Immersive AR Emulation for THREE.js

WebXR gives you the ability to build Augmented Reality experiences in the Web, both for handsets like phones and headsets. It's very possible to build a single code-path which works well for headsets and handsets without needing to detect which kind of hardware you are using.

Unforunately AR headsets are expensive and hard to access to so many AR experiences only work with handsets either through design or accident.

The other type of head mounted WebXR experience is immersive Virtual Reality. Virtual Reality headsets are cheaper and more widely avaialble than VR headsets so what if you could test Headset Augmented Reality on a VR Headset?

"What if you could test Headset AR on a VR Headset?"

NB: This is not designed for use in production code, this method of modifying the XRFrame is inefficient, and will give you poor performance. This is only for testing the AR path of your WebXR app. If you want to provide users a VR fallback for your XR experience you should have a seperate code path which uses THREE.js' Raycaster when the user is in a VR session.

This is a project designed to allow you to test your immersive-ar session in a VR headset it acts kind of like a polyfill, if immersive-ar is already supported then it does nothing. But if immersive-vr is supported and immersive-ar it will let it work by:

• In emulated immersive-ar draw a background scene behind your scene
• Modifying navigator.xr.isSessionSupported to override requests for immersive-ar to let it be allowed.
• Modifying navigator.xr.requestSession to return an immersive-vr session if an immersive-ar session is requested which has been modified such that:
  • It supports requestHitTestSource by testing against the rendered background scene
  • It modifies requestAnimationFrame so that each XRFrame returned has a replacement getHitTestResults

Installation

There are two methods of installation one, for if you have THREE.JS as a script and one for if you are building with Webpack or Rollup

ThreeJS as a script

<script src="js/three.js"></script>
<script type="module">
import {
	init as initEmulateAR,
	requestSession,
	isSessionSupported,
	renderEnvironment,
	applyImmersiveARProxy,
	sceneModelURL
} from "https://adarosecannon.github.io/immersive-ar-emulation/src/EmulateAR.js";
</script>

With WebPack or Rollup

npm install --save immersive-ar-emulation

import {
	init as initEmulateAR,
	requestSession,
	isSessionSupported,
	renderEnvironment,
	applyImmersiveARProxy,
	sceneModelURL
} from "immersive-ar-emulation";

Usage

Unfortunately it does require some integrating into your code, for an example app checkout the demo/ folder of this repo.

Step 1

Import the code as shown above.

You can find the URL of the scene in .glb format to download in sceneModelURL,

Download the model using the ThreeJS GLTF Loader.

Use this model and your scene and renderer to setup the emulator.

const environment = (await loadModel(sceneModelURL)).scene;
initEmulateAR({ scene, renderer, environment });

You can then either apply the immersive-ar proxy to modify to navigator.xr

await applyImmersiveARProxy();

but if you prefer to leave it unmodified you can use immersiveARProxyRequired to see if you need to add a button which can call requestSession and isSessionSupported from the emulator yourself.