Image-Based LightingInserting Synthetic ObjectsSolutionsEnvironment MapsEnvironment MappingWhat approximations are made?Slide 7Cubic MappingCubic Map ExampleSphere MappingExampleWhat about real scenes?Real environment mapsStitching HDR mosaicsScanning Panoramic CamerasSlide 16Slide 17Slide 18Mirrored SphereSlide 20Slide 21Sources of Mirrored BallsSlide 23Real-World HDR Lighting EnvironmentsAcquiring the Light ProbeAssembling the Light ProbeNot just shiny…Illumination ResultsComparison: Radiance map versus single imagePutting it all togetherSlide 31Illuminating Objects using Measurements of Real LightSlide 33Rendering with Natural LightSlide 35Slide 36Image-Based Lighting15-463: Computational PhotographyAlexei Efros, CMU, Fall 2005© 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•Use corresponding points to warp the object/scene–Only works for small warps and/or mostly planar objectsLighting & 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 eye•We can’t store a separate map for each point, so one map is used with the eye 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 one of several 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 Terminator 2Real 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 CamerasScanning 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, Sphereon Pros: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 Balls2-inch chrome balls ~ $20 ea.McMaster-Carr Supply Companywww.mcmaster.com6-12 inch large gazing ballsBaker’s Lawn Ornamentswww.bakerslawnorn.comHollow Spheres, 2in – 4inDube Juggling Equipmentwww.dube.comFAQ on www.debevec.org/HDRShop/2-inch chrome balls ~ $20 ea.McMaster-Carr Supply Companywww.mcmaster.com6-12 inch large gazing ballsBaker’s Lawn Ornamentswww.bakerslawnorn.comHollow Spheres, 2in – 4inDube Juggling Equipmentwww.dube.comFAQ on www.debevec.org/HDRShop/0.34 0.34 0.580.58=> 59% Reflective=> 59% ReflectiveCalibrating Mirrored Sphere ReflectivityCalibrating 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/FunstonBeachUffiziGalleryEucalyptusGroveGraceCathedralAcquiring the Light ProbeAcquiring the Light ProbeAssembling the Light ProbeAssembling the Light ProbeNot just shiny…Not just shiny…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 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 scene-So, all objects (not just shiny) can be lighted-What’s the limitation?Illumination ResultsIllumination ResultsComparison: Radiance map versus single imageComparison: Radiance map versus single imagePutting it all togetherPutting it all togetherSynthetic Objects +Real light!Synthetic Objects +Real light!CG Objects Illuminated by a Traditional CG Light SourceCG Objects Illuminated by a Traditional CG Light SourceIlluminating Objects using Measurements of Real LightIlluminating Objects using Measurements of Real Light ObjectObjectLightLighthttp://radsite.lbl.gov/radiance/http://radsite.lbl.gov/radiance/Environment assigned “glow” material property inGreg Ward’s RADIANCE system.Environment assigned “glow” material property inGreg Ward’s RADIANCE system.Paul Debevec. A Tutorial on Image-Based Lighting. IEEE Computer Graphics and Applications, Jan/Feb 2002.Paul
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