Stereoscopic 3 Dhow It Works

8/2/2019 Stereoscopic 3 Dhow It Works

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Stereoscopic 3DHow it Works

Matt CowanChief Scientific Officer,

REAL D


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Outline

3D Perception How we see 3D

Stereopsis Parallax and Interocular

Colour


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Decoding Depth in Pictures

Monocular cues

Stereo cues

Physiological cues


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Shading


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Relative Size


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InterpositionInterposition


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Textural Gradient


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Relative Size

Foreground Background


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Size


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Bottom of image closer than top


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Perspective


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Shading


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Motion Parallax

-induce parallax byhead movement


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Geometry of Stereoscopy

Boundary conditions

Interocular Parallax

Zero parallax


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Creation Volume Boundary

Pyramid bounded by 4 corners and viewers eyes


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Interocular and Parallax

Essence of stereoscopic production is

separating the objects for different left andright views

A lot of science a lot of art Fundamentally based on interocular

distance of humans 65mm

Creates different view for each eye.


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Horizontal Parallax

Basis for stereopsis

Different parallax indicates different distancefrom the viewer.

Different parallax provides a different view ofobjects by each eye.


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Horizontal Parallax


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Vertical Parallax

Unnatural in real world

Eyes concentrate on small area of interest Real World parallax is always in the

direction of separation of the two eyes Normally horizontal

Vertical fusion limited to about degree Vertical parallax gives headaches


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Vertical Parallax


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Stereo Cues - Parallax

Eyes toe in or out

Brain references angle of eyes and amount ofoccluded information visible to one eye only

Positions interpreted relative to angle

Position interpretation relative to amount ofocclusion

Limits on amount of toe for comfort A dominant cue for depth


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Left eye view Right eye view

L

R


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Screen Plane

Parallax Infinity point

65mm


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Zero Parallax

Defines the point where the eyes converge

Physically the screen plane Creative question place objects in front

of or behind this point


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I f t f th


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In front of the screen

Negative parallax

Screen Plane

65mm on screenPlaces object half wayTo viewer

Behind the Screen


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Behind the Screen

Positive parallax

Screen Plane


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Screen Size

Variable in viewing situation

Parallax defined in mastering by pixels ora relative amount screen

Interocular (65mm) defined by viewer asfixed value

Defines theoretical infinity point

Interocular varies if screen width varies


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Parallax

65mm parallax on 2K screen

6 m screen = 22 pixels 12 m screen = 11 pixels

18 m screen = 7 pixels

What values to use for master?

Good news the eye is very tolerant to difference one moderate value works for most.


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Focus distance

Eye knows where it is focused by the

contraction of the focus muscles Cue stronger in younger people

Cue non existent in those of us who wearbifocals


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Cue Conflicts

When all cues line up, 3D is excellent

When cues conflict, 3D breaks down Not all cues have to be perfect, but it

helps

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Size / foreground

Miniature

Full size


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Breaking the Frame

Projection screen represents window

Window truncates objects normal for objects behind window

Objects inside window must stay inside frame Action in front of screen that breaks frame

degrades stereo image


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Creation Volume Boundary


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M i


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Motion

Apparent Simultaneous Motion

Left and Right eyes want motion to appear atsame time

Sequential frame 3D naturally offsets motion

timing Apparent parallax changes depending on motion

3D S A hi


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3D System Architecture

Left Eye Master

Right Eye Master

Digital Cinema

Package

2 Channel

DC Server

Projector

Left-Right parallel streams

Left-Rightseries stream

Z Screenpolarizationswitch

P

rojection

Screen

PolarizedGlasses

Left circularRight circular

Synchronization

Same lens projects left and right eyes

Motion Double Flash, Triple


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Motion Double Flash, Triple

Flash Single projector systems

Double Flash 96fps presentation

L1, R1, L1, R1, L2, R2, L2, R2 etc

Triple Flash 144 fps presentation

L1, R1, L1, R1,1, R1, L2, R2, L2, R2, L2, R2 etc.

Triple flash exceeds the fusion threshold for muchsmoother motion

Triple flash provides less phase difference betweenleft and right eye views.

Timing Diagram for Double and Triple flash Interleaved 3D. Extend to multiple flash


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Left Eye Input

Right Eye Input

1/24 second = 1 normal film frame time

Left LeftRight Right

Left Left LeftRight Right Right

Input

Interleaveddouble flash

InterleavedTriple flash

96 flashesper second

144 flashesper second

Timing diagram showing how the input signal is sped up and interleaved in the projector to produce sequentialleft and right eye views.Note the switching timing for the modulator corresponding to the projector outputNote the finite rise and fall times resulting in periods of time where the display is not operational.

Switching - lefthigh right low

Switching - lefthigh right low

Phase offset

Phase offset

M ti Li it ti


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Motion Limitations

Sequential approach induces parallax in

motion Eye tracking a movement will place a single

object in different locations

Creates error in apparent Z dimension of theobject

Creates limits on speed of motion (similarto limits on rate of panning)

Colour Shift?


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Colour Shift?

Different systemsintroduce colour shifts

Small for polarized andshutter glasses

colour shift corrected inprojector calibration

Calibrate digital projector

through 3D system Measured shift of order

>.004x and y

S St i Ci m i A ti


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See Stereoscopic Cinema in Action

REAL D System in RAI theatre

Single projector

Passive glasses circular

Z screen for sequentialpolarization

Simple, Reliable >1 million hours

Doremi server

Christie projector Harkness Hall screen

REAL D System -Passive Glasses1 P j t St


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1 Projector Stereo

Left Eye

Right Eye

Left EyeSource

Right Eye

Source

Z ScreenPolarizationswitch

High Frame RateDigital ProjectorChristie CP 2000

Non-depolarizingscreen

Harkness HallPolarized glasses(Circular)

Doremi Server


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Matt CowanChief Scientific Officer

www. Reald. [email protected]

Stereoscopic 3 Dhow It Works

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