ARFace.swift

func renderer(_ renderer: SCNSceneRenderer, nodeFor anchor: ARAnchor) -> SCNNode? {
    guard let faceAnchor = anchor as? ARFaceAnchor,
        let device = sceneView.device else { return nil }
    let faceGeometry = ARSCNFaceGeometry(device: device)
    let node = SCNNode(geometry: faceGeometry)
    node.geometry?.firstMaterial?.fillMode = .lines
        node.geometry?.firstMaterial?.transparency = 0.0 // hide mask line

        let noseNode = EmojiNode(with: noseOptions)
        noseNode.name = "nose"
        node.addChildNode(noseNode)

        let leftEyeNode = EmojiNode(with: eyeOptions)
        leftEyeNode.name = "leftEye"
        leftEyeNode.rotation = SCNVector4(0, 1, 0, GLKMathDegreesToRadians(180.0))
        node.addChildNode(leftEyeNode)

        let rightEyeNode = EmojiNode(with: eyeOptions)
        rightEyeNode.name = "rightEye"
        node.addChildNode(rightEyeNode)

        let mouthNode = EmojiNode(with: mouthOptions)
        mouthNode.name = "mouth"
        node.addChildNode(mouthNode)

        let hatNode = EmojiNode(with: hatOptions)
        hatNode.name = "hat"
        node.addChildNode(hatNode)

    DispatchQueue.main.async {
        self.updateFeatures(for: node, using: faceAnchor)
    }

    return node
}