Han Lingyun now aimed at building an array with a practical use, one he could simply install in front of a cave or could use around his resting place in the wild.
As he thought of his needs, the different categories of array formations came to his mind:
-defensive or protective types,
-attack or killing types,
- imprisoning or sealing types.
Right now, the use case he was thinking of wasn't geared towards attack and entrapment areas.
Fully functional protective array formations would necessitate a huge amount of work and resources. Generally, those types of formations cannot be moved around and are placed around a strategic building or location.
Han Lingyun surmised that a giant array formation was guarding the school at all times, monitoring entries or departures, and perhaps had even more functionalities.
All this left Han Lingyun with a choice between detection and illusory array formations.
An illusory formation could hide a cave entrance for example. This could be quite useful. But he judged that a detection type array formation should come first. That would serve him all the time.
There was an infinite number of possible ways to create a detection formation. However, Han Lingyun had to work with very limited resources right now. He also wanted to make it portable, invisible, and not too costly to operate.
'The detection formation should be able to return a signal when qi attacks, cultivators and magic beasts are passing through. But it should not activate when a random leaf is crossing its borders.'
Han Lingyun thought of having an activation based on movement. This shouldn't be too hard to put in place. But in that case, the formation might be frequently having false alarms.
Another method could be to try to detect any qi concentration. Both cultivators and magic beasts were essentially qi reservoirs. This wouldn't detect a normal bear or a normal poisonous snake though. This would also be returning false positives in areas with high qi concentrations.
Han Lingyun then thought of more unorthodox solutions like heat sensors. Again, he could think of situations where it could be defective: activating due to heat changes because of the sun, not activating when cold bodies or blades passed through…
In the end, Han Lingyun settled on a double detection: one for movement and one for qi. This seemed like a decent compromise, with not too much additional complications and while remaining feasible.
So how to design those sensors?
Han Lingyun had an idea to combine both sensors into one using qi.
To build a sensor, Han Lingyun imagined two points between which a constant qi flow would be maintained.
Point A constantly emits qi towards point B. When an object passes through, the flow of qi is blocked and interrupted, thus triggering a notification from point B. This is the movement detection.
The process to detect qi that Han Lingyun had in mind was slightly more complex.
With the previous montage, Han Lingyun thought of maintaining the flow of qi in an energetic and reactive state.
All objects and particles are attracted to their state of lower energy. For example, a ball at the top of a hill will have high potential energy due to its height and the effect of the force of gravity. It will tend to fall down the hill, in effect lowering its potential energy.
A similar phenomenon can take place with some special states of qi. Qi in the energetic state will naturally change to reach its state minimizing the potential energy.
That is why such an energetic state is not stable. A slight nudge to the ball up the hill might make it fall.
Similarly, the qi in that special energetic state would change immediately when in close proximity of any other form of qi. But when one qi particle changes its state to a lower energy level, its neighbors would now be in close proximity to qi not in their own energetic state and would thus also shift to a lower energy thus causing a chain reaction were all the qi changes state. When Point B detects a change in the state of qi, another notification will be made.
If Han Lingyun wanted to have a formation, he just needed 3 nodes A B and C, each functioning as a sensor. He would then make the qi move in a triangle from A to B, from B to C from C to A and so on.
That would miss something coming from the skies though, he thus needed at least a 4th node to form a tetrahedral detection zone with detectors being its edges.
But these forms were not maximizing the volume under detection protection. As he thought back to his first dome, Han Lingyun had a better idea: because it wasn't hard to make the qi flow follow a curve rather than straight line.
'I will make the qi flow horizontally following the surface of a dome like I just already made. In that case, every qi particle will be describing a horizontal circle and should be maintaining a constant speed on that circle. Then I only need a detector that determines the speed and state of qi on section of the semi sphere.
Detecting a change of state is easy and detecting a change of speed or qi blockage could be simply done by counting the number of qi particles per second, or in other words, detecting the qi level on a section.
For the highly reactive qi state, I should make it so it won't change state unless the concentration of different qi is too high, that way, there won't be chain reactions for a water droplet for example. I'll have to calibrate the threshold carefully.'
The calibration was one of the most difficult elements to outline.
To come back to the analogy of the ball at the top of the hill: Han Lingyun wanted to create a small base around the ball to make sure that a slight wind wouldn't make the ball fall down the slope, while keeping the ball unstable enough so that a nudge from a human would be sufficient to make it fall down.
After feeling satisfied with the level of precision for the qi states, Han Lingyun went to back to designing the array.
Finally, he decided on using detectors on the 4 cardinal directions, to be able to determine from which quarter the intrusion comes simply by knowing which detector reacted first, as the qi will be going in circles around Han Lingyun's location. Those four detectors would then be connected to a small disc like interface that would give Han Lingyun all the alarms and notifications he needed.
Now that Han Lingyun had the concept done, he had to calculate the runes and their configurations that would be encoding his wishes, and these calculations were thousands of times more complicated than for his first array.
That is why qi condensation disciples could only dabble in the field of creating array formations, building a useful and functional array wasn't achievable with their rune comprehension and mental capacities.
One might think that a qi condensation cultivator could always learn some runic code by heart and copy it. In practice, attempting to copy an array without understanding its runes, their interactions and their use was often impossible, at least if one's cultivation was not higher than the cultivation of the original creator.
In general, trying to copy someone else's work was more difficult than creating a similar version from scratch. This was because everyone had their own understanding and unique way of thinking. For two array formation's masters at the same level, it was an impossible task for one to try and copy the other. He would have to decipher what every detail meant, what the designer's exact thought process was to understand each minute intent.
This made identifying an array formation's creator a simpler task, as he would be the only one that could recreate that array formation at the same cultivation level.
Han Lingyun's calculations took him a lot longer than expected. He hadn't finished by the time he had to move on with his schedule. And so, Han Lingyun continued day after day to work on that project while still keeping on cultivating.
Even with this exciting project at hand, his cultivation still took precedent. After his previous cultivation's discoveries, Han Lingyun would now head to a waterfall array for every session.
Nearly two weeks after starting this project, Han Lingyun was finally confident with his calculation's result. He now faced the daunting task of inscribing the runes on the 4 flags and on his pocket disk. His brush and ink wouldn't be precise enough though so he headed to the Array Pavilion.
Elder Wen had been astonished by Han Lingyun time and time again so by now he thought that nothing Han Lingyun could do would manage to shock him one more time. Today he was proved wrong once again when Han Lingyun described his project.
"Do you realize that if you complete your design, you will become a grade 1 array formation master?"
Han Lingyun jumped. "Really?"
"Yes, if you agree and are confident with your chances of success, I will even bring the elders responsible to evaluate the grade of array formation masters and we will watch you complete it to officially enter the ranks of array masters."
"But what does that do to me?"
"This status is recognized throughout the continent. It allows you to sell your own array formations through the main channels and provides a guarantee for customers. Your importance for the sect will sky rocket, especially considering your age and potential. I know you won't necessarily like this side, but it also means that the Elders will take notice of you and your special talent. You won't be able to pass as an above average disciple ever again in the sect, at least in the circle of elders.
On the other side, you will be entitled to additional benefits only meant for older disciples and be provided important discounts on the resources used for array formation making. In exchange, the sect will be counting on your helping hand for its array formations when you reach a sufficient level in the future. Now what is your choice?"
Han Lingyun had yet to realize his project but both he and Elder Wen already had great confidence in his abilities. Now Han Lingyun was facing an important decision for his future path. Often, he would avoid unnecessary attention but staying low key wasn't always the best solution to accomplish his goals.
He wanted to become an array master, he wanted to dive further into runes and their laws. And now, he essentially had the opportunity to be sponsored by the sect for his passion. Of course, he would accept!
On the other hand, his priority is cultivation and would still be cultivation. He planned to dabble in arrays in his free time but it would be quite troublesome if he loses cultivation time because of array making.
"I do want to become an array formation master but I am not totally confident to making it my primary field. However, for that first array, I also wish to complete a functioning array formation before an assessment as I'm still taking a major step from my first trivial array formation. I would be even less confident with examiners breathing down my neck. I don't want to humiliate myself…"
"All right you can make your inscription here then. Don't mind me."