lightingPleaseread2.2.2,Page27…Backgroundknowledge光線是有反射、折射、衍射等特性的。對這些基本特性的模擬一直以來都是計算機圖形圖像學(xué)的重要研究方向。完全真實模擬光線的物理過程，計算量非常大，在實時系統(tǒng)中使用有一定難度。對于靜態(tài)物體來說，大多使用光照貼圖來模擬間接光的照明效果，然后加上直接光源的動態(tài)照明效果。對于運動物體來說，則僅用直接光源的動態(tài)照明效果，或者使用光照探針來模擬間接光的照明效果。實時光照技術(shù)EnlightenEnlighten基于GI(GlobalIllumination)算法實現(xiàn)全局光照。GI算法是基于模擬光傳輸?shù)奈锢硖匦浴?.直接照明（DirectLighting）

Unity3D中的直接照明主要來源于各種燈光物體，而燈光物體本質(zhì)上是:空物體+燈光組件。直接照明可以產(chǎn)生陰影，但光線不會反射、也不會折射，但可以穿透半透明材質(zhì)物體。Inordertocalculatetheshadingofa3Dobject,Unityneedstoknowtheintensity,directionandcolorofthelightthatfallsonitLightcomponentTypeThecurrenttypeoflight.Possiblevaluesare

Directional,

Point,

Spot

and

Area

(seethe

lightingoverview

fordetailsofthesetypes).RangeDefinehowfarthelightemittedfromthecenteroftheobjecttravels(Point

and

Spot

lightsonly).SpotAngleDefinetheangle(indegrees)atthebaseofaspotlight’scone(Spot

lightonly).ColorUsethecolorpickertosetthecoloroftheemittedlight.ModeSpecifythe

LightMode

usedtodetermineifandhowalightis“baked”.Possiblemodesare

Realtime,

Mixed

and

Baked.Seedocumentationon

RealtimeLighting,

MixedLighting

,and

BakedLighting

formoredetailedinformation.ShadowTypeDeterminewhetherthisLightcastsHardShadows,SoftShadows,ornoshadowsatall.LighttypesThreelighttypes：DirectionalLight(方向光，平行光，可以改變角度)，太陽。PointLight

(點光源，由一個點向四周發(fā)射光源

可以改變位置)，燈泡。SpotLight

(聚光燈，可以改變位置和角度)，手電光。directionallightDirectionallightsrepresentlarge,distantsourcesthatcomefromapositionoutsidetherangeofthegameworld.Inarealisticscene,theycanbeusedtosimulatethesunormoon.PointlightApointlightislocatedatapointinspaceandsendslightoutinalldirectionsequally.SpotlightLikeapointlight,aspotlighthasaspecifiedlocationandrange.However,thespotlightisconstrainedtoanangle,resultinginacone-shapedregionofillumination.artificiallightsourcessuchasflashlights,carheadlightsandsearchlightsArealightAnAreaLightisdefinedbyarectangleinspace.Lightisemittedinalldirectionsuniformlyacrosstheirsurfacearea,butonlyfromonesideoftherectangle.Sincethelightingcalculationisquiteprocessor-intensive,arealightsarenotavailableatruntime.LightisemittedacrossthesurfaceofanAreaLightproducingadiffuselightwithsoftshadowing.LightMode

Realtime;Mixed:BakedIndirect;

Shadowmask;DistanceShadowmask;

Subtractive;

Baked;RealtimeBydefault,lightsinUnity-directional,spotandpoint,arerealtime.Thismeansthattheycontributedirectlighttothesceneandupdateeveryframe.AslightsandGameObjects

aremovedwithinthe

scene,lightingwillbe

updatedimmediately.Bakedcalculatecomplexstaticlightingeffects(GI)andstoretheminareferencetexturemapcalledalightmap(光照貼圖).Thiscalculationprocessisreferredtoasbaking(烘焙).theeffectsoflightsourcesonstaticobjectsinthescenearecalculatedandtheresultsarewrittentotextures.Withbakedlighting,theselightmapscannotchangeduringgameplayandsoarereferredtoas‘static’.Mixedlighting

MixedLightscanchangetheirTransformandvisualproperties(suchascolourorintensity)duringruntime,butonlywithinstronglimitations.TheyilluminatebothstaticanddynamicGameObjects,alwaysprovidedirectlighting,andcanoptionallyprovideindirectlighting.DynamicGameObjectslitbyMixedLightsalwayscastreal-timeshadowsonotherdynamicGameObjects.HowModeswork?EachModeintheLightInspectorwindowcorrespondstoagroupofsettingsintheLightingwindow(menu:Window

>Lighting>Settings).ShadowslightscancastShadowsfromaGameObjectontootherpartsofitselforontoothernearbyGameObjects.Howdoshadowswork?Shadowtypes

HardShadows:producesshadowswithasharpedge.SoftShadows:contrastedtoHardshadows,canalsoreducethealiasingeffect(鋸齒效應(yīng))，antialiasing(抗鋸齒).hardsoftStrength,resolutionBias(canbeignored)ThisisrelatedwithShadowmappingorshadowingprojection.Shadowmappingisaprocessbywhichshadowsareaddedto3Dcomputergraphics.Shadowsarecreatedbytestingwhetherapixelisvisiblefromthelightsource.Createalightfromc#codesvoidStart(){