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(Active) 3D Scanning(Active) 3D Scanning
Theory and Case StudiesTheory and Case Studies
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3D Scanning Applications3D Scanning Applications
• Computer Computer graphicsgraphics
• Product Product inspectioninspection
• Robot navigationRobot navigation
• As-built floorplansAs-built floorplans
• Product designProduct design
• ArchaeologyArchaeology
• Clothes fittingClothes fitting
• Art historyArt history
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Industrial InspectionIndustrial Inspection
• Determine whether manufactured partsDetermine whether manufactured partsare within tolerancesare within tolerances
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MedicineMedicine
• Plan surgery on computer model,Plan surgery on computer model,visualize in real timevisualize in real time
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MedicineMedicine
• Plan surgery on computer model,Plan surgery on computer model,visualize in real timevisualize in real time
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MedicineMedicine
• Plan surgery on computer model,Plan surgery on computer model,visualize in real timevisualize in real time
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MedicineMedicine
• Plan surgery on computer model,Plan surgery on computer model,visualize in real timevisualize in real time
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Scanning BuildingsScanning Buildings
• Quality control during constructionQuality control during construction
• As-built modelsAs-built models
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Scanning BuildingsScanning Buildings
• Quality control during constructionQuality control during construction
• As-built modelsAs-built models
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ClothingClothing
• Scan a person, custom-fit clothingScan a person, custom-fit clothing
• U.S. Army; booths in mallsU.S. Army; booths in malls
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Range Acquisition TaxonomyRange Acquisition Taxonomy
RangeRangeacquisitionacquisition
ContactContact
TransmissiveTransmissive
ReflectiveReflectiveNon-opticalNon-optical
OpticalOptical
Industrial CTIndustrial CT
Mechanical Mechanical (CMM, jointed arm)(CMM, jointed arm)
RadarRadar
SonarSonar
UltrasoundUltrasound
MRIMRI
Ultrasonic trackersUltrasonic trackersMagnetic trackersMagnetic trackers
Inertial Inertial (gyroscope, accelerometer)(gyroscope, accelerometer)
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Touch ProbesTouch Probes
• Jointed arms with Jointed arms with angular encodersangular encoders
• Return position, Return position, orientation of tiporientation of tip
Faro Arm – Faro Technologies, Inc.Faro Arm – Faro Technologies, Inc.
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Range Acquisition TaxonomyRange Acquisition Taxonomy
OpticalOpticalmethodsmethods
PassivePassive
ActiveActive
Shape from X:Shape from X:stereostereomotionmotionshadingshadingtexturetexturefocusfocusdefocusdefocus
Active variants of passive methodsActive variants of passive methodsStereo w. projected textureStereo w. projected textureActive depth from defocusActive depth from defocusPhotometric stereoPhotometric stereo
Time of flightTime of flight
TriangulationTriangulation
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Active Optical MethodsActive Optical Methods
• Advantages:Advantages:– Usually can get dense dataUsually can get dense data
– Usually much more robust and accurate Usually much more robust and accurate than passive techniquesthan passive techniques
• Disadvantages:Disadvantages:– Introduces light into scene (distracting, etc.)Introduces light into scene (distracting, etc.)
– Not motivated by human visionNot motivated by human vision
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Active Variants of Passive Active Variants of Passive TechniquesTechniques
• Regular stereo with projected textureRegular stereo with projected texture– Provides features for correspondenceProvides features for correspondence
• Active depth from defocusActive depth from defocus– Known pattern helps to estimate defocusKnown pattern helps to estimate defocus
• Photometric stereoPhotometric stereo– Shape from shading with multiple known Shape from shading with multiple known
lightslights
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Pulsed Time of FlightPulsed Time of Flight
• Basic idea: send out pulse of light Basic idea: send out pulse of light (usually laser), time how long it takes to (usually laser), time how long it takes to returnreturn tcd
2
1tcd
2
1
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Pulsed Time of FlightPulsed Time of Flight
• Advantages:Advantages:– Large working volume (up to 100 m.)Large working volume (up to 100 m.)
• Disadvantages:Disadvantages:– Not-so-great accuracy (at best ~5 mm.)Not-so-great accuracy (at best ~5 mm.)
• Requires getting timing to ~30 picosecondsRequires getting timing to ~30 picoseconds
• Does not scale with working volumeDoes not scale with working volume
• Often used for scanning buildings, Often used for scanning buildings, rooms, archeological sites, etc.rooms, archeological sites, etc.
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AM Modulation Time of FlightAM Modulation Time of Flight
• Modulate a laser at frequencyModulate a laser at frequencym m ,, it it
returns with a phase shift returns with a phase shift
• Note the ambiguity in the measured Note the ambiguity in the measured phase!phase! Range ambiguity of Range ambiguity of 11//22mmnn
2
2
2
1 n
ν
cd
m
2
2
2
1 n
ν
cd
m
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AM Modulation Time of FlightAM Modulation Time of Flight
• Accuracy / working volume tradeoffAccuracy / working volume tradeoff(e.g., noise ~ (e.g., noise ~ 11//500 500 working volume)working volume)
• In practice, often used for room-sized In practice, often used for room-sized environments (cheaper, more accurate environments (cheaper, more accurate than pulsed time of flight)than pulsed time of flight)
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TriangulationTriangulation
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Triangulation: Moving theTriangulation: Moving theCamera and IlluminationCamera and Illumination
• Moving independently leads to Moving independently leads to problems with focus, resolutionproblems with focus, resolution
• Most scanners mount camera and light Most scanners mount camera and light source rigidly, move them as a unitsource rigidly, move them as a unit
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Triangulation: Moving theTriangulation: Moving theCamera and IlluminationCamera and Illumination
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Triangulation: Moving theTriangulation: Moving theCamera and IlluminationCamera and Illumination
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Triangulation: Extending to 3DTriangulation: Extending to 3D
• Possibility #1: add another mirror (flying spot)Possibility #1: add another mirror (flying spot)
• Possibility #2: project a stripe, not a dotPossibility #2: project a stripe, not a dot
ObjectObject
LaserLaser
CameraCameraCameraCamera
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Triangulation Scanner IssuesTriangulation Scanner Issues
• Accuracy proportional to working volumeAccuracy proportional to working volume(typical is ~1000:1)(typical is ~1000:1)
• Scales down to small working volumeScales down to small working volume(e.g. 5 cm. working volume, 50 (e.g. 5 cm. working volume, 50 m. accuracy)m. accuracy)
• Does not scale up (baseline too large…)Does not scale up (baseline too large…)
• Two-line-of-sight problem (shadowing from Two-line-of-sight problem (shadowing from either camera or laser)either camera or laser)
• Triangulation angle: non-uniform resolution if Triangulation angle: non-uniform resolution if too small, shadowing if too big (useful range: too small, shadowing if too big (useful range: 1515-30-30))
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Triangulation Scanner IssuesTriangulation Scanner Issues
• Material properties (dark, specular)Material properties (dark, specular)
• Subsurface scatteringSubsurface scattering
• Laser speckleLaser speckle
• Edge curlEdge curl
• Texture embossingTexture embossing
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Multi-Stripe TriangulationMulti-Stripe Triangulation
• To go faster, project multiple stripesTo go faster, project multiple stripes
• But which stripe is which?But which stripe is which?
• Answer #1: assume surface continuityAnswer #1: assume surface continuity
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Multi-Stripe TriangulationMulti-Stripe Triangulation
• To go faster, project multiple stripesTo go faster, project multiple stripes
• But which stripe is which?But which stripe is which?
• Answer #2: colored stripes (or dots)Answer #2: colored stripes (or dots)
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Multi-Stripe TriangulationMulti-Stripe Triangulation
• To go faster, project multiple stripesTo go faster, project multiple stripes
• But which stripe is which?But which stripe is which?
• Answer #3: time-coded stripesAnswer #3: time-coded stripes
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Time-Coded Light PatternsTime-Coded Light Patterns
• Assign each stripe a unique illumination codeAssign each stripe a unique illumination codeover time [Posdamer 82]over time [Posdamer 82]
SpaceSpace
TimeTime
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Range Processing PipelineRange Processing Pipeline
• StepsSteps1. 1. manual initial alignmentmanual initial alignment
2. ICP to one existing scan2. ICP to one existing scan
3. automatic ICP of all 3. automatic ICP of all overlapping pairsoverlapping pairs
4. global relaxation to spread 4. global relaxation to spread out errorout error
5. merging using volumetric 5. merging using volumetric methodmethod
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Range Processing PipelineRange Processing Pipeline
• StepsSteps1. manual initial alignment1. manual initial alignment
2. 2. ICP to one existing scanICP to one existing scan
3. automatic ICP of all 3. automatic ICP of all overlapping pairsoverlapping pairs
4. global relaxation to spread 4. global relaxation to spread out errorout error
5. merging using volumetric 5. merging using volumetric methodmethod
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Range Processing PipelineRange Processing Pipeline
• StepsSteps1. manual initial alignment1. manual initial alignment
2. 2. ICP to one existing scanICP to one existing scan
3. automatic ICP of all 3. automatic ICP of all overlapping pairsoverlapping pairs
4. global relaxation to spread 4. global relaxation to spread out errorout error
5. merging using volumetric 5. merging using volumetric methodmethod
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Range Processing PipelineRange Processing Pipeline
• StepsSteps1. manual initial alignment1. manual initial alignment
2. ICP to one existing scan2. ICP to one existing scan
3. 3. automatic ICP of all automatic ICP of all overlapping pairsoverlapping pairs
4. 4. global relaxation to spread global relaxation to spread out errorout error
5. merging using volumetric 5. merging using volumetric methodmethod
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Range Processing PipelineRange Processing Pipeline
• StepsSteps1. manual initial alignment1. manual initial alignment
2. ICP to one existing scan2. ICP to one existing scan
3. automatic ICP of all 3. automatic ICP of all overlapping pairsoverlapping pairs
4. global relaxation to spread 4. global relaxation to spread out errorout error
5. 5. merging using volumetric merging using volumetric methodmethod
+
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Range Processing PipelineRange Processing Pipeline
• StepsSteps1. manual initial alignment1. manual initial alignment
2. ICP to one existing scan2. ICP to one existing scan
3. automatic ICP of all 3. automatic ICP of all overlapping pairsoverlapping pairs
4. global relaxation to spread 4. global relaxation to spread out errorout error
5. 5. merging using volumetric merging using volumetric methodmethod
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Applications of 3D Scanning – Applications of 3D Scanning – Scanning SculpturesScanning Sculptures
• The Pietà ProjectThe Pietà ProjectIBM ResearchIBM Research
• The Digital Michelangelo ProjectThe Digital Michelangelo ProjectStanford UniversityStanford University
• The Great Buddha ProjectThe Great Buddha ProjectUniversity of TokyoUniversity of Tokyo
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Why Scan Sculptures?Why Scan Sculptures?
• Sculptures interesting objects to look atSculptures interesting objects to look at
• Introduce scanning to new disciplinesIntroduce scanning to new disciplines– Art: studying working techniquesArt: studying working techniques
– Art historyArt history
– Cultural heritage preservationCultural heritage preservation
– ArcheologyArcheology
• High-visibility projectsHigh-visibility projects
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Why Scan Sculptures?Why Scan Sculptures?
• ChallengingChallenging– High detail, large areasHigh detail, large areas
– Large data setsLarge data sets
– Field conditionsField conditions
– Pushing hardware, software technologyPushing hardware, software technology
• But not too challengingBut not too challenging– Simple topologySimple topology
– Possible to scan most of surfacePossible to scan most of surface
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Issues AddressedIssues Addressed
• ResolutionResolution
• CoverageCoverage– Theoretical: limits of scanning technologiesTheoretical: limits of scanning technologies
– Practical: physical access, timePractical: physical access, time
• Type of dataType of data– High-res 3D data vs. coarse 3D + normal High-res 3D data vs. coarse 3D + normal
mapsmaps
– Influenced by eventual applicationInfluenced by eventual application
• Intellectual PropertyIntellectual Property
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IBM’s Pietà ProjectIBM’s Pietà Project
• Michelangelo’s Michelangelo’s “Florentine Pietà”“Florentine Pietà”
• Late work (1550s)Late work (1550s)
• Partially destroyed by Partially destroyed by Michelangelo, Michelangelo, recreated by his recreated by his studentstudent
• Currently in the Museo Currently in the Museo dell’Opera del Duomodell’Opera del Duomoin Florencein Florence
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Who?Who?
• Dr. Jack Wasserman, professor emeritus Dr. Jack Wasserman, professor emeritus of art history at Temple Universityof art history at Temple University
• Visual and Geometric Computing groupVisual and Geometric Computing group@ IBM Research:@ IBM Research:
Fausto BernardiniHolly RushmeierIoana MartinJoshua Mittleman
Gabriel TaubinAndre GueziecClaudio Silva
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ScannerScanner
• Visual Interface “Virtuoso”Visual Interface “Virtuoso”
• Active multibaseline stereoActive multibaseline stereo
• Projector (stripe pattern),Projector (stripe pattern),6 B&W cameras, 1 color camera6 B&W cameras, 1 color camera
• Augmented with 5 extraAugmented with 5 extra“point” light sources for“point” light sources forphotometric stereophotometric stereo(active shape from shading)(active shape from shading)
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DataData
• Range data has 2 mm spacing, 0.1mm Range data has 2 mm spacing, 0.1mm noisenoise
• Each range image: 10,000 points, Each range image: 10,000 points, 202020 cm20 cm
• Color data: 5 images with controlled Color data: 5 images with controlled lighting, 1280lighting, 1280960, 0.5 mm resolution960, 0.5 mm resolution
• Total of 770 scans, 7.2 million pointsTotal of 770 scans, 7.2 million points
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ScanningScanning
• Final scan June 1998, Final scan June 1998, completed July 1999completed July 1999
• Total scanning time: Total scanning time: 90 hours over 14 90 hours over 14 daysdays(includes equipment (includes equipment setup time)setup time)
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PostprocessingPostprocessing
• Use 11Use 1111 grid of projected laser dots 11 grid of projected laser dots to help with pairwise alignmentto help with pairwise alignment
• Align all scans to each other, then apply Align all scans to each other, then apply nonrigid “conformance smoothing”nonrigid “conformance smoothing”
• Reconstruct surface using BPAReconstruct surface using BPA
• Compute normal and albedo maps,Compute normal and albedo maps,align to geometryalign to geometry
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ResultsResults
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The Digital Michelangelo ProjectThe Digital Michelangelo Project
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GoalsGoals
• Scan 10 sculptures by MichelangeloScan 10 sculptures by Michelangelo
• High-resolution (“quarter-millimeter”) High-resolution (“quarter-millimeter”) geometrygeometry
• Side projects: architectural scanning Side projects: architectural scanning (Accademia and Medici chapel), (Accademia and Medici chapel), scanning fragments of Forma Urbis scanning fragments of Forma Urbis RomaeRomae
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Why Capture Chisel Marks?Why Capture Chisel Marks?
Atlas Atlas (Accademia)(Accademia)
ugnettougnettougnettougnetto
??
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Why Capture Chisel MarksWhy Capture Chisel Marksas Geometry?as Geometry?
Day (Medici Day (Medici Chapel)Chapel)
2 mm2 mm
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Who?Who?
Faculty and staffFaculty and staffProf. Brian CurlessProf. Brian Curless John GerthJohn Gerth
Jelena JovanovicJelena Jovanovic Prof. Marc LevoyProf. Marc Levoy
Lisa PacelleLisa Pacelle Domi Pitturo Domi Pitturo
Dr. Kari PulliDr. Kari Pulli
Graduate studentsGraduate studentsSean AndersonSean Anderson Barbara CaputoBarbara Caputo
James DavisJames Davis Dave KollerDave Koller
Lucas PereiraLucas Pereira Szymon RusinkiewiczSzymon Rusinkiewicz
Jonathan ShadeJonathan Shade Marco TariniMarco Tarini
Daniel WoodDaniel Wood
UndergraduatesUndergraduatesAlana ChanAlana Chan Kathryn ChinnKathryn Chinn
Jeremy GinsbergJeremy Ginsberg Matt GinztonMatt Ginzton
Unnur GretarsdottirUnnur Gretarsdottir Rahul GuptaRahul Gupta
Wallace HuangWallace Huang Dana KatterDana Katter
Ephraim LuftEphraim Luft Dan PerkelDan Perkel
Semira RahemtullaSemira Rahemtulla Alex RoetterAlex Roetter
Joshua SchroederJoshua Schroeder Maisie TsuiMaisie Tsui
David WeeklyDavid Weekly
In FlorenceIn FlorenceDottssa Cristina Acidini Dottssa Cristina Acidini Dottssa Franca FallettiDottssa Franca Falletti
Dottssa Licia BertaniDottssa Licia Bertani Alessandra MarinoAlessandra Marino
Matti AuvinenMatti Auvinen
In RomeIn RomeProf. Eugenio La RoccaProf. Eugenio La Rocca Dottssa Susanna Le PeraDottssa Susanna Le Pera
Dottssa Anna SomellaDottssa Anna Somella Dottssa Laura FerreaDottssa Laura Ferrea
In PisaIn PisaRoberto ScopignoRoberto Scopigno
SponsorsSponsorsInterval ResearchInterval Research Paul G. Allen Foundation for the Paul G. Allen Foundation for the
ArtsArts
Stanford UniversityStanford University
EquipmentEquipment donorsdonorsCyberwareCyberware Cyra TechnologiesCyra Technologies
Faro TechnologiesFaro Technologies IntelIntel
Silicon GraphicsSilicon Graphics SonySony
3D Scanners3D Scanners
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Scanner DesignScanner Design
• FlexibilityFlexibility– outward-lookingoutward-looking
rotational scanningrotational scanning
– 16 ways to mount 16 ways to mount scan head on armscan head on arm
• AccuracyAccuracy– center of gravitycenter of gravity
kept stationarykept stationaryduring motionsduring motions
– precision drives,precision drives,vernier homing,vernier homing,stiff trussesstiff trusses
4 motorized 4 motorized axesaxes4 motorized 4 motorized axesaxes
laser, range camera,laser, range camera,white light, and color camerawhite light, and color camera
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Scanning a Large ObjectScanning a Large Object
• Calibrated motionsCalibrated motions– pitch pitch (yellow)(yellow)
– pan pan (blue)(blue)
– horizontal translation horizontal translation (orange)(orange)
• Uncalibrated motionsUncalibrated motions– vertical translationvertical translation
– rolling the gantryrolling the gantry
– remounting the scan headremounting the scan head
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Single Scan of St. MatthewSingle Scan of St. Matthew 1 mm1 mm1 mm1 mm
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PostprocessingPostprocessing
• Manual initial alignmentManual initial alignment
• Pairwise ICP, then global registrationPairwise ICP, then global registration
• VRIP (parallelized across subvolumes)VRIP (parallelized across subvolumes)
• Use high-res geometry to discard bad Use high-res geometry to discard bad color data, perform inverse lighting color data, perform inverse lighting calculationscalculations
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Statistics About the Scan of DavidStatistics About the Scan of David
• 480 individually aimed 480 individually aimed scansscans
• 0.3 mm sample spacing0.3 mm sample spacing
• 2 billion polygons2 billion polygons
• 7,000 color images7,000 color images
• 32 gigabytes32 gigabytes
• 30 nights of scanning30 nights of scanning
• 22 people22 people
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Head of Michelangelo’s Head of Michelangelo’s DavidDavid
PhotographPhotograph 1.0 mm computer model1.0 mm computer model
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Side project:Side project:The Forma Urbis RomaeThe Forma Urbis Romae
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Forma Urbis Romae FragmentForma Urbis Romae Fragment
side face
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Hard ProblemsHard Problems
• Keeping scanner calibrated is hard in Keeping scanner calibrated is hard in the lab, the lab, reallyreally hard in the museum hard in the museum
• Dealing with large data sets is painfulDealing with large data sets is painful
• Filling all the holes converges only Filling all the holes converges only asymptotically (if it converges at all…)asymptotically (if it converges at all…)
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The Great Buddha ProjectThe Great Buddha Project
• Great Buddha of KamakuraGreat Buddha of Kamakura
• Original made of wood, completed 1243Original made of wood, completed 1243
• Covered in bronze and gold leaf, 1267Covered in bronze and gold leaf, 1267
• Approx. 15 m tallApprox. 15 m tall
• Goal: preservation ofGoal: preservation ofcultural heritagecultural heritage
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Who?Who?
• Institute of Industrial Science,Institute of Industrial Science,University of TokyoUniversity of Tokyo
Daisuke MiyazakiDaisuke MiyazakiTakeshi OoishiTakeshi OoishiTaku NishikawaTaku NishikawaRyusuke SagawaRyusuke Sagawa
Ko NishinoKo NishinoTakashi TomomatsuTakashi TomomatsuYutaka TakaseYutaka TakaseKatsushi IkeuchiKatsushi Ikeuchi
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ScannerScanner
• Cyrax range scannerCyrax range scannerby Cyra Technologiesby Cyra Technologies
• Laser pulse time-of-flightLaser pulse time-of-flight
• Accuracy: 4 mmAccuracy: 4 mm
• Range: 100 mRange: 100 m
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ProcessingProcessing
• 20 range images (a few million points)20 range images (a few million points)
• Simultaneous all-to-all ICPSimultaneous all-to-all ICP
• Variant of volumetric merging Variant of volumetric merging (parallelized)(parallelized)
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ResultsResults