How do I get shadows work on reality file or usdz without composer

Hello,

I found I can't let shadows work on entity with reality file or usdz, but it works on entity with reality composer.

Here is the code snippet:

//no shadows
  penguin = try? Entity.loadModel(named: "penguin", in: nil)
  penguinAnchor.addChild(penguin!)

//shadows
  penguinScene = try! PenguinRC.loadPenguinScene()
  arView.scene.addAnchor(penguinScene)

And I had tried with PointLightComponent.Shadow with following code, but it still can't work.

model.components[DirectionalLightComponent.Shadow.self] = DirectionalLightComponent.Shadow.init()

So how can I enable shadows on the model ?

Thanks