code: public void updateTracks( I input ,
  							  PyramidDiscrete<I> pyramid ,
  							  D[] derivX,
  							  D[] derivY ) {
  		// forget recently dropped or spawned tracks
  		tracksSpawned.clear();
  
  		// save references
  		this.input = input;
  
  		trackerKlt.setInputs(pyramid, derivX, derivY);
  
  		trackUsingKlt(tracksPureKlt);
  		trackUsingKlt(tracksReactivated);
  	}
docs: Updates the location and description of tracks using KLT.  Saves a reference
  to the input image for future processing.
  
  @param input Input image.
  @param pyramid Image pyramid of input.
  @param derivX Derivative pyramid of input x-axis
  @param derivY Derivative pyramid of input y-axis