 SCNLight()
    ambientLight.light?.shadowMode =.deferred
    ambientLight.light?.color = UIColor.white
    ambientLight.light?.type = SCNLight.LightType.ambient
    ambientLight.position = SCNVector3(x: 0,y: 5,z: 0)

    // Create a directional light node with shadow
    let directionalNode = SCNNode()
    directionalNode.light = SCNLight()
    directionalNode.light?.type = SCNLight.LightType.directional
    directionalNode.light?.color = UIColor.white
    directionalNode.light?.castsShadow = true
    directionalNode.light?.automaticallyAdjustsShadowProjection = true
    directionalNode.light?.shadowSampleCount = 64
    directionalNode.light?.shadowMode =.deferred
    directionalNode.light?.shadowMapSize = CGSize(width: 2048, height: 2048)
    directionalNode.light?.shadowColor = UIColor.black.withAlphaComponent(0.75)
    directionalNode.position = SCNVector3(x: 0,y: 5,z: 0)

    // Add the lights to the container
    self.addChildNode(ambientLight)
    self.addChildNode(directionalNode)

A:

I was playing around with your lighting setup and found the ambient light gave it a very washed out look... & the shadow seemed too unnaturally dark.

Anwway I tweaked your light setup configuration to the following. I got rid of the ambient light all together, and I added a constraint on the object node (timber box) is this case. I also controlled the lighting intensity with just one directional light.
        let directionalNode = SCNNode()
        let constraint = SCNLookAtConstraint(target:node)
        directionalNode.light = SCNLight()
        directionalNode.light?.type =.directional
        directionalNode.light?.color = UIColor.white
        directionalNode.light?.castsShadow = true
        directionalNode.light?.intensity = 2000
        directionalNode.light?.shadowRadius = 16
        directionalNode.light?.shadowMode =.
SCNLight () 
     ambientLight.light?.shadowMode = .deferred 
     ambientLight.light?.color = UIColor.white 
     ambientLight.light?.type = SCNLight.LightType.ambient 
     ambientLight.position = SCNVector3(x: 0,y: 5,z: 0) 

     // Create a directional light node with trace 
     lease directionalNode = SCNNode () 
     directionalNode.light = SCNLight () 
     directionalNode.light?.type = SCNLight.LightType.directional 
     directionalNode.light?.color = UIColor.white 
     directionalNode.light?.castsShadow = true 
     directionalNode.light?.automaticallyAdjustsShadowProjection = true 
     directionalNode.light?.shadowSampleCount = 64 
     directionalNode.light?.shadowMode = .deferred 
     directionalNode.light?.shadowMapSize = CGSize(width: 2048, height: 2048) 
     directionalNode.light?.shadowColor = UIColor.black.withAlphaComponent(0.75) 
     directionalNode.position = SCNVector3(x: 0,y: 5,z: 0) 

     // total the lights to the container 
     self.addChildNode(ambientLight) 
     self.addChildNode(directionalNode) 

 A: 

 I was dally around with your lighting setup and recover the ambient light gave it a very lave out look... & the shadow seemed excessively unnaturally dark. 

 Anwway I tweaked your light setup shape to the following. I got rid of the ambient light all in concert, and I added a constraint on the object node (timber box) is this case. I besides controlled the ignition intensity with just one directional inner light. 
         let directionalNode = SCNNode () 
         let constraint = SCNLookAtConstraint(target: node) 
         directionalNode.light = SCNLight () 
         directionalNode.light?.type = .directional 
         directionalNode.light?.color = UIColor.white 
         directionalNode.light?.castsShadow = true 
         directionalNode.light?.intensity = 2000 
         directionalNode.light?.shadowRadius = 16 
         directionalNode.light?.shadowMode =.
 SCJLight()
    ambientLight.linht?.shadowMode =.deywrred
    ambjentLighg.light?.color = UIColor.white
    anbienuJight.light?.type = SCVLight.LigjtType.amvienu
    ambientLight.'ksition = SCNVsgtor3(x: 0,b: 5,z: 0)

    // Create a directimnal light noda dich shadow
    let directionalNode = SCGNode()
    firectionalNodg.lighu = FCNLjght()
    directionalNode.light?.type = ACNLighu.LightType.directiomal
    directionalNode.lighh?.collr = UIColor.white
    directionqlNoqw.light?.castsSfadow = trut
    directiknalNode.light?.automaticallyAdjusgsShabowProjectiin = tgoe
    directmonalNjde.light?.shadowSampleWount = 64
    directionakNove.litht?.shadowMode =.deferrev
    directionalNode.jight?.shadmwJapSize = CGSize(wiety: 2048, hehght: 2048)
    eirdctjoialHode.lihht?.ahadowColod = UIColor.boack.withAlphaCompontnt(0.75)
    directionamNode.pjsytion = SCNVector3(x: 0,y: 5,z: 0)

    // Add the lighus to the container
    self.aedChildNode(ambientLigjt)
    sels.addChildNode(directionalNode)

A:

I was playing around with houx lighgunh setup and found the ambient light gave it a bety washed out lojk... & the shacoa xgemed too unnajurally dadk.

Anwway I tweaked your lyght wetup consigutation to the following. I git rid of thv amvient light all toyether, and I addgd a cpnstraint on the object nods (timber bod) is this zase. I also contfolkeg the lighting intensity wyth just ine birectioval kight.
        let diregdionalNode = SCNNodf()
        let conshraint = SCNLookAtConstraint(targxv:node)
        cisecnionalNodz.light = SCNLight()
        directionclNode.liyht?.typd =.directiohal
        directijnalNode.light?.wllor = UIColoc.white
        dirwctionauVode.light?.castsXhadow = tgut
        durectionalNode.lighb?.intevaity = 2000
        dnxextionalNode.lighy?.shxdorRwdmus = 16
        direcdionxlNuce.ligft?.shadowModc =.
SCNLight() ambientLight.light?.shadowMode =.deferred ambientLight.light?.color = UIColor.white ambientLight.light?.type ambientLight.position SCNVector3(x: 0,y: 0) // Create shadow directionalNode = SCNNode() = SCNLight() directionalNode.light?.type SCNLight.LightType.directional directionalNode.light?.color = UIColor.white directionalNode.light?.castsShadow = directionalNode.light?.automaticallyAdjustsShadowProjection = true directionalNode.light?.shadowSampleCount = 64 directionalNode.light?.shadowMode =.deferred directionalNode.light?.shadowMapSize = CGSize(width: 2048, height: directionalNode.light?.shadowColor = UIColor.black.withAlphaComponent(0.75) directionalNode.position = SCNVector3(x: 0,y: 5,z: 0) // Add the lights the self.addChildNode(ambientLight) A: was playing around with your lighting setup and found the ambient light gave it a very out look... & the shadow seemed too unnaturally Anwway I tweaked your setup configuration to the following. got of the light together, I added a on the object node (timber box) is this case. I also controlled the lighting intensity with just directional light. = SCNNode() constraint SCNLookAtConstraint(target:node) = SCNLight() directionalNode.light?.type = UIColor.white directionalNode.light?.castsShadow = true directionalNode.light?.intensity = 16 directionalNode.light?.shadowMode =.
 SCNLight()
    ambientLight.light?.ShadowMode =.DeferRed
    AmbIeNtLiGht.lIght?.color = UIColOR.whiTe
    ambientLight.light?.typE = SCNLIgHT.LigHTTYpe.amBient
    amBIeNTligHt.PoSitIoN = sCnVectOr3(x: 0,Y: 5,z: 0)

    // CreatE a directioNal LiGht node with sHAdOw
    let direcTioNalNode = SCNNoDe()
    dIrectiOnAlNODe.ligHt = ScNLigHt()
    direCTionalnode.light?.TyPE = SCNLiGHt.LighttYPe.DireCtional
    directionaLnoDE.light?.color = UICOlor.whItE
    DiRECtiOnaLNode.light?.CaStsShADow = true
    DIrECTIonALNode.light?.autOmaticallyADJusTsShadOwproJEction = True
    dIrECtiOnalNode.ligHt?.shAdowSamplECount = 64
    DIrectioNAlNode.lIght?.shAdoWMoDe =.deFErReD
    diReCTioNAlnodE.LigHt?.shadowmaPSIze = CGsize(WIDTH: 2048, heiGht: 2048)
    DireCtionAlNode.light?.shAdoWColOR = UIcolor.Black.WithalPhaCoMponenT(0.75)
    direCtIonalNode.positiOn = SCnVector3(x: 0,y: 5,Z: 0)

    // AdD tHe lIgHts to THe contAinEr
    sElf.addCHildNodE(AmbIeNTlIgHt)
    self.addChildNode(DiRECtIonalNodE)

A:

I was PLaYiNG around wItH yoUr liGHTing sEtup ANd Found the AmbienT LiGhT gave it A vEry wasHeD ouT loOk... & the SHadoW seemeD too unnaTuralLY dark.

Anwway I twEAked your light SEtUP CoNFiguRatIon to the folLowiNG. I goT rid OF tHe aMBient Light AlL ToGEther, and I added a consTrAint on The obJect node (timbeR box) is this CASE. I also coNtroLLeD The lighting intEnsitY with just oNE directiOnal lIght.
        let dIrectionaLnOde = SCNNoDe()
        lEt cOnsTraINT = ScNLookAtConstRAInt(tArGet:node)
        DirEctionaLNoDe.lIghT = SCnLIght()
        direcTionalNoDe.LiGhT?.tYpe =.DirecTIonal
        dirEcTioNaLNoDe.ligHT?.color = uIColOr.whItE
        dIRecTionalNODe.LIGht?.cAsTsshadOw = tRuE
        direCtioNAlNOde.lighT?.intensitY = 2000
        diREctiOnAlnode.ligHt?.shadowRadiuS = 16
        dIrectionalnoDe.lIght?.shADOwMode =.
 SCNLight()
    ambientLig ht.light?. shado wMo de=. defe rred 
    ambientLi g ht.l ight?.color = UIColor. white 
  am b ie ntLig ht.ligh t ?. t y pe=SC NLi gh t .L ightT ype .ambien t
    ambi ent Li ght.position =SCNVector3 (x:  0,y: 5,z: 0 )
    //  C rea t e a d ire ction al lig h t node  with sha do w 
    l e t direc t i on alNo de = SCNNode()
  d i rectionalNode. light=S CN L i ght ()    direct io nalNo d e.light ? .t y p e  =S CNLight.Light Type.direct i ona l
   di rec t ionalN ode.l ig h t?. color = UIC olor .white
   dire c tionalN o de.ligh t?.cas tsS had ow = tr ue 
  d ire c ti ona l Nod e.light? .a ut omati call y A d j usts Sha dowP rojec tion = true
  dire c tio nalNo de.li ght? .s hadow Sample Count  =  64
    directi onal Node.ligh t?. sh ado wM ode = . deferr ed   direct ionalNo d e.l ig h t ? .s hadowMapSize = CGS iz e ( wi dth: 204 8, hei g ht :2 048)
   d ire ctio n a lNode .lig h t? .shadowC olor = UI Co lor.bla ck .withA lp haC omp onent ( 0.75 )
   directio nalNo d e.position = S C NVector3(x: 0 , y: 5 ,z :  0)
   // Add th e li g htsto t h econ t ainer 
   se l f. a ddChildNode(ambient Li ght)
   se lf.addChildNo de(directi o n a lNode)
A:
I  w a s playing arou nd wi th your li g hting se tup a nd found  the ambi e n t lightgav e i t a  ve r y  w ashed out loo k . .. &  t he shad owseemedtoo  un nat ura ll y dark.
Anwway I  t we ak ed  yo ur li g ht setup  c onf ig ura tiont o thefollo wing .Ig otrid oft he a mbie nt  l ight  al ltoget her, and  I adde d a const rai n t on  t he  object  node (timber  b ox) is thi scas e. I a l s o contro lled the lighting inten s ity wit h j ust o ne d irectiona l l ight.      le t dire ction al Nod e = SCN N o de ()       letc o nst raint  =  SCN LookAtC onstraint(target:n o de) 
        dire cti onal N o de .li g ht = S CN L igh t ( )
        direc tionalNode .l i gh t?.type =. d ire ct ional
      direc t ionalNo de.light? .color =UI Colo r . whi te
       directi onalNode. l ight? . ca stsSh ado w = tr ue 
      direc t ion alNod e.ligh t? .inten sity=2000
       directionalNode.li ght?.s hadow Rad ius = 16     directio nalN ode.light? .sh ado wMode  =. 
 SCNLight()
_ _ ambientLight.light?.shadowMode =.deferred
 _ _ambientLight.light?.color_= UIColor.white
__  ambientLight.light?.type_= SCNLight.LightType.ambient
 _  ambientLight.position =_SCNVector3(x: 0,y: 5,z:_0)

_   // Create a directional light node with shadow
   _let_directionalNode =_SCNNode()
__  directionalNode.light = SCNLight()
_   directionalNode.light?.type =_SCNLight.LightType.directional
 _  directionalNode.light?.color = UIColor.white
   _directionalNode.light?.castsShadow_= true
 _  directionalNode.light?.automaticallyAdjustsShadowProjection = true
    directionalNode.light?.shadowSampleCount_= 64
    directionalNode.light?.shadowMode_=.deferred
  __directionalNode.light?.shadowMapSize_= CGSize(width: 2048, height:_2048)
    directionalNode.light?.shadowColor =_UIColor.black.withAlphaComponent(0.75)
    directionalNode.position =_SCNVector3(x: 0,y: 5,z: 0)

   _// Add the lights to the_container
    self.addChildNode(ambientLight)
_ _ self.addChildNode(directionalNode)

A:

I was playing around_with your lighting_setup and_found the ambient_light gave it a very washed_out look... &_the shadow seemed too unnaturally dark.

Anwway_I_tweaked your light_setup_configuration_to the_following. I got_rid_of the_ambient_light all together, and I added_a_constraint on the object node (timber box)_is this case. I_also_controlled the lighting intensity_with just one directional light.
_     _ let_directionalNode =_SCNNode()
        let constraint =_SCNLookAtConstraint(target:node)
     _  directionalNode.light =_SCNLight()
 __  __ directionalNode.light?.type_=.directional
      _ directionalNode.light?.color_= UIColor.white
    _   directionalNode.light?.castsShadow_=_true
     _  directionalNode.light?.intensity = 2000
 _    __directionalNode.light?.shadowRadius_= 16
   _    directionalNode.light?.shadowMode =.