Image-Based LightingInserting Synthetic ObjectsSolutionsEnvironment MapsEnvironment MappingWhat approximations are made?Environment MapsCubic MappingCubic Map ExampleSphere MappingExampleWhat about real scenes?What about real scenes?It’s not that hard!Real environment mapsStitching HDR mosaicsScanning Panoramic CamerasSlide Number 18Slide Number 19Slide Number 20Mirrored SphereSlide Number 22Slide Number 23Sources of Mirrored BallsSlide Number 25Real-World HDR Lighting EnvironmentsAcquiring the Light ProbeAssembling the Light ProbeNot just shiny…Illumination ResultsComparison: Radiance map versus single imagePutting it all togetherSlide Number 33Illuminating Objects using Measurements of Real LightSlide Number 35Rendering with Natural LightSlide Number 37Slide Number 38Illuminating a Small SceneSlide Number 40Slide Number 41Real Scene ExampleLight Probe / Calibration GridModeling the SceneThe Light-Based Room ModelModeling the SceneThe Lighting ComputationRendering into the SceneRendering into the SceneDifferential RenderingDifferential Rendering (2) Difference in local sceneDifferential RenderingSlide Number 53Slide Number 54Slide Number 55HDR Image SeriesStp1 PanoramaAssembled PanoramaLight Probe ImagesCapturing a Spatially-Varying Lighting EnvironmentThe MovieSimulating the Glare in the Human EyeScattering in the eyeSlide Number 64Slide Number 65Slide Number 66Slide Number 67Slide Number 68Image-Based Lighting15-463: Computational PhotographyAlexei Efros, CMU, Fall 2007© Eirik Holmøyvik…with a lot of slides donated by Paul DebevecInserting Synthetic ObjectsWhy does this look so bad?• Wrong camera orientation• Wrong lighting• No shadowsSolutionsWrong Camera Orientation• Estimate correct camera orientation and renender object– Requires camera calibration to do it rightLighting & Shadows• Estimate (eyeball) all the light sources in the scene and simulate it in your virtual renderingBut what happens if lighting is complex? • Extended light sources, mutual illumination, etc.Environment MapsSimple solution for shiny objects• Models complex lighting as a panoramic image• i.e. amount of radiance coming in from each direction• A plenoptic function!!!reflective surfaceviewerenvironment texture imagevnrprojector function converts reflection vector (x, y, z) to texture image (u, v)Environment MappingReflected ray: r=2(n·v)n-vTexture is transferred in the direction of the reflected ray from the environment map onto the objectWhat is in the map?What approximations are made?The map should contain a view of the world with the point of interest on the object as the Center of Projection• We can’t store a separate map for each point, so one map is used with the COP at the center of the object• Introduces distortions in the reflection, but we usually don’t notice• Distortions are minimized for a small object in a large roomThe object will not reflect itself!Environment MapsThe environment map may take various forms:• Cubic mapping• Spherical mapping• otherDescribes the shape of the surface on which the map “resides”Determines how the map is generated and how it is indexedCubic MappingThe map resides on the surfaces of a cube around the object• Typically, align the faces of the cube with the coordinate axesTo generate the map:• For each face of the cube, render the world from the center of the object with the cube face as the image plane– Rendering can be arbitrarily complex (it’s off-line)To use the map:• Index the R ray into the correct cube face• Compute texture coordinatesCubic Map ExampleSphere MappingMap lives on a sphereTo generate the map:• Render a spherical panorama from the designed center pointTo use the map:• Use the orientation of the R ray to index directly into the sphereExampleWhat about real scenes?From Flight of the NavigatorWhat about real scenes?from Terminator 2It’s not that hard!http://www.nickbertke.com/Real environment mapsWe can use photographs to capture environment maps• The first use of panoramic mosaicsHow do we deal with light sources? Sun, lights, etc?• They are much much brighter than the rest of the enviarnmentUser High Dynamic Range photography, of course!Several ways to acquire environment maps:• Stitching mosaics• Fisheye lens• Mirrored BallsStitching HDR mosaicsStitching HDR mosaicshttp://www.gregdowning.com/HDRI/stitched/http://www.gregdowning.com/HDRI/stitched/Scanning Panoramic Cameras Scanning Panoramic CamerasPros:very high res (10K x 7K+)Full sphere in one scan – no stitchingGood dynamic range, some are HDRIssues:More expensiveScans take a whileCompanies: Panoscan, SphereonPros:very high res (10K x 7K+)Full sphere in one scan – no stitchingGood dynamic range, some are HDRIssues:More expensiveScans take a whileCompanies: Panoscan, SphereonSee also www.kaidan.comSee also www.kaidan.comFisheye ImagesFisheye ImagesMirrored SphereMirrored SphereSources of Mirrored BallsSources of Mirrored Balls 2-inch chrome balls ~ $20 ea. McMaster-Carr Supply Companywww.mcmaster.com 6-12 inch large gazing balls Baker’s Lawn Ornamentswww.bakerslawnorn.com Hollow Spheres, 2in – 4in Dube Juggling Equipmentwww.dube.com FAQ on www.debevec.org/HDRShop/ 2-inch chrome balls ~ $20 ea. McMaster-Carr Supply Companywww.mcmaster.com 6-12 inch large gazing balls Baker’s Lawn Ornamentswww.bakerslawnorn.com Hollow Spheres, 2in – 4in Dube Juggling Equipmentwww.dube.com FAQ on www.debevec.org/HDRShop/0.34 0.34 0.580.58=> 59% Reflective => 59% ReflectiveCalibrating Mirrored Sphere Reflectivity Calibrating Mirrored Sphere ReflectivityReal-World HDR Lighting EnvironmentsLighting Environments from the Light Probe Image Gallery: http://www.debevec.org/Probes/ Lighting Environments from the Light Probe Image Gallery: http://www.debevec.org/Probes/Funston BeachUffizi GalleryEucalyptus GroveGrace CathedralAcquiring the Light ProbeAcquiring the Light ProbeAssembling the Light ProbeAssembling the Light ProbeNot just shiny…Not just shiny…We have captured a true radiance map We can treat it as an extended (e.g spherical) light source Can use Global Illumination to simulate light transport in the scene • So, all objects (not just shiny) can be lighted • What’s the limitation?We have captured a true radiance mapWe can treat it as an extended (e.g spherical) light sourceCan use Global Illumination to simulate light transport in the
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