How research options are selected
Original text by jpd at the Paradox forums
Until recently, it seemed completely random to me how the game chooses which tech applications are selectable to choose from, when you need to pick a new one to research. Until now ....
By closely following the available researchable applications each time a tech was completed, I finally noticed a pattern emerging. This pattern is extremely methodical and predicatable.
Each tech area is divided up in 5 application areas, with 5 applications each. I'm sure you all know that. When the game needs to pick a new researchable application, it takes one of each tech area, if available. What I failed to see, until this week, was how the game does it. It's not random at all.
The game simply cycles through the five application areas for each new research program. It uses some sort of internal index value, derived from the amount of research programs completed, which iterates through the 5 application areas. So, if for the current research project it picked from the first application area for each of the tech groups, your next selectable technology applications will all come from the second application areas, and after that the third application areas, etc.
So, to give an example, let's take the industry tech tree to get to our interchangeable parts:
appl. area 1: water wheel power practical steam high and low appl. area 2: publishing industry mechanical prod interchangeable parts appl. area 3: mechanized mining clean coal cheap iron appl. area 4: experimental rail early rail iron rail appl. area 5: basic chemistry medicine inorganic
Let's say we are Austria, and starting a GC. We have 26 starting techs, and so, like clockwork, the game picks the researchable tech applications all from the second application areas, which for our industry focus here is the mechanical production tech. The only deviation is the navy tech tree. There the choice is Fire Control Systems, but that's only because the Steamers tech from the second area is non-researchable yet, as it needs the Battleship Column Doctrine from the first area, which we haven't got yet.
Right. If you pick the mechanical production now, then your next available choice will become the clean coal, followed by early rail, and medicine. That was area 5, so it resets to area 1 after this, and thus we end up with a choice for High and Low Pressure Steam Engine. That's another prerequisite for our Interchangeable parts. Pick it, and the Interchangeable Parts will follow as next in line.
Now, what happens if you don't pick the suggested Mechanical Production as first tech to research? Well, being the thoroughly dependable scientists, the choices neatly rotate in sequence, thus we end up with the first available tech in area 2 five research projects later. Then, and only then, will the Mechanical Production be available to pick again. And thus we have pushed back getting the Interchangeable Parts for five consecutive research picks, which is at least 5 years.
Same goes for High and Low Pressure Steam Engine. Fail to pick it when the choice is offered, and you have to wait 5 more times before the choice is offered again.