//在 3D 模型上添加阴影 只需复制粘贴此代码，它就会在地面上出现 3D 模型的阴影

// To Add Shadow on 3D Model Just Copy Paste this code and it will appear a shadow of 3D Model on Ground

let flourPlane = SCNFloor()
let groundPlane = SCNNode()
let groundMaterial = SCNMaterial()
groundMaterial.lightingModel = .constant
groundMaterial.writesToDepthBuffer = true
groundMaterial.colorBufferWriteMask = []
groundMaterial.isDoubleSided = true
flourPlane.materials = [groundMaterial]
groundPlane.geometry = flourPlane
//
mainNode.addChildNode(groundPlane)
// Create a ambient light
let ambientLight = SCNNode()
ambientLight.light = 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 myNode = SCNNode()
myNode.light = SCNLight()
myNode.light?.type = SCNLight.LightType.directional
myNode.light?.color = UIColor.white
myNode.light?.castsShadow = true
myNode.light?.automaticallyAdjustsShadowProjection = true
myNode.light?.shadowSampleCount = 64
myNode.light?.shadowRadius = 16
myNode.light?.shadowMode = .deferred
myNode.light?.shadowMapSize = CGSize(width: 2048, height: 2048)
myNode.light?.shadowColor = UIColor.black.withAlphaComponent(0.75)
myNode.position = SCNVector3(x: 0,y: 5,z: 0)
myNode.eulerAngles = SCNVector3(-Float.pi / 2, 0, 0)
// Add the lights to the container
mainNode.addChildNode(ambientLight)
mainNode.addChildNode(myNode)
// End