Passthrough over Link is a feature that significantly decreases the iteration time when developing passthrough-enabled apps. It allows running such apps while using Link⁠, eliminating the need to build the app on a PC and deploy it to a Meta Quest device every time you test it during development. With Passthrough over Link, it is faster than ever to create mixed reality experiences.

Passthrough over Link allows you to:

Use a developer platform such as Unity or Unreal Engine to run a passthrough-enabled app by launching the app directly in the editor.

Quickly iterate during development when using the Passthrough API. (We support passthrough and hands functionalities).

For details about the Passthrough API, read the Passthrough API overview.

Note: Passthrough over Link is a developer-only feature aimed at increasing your development speed by previewing your passthrough-enabled apps while still in development. That being said, the visual appearance and performance characteristics of the experience are slightly different between running over Link and running on a Meta Quest device.

Prerequisites

This section outlines the prerequisites for using Passthrough over Link.

For details on using Link for app development, see Use Link for App Development.

Hardware

To use Passthrough over Link, you need the following hardware:

A PC that meets the specifications⁠ for running Link

A Quest line device (for example, a Quest 2)

A compatible USB-C cable⁠ to use for Link. For Color Passthrough, the USB connection should provide an effective bandwidth of at least 2 Gbps. You can measure the connection speed by using the USB speed tester built into the PC app: go to Devices, select the connected device, click USB Test, and then click Test Connection. If the connection speed is low, try using a different cable and USB adapter.

Software

The essential software for using Passthrough over Link is:

Meta Quest build v37.0 or later

Meta Horizon Link PC app with version v37.0 or later, which you can download from the Meta Quest website⁠

Important: You must enable the Developer Runtime Features and Passthrough over Meta Quest Link toggles in the Meta Horizon Link PC app by clicking Settings > Beta. The Passthrough over Meta Quest Link toggle appears only when you enable the previous toggle.

You must restart Unreal Engine after enabling the toggles.

Passthrough over Link Settings in Meta Horizon Link

Note: You must sign in to your developer account in the Meta Horizon Link PC app and in your Meta Quest headset.

Additionally, you must meet the requirements listed in Getting Started Developing UE4 Apps for Quest. Use Unreal Engine 4 integration version 37 or higher.

Use

Before running your app, you must enable Link.

To connect your Meta Quest device to your PC over Link, follow the instructions in Set up Link⁠

For troubleshooting instructions on Link connection, read Troubleshoot Link and Air Link⁠.

Follow these steps to test your app through Passthrough over Link.

Ensure that Link is started.

To configure an Unreal project for Passthrough, follow the instructions on Configuring Unreal Project.

In UE Project settings, enable alpha channel support in Post Processing by selecting Allow through tonemapper.

Passthrough over Link Unreal Postprocessing

Note (UE4 Only): If you manually use the PokeAHoleMaterial in your app you must change it to the PokeAHoleMaterial_Inverse material.

Note (UE5 Only), known issue:PokeAHoleMaterial is not working with OpenGL preview. A workaround is to use Vulkan preview instead, or to use a material with AlphaHoldout blend mode (will not work over Opaque objects).

In Play, select the VR Preview Mode.

Use your device to see passthrough in your passthrough-enabled app.

Data Privacy

The Passthrough over Link feature is available only to developers, and can be toggled on/off through the host PC using the Meta Horizon Link PC app. When toggled on, data captured from the head-mounted display’s cameras, including camera images of the physical environment, will be transmitted to and processed on the host PC. Passthrough over Link is off by default.

The first time you toggle on Passthrough over Link, the following consent modal appears.

You only need to give your consent once.

At no point during the execution of Passthrough over Link do the camera images sent to the host PC leave the host PC, except to be sent back to the headset to be displayed.

Meta Horizon Link and Screenshots

Be aware that due to the privacy constraints, screenshots you take of your Passthrough application while Link is active may not include background passthrough content but show a dark background. If you have issues with showing Passthrough content in your screenshots, disconnect the Link cable.

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