docs: double computeWeight( double deltaX , double deltaY , double sigma ) {
  		// the exact equation
  //		return Math.exp(-0.5 * ((deltaX * deltaX + deltaY * deltaY) / (sigma * sigma)));
  
  		// approximation below.  when validating this approach it produced results that were within
  		// floating point tolerance of the exact solution, but much faster
  		double d =  ((deltaX * deltaX + deltaY * deltaY) / (sigma * sigma))/approximateStep;
  		if( approximateGauss.interpolate(d) ) {
  			return approximateGauss.value;
  		} else
  			return 0;
  	}