Collisions Three.js Octree

Question

Am Tryning to make that my character dont go inside my glb model of map, I saw this : https://threejs.org/examples/#games_fps and tried using the octree but getting an error if someone can help me setup collisions and if I need to setup something in my map file.

My map loader code :

const worldOctree = new Octree();
export function setupLevel(scene) {
  const loader = new GLTFLoader();
  loader.load(
  "../../models/level.glb",
  (gltf) => {
    scene.add(gltf.scene);
    worldOctree.fromGraphNode(gltf.scene);
    gltf.scene.position.y += 0.1;

    const helper = new OctreeHelper(worldOctree);
    helper.visible = true;
    scene.add(helper);
   },
   (xhr) => {
     console.log((xhr.loaded / xhr.total) * 100 + "% loaded");
   },
   (error) => {
    console.error(error);
   }
 );
 return worldOctree;
}