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Chapter Two. Lighting Basics and Good Practices

Chapter Two. Lighting Basics and Good Practices

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StartingPoints

Wheredoesthelightingprocessstart?Theanswervarieswidely

betweencompaniesandprojects.Sometimes,especiallyat

smallercompaniesoronsmallerprojects,itisassimpleas

havingaconversationwiththeclientordirector.Hemaytell

youthatthesceneissetatnightoutsidethetheateratamovie

premiere,andhewantsablueorpurplegradientforthesky,

cameraflashesilluminatingthecharactersfromalldirections,

andspotlightssweepingthroughtheskyinthebackground.

Fromthatverbaldescription,youcansitdownanddevelop

sometestimagestoshowthedirectorthenextday.

Ifyourlightingbeginswithaconversation,youshouldstart

adding,collecting,anddiscussingreferenceimagesassoonas

possible.GatherimagesfromtheInternet,framesfromrented

moviesthatcontainsimilarscenes,andbooks,magazines,and

stockphotographycatalogs.Thesooneryoucanputsome

imagesinfrontofthedirectorandagreeonwhatyourprojectis

supposedtolooklike,thesooneryoucanbesurethatyour

workisheadedintherightdirection.

Ifyouareworkingonvisualeffectsshots,lightingcreaturesor

vehiclesthatwillbecompositedintoalive-actionmovie,then

youwillbegiventhebackgroundplates(thedigitizedframes

thatwerefilmedasapartofthemovie.)Usuallyyouwillalso

getsomereferenceimagesofasphereorothersimpleobjects

heldinfrontofthecamerafromwhichyoucanattemptto

matchthelightingoftheshootinglocation.Yourbackground

platewillbeyourbibleinlightingyourvisualeffectsshots,and

you'llobserveeverydetailyoucaninit,suchastheangleand

sharpnessoftheshadows,andthecolors,tones,andlevelof

contrastinthescene,thenincorporateyourobservationsinto

yourlighting.Matchingthelightingfromreallocationsis

discussedindetailinChapter11,"RenderingPassesand

Compositing."



Ifyouareworkingonananimatedproduction,theart

departmentwillhavestartedworkingonthelookofthescenes

longbeforeyoubegintolightthem.Therearelikelytobe

paintingsorillustrationsofwhateachsceneshouldlooklike.

Thelightingartistwillusetheartfromtheartdepartmentto

drawinspiration,andtosuggestthecolorsandtonesthat

shouldappearintheimage.However,shewillmakeherown

decisionsaboutexactlyhowtoimplementthelightingdesign

usingthemanytypesoflightsandoptionsavailablein3D

graphics.



TypesofLights

Youbeginsettinguplightingina3Dscenebychoosingwhich

typesoflightstoadd.Theactuallightsthatyoucanuseina3D

programareroughlybasedonreal-worldtypesoflightsources.

Eachhasitsownusesandadvantages,soitpaystoknowyour

toolsandchoosethemcarefullyforeachproject.



PointLights

Pointlights,alsoknownasomnioromnidirectionallights,are

thesimplestlightsourcestousein3D.AsshowninFigure2.1,

apointlightemitslightuniformlyinalldirections.



Figure2.1.Apointlightemitslightuniformlyin

alldirections,castingshadowsthatradiateout

fromthelight'sposition.



Apointlightin3Dgraphicsisbestcomparedtoalightbulb



hanginginthemiddleofaroomasshowninFigure2.2,some

programsevenrepresentpointlightswithalightbulbicon.Yet

unlikeareallightbulb,apointlightisinfinitelysmall,soallof

thelightemittedfromitcomesfromexactlythesamepointin

space.



Figure2.2.IconsforapointlightinLightwave3d,

aRadiallightinElectricImage,apointlightin

Maya,andapointlightinSoftimage.Allperform

similarfunctions.



Whenpointlightsaresettocastshadowsandyoumodelalight

fixturearoundthem,theshadowofthelightfixturewilllimit

andshapewherethelightcanshine,asshowninFigure2.3.

However,mostlightingartistsprefertousespotlightsforthis

kindofeffect,becausespotlightsprovidemorecontrolover

exactlywherethelightisaiming.



Figure2.3.Whenpositionedwithinalightfixture

andsettocastshadows,apointlightcanappear

similartoaspotlight.



Spotlights

Spotlights(alsocalledspots)arethemostpopulartypeoflight

inlightingdesignforcomputergraphics,becausetheycanbe

controlledandadjustedsocompletely.Justlikeapointlight,a

spotlightsimulateslightradiatingfromaninfinitelysmallpoint.

However,insteadofaiminginalldirections,itislimitedtoa

specifiedconeorbeamoflightinacertaindirection,asshown

inFigure2.4.Thespotlight'srotationcandeterminewherethe

beamisaimed,oratargetorinterestmaybelinkedtothelight

sothatthelightisalwaysaimedtowardthetarget.



Figure2.4.Aspotlight'silluminationislimitedto

aconeaimedinaspecificdirection.



Youcoulddoalmostallofyourlightingwithspotlights;even

whenlightneedstobeaimedindifferentdirections,youcan

useseveralspotlightstogether,asshowninFigure2.5.



Figure2.5.Multiplespotlightscanbeaimedin

differentdirections,givingtheappearanceofan

omnidirectionallightwhileallowingmorecontrol

overwherethelightsareaimed.



[Viewfullsizeimage]



Spotlightshavehandycontrolsthatyoucanadjusttoshape

exactlywherelightwillfall.Theconeangledeterminesthe

widthofthespotlight'sbeam,whilethepenumbraangle(also

calledfallofforspreadangle)determinesthesoftnessofthe

edgearoundthespotlight'sbeam.Atapenumbraof0,the

beamwillhaveaperfectlysharpedge,asshownontheleftside

ofFigure2.6.Asyouincreasethepenumbra,thespotlight

beamswillgainasoftedge,asshowninthecenterofthe

figure.Withaverysoftbeam,younolongernoticetheshapeof

thespotlightatall.AsshownontherightsideofFigure2.6,

spotlightscanaddsubtleilluminationtoascene,witheachlight

gentlybrighteningtheareawhereitisaimed,butallofthe

spotlightsblendingtogetherseamlessly.Chapter4,"Lighting

EnvironmentsandArchitecture,"describeshowtoplacelights

asshowninthisfigure.



Figure2.6.Withhard-edgedlights(left),youcan



seeeveryspotlightconedistinctly.Asthe

penumbraangleisincreased(center),thelights

begintomerge;whenthelightsaresoftenough

(right),theymergetogethersothatyoucannot

distinguishbetweentheindividualsources.



Spotlightsalsohaveanoptioncalledbarndoors.Inreallife,

barndoorsaremetalflapsmountedinfrontofaspotlight,as

showninFigure2.7,whichcanbefoldedinfrontofthelightto

cropithorizontallyorvertically.Barndoorsin3Dgraphicsgive

youthesamekindofcreativecontrol,enablingyoutocropout

asquareorrectangleoflight.



Figure2.7.Besideshavingcontroloveraiminga

light,barndoorsalsoallowacinematographerto

limitthecoverageofaspotlighttolessthanits

naturalconeangle.



Spotlightsarealsopopularincomputergraphicsbecausethey

workefficientlywithsomekindsofshadows.InChapter3,

"ShadowsandOcclusion,"Iwilldiscusswhyspotlightsare

usuallythemostefficientkindoflightwhenrenderingdepth

maporshadowmapshadows.



DirectionalLights

Adirectionallight,whichisparticularlyusefulforsimulating

directsunlight,isalsoknownasadistant,direct,infinite,orsun

lightindifferentprograms;thedifferenticonsareindicatedin

Figure2.8.



Figure2.8.A3DStudioMaxtargetdirectlight,

directionallightsinAliasPowerAnimatorand

Maya,andanInfinitelightinSoftimage,allserve

thesamepurpose



Adirectionallightilluminateseveryobjectfromthesameangle,

nomatterwheretheobjectislocatedrelativetothelight.In

Figure2.9,thedirectionallightaimsdownandtotheleft,

causingeveryobjecttobeilluminatedasifitwerebeinglit

fromtheupperleft.



Figure2.9.Adirectionallightcreatesparallel

shadowsandilluminationthatstrikeseachobject

fromthesameangle.



AlthoughthedirectionallightinFigure2.9isrightinthemiddle

ofthescene,itsimulateslightasifitcamefromveryfaraway.

Alloftheshadowscastfromadirectionallightareparallel,



whichissomethingyounormallywouldonlyseeinshadows

fromaverydistantlightsourcesuchasthesun.Contrastthese

shadowswiththeshadowscastbypointlightsandspotlights,

wheretheshadowsdivergeawayfromthelightatdifferent

angles.



AreaLights

Anarealightisatypeoflightthatsimulatesthesizeofa

physicallightsourceinreallife.Withpoint,spot,anddirectional

lights,scalingupthelightinyoursceneonlyscalesuptheicon,

anddoesn'tchangetheillumination.Asyouscaleupanarea

light,however,itwillaccuratelysimulateilluminationfroma

largerpaneloflight.Ifanarealightisscaledverysmall,its

illuminationwillappearsimilartoapointlight.Asshownonthe

rightinFigure2.10,illuminationfromalargerarealightwill

appearsofter,creatingsoftershadowsandemittingillumination

thatcanwraparoundnearbysubjects.



Figure2.10.Anarealightcreatessofter

illuminationandshadowsasitisscaledlarger.



Arealightsareoftenavailableinavarietyofshapes,including



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Chapter Two. Lighting Basics and Good Practices

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