function onDocumentMouseDown( event ) {
  event.preventDefault();
  var vector = new THREE.Vector3();//三维坐标对象
  vector.set(
    ( event.clientX / window.innerWidth ) * 2 - 1,
    - ( event.clientY / window.innerHeight ) * 2 + 1,
    0.5 );
  vector.unproject( camera );
  var raycaster = new THREE.Raycaster(camera.position, vector.sub(camera.position).normalize());
  var intersects = raycaster.intersectObjects(scene.children);
  if (intersects.length > 0) {
    var selected = intersects[0];//取第一个物体
    console.log("x坐标:"+selected.point.x);
    console.log("y坐标:"+selected.point.y);
    console.log("z坐标:"+selected.point.z);
  }