Game AI stuff

[nikolai1962]

This is for stuff not directly related to path-finding.

Used alpaca's stripped down map to make a mini testing map.




The map is set up in such a way as to not have any path-finding problems so i could test other things. Plan is to set up each faction one at a time with one region and change various values to see what moddable values make them expand faster against those rebel settlements.

Some initial observations.

1. I always assumed (with rtw) the only difference with the AI at different difficulty settings was the amount of cash it recieved. Seems to not be so. On medium the AI is much less aggressive even if you give it a lot of cash via king's purse. It doesn't seem to recruit as many units as it does on VH or target settlements as aggressively. The AI still expands, just slowly. On the plus side it doesn't run out of cash like it does on VH.

2. On H and VH the AI will unit spam as much as it can. It has a tendency to overdo this and end up with no income. This means if it isn't constantly expanding or the economy isn't set up to continually increase the cash flow into the game (high pop growth etc) then it gradually slips behind with teching up it's cities especially later on when the new buildings get very expensive.

3. Siege units suck badly in auto-calc. So that means they are bad for the AI to over-produce in every way possible (I thought the high attack might mean they were at least useful to the AI in auto-calc but they're not).

4. The "best unit" council mission rewards can cripple a small faction with limited cash as 4 knights = 1000 upkeep. Making them all cash rewards is better imo as it reduces the number of times the AI will stall through lack of cash. (You can change this in descr_mission.txt.)

5. Family member upkeep is too high for small factions. 200 for the general and 250 for the bodyguard can also economically cripple a small faction if they get too many early on in the game. (If you have recruitable generals you could make the bodyguard a free upkeep unit which would be a neat player/AI thing as the AI likes to keep generals in the cities whereas players like to have them in command. Otherwise just reduce the upkeep of either/both the family member wage and/or the bodyguard upkeep.)

6. Even on my testmap the AI can still get stalled attacking a citiy after a retreat. (On a convex region map it can take quite a lot of retreats before it stalls though.) So MTW2 still needs an AI movement bonus trait that triggers for AI generals that end their turn outside a settlement with 100% movement points. It wants to go up to 100% bonus depending on the scale of your map and your base movement points) and have an anti-trait that triggers when they end their turn in a settlement.

This way if a general is stuck after a retreat eventually the movement bonus will increase to the point where they are within one turn of their target and they'll start moving again. Won't fix all the problems but will reduce it a bit. need an anti-trait to clear the movement bonus again so it can re-trigger if they get stuck later on.

7. The unit recruitment settings can have a massive impact on how well the AI expands. If the available recruitment allows the AI to build lots of crap units then they expand much slower. Constraining the unit choices can lead both to more fun tactical battles (which was the thing i was originally thinking about) and to better autocalc expansion against rebels etc.

This is the kind of french army i want to see in a battle :)



Can't stress enough how big an effect changing the recruitment limits/refresh rates can have on the AI expansion. With one setup the french AI on VH could take all the rebel regions in 30 turns, with a slightly different early recruitment they'd barely get 4 or 5 regions within 30 turns. Removing obsolete units from the recruitment pools as buildings upgraded, reducing the amount of militia buildable in towns (for the french anyway) and having knights easy to recruit was best for the early french.

The key thing is whether the units they can build are capable of beating the rebel garrisons or not. If they can't then the rebels keep getting experience upgrades (which seem to have a big effect in autocalc) so the AI keeps retreating over and over until they get stuck. In the screenshot above it took about 90 turns to get all the rebs as opposed to 30-ish when i had higher levels of knight recruitment.

8. Revolts and brigand activity can be quite useful as a cleaning mechanism for an AI faction that has run out of cash or has stalled some other way and also to remove obsolete armies but it depends a lot on difficulty level. On VH a higher level of brigands/revolts can be indirectly helpful to the AI whereas on M it is pretty much all negative. Seems to me it is best to mod for a specifc difficulty level and always play test at that level to get the balances right.

9. Knight dominated armies are great for the french faction. Move fast, can't assault so they siege out a city instead then cream the garrison in a sally auto calc. Great stuff.

10. In rtw, when the AI had no targets they'd concentrate round the capital. Now they congregate somewhere more sensible, either a central spot or near an enemy even if they can't attack (I have the AI set to only attack rebels currently but thye group around my border anyway after all the reb regions are gone.)
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Will add more as i spot new things.