title: Vtk Qt scene with >50 (moving) actors
body: <p>I am trying to implement (fairly) simple scene where I have ~50 cubes which are moving in certain directions. The position of the cubes changes 20 times per second.</p>
  
  <p>My first shoot was adding and removing actors from the scene. This approach just doesn't scale. Whole scene lags and user is unable to move the camera.</p>
  
  <pre><code>void draw(vtkRenderer *renderer)
  {    
      renderer-&gt;RemoveAllViewProps(); 
      for(const Cube&amp; cube : cubes_)
      {
          vtkSmartPointer&lt;vtkCubeSource&gt; cube_source = vtkSmartPointer&lt;vtkCubeSource&gt;::New();  
          cube_source-&gt;Update();
          cube_source-&gt;SetXLength(cube.lengt());
          cube_source-&gt;SetYLength(cube.width());
          cube_source-&gt;SetZLength(cube.height());
  
          vtkSmartPointer&lt;vtkPolyDataMapper&gt; poly_mapper = vtkSmartPointer&lt;vtkPolyDataMapper&gt;::New();
          poly_mapper-&gt;SetInputConnection(cube_source-&gt;GetOutputPort());
  
          vtkSmartPointer&lt;vtkActor&gt; actor = vtkSmartPointer&lt;vtkActor&gt;::New();
          actor-&gt;SetMapper(poly_mapper);
          actor-&gt;SetPosition(cube.x(), cube.y(), cube.z());
  
          renderer-&gt;AddActor(actor);
      }
  }
  </code></pre>
  
  <p>Second shot is a bit better. I have created "actor pool" where I reuse the actors and hide the ones which are not needed.
  Still, moving camera is laggy and the rest of my UI (I have some additional widgets inside Vtk widget) seems to be laggy.</p>
  
  <p>I couldn't find any relevant source for Vtk where scene is "dynamic". All examples preload all scene elements and further work with them. Can anyone tell me what am I doing wrong here?</p>