code: protected PointTrack addNewTrack( int setIndex, double x , double y , Desc desc ) {
  		PointTrack p = getUnused();
  		p.set(x, y);
  		((Desc)p.getDescription()).setTo(desc);
  		if( checkValidSpawn(setIndex,p) ) {
  			p.setId = setIndex;
  			p.featureId = featureID++;
  
  			sets[setIndex].tracks.add(p);
  			tracksNew.add(p);
  			tracksActive.add(p);
  			tracksAll.add(p);
  			return p;
  		} else {
  			unused.add(p);
  			return null;
  		}
  	}
docs: Adds a new track given its location and description