How to enable AR and Hit-test?

Similar to VR experience, you can add AR Button to enable AR experiences. Additionally, you can specify the required and optional AR features your experience will use.

import { ARButton } from "/jsm/webxr/ARButton";

document.body.appendChild(ARButton.createButton(renderer, { requiredFeatures: ["hit-test"] }));

Add a controller: Returns a Group representing the so called target ray space of the controller. Use this space for visualizing 3D objects that support the user in pointing tasks like UI interaction.

	controller = renderer.xr.getController(0);
	controller.addEventListener("select", onSelect);
	scene.add(controller);

When we are hitting a surface, to indicate the surface, we will create a reticle to our scene.

	//Hit-test indicator
	reticle = new Mesh(new RingBufferGeometry(0.15, 0.2, 32).rotateX(-Math.PI / 2), new MeshBasicMaterial());
	reticle.matrixAutoUpdate = false;
	reticle.visible = false;
	scene.add(reticle);

Let's define the onSelect event that we attached to controller. When the select event happen, meaning user decides to place the object and we create it on the chosen location.

function onSelect() {
	if (reticle.visible) {
		const mesh = new Mesh(geometry, phongMaterial);
		mesh.position.setFromMatrixPosition(reticle.matrix);
		mesh.scale.y = Math.random() * 2 + 1;
		scene.add(mesh);
	}
}

Finally in our render function, we will check in every XRFrame if we have an hit-test source to display the reticle on the surface.

function render(timestamp: number, frame: any) {
	if (frame) {
		earth.visible = false;
		const referenceSpace = renderer.xr.getReferenceSpace();
		const session = renderer.xr.getSession();
		if (hitTestSourceRequested === false) {
			session.requestReferenceSpace("viewer").then((referenceSpace) => {
				session.requestHitTestSource({ space: referenceSpace }).then((source) => {
					hitTestSource = source;
				});
			});

			session.addEventListener("end", () => {
				hitTestSourceRequested = false;
				hitTestSource = null;
			});
			hitTestSourceRequested = true;
		}
		if (hitTestSource) {
			const hitTestResults = frame.getHitTestResults(hitTestSource);
			if (hitTestResults.length) {
				const hit = hitTestResults[0];
				reticle.visible = true;
				reticle.matrix.fromArray(hit.getPose(referenceSpace).transform.matrix);
			} else {
				reticle.visible = false;
			}
		}
	}
	renderer.render(scene, camera);
}

To run the code on your device, you have to give access to your camera when prompted.