Game AI stuff (1.5)

[nikolai1962]

IT WORKED !! A HEARTY THANK TO YOU nikolai1962

I hope those britons will not invade the mainland

Good :)

[nikolai1962]

Some general things

1) Happy AI

This is what Iberia should look like after a faction has conquered it all and moved on.



Minimal garrisons (which is why they need help with unrest imo) and no stationary stacks hanging round. They have close adjacent land regions on the other side of their empire so all their armies head there. Might see a stack chasing rebels but that should be it.

General how AI should look away from war zone pics:






2) Stationary stacks

As mentioned before the AI stacks shouldn't be stationary except under limited conditions.

a) No targets/rebels so hanging round capital region
b) Waiting for a ship mode
c) Sentry position outside city waiting for extra units (sometimes bugged i think. hard to be sure)

Another exception is guard mode.

When a faction neighbours another who they are at peace with they often move stacks to what i am calling guard positions which are spots on the LMC path on the border of the adjacent region. They can sit in these spots or move between different ones while the ceasefire lasts. Some examples in the images where Rome had made Iberia a protectorate and the carths didn't want to attack.





3) Unusual stall

This is sort of related to path-finding.

Carthage was fighting the gauls for Iberia. They'd been pushed out but were sending stacks west and shipping them over fine to continue the war. Sicily had the normal AI minimal garrisons but was otherwise empty. The gauls were also fighting the romans for Italy. When the gauls finished the romans off by taking croton the carth AI seemed to switch priorities to Italy because they were already at war with the gauls from spain. Unfortunately there is noi naval landing path (yet) between Croton and Messana so what happened was this:



This would actually be pretty cool AI if there was a path tween italy and sicily. But on the vanilla map it basically made carthage stall as the ever-increasing armies on sicily couldn't get to croton which reduced the armies they were sending to iberia. Also even when the stalemate battle in iberia was broken temporarily by a carth victory the stacks in iberia didn't attack corduba. They'd land and fight endless battles with gaul reinforcements but not advance beyond the coast.




I saw this once before and thought it was path-finding problem caused by the mountain but i now think it was this same situation caused by wanting to attack italy but not being able to.

Just another way for carthage to stall :(

be good to see them land on italy when i eventually work out how to make messana-croton see each other.


4) Name bug?

This is weird. Not even sure if it is a bug but i think it must be.

AI builds units, sends them to sentry position in readiness to attack somewhere.



Some times (often in my setup with only one family member) the captain in command gets promoted.



Then what happens is, nothing. They just sit there. It seems different from the stall where a target settlement keeps building new units as these stacks don't get a new unit every turn, just now and then. There is definitely at least a bug with the move_character command in these situations:



but that doesn't neccessarily mean it is a bug overall?

It was very erratic with the romans but happens all the time with barbs. The reason i think it may be a bug is the surname-less scythians don't seem to have this problem at all. The only difference i can see with the (non-scythian) barbs vs romans is the multi-part surnames "of arvernum", "the turdetani" etc.

Will need more investigation to narrow it down. Weird though.

[Teleklos Archelaou]

Very interesting work indeed nikolai! And a big benefit to the community also.

[nikolai1962]

Ty. It is my current obsession :)

Question: When you have gaul path-finding set up so that starting in Alesia the gaul ai can very rapidly take all its core regions. Then if you're a bit bored and start slapping woods round the place for fun. Could that possibly completely and totally screw the gaul path-finding?

Answer: Yes

[alpaca]

About this name stuff: Maybe this bug causes the game not to update its internal name and the character is still called just Bingen
Anyways, I'm not sure why you think that a screen resolution change would change pathfinding, I guess it'd be the tile distance on the map file. But anyways I'll run a few tests of your ideas to get my stacks in chivalry moving finally.

[nikolai1962]

About this name stuff: Maybe this bug causes the game not to update its internal name and the character is still called just Bingen.

That's what i was thinking. May just be a side-effect of how i have the factions set up with no proper family tree. Time will tell.

I'm not sure why you think that a screen resolution change would change pathfinding, I guess it'd be the tile distance on the map file. But anyways I'll run a few tests of your ideas to get my stacks in chivalry moving finally.

I'm not sure myself if it makes sense.

Simplified example.

Screen resolution A: straight line distance to target of a potential move goes from 60 (pixels) to 59.6 -> rounds up to 60 -> stack stalls

Screen resolution B (double resolution): straight line distance to target of a potential move goes from 120 (pixels) to 119.2 -> rounds down to 119 -> stack doesn't stall.

Dunno. Just a vague theory that popped into my head thinking about my old programming days where bugs could get past testing by the developers cos we had higer spec pcs than a lot of users. I could just imagine the CA devs all testing on massive monitors with max screen resolution. Probably a red herring :)

[alpaca]

Measuring the distance in screen pixels wouldn't make sense really, it'd not be immediately accessible to the AI (because it's very much an engine thing) - differently to the tile distance.
So implementing it that way would actually be more complex and thus probably not be done ;)

[nikolai1962]

I'll forget that theory then.

[nikolai1962]

Name Bug

Not related to surnames per se. Scythians do get it, just not on first turn like some of the other barbs and therefore less noticeable. Partially related to path-finding, not sure how yet (scythian cavalry armies i.e more movement points may be behind its better path-finding as Duke John theorized).

I think i've seen this name bug happen rarely after battles too (Man of the Hour promotion?) In a normal setup with good path-finding most factions will only get this a few times (i think). Factions that start with many provinces and few family members might get it a lot.


edit: removed some stuff that was probably wrong

[nikolai1962]

Bit of a recap/update.

Brigands/Pirates

I've seen posts elsewhere about what value in the strat file stops brigands/pirates. My testing shows:

0 = most
50 = rare
99 = still get some

It may be related to region size (number of fertile tiles?), hence why lower values may seem to work for some people. On the simple map my 15x15 tile regions still get them occasionally with a spawn value of 99. The 5x5 tile island regions never get them.


Pirates

Pirates are critical to ai naval expansion as the ai only seems to target overseas regions if they have no available land targets. (Availability includes ceasefires/alliances making adjacent land regions temporarily unavailable.) There is usually only a short window where the peace holds and naval expansion is an option. The ai,

1) Often builds ships specifically for naval expansion and often only one ship.
2) Once built moves the ship to its waiting-for-an-army spot (outside the safety of a harbour).

This means they are often attacked and retreated by pirates and often sunk with the invading army on board. So basically, because of pirates, new wars usually break out between factions faster than they can mount a successful naval attack and so the faction drops the naval expansion option and goes back to land expansion.


Slave faction building units

I said above that in my simple map the only rebel regions that built units were the ones adjacent to a faction region at the start. This was a coincidence. What happens on my simple map is the slave faction only builds units in the regions with romans as the faction creator. Possibly unit size/cost? (edit: on my simple map the faction creator in the regions file is either romans or britons.)


Name bug.

Pretty sure now there are two separate problems.

What definitely happens in my testing setups is if a faction can't find its target region then the first stack they produce will not move once it moves out of the city to that settlement's sentry spot. If the captain of that stack then gets promoted you get the name bug (where the console says "error name not found" when trying to use move-character) but this won't happen if every region on a map can path-find to the settlements of each of its adjacent regions. Or at least the settlement it picks as its first target. Another faction taking the settlement breaks this stall.

Separate to this there is definitely a stall that can happen after fighting a battle. After looking for this specifically on my simple map it can happen to a stack that is general-led and not only to captains i.e it is not a man-of-the hour version of the name problem, not always anyway. (There may be a problem with names as well as some other after-battle bug as very occasionally you get the name error when trying to move a stack stalled by a battle.) Otherwise this stall seems to be broken by any kind of movement, including using move_character or an advance/retreat from a subsequent battle.

It is only critical to the ai faction when the stack involved has been given a settlement to target as the ai designates one stack as the primary attacker and will not siege the settlement while the primary attacker is stuck. Also the ai only targets adjacent regions so if the targeted region is the only target available the whole faction stalls apart from chasing brigands. They won't target available naval expansion regions either when stuck like this.

There may be a way to fix some of this but it will not be easy as the stalls happen too inconsistently to find out what might be the common elements.

On my simple map, starting the britons/romans in the same region, the britons do consistently get more of these stalls. Without me moving the stuck armies the britons usually fail to get all the land regions (on average they get stuck on 1-3) whereas the romans only occasionally fail to get all of them and usually the most they are stuck on is one region. So maybe some clue in that.


Edges

The ai seems to have problems with map edges, at least the right hand and bottom edges. If enemies (brigands) are close to the edge the ai will send stacks that seem to get stuck as they approach. Sometimes the enemy stack will be far enough away from the edge to be attacked once but when it retreats the ai army can't seem to follow. In an extreme case a brigand army retreated right back to the right hand edge and the ai army stalled. I moved the ai army to the tile directly to the left of the brigands and the ai army didn't attack. However when i moved the ai army also to the map edge, one tile below the brigands, they did attack and then carried on. Will test whether having some impassable terrain on the edges cures this.

Region size may effect this.


Region Boundaries

I had chunks of the vanilla map working well with the ai expanding without any hitchs until i accidentally messed it up completely. I thought originally it was because of all the woodland i scattered around out of boredom but i don't think it was now. I'd changed some region boundaries not thinking they would effect the path-finding but they do, sometimes in very weird ways. The strangest was armies moving to Tingi suddenly deciding to not cross one of the bridges any more and instead to make a V shapped detour around the river source back to the road on the other side of the bridge. Will need more testing but two things to look out for specifically are:

1) Parts of a region that can't be reached from that region i.e an army needs to move into another region first then back into unreachable part.

2) Shared boundaries over impassable terrain e.g mountains. if you have two regions whose border is mountains then the path-finding seems to change depending on whether one region has all of it inside its region, the other does, or they share it.

The first in particular seems to be able to mess up path-finding between regions. Will try and create a clear example with my simple map if i can do it deliberately (very easy to do accidentally :) )

[professorspatula]

Very fascinating and indepth research. Well done. How you have the patience, I don't know, but we're all grateful for your efforts for sure!

The thing that bugs me is that all this research is the work of one person. Now surely CA had a whole load of people doing the same kind of tedious testing? I assume they also had a bunch of extra console commands which could tell the programmer/tester the current status/goal of a stack, so if the stack was stuck, they'd have an indication why. With such resources how did some of these AI problems make it into the game, and still not be resolved? You don't even need to go into the depth you did to notice how the AI never targets some settlements (Tribus Sakae) and gets stuck in the desert with stacks it doesn't know what to do with. Obviously the AI will never be perfect, but obvious problems have been around with every version of RTW.

I've long been a believer of adjusting the campaign map to provide 'stepping-stones' for the AI armies by adjusting the position of settlements and adding/removing regions to increase their expansion potential, but I never really put much effort into it, and with the 1.5 patch assumed many of the existing problems were long gone, and to be fair, some are. I think realistically, unless CA decide to release another patch to improve the AI to something resembling acceptable, spending hours and hours tweaking maps hoping it will make all the difference could in some cases just not be worth it. The player's own actions will affect how some of the AI factions expand, and even though say Carthage expands well, there's still a lack of sea invasion from other factions in the maps you show. The AI is too rigid in structure and it clearly needs a kick up the toga. It's inability to deal will multiple threats and targets is probably why, in part, CA separated the Romans into 3 competing factions (and the Senate) so collectively the Roman empire would expand in all directions and not just get stuck in Gaul for the next 100 years.

Good luck with your continuing research.

Lets hope CA have improved things greatly with MTW2, or it'll be another reminder to us all that the AI isn't up to the job of coping with a non-Risk style map.

[nikolai1962]

Ty,

I don't really have the patience unfortunately. I get totally sick of it very fast but i have developed a "need to know" whether the campaign ai is capable of dramatic improvement by following some simple map rules and maybe a bit of minor modding. I think it is but working out specifically what those rules are rather than my current vague ones keeps bugging me to come back to this. I'd much rather be playing

I think the reason CA didn't pick up a lot of these is partly because they are really hard to spot on a normal map if you are actually play-testing instead of sitting on an island clicking end turn and watching other factions move. On the other hand it seems to me they badly need to have a very simple test map and people doing what i did. I bet a lot of these bugs are very minor rounding error type things.

With the vast improvement in battle ai of 1.5, the battle and immersion improvements of various mod teams, that only leaves good campaign ai as the big hurdle to a scary immersive strategy game.

It is very tedious though.

[shaggy1973]

dont want to teach a good modder to suck eggs but you know about the -ai command dont you. In your shortcut properties add -ai at the end of the line to have the game play itself. makes it easier to just sit back and watch the game unfold.

[nikolai1962]

dont want to teach a good modder to suck eggs but you know about the -ai command dont you. In your shortcut properties add -ai at the end of the line to have the game play itself. makes it easier to just sit back and watch the game unfold.

I'm not a good modder at all I just randomly change stuff to see what happens. If anything works it is sheer luck So ty for that, i will try it (had heard of the -ai switch once but forgot)

have you tested wether lots of movement points (MP) decreases pathfinding problems? If so you might want to test giving AI characters a movement bonus trait when they have not used any MP for a few turns and are not in a settlement; they are stuck. The sudden increase in MP might open a different path

Comment from duke john i just re-read. Originally i wanted to see what caused the stalls so i didn't want to just increase movement distances in case it worked (if that makes sense). However now i know for sure that some ai stacks stall for some reason after some battles and that the ai stacks should nearly always be moving if they are at war with anyone then messing somehow with the traits of generals who are outside a settlement with full MP for a number of consecutive turns might very well prove to be a solution somehow. Hmmm

[nikolai1962]

Hands Duke john a balloon


Update in a bit when i have worked out how to make a new trait

[nikolai1962]

A partial solution to the post-battle stall that effects the AI so badly and some other stuff. A lot of the images are unneccessary to the conclusions but they are useful to me to look back on to remind myself of things to look into more.

Post-Battle Stall

I wanted to clear up a few of the things I'd been noticing to reduce the size of the list of things that need further investigation. The post-battle stall was the most confusing so i started with that. On my simple map I set the romans up in Tarentum where they had just one available adjacent target region. This time i gave them a small starting stack as i wanted them to attack on the first turn a small stack of rebels i placed just to the west. The idea being to see how often they stalled and if it was just after losing or if it also happened when they won and if there were any common elements on the occasions when they stalled. The idea for setting them up with just one available target was to (hopefully) ensure their first stack had orders to attack Rome as it seemed to be only stacks with orders to attack settlements that stalled if they got into a battle before reaching their target.



The consistent pattern over a few test runs was the starting hastati would attack and win.



On the end turn their captain would be promoted.



And then they'd stall. The original stack would remain stationary while the roman ai produced a few more units. Those units would move to Tarentum's sentry spot.



On the next end turn the second stack's captain was promoted.



The turn after the second stack was *ready* the stalled stack moved to Rome.



This happened consistently 3-4 times and wasn't what i'd been expecting. Neither the always stalling, stalling after a win or captain's stalling. I wish i'd thought of testing it like this before instead of trying to guess what was happening when dozens of stacks were on the move making it too confusing.

This led me to thinking (wrongly) that maybe the stall was something to do with the ai re-assessing all it's stacks movement orders when a new stack was formed and that the permanent stalls i'd seen were some side-effect of that going wrong sometimes

I moved the starting rebels left into the rebel region to see if things were different if the romans had a general led army (because if the rebels were outside roman terriotory the roman ai wouldn't attack first turn and instead would move their starting hastati out of the city and then promote the captain before moving). This didn't work as the romans bypassed the rebels on the way to rome and then attacked afterwards.

Next step was to try to set up the starting armies so the romans would lose the first battle a lot to see if that made a difference. So the rebel stack got a general and 9 exp warbands.



This made the romans lose a lot and retreat to rome but they never stalled here. They just attacked and won the next turn in a second battle.



The next end turn the captain was promoted.



On the first test of this setup the same thing happened as before. After their victory the fist stack stalled until a second stack had been built.



The turn after they moved to Rome.



Except on the next test it wasn't the turn after the new stack had been built (note dates).



Ran it a few times and got a semi-random number of turns before the first stack moved (between 1-4).

Then thanks to Duke John making me think about movement points instead of focusing on names i spotted the common element that made both this setup and the previous one make sense. The first stack moved after its stall the turn after the slave faction built roads in the rome region. It was just coincidence that this mostly coincided with the roman ai building its second stack.

To double-check i made basic roads cost 40000. The slave faction didn't build roads in the rome region and the roman ai never got unstalled. (Which may explain why the ai problems were more pronounced when i was first trying out building mods that included much more expensive roads.)



Following Duke John's suggestion I added a trigger for a trait that gave extra movement points (Energetic it think) that fired if a general ended his turn outside a settlement with full MP.



This unblocked the stall (in this case). I wanted to check if it was somehow the change in their movement potential that unstalled them or something else so I then changed the base MP in the descr-character.txt from 80 to 100. This stopped them stalling too (in this case).

Lastly, as this seemed a bit weird, I added a load of swamp between rome and tarentum to increase the movement cost. In this test the stack remained stalled even with the extra base movement points plus the added 10% when the trait was triggered. They only unstalled when the rome region built roads (i'd changed the cost back to 400).



So i think this post-battle stall gets unblocked when the stack can reach its target in one turn's worth of MP If it takes multiple turns they stall. So if any combination of factors, roads, extra MP, advancing one tile after a second battle etc, brings the stack within one turn of its target then they get unstalled.

Increasing MP overall may be a good thing in itself and help a lot of these problems but regardless of whether you want to do that in your mod or not i think to greatly reduce the number of post-battle stalls all mods need something like:

A trait (preferably AI only) with incremental levels all giving +10% MP, so the first level they get +10%. The second level they get +20% etc and it keeps going up until they get unstuck. (nb I don't think i've ever seen this happen a long way from a target settlement. The way you can tell which is the stalled attacking stack for an untaken settlement is that it is the one that is close by but not moving.) The trigger being an ai stack ending its turn outside a settlement with 100% MP firong evry turn they are still stationary and increasing the trait every turn. (May be better if slave faction was excluded as otherwise brigands might be retreating for ten minutes.)

Then, and this is the bit i don't know how to do, preferably the trait is reset to zero when they end their turn with less than 100% MP.

There are some cases when the ai has a reason for being outside a settlement and stationary (like guard mode or waiting for a ship) but i don't think them getting a few extra MP in those situations will unbalance things.

This MP solution also explained why the britons stalled on up to 3 (of the 18) land regions on my simple map whereas the romans on average only stalled on 1, if any. Nothing to do with names but to do with the fact that the roman faction gets more traits with extra MP.

I don't think this will stop all stalls, especially the path-finding type ones from retreating behind mountains etc, and i *think* there may be other types of glitch related to battles too but i'll finish my incremental MP trait and see if the britons can consistently take all the land regions in my simple map with that trait in place.


Brigand spawns.

While i had my swamp there i wanted to test another idea.

Brigands only spawn on faction owned terriotory and a spawn "event" only occurs on the rebel turn if there aren't any rebel stacks in that region. (An event may include multiple spawns in the same region though.) i wanted to see if it was related to the number of fertile tiles. I set the brigand spawn rate to 0. None spawned until the roman ai killed the placed stack. (Otherwise brigands always spawn the first rebel turn if the rate is et to 0.)



When the roman ai killed that stack the tarentum region got 3 spawns. It was consistently 3-4 spawns every "event" after the romans had cleared the previous stacks.



When eventually they took the mostly swampless rome region it was consistently 6-7 spawns per event. (Something I'd noticed previously when testing the effect of different spawn rates on the ai expansion speed.)



So I'm pretty convinced brigand spawning is related to a combination of the spawn rate and the quantity of fertile tiles in a region.

What i was actually hoping was that brigands would only spawn on or near fertile tiles in the hope that i could use that in large desert/steppe regions to make them spawn closer to roads/settlements and therefore make it easier for the ai to chase them but they seemed to spawn in the middle of the swamp just as much.


Minor map glitch.

In one of the earlier posts i mentioned a stall that happened on completely diagonal paths from attacker to settlement (possibly just a side-effect of square regions). Attacking the region SW of capua, from capua, a stack will head diagonally until it hits the forest.



Then the next turn it will move only one tile (west) then carry on normally. I just mention it as if you watch your map and ever see a stack only move one tile on its path it is a sign that the path-finding ai is almost stuck and in some cases there might be something you can do to fix it. Not all.


New river bug

This illustrates a stall that won't be solved by an extra MP trait. Originally the ai had a problem crossing the bridge to attack the settlement of my mega-region. I fixed it by adding some dense forest to the tile it kept moving back and forth onto instead of moving onto the bridge. However in the case shown below a brigand stack had spawned in the mega region in a spot that made the roman army chasing it need to move in a sharp upside-down V path with the apex at the bridge. The roman stack looped between the position shown, up to the tile west of the bridge, onto the bridge, and then back down to the original position.



You see this occasionally where an ai stack is looping between 2 or 3 positions. I don't know if a general increase in MP would help this sort of thing in all cases but the triggered trait would never fire as stacks like this aren't stationary.

Now i know more about path-finding i'll have to see if i can find a better solution than the dense forest.

Odd naval thing.

I've seen this a few times in games where a faction would land a small stack by sea and then not attack.



The Iberians do it on palma a lot. I'm not sure if it is an explorer stack or a supporting army stack that somehow got to the island first before the designated attacking stack arrived.



Just an odd thing i may look at again sometime.

~~~

The main thing is the post-battle stall. After fixing path-finding between settlements and reducing rebellions this is the third biggest cause of the ai under-performing I've seen in my testing.

~~~

Finally, a complete pointless thing but it made me happy lol. From before i messed up the path-finding changes I'd made on the vanilla map.



(It took them a while though)

[Monkwarrior]

Just to complement this excellent research about the geographic limitations of the AI, we think that it is interesting for the community to share our own findings about the AI behaviour. These are the conclusions of a long research work done by Asdrubal, one new member of the ITW team, with the aim to improve the AI behaviour in the ITW campaigns, closer to the historical facts.

In the next picture you can see the initial distribution of regions, with two great super-powers: romans and Carthaginians.

White arrows show the normal advance of romans, expanding to the north in detriment of the padane gauls, then to the east to capture the rebel regions of Dalmatia and Illyria, and to the west against the transalpine gauls. In some cases, Africa is invaded from Sicily when land expansion is not evident. Yellow arrows show the advances of Carthaginians, involved in different fronts, one in Africa against numidians and other in Iberia, together with important rebellions in the mother land. In both fronts Carthaginians are stuck and they don’t progress too much. Romans do not show any interest for Iberia, even if the win_conditions include mainly Iberian settlements. These behaviours were nearly independent of the core attitudes, starting diplomatic stances or any other evident parameters. Thus we decided to perform some research about this question.

Parameters influencing the advance of the AI: sea vs land advance, agressive vs passive

1- Land limits to expand and suitable navy

a) As told in other posts, the AI tends to expand always by land routes, with special tendency to attack first the rebel regions in the neighbourhood and after that the rest of factions. Thus, if sea advances must be promoted, it is necessary to close the possibilities of land expansion.

b) First of all it is necessary to establish an impassable limit through the inclusion of another faction, preferably ally, eliminating all the possibilities of war between them (we will see how in the next points). But this is not enough, given that if land expansion is not possible, but there is not a driving force to sea expansion, the faction will remain stuck in its homeland until the conditions are suitable to declare war against the allied neighbour.

To illustrate this point, here you can see our initial set-up for a campaign starting just before the II Punic War. We wanted to start hostilities in Iberia, with reinforcements arriving by sea.

A second roman faction (blue) blocks the possible advance in north Italy. In this way, the active Romans (red) have no land expansion possibilities.

c) In order to force the sea invasion, it is necessary to provide the faction with a small region in the zone where we want to promote landing. This territory will act as the driving force. This is due to the land limits of that region, which are the only possibilities of land expansion for this faction. As it is a small territory, the AI will send reinforcements from the mainland in a constant way. One important requirement is that this region must have coast to facilitate landing. If the region is an inland territory, the AI doesn’t find the way to send reinforcements and gets stuck.

In the previous image, you can see how Carthage had already some territories in south Iberia, but it is necessary to include one roman region in the north.
We tried to put an inland region as the driving force, but it didn’t work.

We tried also to put a Carthaginian region in north Italy (Liguria), but it had no effect on the Carthaginian AI, as they have a closer destiny in Iberia.

This is the only method we have found to really promote sea invasions where we want. However, one important disadvantage of this system is that the driving force disappears if the settlement falls in hands of the enemy (conquest or rebellion). I that case the AI has no “historical memory”, and it suddenly forgets its interest in that zone. Even we have observed how ships loaded with troops in the way to that region returns to the mainland just after the lost of the far territory.

d) One additional requirement for sea invasions is that the AI must have ships in the suitable positions, preferably one float near the boarding zone and one near the landing zone. The preferred boarding zone seems to be the region with the X coordinate closer to the landing zone. In this map you can see how Etruria is the preferred one for romans, but if it is lost, Lylibaeum (in Sicily) is then used for boarding and in case they don’t own this city, troops board in Latium. It seems that for good development of boarding-landing operations, it is important the synchrony between trips of the floats and troops creation. If ships are delayed and the troops are ready, they start to move trying to find a land route to the target. In our case the target is so far that they don’t find a way and return to the boarding point, although boarding is then delayed.

Here you can see the three boarding zones we have observed in the preferred order.

and in these three images you can see how it works, depending on the owner of the different regions.

And here you can see the simultaneous arrival of reinforcements for Carthaginians and Romans to Iberia.



2- Superfactions

a) We have observed that all the factions, even rebels, can be considered as superfactions, either of the other faction or even of itself. When a faction is considered as superfaction, it assumes the behaviour of senate in RTW, with an extremely defensive attitude, without expansion, but recruiting a big amount of defensive troops. This type of behaviour can be used to simulate factions that historically were not expansionists, but that presented strong resistance to conquest, for example the Celts in the Iberian peninsula.

b) One problem, if rebels are considered as superfaction, is that in case of a rebellion in a settlement of another faction, this faction will find great difficulties to recover the settlement. We have observed this problem in Carthage.

c) In spite of being superfaction, the core attitude between this faction with its “vassal” can be of any type, even clearly hostile, and the starting diplomatic stance may not be allied.
The best way to establish a limit for land expansion is to give the limit regions to an allied superfaction. This will act as shield against possible invasions and won’t attack to its vassal faction. However, this is not enough to prevent attacks from the vassal to the superfaction.

3- Economical-military dissuasion

a) This is an important parameter to establish stable and durable limits. If one faction has not simple ways for land advance and it is blocked by a weak superfaction, it will decide to attack this superfaction as it considers this solution easier than the sea expansion.
It is necessary then to equilibrate the starting situation, in treasury, starting troops and settlement development, to prevent this attack.

We can see again the set-up.

The blue romans are superfaction of the red ones, but they must have enough troops to dissuade the red romans from a possible attack. In the same way, Numidia (dark blue) is superfaction of Carthage, preventing in this way the fight in Africa.

b) This parameter is also important in the landing zone. If the factions surrounding this zone are extremely strong, they act as dissuasion powers for landing. Even worse, they can decide to attack the settlement, disappearing in this way the driving force for sea invasion. If those factions are too weak, the first reinforcements will be enough to destroy them.

With all those equilibria well-established, the AI is forced to the required situation, as in this case: Romans and Carthaginians will converge to Saguntum to begin the conflict.


c) Another important dissuasion factors are walls. Their widespread presence dramatically reduces the aggressiveness of the AI. For a more dynamic campaign, it is necessary to limit walls, both at the beginning (descr_strat) and along the campaign (higher settlement requirements and prices).

4- Behaviour parameters

Finally this parameter seems to have an influence more important than expected. One faction limited by an allied superfaction cannot have the attributes “Caesar”, “Genghis” or “Napoleon” because it will attack to the neighbour superfaction. It seems that parameters such as “smith” or “stalin” are more suitable, as better equilibrium between economy and aggressiveness is obtained. The parameter “sailor” is devoted to ship building, but it doesn’t promote sea invasions.

I hope this long post will be useful for the design of new exciting campaigns.

[Monkwarrior]

I see that this subject was less interesting than I thought.

[shaggy1973]

I think many people knew some portions of your post already, although I learnt a few more tips and tricks as was unaware of. Thanks monk warrior :)

It is certainly good that it has been set out in b&w though, and a good idea to collect it into one thread. I am certainly referring back to all the posts here when setting up my own little campaign, and will be making use of your superfactions work, as well as the more general AI stuff from nikolai.

Thanks guys

[Myrddraal]

The detail in which this research is being carried out is outstanding. Many thanks for the info.

[DimeBagHo]

This is great stuff. I'm in the middle of redesigning the XGM campaign, and the research in this thread has been immensely useful.

[Quintilianus]

Hi everybody, I'm new in this forum. I'd like to know whether there are any discussions about the AI behaviour with diplomacy...

[DVK901]

Just a '2 cents' worth on my part, and a thanks to all those who contributed to this thread.....one of the things I really 'took up on' from the ideas in here was the problem of the AI factions being able to 'see' the target they were interested in, and their ability to continue 'seeing' it. I've been working on a Mod for quite some time, on the Mundus Magnus3 map, and was not happy with the way the AI was building hundreds of little stack of armies, sending them off somewhere, and then stranding them all there forever. This was particularly evident in Egypt's case, as they tried going after the few Rebel settlements in Arabia after they too Petra. They build close to 40 little 1/3 to half stack armies, sent them off into Arabia, and stranded so many there they had to move around to make room for each other. Not one ever continued on to a target.
I corrected this by changing the 'starting_action_points' in descr_character.txt from the default 80 to 160. This one small change eliminated all the little stacks and impressed upon me that the AI was originally 'seeing' it's target from a settlement across the Red Sea...a short distant....but when the stacks got up and just past Petra, they lost 'sight' of whatever it was they were sent to attack.
Oddly enough (and I had always wondered about this, the doubled distance had no adverse affect on anything. The AI could move further, but they still had 'objectives' and didn't pass them up because they could. Also, I saw a tremendous increase in creation of FULL stacks. This leads me to believe that all the 'stuck' little stacks are actually 'destroyed' as far as the AI knows, which explains why they never merge into bigger stacks.
So I would advise that at the very least, this single value should be increased greatly, especially on the very large maps. I currently have a setting of 200 on the Europa270 map, and it works fine...the AI even manages to get past the 'bendy' roads without too much difficulty.

[DaVinci]

Hi nikolai, you're leading (and has initiated) a great AI behaviour thread, keep it up.
Monkwarriors threads/observations are as well very true.

I still can remember as we discussed a few similar things, as you played my RTR submod MRR, and i always was searchin' out ways to balancing + AI-finding its historical preferred targets on the campaign map.

So i give as little addition my 2 cents atm. only as short hints (as i have not the time to discuss/describe in a full length, or give examples).

I'm pretty convinced that the AI behaviour has still more parameters/influences to decide where it goes, than the one mentioned in all above threads.

- One of them is, that you can lure the AI into certain regions (to have interest to conquer), if they get certain advantages through the tech-tree codes (requirements) plus in addition with hidden_resources, ie. exp boni, moral boni, especially any kind of income boni, or just the possible recruitment of units/buildings that would give a significant advantage or disadvantage to potencial enemies, and also to provoke wars in this relation or a rather peaceful behaviour.

- Second, with descr_regions codes, just due to these hidden_resources, and due to the initial farming income, with the possible harvest codes.

- In this relation, the start setting of descr_strat, available buildings per region with the possible or impossible recruitment of certain units and the start money, influences the expansion-ability immense (just an important balancing campain part).

- And i just think, the different AI characters have an, not decisive, but quite important influence, initially rather or especially with the diplomatic behaviour.

... maybe i have more thoughts, but not atm., brain-dead due to modding burn-out syndrome.

[nikolai1962]

Apologies for not replying to these posts--especially Monkwarriors very detailed one. I accidentally over-wrote the folder I had all my test stuff and my (2/3 perfectly working) vanilla map in and gave up Rome modding for a bit from the shock

Very interesting posts.

I did have two conclusions from this earlier experience, one of which mirrors shaggy's, for things you can do which are relatively easy and yet help the AI a great deal in many cases.

1) Region Boundaries.
The AI often has path-finding problems when a region has traversable terrain that can't be reached without leaving the region. For example some fertile tiles on the other side of a river without a ford. Simply changing region boundaries can fix a lot of situations where the AI gets stuck through path-finding problems.

As I'm back modding RTR to suit my preferences I've started doing simple map fixes like this as i see them, (can't stand the thought of all the hours fixing the harder ones lol), and it definitely works without taking too much time.

I'll take and post some example screenshots of the sort of situations I mean in a bit. It can really make the game much better when the AI is operating as intended and it doesn't take long.

~~~

There are much more tricky ones that involve the situation where somewhere along it's path an AI stack would have to move further away from it's target than where it currently is e.g it is close to a city but with some impassable terrain in the way so it would have to move away from the target to get round the impassable terrain. A good example of this is the bit of land approaching the chersonesus area from the east. AI armies tend to get stuck in that corner instead of going backwards to cross the ford. These problems take a lot of trial and error making terrain changes and testing and are a total pain in the arse. However the region change mentioned above could improve a map by about 50% with minimal effort.


2) Movement Bugs
There is definitely a bug where if an AI stack loses a battle and retreats they can sometimes get stuck in that spot. This is related to path-finding in some cases but not all. They can definitely get unstuck in many cases when their movement potential changes e.g if the target region builds roads or they get a movement bonus trait.

This bug effects roman and greek culture factions less than others because they get a movement trait that triggers from being outside a city (which a stuck army often is).

Either the problem is related to the total movement points they have, or the AI re-calculates the stack's movement when it's movement potential changes, possibly both. There are two things, either or both of which are definitely worth doing if you are creating or trying to improve AI performance on your map.

a) Try different amounts of movement points. Personally i don't think higher movement points is the solution as such to the post-retreat bug--I think it depends on the scale of your map. In some cases higher movement points will just mean the AI armies get stuck further away from their target (as they'll retreat further). However I think it will fix other path-finding problems as the AI seems to have less problems when it can reach it's target in one turn.

As DVK's post mentions if you see the AI with a lot of small stacks clustered together and not moving much then it is always a sign that the faction has a path-finding problem or a stuck army problem. If the faction gets over the problem the AI will combine those stacks and move them to their next target. In his case I think the higher movement points fixed some normally recurring path-finding problem so that the faction didn't get stuck in their normal place. (The multi-stack thing is a symptom rather than a problem in itself.)

(There are two semi-exceptions to the always. One is if they are land-blocked and have no naval expansion route. In this case they have the same problem. They are stuck. And the same symptom--lots of small stacks standing around. But in this case they cluster around their capital and not around the problem region. The second semi-exception is when they are land-blocked and have a naval expansion route but no ships. In this case the small stacks cluster near the region they'd launch their invasion from if they had a ship.)


b) Have a trait that adds and removes movement points regularly e.g a winter/summer trait. The constant changing of their movement potential each turn (or each season if you are using 4TPY) may unstick them if indeed the AI re-calculates stuck stacks when their movement changes. Either way it will help in some cases as the extra summer movement points will fix some stuck armies if it means they can then reach their target in one turn.


I'm not very good with traits personally so if anyone knows of a mod that adds movement in summer turns and subtracts in winter turns I'd be pleased to know of it (so I can steal the code for my mod :) )

Apologies again for not replying for so long.

[nikolai1962]

Hi everybody, I'm new in this forum. I'd like to know whether there are any discussions about the AI behaviour with diplomacy

I don't know of any discussions as such. The AI diplomacy is not very good imo. One thing that seems to be true when i play is that the stronger you are militarily the more reluctant the AI is to attack you. The other thing is if you have enough cash you can get the AI to agree to anything. The second however is semi-pointless as if you have that much money then you could probably bribe all their cities/armies. You can't really use diplomacy as an *alternative* strategy as the amount of cash it requires would enable you to blitz the map anyway.

If you see what I mean.

[nikolai1962]

Forgotten how to take screenshots, so some other AI stuff

d) One additional requirement for sea invasions is that the AI must have ships in the suitable positions, preferably one float near the boarding zone and one near the landing zone... ...it is important the synchrony between trips of the floats and troops creation. If ships are delayed and the troops are ready, they start to move trying to find a land route to the target. In our case the target is so far that they don’t find a way and return to the boarding point, although boarding is then delayed.

This can cause permanent stalls too where the armies and fleets are permenently out of step e.g armies in carthage looking for ships while the ships are by icosium waiting for the armies, then after a turn the armies move to icosium and the ships move to carthage. Then back and forth like that for ages.

I wanted to create a free upkeep ship and spawn one every 20 turns or so to see if it got round this bug. Not sure if you can spawn ships though.


~~~

c) Another important dissuasion factors are walls. Their widespread presence dramatically reduces the aggressiveness of the AI. For a more dynamic campaign, it is necessary to limit walls, both at the beginning (descr_strat) and along the campaign (higher settlement requirements and prices).

This works the other way too. *Lack* of walls makes the AI more aggressive. So, for example, if you mod a faction to not be able to build walls then the other factions are much more aggressive to them.

Walls, or the lack of them also effects the size of garrison the AI leaves behind (especially at game start it seems). So if you remove walls from a faction the AI will want to leave a much larger higher percentage of it's starting units behind on the first few turns.

~~~

4- Behaviour parameters

Finally this parameter seems to have an influence more important than expected. One faction limited by an allied superfaction cannot have the attributes “Caesar”, “Genghis” or “Napoleon” because it will attack to the neighbour superfaction. It seems that parameters such as “smith” or “stalin” are more suitable, as better equilibrium between economy and aggressiveness is obtained. The parameter “sailor” is devoted to ship building, but it doesn’t promote sea invasions.

I need to look at this more. I thought they only effected build priorities.

(May however be an indirect side-effect of what type of units they build--see "AI and cavalry" below)

~~~

Some new stuff from trying to make the sarmatians less passive in RTRPE.


AI and cavalry

I always thought the AI wouldn't siege if they had an all-cavalry stack but they do. They even build siege equipment although they never use it as they can't assault. They will wait out the siege instead. They very rarely do it because of the way the AI calculates the strength of stacks.

Numbers count for a lot. Large units are important and cav units are generally smaller. Also it seems high missile attack ratings are wieghted much lower than high melee attack ratings. What this means is that horse archer type factions have a huge differential between how strong their stacks are for auto-calc compared with how strong they are when a player uses them in a battle.

This doesn't only affect their chances in auto-calc though--it also decides their expansion behaviour. They won't initally attack a target if they calculate the garrison to be too strong for them. (This seems to be initially only. Once they have decided to attack a settlement they'll keep attacking with very weak armies but initially the relative strength of the garrison and their own armies affects them.)

So cavalry-heavy armies and especially horse-archer factions will be extremely passive unless you give them infantry units too or make the cavalry units much larger etc.

If you want to set up a faction as primarily horse archer with few or no native infantry units then one thing you can do is create a second version of their standard horse archer unit. Make them unbuildable, max size and zero upkeep and then spawn a bunch of them with a campaign script for AI only. Tweak the number of units until a starting army moves to attack a nearby rebel settlement. (If there's enough of them they will siege.) As they are unbuildable the AI won't get any more and as they lose men taking the rebel settlements they don't unbalance the faction long-term. Eventually they'll take some regions with AOR type infantry so they'll have a chance to expand normally after that.

This way you can have a very interesting faction for the player, with a very different style (as at the start they have tiny all-cavalry armies) but at the same time the AI version of the faction isn't totally passive.


~~~

Creating campaign timers.

Inspired by a thread on the EB forum and Monkwarriors stuff on superfactions.

1) As mentioned the AI is influenced by the strength of garrisons/walls etc whether or not to attack. The strength calculation is very influenced by sheer numbers of enemy soldiers and their melee attack rating.

2) A number of mods set up immoveable rebel garrisons by having a starting general with a trait that prevents movement.

3) Normally, if a rebel garrison is very large and their movement is not inhibited by a general's trait they'll move out of the city leaving only a small contingent behind.

So, by having a very large immobile rebel garrison and tweaking the starting general's age you can create a kind of timer to influence AI expansion.

For example, you could have some rebel cities where the general is 16 and others where he is 50. If the stack is huge enough to guarantee the AI won't attack then that region will remain as a buffer zone for a very long time. If the starting general's age is set to 50 then it will be shorter.

I was thinking if you had Messana and Saguntum for example set up as rebel with a strong garrisons, romans as faction creator and a high unrest setting (the "chance" field in descr_rebel_factions.txt), you could set the two general's ages to x number of years before the historical roman intervention in Sicily/Iberia. The general would die at some randon time close to this date, the army would move out of the city meaning nearby factions were more likely to target it. Eventually they'd take it and the unrest number would make a revolt to romans likely. Hence providing the reason for naval re-inforcements.

(probably easier ways to do this with script)

[outkast]

@nikolai and monk

Really great work. Really hats off for all this work. My old username doesn't work for some reason and I can't get it back so I've re-registered just to say- respect.

With all this great work has anyone made any progress on a map for vanilla total war that you can plug in and play easily enough (perhaps with a new desc_strat).

The work on this community is great but I wish there were more minimods that fiddle with minor things to improve playability rather than huge mods that change the game completely.

[nikolai1962]

Real life dragged me away from modding again but i did say i was going to illustrate the most important thing from i got from all this with some screenshots. The most important thing is "convex" shapes. I tried to explain it in text before but a screenshot is better.

Jerome Grasdyke posted this info about map-making ages ago:

A few other caveats about regions:
- they should be 'convex' (one landmass, no inaccessible areas)*- they should have only one settlement and only one port
- all land tiles should be part of a known region
- each non-sea region should contain at least some fertile tiles
- continuous sea surfaces should form one region
- the maximum number of regions supported is 200
- the distance between the centres of any two adjacent regions should not exceed 50 tiles*

*: not doing these things shouldn't cause a crash, but it may cause the AI to mess up.

I had no idea what the first caveat meant when i read it as i think the average person has a different definition of "convex" to how it is used here. I think convex means something speciifc in whatever branch of mathematics is used with figuring out the AI movement in regions. (probably called something star trakkish like n-space topology.)

What i think it means now is illustrated by this.



I used MTW2 as the problem still exists in MTW2 and this example is so clear. I'm guessing the guy who originally did the code has moved on and no-one there knows what he meant by convex either as the MTW2 map is littered with examples.

A slightly harder to spot example is:



~~~

As a quick test i started a new campaign as Russia ten times with fow off and hit end turn 20 times. Then moved the border to the river and repeated.

Without the fix:
Rennes not taken by turn 20: 4 times
Taken by Portugal 2 times (turns 11 and 13) (gogo naval landings at last :) )
Taken by England 3 times (turns 8, 10, 19)
Taken by France 1 time (turn 19)

With the fix:
Not taken 2 times.
Taken by Portugal 2 times (turns 10 and 11)
Taken by England 3 times (turns 8, 16, 17)
Taken by France 3 times (turns 15, 16, 17)


This fits in with previous experience where the problem was often more pronounced in particular directions e.g the AI had a problem path-finding to a region from the region to the north but not from the region to the south.

Given all the random elements in each game ten iterations isn't really enough to count as conclusive proof but i got bored and i've seen the dramatic effects so often with both the vanilla RTW and the RTR map that i can't be arsed to do more :)

The rennes region example is such an easy one to test that if you're a map modder you can convince yourself if you like.

This is relevant to both RTW and MTW2 modders as the problem has carried over. I don't think CA realizes it is a problem as the MTW2 map has dozens of these.

There are other map/path-finding problems but this one is often the easiest to fix and has the most dramatic results.


~~~

@outkast

sorry for late reply

With all this great work has anyone made any progress on a map for vanilla total war that you can plug in and play easily enough (perhaps with a new desc_strat).

I did the vanilla RTW map first but lost it out of carelessness. Does take a lot of re-balancing the descr_strat as the starting armies are completely unbalanced once the AI is moving properly. For example in the part-finished RTR map i had (and also lost through the same thing) the seleucids got eaten alive by the surrounding factions once I fixed the map.

[professorspatula]

I've been following this thread from the beginning and I have to say hats off to Nikolai and everyone else who's contributed to the discussion. Some of it I've noticed myself before, and other things I've since been made aware of because of this thread. And time and time again you see where the AI is going wrong and you just want to shake your head in disbelief. I think the entire strategic AI needs to be redone from scratch. It's clearly deeply flawed. AI factions have very little awareness of their surroundings, they have no long term goals and everything seems to be done on the spur of the moment and recklessly. You never think you're going up against an enemy that has built a war machine for a specific purpose. Occasionally the AI blunders into your borders with a couple of armies, but once they're disposed of, the AI gets confused and has no real answers what to do, other than send the occasional other stack your way. It's a shame massive improvements weren't made with M2TW. What the genre needs is another historical RTS game of a similar ilk that trounces TW's efforts, or at least enough to make CA wake up and improve the AI's competence.

In the meantime, you can make adjustments to regions borders etc, but it's a heck of an effort, and far from perfect. You're also fighting an uphill battle when it comes to the AI's basic lack of defensive knowledge when it comes to islands. Because as previously mentioned the AI will start gathering armies around the capital when it isn't sure what to do, it will happily leave all it's islands unguarded, even if they're prime targets for neighbouring enemies. Case in point: Carthage and Sicily/Sardinia/Palma etc. Upon thwarting the enemy advance in those places, Carthage will remove all its garrisons and move them into the pauper lands of North Africa, giving the Romans ample chance to take the islands with little effort. Pursuing a town in a desert isn't worth sacrificing your rich island provinces for, but the AI isn't aware of this enough. I had a heavily modified campaign where Carthage was strong enough to see off waves of Romans, and finally put up a worthy challenge in what could be interesting Punic wars. But then they abandon their islands and the joy turns to despair as they gradually lose their cities and their armies because they're nothing short of stupid. A shame for sure.


What amazes me is CA never noticed/did anything about the AI when it came to BI and Tribus Sakae. Seldom attacked in standard RTW, surely it must have been obvious to testers it still isn't a target in BI, and yet nothing was done about it. If a settlement is ignored by the AI (even if its an immensely powerful one like the Sassanids, surely something is wrong with the AI.