swift – 透明SCNFloor上的SceneKit阴影()

我有一个地板节点,我需要从定向光投射阴影.此节点需要透明(在AR环境中使用).
当我使用ARKit时这个工作正常,但使用SceneKit的相同设置显示没有阴影或反射.我怎样才能像这样在SceneKit中投射阴影？
SceneKit的问题是由于我设置了sceneView.backgroundColor = .clear这一事实引起的 – 但我在这个应用程序中需要这种行为.这可以以某种方式避免吗？

示例代码,演示此问题(仅适用于设备,不适用于模拟器)：

@IBOutlet weak var sceneView: SCNView! {
    didSet {

        sceneView.scene = SCNScene()

        let cameraNode = SCNNode()
        cameraNode.camera = SCNCamera()
        sceneView.pointOfView = cameraNode

        let testNode = SCNNode(geometry: SCNBox(width: 1,height: 1,length: 1,chamferRadius: 0))
        testNode.position = SCNVector3(x: 0,y: 0,z: -5)
        sceneView.scene!.rootNode.addChildNode(testNode)

        let animation = SCNAction.rotateBy(x: 0,y: .pi,z: 0,duration: 3.0)
        testNode.runAction(SCNAction.repeatForever(animation),completionHandler: nil)

        let floor = SCNFloor()
        floor.firstMaterial!.colorBufferWriteMask = []
        floor.firstMaterial!.readsFromDepthBuffer = true
        floor.firstMaterial!.writesToDepthBuffer = true
        floor.firstMaterial!.lightingModel = .constant
        let floorNode = SCNNode(geometry: floor)
        floorNode.position = SCNVector3(x: 0,y: -2,z: 0)
        sceneView.scene!.rootNode.addChildNode(floorNode)

        let light = SCNLight()
        light.type = .directional
        light.shadowColor = UIColor(red: 0,green: 0,blue: 0,alpha: 0.5)
        light.color = UIColor.white
        light.castsShadow = true
        light.automaticallyAdjustsShadowProjection = true
        light.shadowMode = .deferred
        let sunLightNode = SCNNode()
        sunLightNode.position = SCNVector3(x: 1_000,y: 1_000,z: 0)
        sunLightNode.rotation = SCNVector4(x: 1,w: .pi * 1.5)
        sunLightNode.light = light
        sceneView.scene!.rootNode.addChildNode(sunLightNode)

        let omniLightNode: SCNNode = {
            let omniLightNode = SCNNode()
            let light: SCNLight = {
                let light = SCNLight()
                light.type = .omni
                return light
            }()
            omniLightNode.light = light
            return omniLightNode
        }()
        sceneView.scene!.rootNode.addChildNode(omniLightNode)
    }
}

override func viewDidLoad() {
    super.viewDidLoad()
    let tapGR = UITapGestureRecognizer(target: self,action: #selector(toggleTransparent))
    view.addGestureRecognizer(tapGR)
}

@objc func toggleTransparent() {
    transparent = !transparent
}

var transparent = false {
    didSet {
        sceneView.backgroundColor = transparent ? .clear : .white
    }
}

以下是macOS的相同示例,构建在SceneKit游戏项目之上：

import SceneKit
import QuartzCore

class GameViewController: NSViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        // create a new scene
        let scene = SCNScene(named: "art.scnassets/ship.scn")!

        // create and add a camera to the scene
        let cameraNode = SCNNode()
        cameraNode.camera = SCNCamera()
        scene.rootNode.addChildNode(cameraNode)

        // place the camera
        cameraNode.position = SCNVector3(x: 0,z: 15)

        let testNode = SCNNode(geometry: SCNBox(width: 1,z: -5)
        scene.rootNode.addChildNode(testNode)

        let animation = SCNAction.rotateBy(x: 0,z: 0)
        scene.rootNode.addChildNode(floorNode)

        let light = SCNLight()
        light.type = .directional
        light.shadowColor = NSColor(red: 0,alpha: 0.5)
        light.color = NSColor.white
        light.castsShadow = true
        light.automaticallyAdjustsShadowProjection = true
        light.shadowMode = .deferred
        let sunLightNode = SCNNode()
        sunLightNode.position = SCNVector3(x: 1_000,w: .pi * 1.5)
        sunLightNode.light = light
        scene.rootNode.addChildNode(sunLightNode)

        let omniLightNode: SCNNode = {
            let omniLightNode = SCNNode()
            let light: SCNLight = {
                let light = SCNLight()
                light.type = .omni
                return light
            }()
            omniLightNode.light = light
            return omniLightNode
        }()
        scene.rootNode.addChildNode(omniLightNode)

        // retrieve the SCNView
        let scnView = self.view as! SCNView

        // set the scene to the view
        scnView.scene = scene

        // allows the user to manipulate the camera
        scnView.allowsCameraControl = true

        // configure the view
        scnView.backgroundColor = .clear
//        scnView.backgroundColor = .white // shadow works in this mode,but I need it to be clear
    }
}

示例项目：

MacOS：https://www.dropbox.com/s/1o50mbgzg4gc0fg/Test_macOS.zip?dl=1

iOS：https://www.dropbox.com/s/fk71oay1sopc1vp/Test.zip?dl=1

在macOS中你可以在ViewController的最后一行更改backgroundColor – 我需要它清楚,所以我可以在它下面显示相机预览.

在下面的图片中,您可以看到当sceneView.backgroundColor为白色时,以及下面 – 清除时的样子.在清晰版本上没有阴影.

let floor = SCNNode()
floor.geometry = SCNFloor()
floor.geometry?.firstMaterial!.colorBufferWriteMask = []
floor.geometry?.firstMaterial!.readsFromDepthBuffer = true
floor.geometry?.firstMaterial!.writesToDepthBuffer = true
floor.geometry?.firstMaterial!.lightingModel = .constant
scene.rootNode.addChildNode(floor)

lightNode.light!.shadowColor = NSColor(calibratedRed: 0,alpha: 0.5)

lightNode.light!.shadowColor = UIColor(white: 0,alpha: 0.5)

@objc func toggleTransparent() {
    transparent = !transparent
}  
var transparent = false {
    didSet {
        // this shadow is very FEEBLE and it's whitening BG image a little bit
        sceneView.backgroundColor = transparent ? 
                                    UIColor(white: 1,alpha: 0.02) : 
                                    .white
    }
}

let light = SCNLight()
light.type = .directional

if transparent == false {
    light.shadowColor = UIColor(white: 0,alpha: 0.9)
}