code: function() {
      var aabb = this.getAABB();
      var sphere = { center: aabb.min.add(aabb.max).divide(2), radius: 0 };
      for (var i = 0; i < this.vertices.length; i++) {
        sphere.radius = Math.max(sphere.radius,
          Vector.fromArray(this.vertices[i]).subtract(sphere.center).length());
      }
      return sphere;
    }
docs: ### .getBoundingSphere()  Computes a sphere that contains all vertices (not necessarily the smallest sphere). The returned object has two properties, `center` and `radius`.