docs: public double pathLengthEstimate(double... controlPoints)
      {
          double maxX = Double.NEGATIVE_INFINITY;
          double maxY = Double.NEGATIVE_INFINITY;
          double minX = Double.POSITIVE_INFINITY;
          double minY = Double.POSITIVE_INFINITY;
          for (int n=0;n<length;n++)
          {
              maxX = Math.max(maxX, controlPoints[2*n]);
              maxY = Math.max(maxY, controlPoints[2*n+1]);
              minX = Math.min(minX, controlPoints[2*n]);
              minY = Math.min(minY, controlPoints[2*n+1]);
          }
          return (maxX-minX+maxY-minY)*1.35;
      }