cameraManager.TryGetIntrinsics returning false [Bug]

[andnovar]

Unity bug report case number Unity bug case number 1257094.

Describe the bug TryGetIntrinsics(out XRCameraIntrinsics) is always returning false. I am using ARFoundation 4.0

To Reproduce Steps to reproduce the behavior:

1. Invoke the function and try to get the intrinsics.focalLength.x and intrinsics.focalLength.y
2. It gave me false in a Pixel phone and a Moto G6

Expected behavior I expect to get the focal length for further CV processing.

Actual behavior GetIntrinsics is not returning any values.

Smartphone (please complete the following information):

• Device: Pixel, Motorola G6
• OS: Android 10 and 9
• Unity version 2020.2.0
• ARFoundation 4.0

[tdmowrer]

I added this script to the AR Camera GameObject in the SimpleAR sample and ran it on a Pixel 3a XL:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.XR.ARFoundation;
using UnityEngine.XR.ARSubsystems;

[RequireComponent(typeof(ARCameraManager))]
public class PrintCameraIntrinsics : MonoBehaviour
{
    XRCameraIntrinsics? m_CameraIntrinsics;

    void Start()
    {
        GetComponent<ARCameraManager>().frameReceived += OnFrameReceived;
    }

    void OnFrameReceived(ARCameraFrameEventArgs eventArgs)
    {
        if (GetComponent<ARCameraManager>().TryGetIntrinsics(out var intrinsics))
        {
            m_CameraIntrinsics = intrinsics;
        }
        else
        {
            m_CameraIntrinsics = null;
        }
    }

    // Update is called once per frame
    void OnGUI()
    {
        if (m_CameraIntrinsics.HasValue)
        {
            GUI.skin.label.fontSize = 100;
            GUILayout.Label($"Camera intrinsics: {m_CameraIntrinsics.Value.ToString()}");
        }
    }
}

Camera intrinsics were displayed as expected.

1. What AR features did you have enabled (e.g., camera facing direction, plane detection, etc)
2. Which alpha of 2020.2 specifically did you use?

[andnovar]

The problem was on my end. Thanks for sharing code about it. I was not doing TryGetIntrinsics inside OnFrameReceived. I am just using XRCpuImage and reading the raw pixels.

[tdmowrer]

You can call TryGetIntrinsics from anywhere (doesn't have to be in the frameReceived callback), but you need to have gotten a new ARFrame that frame. It takes a few frames to establish the session, which is why calling it once from Start would quite likely return false.