Traceprostarylight

1杂散光课程2020年1月10日2光源•格点光源•表面光源•档案光源•表面光源特性3格点光源单位选择–照度–辐度光线能量设定•每根光线能量•总能量•光照度4档案光源单位选择–照度–辐度n-thScaleflux5格点光源，档案光源的变动I6格点光源，档案光源的变动II7SurfaceSourcePropertyGenerator8ExampleDefineSpectrum•CoordinateSystem•EditSpectrumData•Add/Modify/Delete•Units•TraceProcanaccommodatephotometricunits(cd/m2orfoot‐lambert)orradiometricunits(W/m2).DatasheetfromLuxeon®Rebel9DefineRadiationPatternDatasheetfromLuxeon®Rebel•CoordinateSystem•EditAngularDistribution•Add/Modify/Delete10SurfaceSourcePropertyGenerator(续)11BitmapSource12BitmapSourceStepbyStep11导入所需图片2点击Conversion13BitmapSourceStepbyStep2设定取样图片特性1.水平长宽，垂直高度2.初始位置3.方向特性14BitmapSourceStepbyStep3目标特性设置1.目标位置2.方向特性3.几何外形4.大小高低15BitmapSourceStepbyStep4取样设置每像素取样光线数总光线数RGB波长16BitmapSourceStepbyStep5保存设置点击Browse选择保存路径设定文件名设定保存格式为.txt17BitmapSourceStepbyStep5作为档案光源导入TracePro18BitmapSourceStepbyStep6光线追迹后用TrueColorMap查看19BitmapSourceuseinimaginesystemObserver20光线追迹21Image成像光学?Object点对点成像•所有从物方的点在像方合适的位置成像点•物象共轭•这样是达到了非常接近，但是电脑受不了•Butthisisnotagoodapproach!22•我们需要简化问题–取样一些有特征的点–减少光线数目仅考虑通过光学系统的光线–运用一些光学构造来简化(焦距,F/#,NA,…etc.)–如果可能的话使得表面有序化–为成像分析设定一些优化feedbackloop1234成像光学(续)23•为模型设定体材质和表面材质•让光线通过模型•让系统去判定光线怎么传播?•忽略所有的光学构造–不做任何假设•建造真正的3D模型非成像光学24•折射Refract•反射Reflect•吸收Absorb•前向散射ForwardScatter•后向散射BackwardScatter光线碰到物件表面时候会发生5种状况…而且每个面上都会…(nottomentionvolumeeffects)TracePro®keepstrackofwhereallthisfluxisgoingandreportsit!非成像光学(续)25•表面特性:Scatter&BSDF26BSDFvs.ScatteredIntensity•BSDF是描述光散射的一种方法.其中有三种BSDF–BRDF(BidirectionalReflectanceDistributionFunction)–BTDF(BidirectionalTransmittanceDistributionFunction)–BDDF(BidirectionalDiffractionDistributionFunction)•ScatteredIntensity–Intheolddays,peoplemeasuredthescatteringpropertiesofasurfacebymeasuringthescatteredintensity(w/sr)normalizedtotheincidentpower(w).ThisdiffersfromtheBSDFbyafactorofcosq.27BSDF•TheBSDFisdefinedaswheredLsistheradiancescatteredfromanareadAsonthesample,dEiistheincidentirradianceontheareadAs,riistheincidentdirection,rsisthescattereddirection.TomeasureBSDF,oneilluminatesanareadAs,measuresincidentfluxΦi,scatteredfluxΦs,andcalculatesthesolidangledΩssubtendedbythemeasuringdetector.OnecanthencalculatedL,dE,andthusBSDF.Ingeneral,BSDFisafunctionofboththeincidentdirectionandthescattereddirection(hencethenamebidirectional).)()(),(iisssidEdLfrrrr28ScatteredIntensity•ScatteredIntensityisdefinedasisddIS•NoticethatthisdiffersfromtheBSDFbyafactorofcosθ,becausedIs=dΦs/dΩqqddSdndAcosθdA/cosscatincscatBSDFq29•i=incident,0=specular•Intheplaneofincidence,|β-β0|=sinθ-sinθ0•Atnormalincidence,β0=0and|β-β0|=sinθ•Atnormalincidenceandsmallscatteringangles,|β-β0|θHarvey-ShackBSDFShift-InvariantBSDFRepresentation30ABgBSDFModel•TheABgBSDFmodelisamodifiedinverse-power-lawmodel.Ithastheform•wherethebandb0vectorsarefromtheHarvey-ShackBSDFmodel.Inthismodel,thebetavectoristheprojectionofaunitvectorinthescatteringdirectionontothetangentplane,andtheb0vectorisaprojectionoftheunitvectorinthespeculardirectionontothetangentplane.A,B,andgarefittingparameters.•IntheABgmodel,Adeterminestheheightofthecurve,Bdeterminesthepointwherethecurvetransitionsfromflattosloped(onalog-logplotasshownabove)andgdeterminestheslope(onalog-logplot).Theroll-offvalueisequaltoA/B.31ABgBSDFModelwhereA=0.0025,B=0.001,andg=1.8AtypicalABgmodelBSDF,graphedonalog-logscale32TypicalBSDFs•光滑面(拋光面)–g值由1.5到3.5,一般介於2到3–Bissmall,1e-6to1e-10,dependingonsurfacestatistics•散射面(粗造面)–Ifg=0,BSDFisperfectLambertian.Manybafflecoatingscomeclosetothis.–IfnotLambertian,typicallyBislarge,0.1to1,andgislarge,2,3,4,5,6…33Energyconservation34BSDFWizard•TheBSDFWizardisastandaloneprogramtohelpfittingtheABgmodeltomeasureddata.•AfteropeninganASTM-standardorSchmittMeasurementBSDFfile,movethecontrolpoints(blacksquares)withthemousetofitthegreencurvetothemeasureddata.•TheABgvaluesforthefittedgreencurveareshownattherightandcanbeusedtodefinetheBRDForBTDFinasurfaceproperty.35•孔径衍射36孔径衍射•Anysurfacecanbemadeadiffractingsurface.•Youmayneedtoinsertadummyobjectfordiffraction,asinthisexample.•Whenarayintersectsadiffractingsurface,itis“bent”ordeviated.•Importancesamplingcanbeusedwithdiffractingsurfaces.37Example38运用分析工具•AnalysisMode–Raysorting:•Forraydisplaytoseethepathsofstrayrays.•Forirradiancemapstoseeirradiancedistributionsforspecularvsscatteredrays.•Forirradiancemapstoseethepathswherestrayraysforhotspots.–Incidentraytable–Rayhistorytable39Raysortingfordisplay40光线能量选择41显示某一块区域的光线42入射光线表格43光线历史表格44SmartSimulation•阈值Thresholds–光通量阈值Fluxthreshold–光线交叉的界限Interceptlimits•光线分裂Raysplitting–随机光线Randomrays–随机因子Randomseed•重点取样Importantsampling•分析模式Simulationmode–Exitsurfacesetting–Simulationfilemanager45阈值Thresholds•光通量阈值Fluxthreshold•光线交叉的界限Interceptlimits46•MonteCarlo光线追迹47为何使用MonteCarlo光线追迹在TracePro中蒙地卡罗光线追迹法在模拟光由发射源开始采随机数分布，到达物体表面会产生反射折射散射等现象，均采随机数生成继续做光线追迹光经由一表面散射后仍持续会碰上其他介质持续做追迹以此方式描述模拟可以接近现实世界光的行为蒙地卡罗光线追迹为一采随机数分布计算模拟之方法48蒙地卡罗光线追迹•AcrudeMonteCarlocalculationisthesimplestformofaprobabilityexperiment–PerformanexperimentNtimes,countthenumberoftimesnthattheeventoccurs–Anestimateoftheprobabilityis:pe=n/N–Wecanneverget