docs: public void describe(double x, double y, double angle, double scale, BrightFeature ret)
  	{
  		describe(x, y, angle, scale, (TupleDesc_F64) ret);
  
  		// normalize feature vector to have an Euclidean length of 1
  		// adds light invariance
  		UtilFeature.normalizeL2(ret);
  
  		// Laplacian's sign
  		ret.white = computeLaplaceSign((int)(x+0.5),(int)(y+0.5), scale);
  	}