity range ＝ C － A
ConvergenceAC

Accommodation

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Disparity range definition
Disparity range ＝ ｜C1 － C2｜
Far object

Close object

C1C224

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 thelimits
ＯＫＮＧt+1ttt+1Eye precision• Eye can not make the distinction with lessthan 0.016° between two objects• More than 180m in theater?
＜0.016°27

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 eyeto the other– Ghost effect

Ghosteffect• Comfort and Display– Distance + Screen size ⇒ Disparity range
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Pro and Cons of Stereoscopic Display
Display

ProCons

Anaglyph +normal display

Can be seen with Cross Talk
any kind of display Colorization
Simple to use
Tiredness
Cheap

Individual preview
during production

Polarized glass

Light, cheap
glasses
No battery
Few cross talkCinemaEx: realD, IMAX

Shutter glasses

Cheap
Expensive glasses
Simple to use with Need battery
common projector, Synchronization ismonitor
criticalPreview, cinema
Ex: Xpand3D, nVidia
Sony 3D tv…

No glasses

No glasses

ExhibitionGadget?
Ex: Nintendo 3ds

Need specific,
expensive display

Expensive
Fatigue
Image quality
View angle

Application

31Television, personal computer• Distance is related to the screen size
– Can predictD• Audience is at same distance

D32

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

Parallax range (Pain)
Positiveparallax(px)Negativeparallax
Computer(px)Negativeparallax
Cinema(px)045901331772025×450×34

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

Attention!
Contradictory goal!

– 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!

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Example of pain

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Disparity range angle limits (1m screen)• 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
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Other Confusing Pictures38

Place relative to the screen• 3D perception is deformed from the sideSideFront• Need to adapt theater layout?
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From the side, unnatural feeling• Cannot see what we shouldconfusion
Sidefront40

Breaking the stereoscopic window• More details in other course part?
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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 contrast42

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 too43

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°44