#9ScanConversion：#9扫描转换

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1、#9:ScanConversion&MidtermReviewCSE167:ComputerGraphicsInstructor:RonenBarzelUCSD,Winter2006OutlineforTodayRenderingintroCulling&clippingScanconversionMidtermreview1RenderingFancierterm:ImageSynthesisSynthesisofa2Dimagefroma3DscenedescriptionResultisa2DarrayofpixelsRed,Green,Blueva

2、lues(range0-255or0.0-1.0)Canalsohave:opacity(“alpha”),depth(“Z”),…Rasterization=determiningwhichpixelsaredrawnbyagivenobject2Hardwarevs.SoftwareRenderingHighestqualityrenderingisdonebysoftwareAlgorithmssuchas“raytracing”,“photonmaps”,etc…Fanciestlighting,shadowing,surfaceshading,sm

3、oke&fog,etc.CantakeminutesorhourstocomputeanimageRenderMan(Pixar),Dali(HenrikWannJensen),RADIANCE,POVRay,…Moderncomputersoftenhavespecial-purpose3Drenderinghardware.“GPU”==GraphicsProcessingUnit.(Nvidia,ATI)Hardwareimplementsthetraditional3DgraphicsrenderingpipelineVeryfast,butrela

4、tivelysimplealgorithm:Limitsabilitytogetsubtleshadows,reflections,etc.Limitsoncomplexityofsurfaceshadingdescription,etc.Continuallyimproving,drivenbygamesindustry.(Moderngraphicshardwareisprogrammable,blurringthedistinctionbetweenhardware&softwarerendering.)Wewillstartwithalgorithm

5、sthatareusedbyGPUs,butwe’lldotheminsoftware.33-DGraphicsRenderingPipelineNormalizedviewspaceModelingTransformationViewingTransformationLighting&ShadingClippingProjectionScanconversion,HidingPrimitivesImageObjectspaceWorldspaceCameraspaceImagespace,DevicecoordinatesCulling(Iaddedth

6、issteptothediagram)Today4RenderingTriangleSetsWillfocusontrianglesfornowMostbasicandusefulAlgorithmsalsoforlines,points,polygons,circles,ellipses,…AssumewehavecolorsI.e.,colorsassignedper-vertexNextweekwe’lllookatlighting5We’vealreadydonecullingAssumewe’vealreadyculledtotheviewvol

7、ume:We’vetossedoutobjectsthatweknowareoutsidetheviewDoesthatmeaneverythingthatremainswillbedrawn…?6Moreculling,andclippingTheviewvolumecullingmayhavebeencoarseper-triangleviewvolumecullingSometrianglesmayintersecttheedgeoftheviewvolumeclippingSometrianglesmaybeonthebacksidesofobj

8、ectsbackfacecullingSometr