Cesium從入門到放棄11：模擬地球自轉

let viewer = undefined
function icrf() {
  if (!viewer || viewer.scene.mode !== Cesium.SceneMode.SCENE3D) {
    return;
  }
  const icrfToFixed = Cesium.Transforms.computeIcrfToFixedMatrix(
    viewer.clock.currentTime
  );
  if (Cesium.defined(icrfToFixed)) {
    const camera = viewer.camera;
    const offset = Cesium.Cartesian3.clone(camera.position);
    const transform = Cesium.Matrix4.fromRotationTranslation(icrfToFixed);
    camera.lookAtTransform(transform, offset);
  }
}
//option可以設置時鐘的一些參數，比如自轉開始的時間，自轉的速度等
const start = function (cesiumViewer,option={multiplier:1}) {
  viewer = cesiumViewer
  viewer.scene.postUpdate.addEventListener(icrf);
  if(viewer.clock){
    const keys=Object.keys(option)
    for(let k of keys){
      viewer.clock[k]=option[k]
    }
  }
}
const stop = function () {
  if(!viewer){
    return
  }
  viewer.clock.multiplier=1
  viewer.scene.postUpdate.removeEventListener(icrf);
  viewer = undefined
}

//開始自轉
const viewer=new Cesium.Viewer('map')
//爲了能明顯的看到，將時針速度設爲10倍
start(viewer,{multiplier:10})
//停止自轉
stop()