How to convert a 3D coordinate to screen coordinate(Monitor,LeftEye)

Hello everyone ~

I use an HMD with eye tracking, through eye tracking api, I can get the object which was being looked at.

Now I want to display a marker on the monitor to represent this object, so I need to convert the world position of the 3d object to screen position.

Here is my code

Code (CSharp):

1. Transform m_Transform;
2.  
3. // Start is called before the first frame update
4. void Start()
5. {
6.     m_Transform = this.transform;
7.     UnityEngine.XR.XRSettings.gameViewRenderMode = UnityEngine.XR.GameViewRenderMode.LeftEye;
8. }
9. Vector2 ScreenPos = Vector2.zero;
10. // Update is called once per frame
11. void Update()
12. {
13.     CalculateScreenPosition();
14. }
15.  
16. void CalculateScreenPosition()
17. {
18.     var projMatrix = Camera.main.GetStereoProjectionMatrix(Camera.StereoscopicEye.Left);
19.     var viewMatrix = Camera.main.GetStereoViewMatrix(Camera.StereoscopicEye.Left);
20.     Vector4 worldPos = m_Transform.position;
21.     worldPos.w = 1;
22.     Vector4 viewPos = viewMatrix * worldPos;
23.     Vector4 clipPos = projMatrix * viewPos;
24.     ScreenPos = new Vector2(clipPos.x / clipPos.w, clipPos.y / clipPos.w);
25. }
26. private void OnGUI()
27. {
28.     if (ScreenPos != Vector2.zero)
29.     {
30.         GUI.Box(new Rect((ScreenPos.x + 0.5f) * Screen.width, (1 - (ScreenPos.y + 0.5f)) * Screen.height, 100, 100), "test");
31.     }
32. }

but something wrong, the screen position is incorrect, here is the result (gif url: https://i.loli.net/2020/08/06/mTqf1Hb7xY4VsP5.gif):


Can anyone solve this problem? thank u.