113D Scanning3D ScanningSzymon RusinkiewiczSzymon RusinkiewiczPrinceton UniversityPrinceton UniversityCOS 426 Guest LectureCOS 426 Guest LectureSpring 2003Spring 2003Computer Graphics PipelineComputer Graphics Pipeline••Human time = expensiveHuman time = expensive••Sensors = cheapSensors = cheap––Computer graphics increasingly relies onComputer graphics increasingly relies onmeasurements of the real worldmeasurements of the real worldRenderingRenderingRenderingShapeShapeShapeLightingandReflectanceLightingLightingandandReflectanceReflectanceMotionMotionMotionShapeShape3D Scanning3D Scanning3D Scanning Applications3D Scanning Applications••Computer graphicsComputer graphics••Product inspectionProduct inspection••Robot navigationRobot navigation••AsAs--built built floorplansfloorplans••Product designProduct design••ArchaeologyArchaeology••Clothes fittingClothes fitting••Art historyArt historyIndustrial InspectionIndustrial Inspection••Determine whether manufactured partsDetermine whether manufactured partsare within tolerancesare within tolerancesMedicineMedicine••Plan surgery on computer model,Plan surgery on computer model,visualize in real timevisualize in real timeMedicineMedicine••Plan surgery on computer model,Plan surgery on computer model,visualize in real timevisualize in real time22MedicineMedicine••Plan surgery on computer model,Plan surgery on computer model,visualize in real timevisualize in real timeMedicineMedicine••Plan surgery on computer model,Plan surgery on computer model,visualize in real timevisualize in real timeScanning BuildingsScanning Buildings••Quality control during constructionQuality control during construction••AsAs--built modelsbuilt modelsScanning BuildingsScanning Buildings••Quality control during constructionQuality control during construction••AsAs--built modelsbuilt modelsClothingClothing••Scan a person, customScan a person, custom--fit clothingfit clothing••U.S. Army; booths in mallsU.S. Army; booths in mallsThe Digital Michelangelo ProjectThe Digital Michelangelo Project33Why 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••HighHigh--visibility projectvisibility projectGoalsGoals••Scan 10 sculptures by MichelangeloScan 10 sculptures by Michelangelo••HighHigh--resolution (“quarterresolution (“quarter--millimeter”) geometrymillimeter”) geometry••Side projects: architectural scanning (Side projects: architectural scanning (Accademia Accademia and Medici chapel), scanning fragments of and Medici chapel), scanning fragments of Forma Forma Urbis RomaeUrbis RomaeWhy Capture Chisel Marks?Why Capture Chisel Marks?Atlas (Atlas (AccademiaAccademia))ugnettougnettougnetto??Why Capture Chisel MarksWhy Capture Chisel Marksas Geometry?as Geometry?Day (Medici Chapel)Day (Medici Chapel)2 mm2 mmSide project:Side project:The FormaThe FormaUrbis RomaeUrbis RomaeForma Forma Urbis Romae Urbis Romae FragmentFragmentside face44Range Acquisition TaxonomyRange Acquisition TaxonomyRangeRangeacquisitionacquisitionContactContactTransmissiveTransmissiveReflectiveReflectiveNonNon--opticalopticalOpticalOpticalIndustrial CTIndustrial CTMechanical Mechanical (CMM, jointed arm)(CMM, jointed arm)RadarRadarSonarSonarUltrasoundUltrasoundMRIMRIUltrasonic trackersUltrasonic trackersMagnetic trackersMagnetic trackersInertial Inertial (gyroscope, accelerometer)(gyroscope, accelerometer)Range Acquisition TaxonomyRange Acquisition TaxonomyOpticalOpticalmethodsmethodsPassivePassiveActiveActiveShape from X:Shape from X:stereostereomotionmotionshadingshadingtexturetexturefocusfocusdefocusdefocusActive variants of passive methodsActive variants of passive methodsStereo w. projected textureStereo w. projected textureActive depth from defocusActive depth from defocusPhotometric stereoPhotometric stereoTime of flightTime of flightTriangulationTriangulationTouch ProbesTouch Probes••Jointed arms with Jointed arms with angular encodersangular encoders••Return position, Return position, orientation of tiporientation of tipFaro Arm Faro Arm ––Faro Technologies, Inc.Faro Technologies, Inc.StereoStereo••Find feature in one image, search along Find feature in one image, search along epipolar epipolar line in other image for correspondenceline in other image for correspondenceWhy More Than 2 Views?Why More Than 2 Views?••BaselineBaseline––Too short Too short ––low accuracylow accuracy––Too long Too long ––matching becomes hardmatching becomes hard55Why More Than 2 Views?Why More Than 2 Views?••Ambiguity with 2 viewsAmbiguity with 2 viewsCamera 1Camera 1Camera 2Camera 2Camera 3Camera 3Multibaseline StereoMultibaseline Stereo[[OkutomiOkutomi& & KanadeKanade]]Shape from MotionShape from Motion••“Limiting case” of multibaseline stereo“Limiting case” of multibaseline stereo••Track a feature in a video sequenceTrack a feature in a video sequence••For For nnframes and frames and fffeatures, havefeatures, have22⋅⋅nn⋅⋅ffknowns, 6knowns, 6⋅⋅nn+3+3⋅⋅ffunknownsunknownsShape from ShadingShape from Shading••Given: image of surface with known, constant Given: image of surface with known, constant reflectance under known point lightreflectance under known point light••Estimate normals, integrate to find surfaceEstimate normals, integrate to find surface••Problem: ambiguityProblem: ambiguityShape from ShadingShape from Shading••Advantages:Advantages:––Single imageSingle image––No correspondencesNo correspondences––Analogue in human visionAnalogue in human vision••Disadvantages:Disadvantages:––Mathematically unstableMathematically unstable––Can’t have textureCan’t have texture••“Photometric stereo” (active method) more “Photometric stereo” (active method) more practical than passive versionpractical than passive versionShape from TextureShape from Texture••Mathematically similar to shape from shading, but uses Mathematically similar to shape from shading, but uses stretch and shrink of a (regular) texturestretch and shrink of a
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