simplear.html

<!doctype html>
<html>
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
  <title>Simple AR</title>

  <!-- three.js -->
  <script src="https://unpkg.com/three@0.126.0/build/three.js"></script>
  <script src="https://unpkg.com/three@0.126.0/examples/js/loaders/GLTFLoader.js"></script>
</head>
<body>

<button onclick="activateXR()">Start Hit to Place Demo</button>
<script>
async function activateXR() {
  const canvas = document.createElement("canvas");
  document.body.appendChild(canvas);
  const gl = canvas.getContext("webgl", {xrCompatible: true});

  const scene = new THREE.Scene();
  const directionalLight = new THREE.DirectionalLight(0xffffff, 1.0);
  directionalLight.position.set(10, 15, 10);
  scene.add(directionalLight);

  const renderer = new THREE.WebGLRenderer({ alpha: true, preserveDrawingBuffer: true, canvas: canvas, context: gl });
  renderer.autoClear = false;

  const camera = new THREE.PerspectiveCamera();
  camera.matrixAutoUpdate = false;

  const session = await navigator.xr.requestSession("immersive-ar", { requiredFeatures: ['hit-test'] });
  session.updateRenderState({ baseLayer: new XRWebGLLayer(session, gl) });

  const referenceSpace = await session.requestReferenceSpace('local');
  const viewerSpace = await session.requestReferenceSpace('viewer');
  const hitTestSource = await session.requestHitTestSource({ space: viewerSpace });

  const loader = new THREE.GLTFLoader();
  let reticle;
  loader.load("https://immersive-web.github.io/webxr-samples/media/gltf/reticle/reticle.gltf", function(gltf) {
    reticle = gltf.scene;
    reticle.visible = false;
    scene.add(reticle);
  });

  let flower;
  loader.load("https://immersive-web.github.io/webxr-samples/media/gltf/sunflower/sunflower.gltf", function(gltf) {
    flower = gltf.scene;
  });

  let selectedObject = null;
  let initialHitTestSource = null;

  session.addEventListener("selectstart", (event) => {
    if (reticle.visible) {
      const hitTestResults = event.frame.getHitTestResults(hitTestSource);
      if (hitTestResults.length > 0) {
        const hitPose = hitTestResults[0].getPose(referenceSpace);
        selectedObject = flower.clone();
        selectedObject.position.set(hitPose.transform.position.x, hitPose.transform.position.y, hitPose.transform.position.z);
        scene.add(selectedObject);
        initialHitTestSource = hitTestSource;
      }
    } else {
      const raycaster = new THREE.Raycaster();
      const mouse = new THREE.Vector2();
      raycaster.setFromCamera(mouse, camera);

      const intersects = raycaster.intersectObjects(scene.children, true);
      if (intersects.length > 0) {
        selectedObject = intersects[0].object;
        initialHitTestSource = hitTestSource;
      }
    }
  });

  session.addEventListener("selectend", () => {
    selectedObject = null;
  });

  const onXRFrame = (time, frame) => {
    session.requestAnimationFrame(onXRFrame);
    gl.bindFramebuffer(gl.FRAMEBUFFER, session.renderState.baseLayer.framebuffer);

    const pose = frame.getViewerPose(referenceSpace);
    if (pose) {
      const view = pose.views[0];
      const viewport = session.renderState.baseLayer.getViewport(view);
      renderer.setSize(viewport.width, viewport.height);

      camera.matrix.fromArray(view.transform.matrix);
      camera.projectionMatrix.fromArray(view.projectionMatrix);
      camera.updateMatrixWorld(true);

      const hitTestResults = frame.getHitTestResults(hitTestSource);
      if (hitTestResults.length > 0 && reticle) {
        const hitPose = hitTestResults[0].getPose(referenceSpace);
        reticle.visible = true;
        reticle.position.set(hitPose.transform.position.x, hitPose.transform.position.y, hitPose.transform.position.z);
        reticle.updateMatrixWorld(true);
      }

      if (selectedObject && initialHitTestSource) {
        const hitTestResults = frame.getHitTestResults(initialHitTestSource);
        if (hitTestResults.length > 0) {
          const hitPose = hitTestResults[0].getPose(referenceSpace);
          selectedObject.position.set(hitPose.transform.position.x, hitPose.transform.position.y, hitPose.transform.position.z);
          selectedObject.updateMatrixWorld(true);
        }
      }

      renderer.render(scene, camera);
    }
  };
  session.requestAnimationFrame(onXRFrame);
}
</script>
</body>
</html>