three.js的raycaster射线无法获取visible为false的网格对象

在做网格对象拖放时，需要创建一个不可见的参考平面，如果将平面对象设置为visible，则射线对象无法获取该平面，就无法进行位置计算。

onDocumentMouseMove: function (e) {

  var event = e || window.event;

  var mouse = new THREE.Vector2();

  mouse.x = (event.clientX / map3d.width) * 2 - 1;//标准设备横坐标

  mouse.y = -(event.clientY / map3d.height) * 2 + 1;//标准设备纵坐标

  // 通过摄像机和鼠标位置更新射线

  map3d.raycaster.setFromCamera(mouse, map3d.camera);

  if (map3d.selection && e.which == 1) {

    //移动物体

    var intersects = map3d.raycaster.intersectObject(map3d.hidePlane);

    var position = intersects[0].point.sub(map3d.offset);

    map3d.selection.position.set(parseFloat(position.x.toFixed(2)),parseFloat(position.y.toFixed(2)),parseFloat(position.z.toFixed(2)));

  } else {

    //1：如果聚焦到了需要移动位置的物体上

    var intersects = map3d.raycaster.intersectObjects(map3d.objects);

    if (intersects.length > 0) {

      //让参考平面的中心点移动到物体的位置

      map3d.hidePlane.position.copy(intersects[0].object.position);

  }

},

　　这时候可以将网格对象的材质的visible属性设置为false

// 辅助移动物体

this.hidePlane = new THREE.Mesh(

  new THREE.PlaneBufferGeometry(500, 500, 8, 8),

  new THREE.MeshBasicMaterial({ color: 0xffffff, visible: false})

);

this.hidePlane.needsUpdate=true;

this.scene.add(this.hidePlane);

this.raycaster = new THREE.Raycaster();

this.offset = new THREE.Vector3();