rendering slows down

Adding same actor multiple times on first time added point cloud is ok. After that I have attached another point cloud, but now rendering and all other operations slowed down (even i have removes all actors). Any suggestion?

I experienced a similar issue when rendering a point cloud and adding more points to the cloud. I have not figured out how to solve it, but my initial thought would be using vtkPointGaussianMapper to visualize the point cloud.