This guide provides step-by-step instructions for migrating existing Unity projects from WebCamTexture-based Passthrough Camera API (PCA) implementation to the PassthroughCameraAccess component. The PassthroughCameraAccess component offers significant improvements in functionality, performance, and developer experience.

PassthroughCameraAccess introduced in v81

The PassthroughCamera component is available in Horizon OS v81 and later.

Migration Overview

The PassthroughCameraAccess component from MRUK v81 replaces the previous approach that used WebCamTextureManager as a wrapper around Unity’s standard WebCamTexture class, combined with the PassthroughCameraUtils helper class for additional functionality.

Key Benefits of Migration

Timestamp Support: Access precise image timestamps for better camera-world alignment

Simultaneous Access to Both Cameras: Access both left and right cameras concurrently

Simplified Permissions: Single permission requirement eliminates duplicate permission dialogs

Unified API: All camera functionality consolidated in a single component

Enhanced Metadata: Complete camera intrinsics, extrinsics, and pose information in one place

Prerequisites

Before starting the migration, ensure your project meets these requirements:

Supported Meta Quest headsets:

Quest 3

Quest 3S and 3S Xbox Edition

Note: You must use a headset to preview the passthrough camera because XR Simulator and Meta Horizon Link do not currently support previewing passthrough cameras.

Horizon OS v74 or later installed on your supported headset.

MRUK v81 or later installed in your Unity project. Follow the Mixed Reality Utility Kit - Getting Started guide for installation instructions

Step-by-Step Migration Guide

Step 1: Update the Android Manifest

Open AndroidManifest.xml and remove the following line if present:

<uses-permission android:name="android.permission.CAMERA" />

Add the following line:

<uses-permission android:name="horizonos.permission.HEADSET_CAMERA" />

The PassthroughCameraAccess implementation only requires the horizonos.permission.HEADSET_CAMERA permission, avoiding any duplicate permission requests.

Step 2. Replace Component References

Old WebCamTextureManager Component:

Remove all of the following WebCamTextureManager references:

WebCamTextureManagerPrefab in the scene

All references to the WebCamTextureManager script

WebCamTextureManager component from GameObjects

All PassthroughCameraUtils script references

Any PassthroughCameraPermissions components

New PassthroughCameraAccess Component:

Add the PassthroughCameraAccess component to a GameObject in Inspector or configure it by using the following code:

PassthroughCameraAccess cameraAccess = gameObject.AddComponent<PassthroughCameraAccess>();
cameraAccess.CameraPosition = PassthroughCameraAccess.CameraPositionType.Left;
cameraAccess.RequestedResolution = new Vector2Int(1280, 960);

Step 3. Update the Code

The previous WebCamTextureManager integration into a project typically looked like this:

public class WebCamTextureManagerExample : MonoBehaviour
{
    [SerializeField] private WebCamTextureManager webCamTextureManager;

    void Update()
    {
        // Wait until WebCamTexture is available
        if (webCamTextureManager.WebCamTexture != null)
        {
            // Use WebCamTexture as Texture
            Texture texture = webCamTextureManager.WebCamTexture;

            // Get additional data via PassthroughCameraUtils
            var intrinsics = PassthroughCameraUtils.GetCameraIntrinsics(webCamTextureManager.Eye);
            Pose pose = PassthroughCameraUtils.GetCameraPoseInWorld(webCamTextureManager.Eye);
            Ray ray = PassthroughCameraUtils.ScreenPointToRayInWorld(webCamTextureManager.Eye, screenPoint);
        }
    }
}

After replacing the WebCamTextureManager component with the new PassthroughCameraAccess component, update the code as follows:

public class PassthroughCameraAccessExample : MonoBehaviour
{
    [SerializeField] private PassthroughCameraAccess cameraAccess;

    void Update()
    {
        if (cameraAccess.enabled)
        {
            // Texture can be accessed immediately after enabling the component.
            // The texture itself can be black for a couple of frames, but it's already safe to use.
            Texture texture = cameraAccess.GetTexture();
        }

        // Wait until PassthroughCameraAccess.IsPlaying is true
        if (cameraAccess.IsPlaying)
        {
            // Camera data is available only when IsPlaying is true
            PassthroughCameraAccess.CameraIntrinsics intrinsics = cameraAccess.Intrinsics;
            Pose pose = cameraAccess.GetCameraPose();
            Ray ray = cameraAccess.ViewportPointToRay(normalizedViewportPoint);

            // Newly added properties:
            Vector2Int resolution = cameraAccess.CurrentResolution;
            DateTime timestamp = cameraAccess.Timestamp;
        }
    }
}

Step 4. API Migration

Here’s a complete mapping of the WebCamTextureManager component API to the PassthroughCameraAccess methods:

Old API	New PassthroughCameraAccess Method
`PassthroughCameraUtils.GetOutputSizes(cameraEye)`	`GetSupportedResolutions(cameraPosition)`	Returns a list of available camera resolutions. A static method which can be called before creating PassthroughCameraAccess instance.
`webCamTextureManager.Eye`	`CameraPositionType CameraPosition`	Controls which camera (Left or Right) will be used. Use instead of PassthroughCameraEye enum.
`webCamTextureManager.WebCamTexture.width/height`	`Vector2Int CurrentResolution`	Returns current camera resolution.
`webCamTextureManager.WebCamTexture`	`GetTexture()`	Retrieves GPU texture of the latest camera image. Use this method to access camera images on GPU. Available immediately after enabling PassthroughCameraAccess if permission is granted.
`PassthroughCameraUtils.GetCameraIntrinsics(cameraEye)`	`Intrinsics`	Returns static intrinsic parameters of the sensor. Available immediately after enabling PassthroughCameraAccess if permission is granted.
`PassthroughCameraUtils.GetCameraPoseInWorld(cameraEye)`	`GetCameraPose()`	Return Camera’s world-space pose. Uses current timestamp to return precise camera pose.
`PassthroughCameraUtils.ScreenPointToRayInWorld(cameraEye, screenPoint)`	`ViewportPointToRay(viewportPoint)`	Returns a world-space ray going from camera through a viewport point. Viewport-space is normalized and relative to the camera. The bottom-left of the camera is (0,0); the top-right is (1,1).
N/A (not available)	`WorldToViewportPoint(worldPosition)`	Transforms worldPosition from world-space into viewport-space.
N/A (not available)	`Timestamp`	Timestamp associated with the latest camera image.

Step 5. Update Coordinate System Conversion

The coordinate system for screen-to-world conversion changed from sensor resolution coordinates to normalized viewport coordinates. The following code example shows how to construct a ray which goes through a texturePoint point:

Vector2 texturePoint = ...; // Texture pixel coordinates
Vector2 currentResolution = new Vector2(webCamTextureManager.WebCamTexture.width, webCamTextureManager.WebCamTexture.height);
Vector2 sensorResolution = PassthroughCameraUtils.GetCameraIntrinsics(webCamTextureManager.Eye).Resolution;
var sensorCoord = new Vector2Int(
    Mathf.RoundToInt(texturePoint.x / currentResolution.x * sensorResolution.x),
    Mathf.RoundToInt(texturePoint.y / currentResolution.y * sensorResolution.y));
var ray = PassthroughCameraUtils.ScreenPointToRayInWorld(
    PassthroughCameraEye.Left,
    sensorCoord
);

The following code example shows how to convert texturePoint to normalized viewport coordinates before passing them to ViewportPointToRay:

Vector2 texturePoint = ...; // Texture pixel coordinates
var viewportPoint = new Vector2(
    (float)texturePoint.x / cameraAccess.CurrentResolution.x,  // Normalize to 0-1
    (float)texturePoint.y / cameraAccess.CurrentResolution.y   // Normalize to 0-1
);
var ray = cameraAccess.ViewportPointToRay(viewportPoint);

// New reverse conversion also available
Vector3 worldPos = hitPoint;
Vector2 backToViewport = cameraAccess.WorldToViewportPoint(worldPos);

Step 6. Test the Migration

After completing the migration steps, rebuild your app and test thoroughly on the headset. Refer to the Troubleshooting section for common issues and their resolutions.

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