text: import UEngine       from '../Base/UEngine.js'
  import Camera        from './Camera.js'
  import CameraManager from './CameraManager.js'
  import SceneManager  from '../Scene/SceneManager.js'
  
  export default class CameraEngine extends UEngine
  {
    exec ()
    {
      this._collect()
    }
  
    _collect ()
    {
      let rootObject = SceneManager.instance.currentSceneInstance
  
      let cameraList = rootObject.findComponentsInSelfChildrenByType(Camera)
  
      cameraList.sort
      (
        (rLeft, rRight) =>
        {
          return rLeft.depth < rRight.depth
        }
      )
  
      CameraManager.instance.cameraList = cameraList
    }
  }