# File easy_vtk.rb, line 1059
  def loop( count, options={} )
    interval = 0.03
    clear = false
    filename = false
    options.each{ |key, val|
      case key
      when 'interval'
        interval = val
      when 'clear'
        clear = val
      when 'filename'
        filename = val
      else
        raise "option (#{key}) is invalid"
      end
    }
    if filename
      w2i = Vtk::WindowToImageFilter.new
      w2i.SetInput( @renWin )
      w2i.Update
      writer = Vtk::MPEG2Writer.new
      writer.SetInput( w2i.GetOutput )
      writer.SetFileName( filename )
      writer.Start
    end
    count.times{|i|
      EasyVtk::clear if clear
      yield( i )
      @renWin.Render
      writer.Write if filename
      sleep( interval )
    }
    writer.End if filename
    return nil
  end