Stereogram Generation Workshop - comp.nus.edu.sgbleong/stereo/StereogramWorkshop.pdf · 1 NUS Computing Camp for Junior Colleges & Junior Colleges & High School StudentsHigh School

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NUS Computing Camp for NUS Computing Camp for Junior Colleges & Junior Colleges & High School StudentsHigh School Students

Stereogram Stereogram Generation WorkshopGeneration Workshoppp

Dr Ben LeongDr Ben LeongNUS School of ComputingNUS School of Computing

28 Nov 201228 Nov 2012

What are stereograms?What are stereograms?

How do stereograms work?How do stereograms work?

Because there is a small separation Because there is a small separation between our eyes, they perceive slightly between our eyes, they perceive slightly different imagesdifferent images

These differences allow us to perceiveThese differences allow us to perceive These differences allow us to perceive These differences allow us to perceive depth. depth.

Autostereograms work by repeating Autostereograms work by repeating patterns in such a way as to give us an patterns in such a way as to give us an illusionillusion of depthof depth

How do stereograms work?How do stereograms work?

Image plane

A BC D

Generation of stereogramsGeneration of stereograms

Key idea: compute the sets of points Key idea: compute the sets of points that are constrained to be of the that are constrained to be of the same coloursame colour

Note that we can compute the Note that we can compute the required image one line at a timerequired image one line at a time

How do we compute these sets? How do we compute these sets?

Use simple geometryUse simple geometry


1.1. Create a 3Create a 3--d model of the objectd model of the object Use a function Use a function f(x,y)f(x,y) to define the depth of to define the depth of

an objectan object

22 Decide on some parametersDecide on some parameters2.2. Decide on some parametersDecide on some parameters Distance between eyes and imageDistance between eyes and image

Position of object relative to image planePosition of object relative to image plane

Distance between the two eyesDistance between the two eyes

3.3. Compute one line at a timeCompute one line at a time

2


Image plane


Image plane


Image plane

How far?


Image plane

AD

-z

E

s

zD

E

z

s

How would YOU create a How would YOU create a stereogram? stereogram?

We have already written the program that We have already written the program that will automatically generate a stereogram will automatically generate a stereogram based on the method described.based on the method described.

What you need to do is to create a depthWhat you need to do is to create a depth What you need to do is to create a depth What you need to do is to create a depth map and feed it to the stereogram map and feed it to the stereogram generator:generator:

STEREOGRAM

GENERATOR

depth map

stereogram

How would YOU create a How would YOU create a stereogram?stereogram?

Our stereogram generator is written in Our stereogram generator is written in SchemeScheme

You will learn how to manipulate You will learn how to manipulate some simple objects to build your some simple objects to build your own depth maps and create your own own depth maps and create your own stereogramsstereograms

Simple programming Simple programming

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Plan for TodayPlan for Today

You will get a worksheet that will You will get a worksheet that will guide you through what we have guide you through what we have discusseddiscussed

My lab assistants will help youMy lab assistants will help you

Create Create cool stereogramscool stereograms and and share with your friends and familyshare with your friends and family

Primitive building blocksPrimitive building blocks

(show rcross(show rcross--bb)bb)


(show corner(show corner--bb)bb)


(show sail(show sail--bb)bb)


(show nova(show nova--bb)bb)


(show heart(show heart--bb)bb)

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(show circle(show circle--bb)bb)


(show spiral(show spiral--bb)bb)

Primitive Operation:Primitive Operation:Rotating to the RightRotating to the Right

(clear)(clear)

(show (quarter(show (quarter--turnturn--right sailright sail--bb))bb))

Derived Operation:Derived Operation:Rotating Upside DownRotating Upside Down

(clear)(clear)

(show (turn(show (turn--upsideupside--down saildown sail--bb))bb))

How about How about Rotating to the Left?Rotating to the Left?

(clear)(clear)

(show (turn(show (turn--quarterquarter--left sailleft sail--bb))bb))

Flipping ObjectsFlipping Objects

(clear)(clear)

(show (flip(show (flip--horiz novahoriz nova--bb))bb))

(clear)(clear)

(show (flip(show (flip--vert novavert nova--bb))bb))(show (flip(show (flip--vert novavert nova--bb))bb))

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Means of Combination:Means of Combination:StackingStacking

(clear)(clear)

(show (stack rcross(show (stack rcross--bb sailbb sail--bb))bb))

Multiple StackingMultiple Stacking

(clear)(clear)

(show (stack rcross(show (stack rcross--bb bb

(stack rcross(stack rcross--bb sailbb sail--bb)))bb)))

Placing objects one beside Placing objects one beside the otherthe other

(clear)(clear)

(show (beside sail(show (beside sail--bb rcrossbb rcross--bb))bb))

A complex objectA complex object

(clear)(clear)

(show(show

(stack(stack

(beside(beside(beside (beside

(quarter(quarter--turnturn--right rcrossright rcross--bb)bb)

(turn(turn--upsideupside--down rcrossdown rcross--bb))bb))

(beside (beside

rcrossrcross--bbbb

(quarter(quarter--turnturn--left rcrossleft rcross--bb))))bb))))

This operation is also known asThis operation is also known asmakemake--crosscross

Naming your objects with defineNaming your objects with define

(clear)(clear)

(define myPic (define myPic

(make(make--cross sailcross sail--bb))bb))

(show myPic)(show myPic)

(define myPic2 (define myPic2

(make(make--cross novacross nova--bb))bb))

(show myPic2)(show myPic2)

Repeating the patternRepeating the pattern

(clear)(clear)

(show (make(show (make--cross (makecross (make--cross novacross nova--bb)))bb)))

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Repeating multiple timesRepeating multiple times

(clear)(clear)

(show (repeat(show (repeat--pattern 4 makepattern 4 make--cross novacross nova--bb))bb))

What about 3 rows?What about 3 rows?(clear)(clear)

(show (stack(show (stack--frac 1/3 rcrossfrac 1/3 rcross--bb sailbb sail--bb))bb))

(clear)(clear)

(show (stack(show (stack--frac 1/3 rcrossfrac 1/3 rcross--bbbb

(stack rcross(stack rcross--bb rcrossbb rcross--bb)))bb)))

Repeating n timesRepeating n times

(clear)(clear)

(show (stackn 3 nova(show (stackn 3 nova--bb))bb))

(clear)(clear)

(show (stackn 5 nova(show (stackn 5 nova--bb))bb))(show (stackn 5 nova(show (stackn 5 nova bb))bb))

A rectangular repeated patternA rectangular repeated pattern

(clear)(clear)

(show (stackn 5 (quarter(show (stackn 5 (quarter--turnturn--right right

(stackn 5 (quarter(stackn 5 (quarter--turnturn--left novaleft nova--bb)))))bb)))))

Another regular patternAnother regular pattern

(clear)(clear)

(show (nxn 3 (make(show (nxn 3 (make--cross rcrosscross rcross--bb)))bb)))

Creating 3D objects Creating 3D objects

We use greyscale to represent depthWe use greyscale to represent depth Black is nearest to youBlack is nearest to you

White is furthest awayWhite is furthest away

means

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Creating 3D objectsCreating 3D objects

means

Overlay OperationOverlay Operation

(clear)(clear)

(show (overlay sail(show (overlay sail--bb rcrossbb rcross--bb))bb))

Advanced Overlay OperationAdvanced Overlay Operation

(clear)(clear)

(show (overlay(show (overlay--frac 1/4 cornerfrac 1/4 corner--bb heartbb heart--bb))bb))

ScalingScaling

(clear)(clear)

(show (scale 1/2 heart(show (scale 1/2 heart--bb))bb))

Wait, did we say we’re creating Wait, did we say we’re creating stereograms?stereograms?

Yeah, that’s the easy part!Yeah, that’s the easy part!

Do: Do: (stereogram <depth map>)(stereogram <depth map>)

Example:Example:(show (overlay sail(show (overlay sail--bb rcrossbb rcross--bb))bb))

(stereogram (stereogram

(overlay sail(overlay sail--bb rcrossbb rcross--bb))bb))

Your First StereogramYour First Stereogram

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Loading from/Saving to FileLoading from/Saving to File

You can also create a depth map using You can also create a depth map using some paint program and load using:some paint program and load using:

(load(load--map <filename>)map <filename>)

You can save your work with:You can save your work with:(save <filename>)(save <filename>)

What if you What if you cannot seecannot seecannot see cannot see

stereograms? stereograms?

Think DifferentThink Different

Image plane


Image plane


Image plane

3D Anaglyphs3D Anaglyphs

Image plane

Use filters to show one image to each eye!Use filters to show one image to each eye!

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What else can we What else can we do to create ando to create ando to create an do to create an illusion of 3D? illusion of 3D?

Simulating 3D Effect with AnimationSimulating 3D Effect with Animation

Image plane


Image plane


Image plane


Image plane

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Image plane


Image plane


Image plane

QUESTIONSQUESTIONS What you have What you have seen are the seen are the

basics of basics of programming! programming!

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The World of Computer ScienceThe World of Computer Science

Artificial IntelligenceLogic

G hi

Vision

Human-Computer InteractionProgramming Languages

Programming

Database

Data Structures & AlgorithmsCompilers

Graphics

Software EngineeringTheory

Architecture

Operating SystemsNetworks

Security

Words of AdviceWords of Advice

Consider Computer Science if:Consider Computer Science if:Like Maths (esp. ‘elegant’ Maths)Like Maths (esp. ‘elegant’ Maths)Like to ‘create’ or build thingsLike to ‘create’ or build thingsWant to make a difference to society in Want to make a difference to society in

the work you dothe work you doYou are impatient and you want to see You are impatient and you want to see

your work out there in the real world in a your work out there in the real world in a hurryhurry

Words of AdviceWords of Advice

Follow your heart, Follow your heart, NOTNOT the marketthe marketFigure out what you like and what Figure out what you like and what

you’re good atyou’re good at –– and keep doing itand keep doing ityou re good at you re good at and keep doing itand keep doing itTry and explore different thingsTry and explore different thingsAsk yourself: What do you want to Ask yourself: What do you want to

do with your life? WHY?do with your life? WHY?

Documents

Stereogram Generation Workshop - comp.nus.edu.sgbleong/stereo/StereogramWorkshop.pdf · 1 NUS Computing Camp for Junior Colleges & Junior Colleges & High School StudentsHigh School