Resolved Ar Foundation with windows webcam, XRFaceSubsystem.GetFaceMesh, Error can't convert void to bool

What am i trying to achieve with this Script, i want to use arkit face tracking on windows with a webcam.
What is the error about error: Cannot implicitly convert type 'void' to 'bool'
The line of code where the error is located: if (m_faceManager.GetFaceMesh(faceId, Allocator.Temp, ref faceMesh))

the questions i have is how can i fix the error and is this a good way to use a webcam with ar foundation.
i use:
Unity version: 2021.3.9f1, Render Pipeline Universal RP,
ar foundation: 4.2.7,
arkit xr plugin: 4.2.7,
arkit face tracking: 4.2.7 and
arcore xr plugin: 4.2.7(not used in this script).
OpenCvSharp: https://assetstore.unity.com/packages/tools/integration/opencv-plus-unity-85928

documentation of XRFaceSubsystem.GetFaceMesh: https://docs.unity3d.com/Packages/c...ator_UnityEngine_XR_ARSubsystems_XRFaceMesh__

Code (CSharp):

1. using System;
2.  
3. using System.Collections;
4. using System.Collections.Generic;
5. using System.Runtime.InteropServices;
6. using UnityEngine;
7. using Unity.Collections;
8. using UnityEngine.XR.ARFoundation;
9. using UnityEngine.XR.ARKit;
10. using UnityEngine.XR.ARSubsystems;
11. using OpenCvSharp;
12. public class EyeTracking : MonoBehaviour
13. {
14.     private ARCameraBackground arCamera;
15.     private Mat mat;
16.     private Texture2D texture;
17.     private ARKitFaceSubsystem m_faceSubsystem;
18.     private XRFaceSubsystem m_faceManager;
19.     WebCamTexture InputImage;
20.     void Start()
21.     {
22.         // Get the ARKitFaceSubsystem component
23.         m_faceSubsystem = GetComponent<ARKitFaceSubsystem>();
24.         if (m_faceSubsystem == null)
25.         {
26.             Debug.LogError("ARKitFaceSubsystem is not found in the scene.");
27.             return;
28.         }
29.         // Get the list of available webcams
30.         WebCamDevice[] devices = WebCamTexture.devices;
31.         // Initialize the webcam texture with the first available webcam
32.         InputImage = new WebCamTexture(devices[0].name);
33.         InputImage.Play();
34.     }
35.     void Update()
36.     {
37.         if (InputImage != null)
38.         {
39.             // Capture image using OpenCVSharp
40.             mat = OpenCvSharp.Unity.TextureToMat(InputImage);
41.             // Create the data array with the correct size
42.             int bytesPerPixel = 3; // assuming the image is in RGB format
43.             int dataSize = mat.Width * mat.Height * bytesPerPixel;
44.             byte[] data = new byte[dataSize];
45.             // Copy the data from the Mat object to the data array
46.             Marshal.Copy(mat.Data, data, 0, dataSize);
47.             // Convert Mat to Texture2D
48.             texture = new Texture2D(mat.Width, mat.Height, TextureFormat.RGB24, false);
49.             texture.LoadRawTextureData(data);
50.             texture.Apply();
51.             // Use the face subsystem to get the face mesh data
52.             if (m_faceSubsystem != null)
53.             {
54.                 using (var faceChanges = m_faceSubsystem.GetChanges(Allocator.Temp))
55.                 {
56.                     for (int i = 0; i < faceChanges.added.Length; i++)
57.                     {
58.                         var faceId = faceChanges.added[i].trackableId;
59.                         XRFaceMesh faceMesh = new XRFaceMesh();
60.                        [U] if (m_faceManager.GetFaceMesh(faceId, Allocator.Temp, ref faceMesh))    < Error [/U]
61.                         {
62.                             // Process the face mesh data here, for example, by getting the positions of the eyes
63.                             //Vector3 leftEyePosition = faceMesh.vertices[362];
64.                             //Vector3 rightEyePosition = faceMesh.vertices[984];
65.                             // Do something with the eye positions, such as rendering them on the screen
66.                         }
67.                     }
68.                 }
69.             }
70.         }
71.     }
72. }

thanks in advance.

 

thank you, i will try to make my own face tracking. for now my question is answered.