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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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