当直接从usdz文件而不是Reality Composer文件加载模型时，如何在RealityKit中渲染阴影？

import RealityKit
import ARKit

let arView = ARView(frame: .zero)
view.addSubview(arView)

let modelEntity = try! Entity.loadModel(named: "model.usdz")

let light = DirectionalLight()
light.intensity = 100000
light.shadow = DirectionalLightComponent.Shadow()
arView.scene.addAnchor(light)

let shadowPlane = ModelEntity(mesh: .generatePlane(width: 1, height: 1))
shadowPlane.position.y = 0 // 设置阴影平面的高度
shadowPlane.orientation = simd_quatf(angle: .pi / 2, axis: SIMD3(x: 1, y: 0, z: 0)) // 旋转阴影平面以使其与地面平行
shadowPlane.generateCollisionShapes(recursive: true) // 生成碰撞形状以接收阴影
arView.scene.addAnchor(shadowPlane)

light.shadow?.addChild(shadowPlane)

arView.scene.addAnchor(modelEntity)