RealityKit中的标准面网格

要在RealityKit 2.0中以编程方式生成和渲染ARKit的canonical face mesh（由1220个顶点组成的ARFaceGeometry对象），请使用以下代码：

import ARKit
import RealityKit

class ControllerView: UIViewController {
    
    @IBOutlet var arView: ARView!
    var anchor = AnchorEntity()
    var model = ModelEntity()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        arView.automaticallyConfigureSession = false
        arView.session.delegate = self

        guard ARFaceTrackingConfiguration.isSupported
        else { 
            fatalError("We can't run face tracking config") 
        }
                
        let config = ARFaceTrackingConfiguration()
        config.maximumNumberOfTrackedFaces = 1
        arView.session.run(config)
    }
}

然后创建一个方法来转换面锚的子属性。注意，我使用了for-in循环来将索引从[Int16]转换为[UInt32]类型（类型转换在这里没有帮助）。

extension ControllerView {
    
    private func nutsAndBoltsOf(_ anchor: ARFaceAnchor) -> MeshDescriptor {
        
        let vertices: [simd_float3] = anchor.geometry.vertices
        var triangleIndices: [UInt32] = []
        let texCoords: [simd_float2] = anchor.geometry.textureCoordinates
        
        for index in anchor.geometry.triangleIndices {         // [Int16]
            triangleIndices.append(UInt32(index))
        }
        print(vertices.count)         // 1220 vertices
        
        var descriptor = MeshDescriptor(name: "canonical_face_mesh")
        descriptor.positions = MeshBuffers.Positions(vertices)
        descriptor.primitives = .triangles(triangleIndices)
        descriptor.textureCoordinates = MeshBuffers.TextureCoordinates(texCoords)
        return descriptor
    }
}

最后，让我们运行一个委托的方法来提供一个网格资源：

extension ControllerView: ARSessionDelegate {
    
    func session(_ session: ARSession, didAdd anchors: [ARAnchor]) {

        guard let faceAnchor = anchors[0] as? ARFaceAnchor else { return }
        arView.session.add(anchor: faceAnchor)
        self.anchor = AnchorEntity(anchor: faceAnchor)
        self.anchor.scale *= 1.2

        let mesh: MeshResource = try! .generate(from: [nutsAndBoltsOf(faceAnchor)])
        var material = SimpleMaterial(color: .magenta, isMetallic: true)
        self.model = ModelEntity(mesh: mesh, materials: [material])
        self.anchor.addChild(self.model)
        arView.scene.anchors.append(self.anchor)
    }
}

结果（在iPadOS 16.2中的第四代iPad Pro上测试）。

我还建议您看一下关于在RealityKit 2.0中可视化检测到的平面的帖子。
圣诞快乐！