text: # ----------------------------------------------------------------------------
  # -                        Open3D: www.open3d.org                            -
  # ----------------------------------------------------------------------------
  # The MIT License (MIT)
  #
  # Copyright (c) 2018-2021 www.open3d.org
  #
  # Permission is hereby granted, free of charge, to any person obtaining a copy
  # of this software and associated documentation files (the "Software"), to deal
  # in the Software without restriction, including without limitation the rights
  # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  # copies of the Software, and to permit persons to whom the Software is
  # furnished to do so, subject to the following conditions:
  #
  # The above copyright notice and this permission notice shall be included in
  # all copies or substantial portions of the Software.
  #
  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  # FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  # IN THE SOFTWARE.
  # ----------------------------------------------------------------------------
  
  import open3d as o3d
  import numpy as np
  import time
  import copy
  
  
  def visualize_non_blocking(vis, pcds):
      for pcd in pcds:
          vis.update_geometry(pcd)
      vis.poll_events()
      vis.update_renderer()
  
  
  pcd_data = o3d.data.PCDPointCloud()
  pcd_orig = o3d.io.read_point_cloud(pcd_data.path)
  flip_transform = [[1, 0, 0, 0], [0, -1, 0, 0], [0, 0, -1, 0], [0, 0, 0, 1]]
  pcd_orig.transform(flip_transform)
  n_pcd = 5
  pcds = []
  for i in range(n_pcd):
      pcds.append(copy.deepcopy(pcd_orig))
      trans = np.identity(4)
      trans[:3, 3] = [3 * i, 0, 0]
      pcds[i].transform(trans)
  
  vis = o3d.visualization.Visualizer()
  vis.create_window()
  start_time = time.time()
  added = [False] * n_pcd
  
  curr_sec = int(time.time() - start_time)
  prev_sec = curr_sec - 1
  
  while True:
      curr_sec = int(time.time() - start_time)
      if curr_sec - prev_sec == 1:
          prev_sec = curr_sec
  
          for i in range(n_pcd):
              if curr_sec % (n_pcd * 2) == i and not added[i]:
                  vis.add_geometry(pcds[i])
                  added[i] = True
                  print("Adding %d" % i)
              if curr_sec % (n_pcd * 2) == (i + n_pcd) and added[i]:
                  vis.remove_geometry(pcds[i])
                  added[i] = False
                  print("Removing %d" % i)
  
      visualize_non_blocking(vis, pcds)
  