How to use three-mesh-bvh - 2 common examples

object3D.traverse(obj => {
    // note that we might already have a bounds tree if this was a clone of an object with one
    const hasBufferGeometry = obj.isMesh && obj.geometry.isBufferGeometry;
    const hasBoundsTree = hasBufferGeometry && obj.geometry.boundsTree;
    if (hasBufferGeometry && !hasBoundsTree && obj.geometry.attributes.position) {
      const geo = obj.geometry;
      const triCount = geo.index ? geo.index.count / 3 : geo.attributes.position.count / 3;
      // only bother using memory and time making a BVH if there are a reasonable number of tris,
      // and if there are too many it's too painful and large to tolerate doing it (at least until
      // we put this in a web worker)
      if (triCount > 1000 && triCount < 1000000) {
        // note that bounds tree construction creates an index as a side effect if one doesn't already exist
        geo.boundsTree = new MeshBVH(obj.geometry, { strategy: 0, maxDepth: 30 });
      }
    }
  });
}

function generateHeightfield(geometry, params) {
  geometry.computeBoundingBox();
  const size = new THREE.Vector3();
  geometry.boundingBox.getSize(size);

  const bvh = new MeshBVH(geometry);

  const heightfieldMesh = new THREE.Mesh(geometry);

  const maxSide = Math.max(size.x, size.z);
  const distance = params.hasOwnProperty("distance") ? params.distance : Math.max(0.25, Math.pow(maxSide, 1 / 2) / 10);
  const resolution = Math.ceil(maxSide / distance);

  const data = [];

  const offset = new THREE.Vector3();
  geometry.boundingBox.getCenter(offset);

  const down = new THREE.Vector3(0, -1, 0);
  const position = new THREE.Vector3();
  const raycaster = new THREE.Raycaster();