How does siege-resolution work?

[JacquesDeLalaing]

Hello!

In spring, I regularly get some appetite for AGEOD-games. I'd really like to continue to work on my ("small war and supply"-centered) mod for the 1741-scenario in Rise of Prussia. Unfortunately, there are still two big issues that prevent me from doing so: 1) intransparent siege-resolution (essential for this scenario), 2) local supply/foraging-resolution.

In this thread, I'd like to ask if someone could perhaps kindly explain in detail how siege works. As the engine is roughly the same for all games, with only the variables differing, I thought it would be best to post this question here in the general modding forum.

I guess it's a good start to post what is written in the ROP game files (ROP/GameData/Settings/Bombard&Blockade&Siege):

// ***** SIEGE *****
sieValueForSiegeBonus = 10 // How many Artillery Combat Pts needed to get a +1/-1 modifier to siege
sieOutcomeDiceRollSides = 15 // Sides of the Siege Outcome rolls / compared to TQ/Discipline
sieWagonDepotProtectChance = 95 // Chance that a non empty depot/wagon protects against surrender {increased from 50 => 80 March 11, 2010, then from 80 => 95 March 17, 2010}
baseProdCoefLocked = 25 // Percent of base supply when under siege with port unblocked
sieExtraModifier = 1 // Extra Modifier (positive: help the besieger)
sieSurrenderModEndangered = - 3 // If structure breached, lack of supply and weaker than besieger, get this penalty to surrender

Based on this, I've come up with an explanation that is most certainly wrong:

The besieger rolls a d15, and adds points to this roll according to:
1) leader and unit abilities (siege specialist, sappeurs, siege artillery, etc.), the exact amount of these boni are unknown to us players
2) the amount of artillery he can bring (+1 Siege point per 10 points artillery combat power - I guess that there's some kind of cap on this?)
3) & 4) According to the manual, there is also a bonus for having already made breaches (seems to be missing in the formula above), and if the defender is out of supply.
5) According to the formula above, the besieger gets an automatic bonus of +1

The besieged also rolls 1d15, and adds points according to:
1) amount of artillery combat power (as above)
2) special abilities (as above)
3) +1-3 points acoording to fortification level (- breaches already made!)

As described in the manual, the final siege values of besieged and besieger are then compared:

If the besiegers' value is lower than the value of the besieged, the besieged can repair a breach if there's one.
If the besiegers' value is greater than the value of the besieged, then the besieged suffer 5 hits per surplus siege point.
If the besiegers' value is greater by at least 3 points, then a breach is made (additionally to the hits inflicted).
If the difference between the besiegers' and the besieged value is greater (in favour of the besieger) than the average troop quality of the defernders (Discipline/Troop Quality in the element details), then the besieged surrender. If some conditions are met (see sieSurrenderModEndangered) there's an extra penatly for the besieged. If there's a non depleted supply wagon (or those general supply packages) present in the city, however, then there's only a 5% chance that the besieged surrender (if they don't, a breach is made).

I've been changing all kinds of factors last year, but I could only figure out as much to say that the description above is NOT how it works.

This is clear, but unfortunately it doesn't seem to work this way. I've tested it by setting the sides of the dice from 15 to 1, to get rid of randomness for singling out the other factors. I've set the artillery Power-points needed for additional siege-resultion-points really high (500) so that no faction should get one. Then I've increased the "bonus for the attacker" step by step. I started at +7 and tested it out by besieging a level 2 fortress (without artillery, with artillery, with siege artillery). What can I say. At +100, the besiegers still didn't manage to inflict hits or cause a breach. I left the bonus for the besieger at 100 and increased the sides of the siege-dice from 1 to 30 and still the same result.

Is there perhaps anyone who can bring light into this once and for all?

[PhilThib]

Send a PM to Pocus

[Pocus]

Let me see when I can gather enough wits to comment on these posts

[JacquesDeLalaing]

Thanks!

[Pocus]

Checking your initial message and then the code, there is mostly one thing that differs, but this is a biggy. We have a BesiegerValue, a BesiegedValue and a SiegeModifier. This last one is only used to see how many hits we can inflict by attrition to the besieged. So sieExtraModifier alters this variable, but won't increase surrender chance.

Try instead sieging a defender without artillery, with besieger having some, and with sieValueForSiegeBonus at 1, you should get an almost instant surrender.

[JacquesDeLalaing]

Dear Pocus! Thanks a lot! Your tip/correction was spot-on. I really wonder about my own stupidity not to have tried out this combination.

I've tested the proposed setting (sieValueForSiegebonus=1) and indeed I get surrenders as soon as the besiegers bring slightly more artillery power than the besieged (with "WagonDepotProtectChance" set to 1, of course). It works like a charm. I can now create my desired results and generate more predictable sieges. But I still have to find the right balance. For example, setting both, the "dice-roll-sides" and the "value for siege bonus" very low, and setting the Wagon/DepotProtectChance to 100 will give besiegers automatically one breach per turn (if they bring a bit more arty than the besieged). But in order to make surrenders still happen, I have to fine-tune via the "value for siege bonus" and the "dice-sides", not via the brute way (Wagon/DepotProtection).

So, to sum up what I think I've learned so far about modding sieges:

The randomness/luck-factor - as opposed to the non-random factor (which is: artillery power) - of sieges can be controlled via the balance between "sieOutcomeDiceRollSides" and "sieValueForSiegeBonus". The higher the side of outcome-dice-rolls and - in relation to this - the higher the value for siegebonus (-->differences in artillery-power matter less), the more will a siege be based on luck, and vice versa.

I also need to remember that an implication of very low values for "siegebonus" and high values for "outcome-dice-rolls" is that special abilities that add a point to a siege-value are less important, since siege-outcome-values will in general be very high with this setting - one point more or less doesn't really matter. But I guess one can alter the corresponding parameter for the siege-weapon/expert-ability (EDIT: Yes, see post #8 below).

The same is true for the fortification level. If you're using a setting that creates very high siege values, the siege points generated by the fort-level matter less. I'm not sure if one can adjust the siegepoints that a fort-level provides. (no corresponding variable in the structures-file)

In the same vein, those generally high siege values that you get when you decrease the "value for siege bonus" or increase the sides of the siege-dice-roll probably lead to a lot of surrenders, since the surrender-check is made against the average troop quality of the besieged, which usually fluctuates between 6 and 12. So, I can't actually tweak sieges without "breaking" this mechanism. But for my purposes, I'm positive that it can be compensated via the Depot/Wagon-protection.

And I think I also have to be carefull with the dice-sides. If I set them so low that they cannot equal the besieged average troop quality (6-12), then besiegers without artillery have no chance to incite the besieged to surrender. But of course there should still be an albeit smaller (less dice-sides --> less room for deviation between the besieged and the besiegers' rolls; difference of 3 needed for a breach) chance to create a breach and assault.

Anyway, thanks a lot for your tip/correction, Pocus! I can now continue to work on my mod!

[JacquesDeLalaing]

PS: The RoP modding-files link is broken. I still got the old database, but it does not include the new 1st and 2nd Silesian War files.

http://www.ageod-forum.com/showthread.php?5358-Official-Files-for-modding

Is there perhaps some fellow modder who still got the gold-DB-file (or just the 1st and 2nd silesian war-setup files) and could help me out?

[JacquesDeLalaing]

Here are some observations on the "siege expert"-ability (for RoP: 34Siege_Expert.abi). Perhaps it's usefull for modders and for myself (I tend to get lost in my hand written notes).

1. Parameter0 needs to stay at 1. This tells the game that the ability is used when the unit is besieging. Allegedly, Parameter1 tells the game whether the ability is used when the unit is besieged; but I haven't tested this out. Source (abiSiege-ability group; note that adding a Parameter3 - allegedly for the bonus amount - does not work/affect anything) The ability "fortdefender" seems to confirm this (Param1=1, Param0=0).
2. You can set the amount of the siege-bonus via the ability "Level" (1 in the vanilla game). Setting it to 50, for example, results in instant surrenders of the besieged. Luckily, changing the ability-level does not affect the "power" of the unit. So, a siege artillery unit with a power of 81 stays at 81 even if you increase its ability level.
3. The effect of several units with this ability does NOT stack/accumulate. This has been officially confirmed somewhere (can't find the post right now...) and my tests also point in that direction:

I used a half-way controlled setting (100 points atillery power needed for 1 siege point; 1 dice-side only), and tested several situations:
Two siege units (ability level 5) --> 5 hits per turn inflicted on the besieged; no breaches
One siege unit (ability level 10) --> 1 breach per turn, surrender in turn 4
One siege unit (ability level 5) --> 5 hits per turn inflicted on the besieged; no breaches
Two siege units (ability level 10) --> 1 breach per turn, surrender in turn 3 or 4
One siege unit (ability level 20) --> instant surrender

As you can see, the result is not affected by the number of units, only by the level/quality of the ability.
(Note that I added some ordinary artillery in all situations with only one siege unit, in order to compensate for the difference in artillery combat power)


---------------------------------

I suppose that all that I've written above also holds true for the abilities "fortdefender" and "siegeengineer".

PS: Sorry for the triple post.

[Pocus]

Yes, if the abilities are of same category 'Siege Ability' then parameters mean the same.

I'll upload the latest ROP database.

[JacquesDeLalaing]

I'll upload the latest ROP database.

Thanks a lot! I've just increased hits for all inf and cav units in the 1st silesian war from 10 to 20 in the scn-file. But I'm eager to add a few units (Prussians need some bateaux on the Oder, and I might split up some light units) and I think one can't do without the database here.

By the way I'm totally in love with the engine and the almost unlimited modding possibilities (and the support for modding from your side!). Now that I think I have at least a basic understanding of all game aspects and how they're interlinked with each other, I'm actually daring enough to create a kind of total overhaul-mod for the 1st Silesian War. I'm not so much changing the OOB and events - I can't really do that - but primarily mechanics, terrain-effects, troop stats, abilities and attributes, supply stores and supply consumption, siege resolution, etc. In some cases, I'm actually reducing the amount of modifications and variables so that the game should be more predictable/transparent for the player. And I got to say I really like my results so far. I hope I'm ready soon for some "test"-AAR, focused on the conflict in Silesia (Bavarian, French, Saxon troops are left aside for now). The mod is meant for people who want to focus a bit more on the details and the micro-level, and less on the grand scope (both are of course legitimate preferences).

The only thing I still don't understand at all is local supply/foraging. May I bother you one last time and describe my uncertainties sometime?

[Pocus]

Yes, I can probably give some tidbits of infos.

Modding a scenario with the intent of fine tuning it is great, it demands patience and thorough testing, a thing that is always appreciated.

[JacquesDeLalaing]

Here is just an idea for a more transparent siege-resolution that I'm implementing in my mod, based on the great unit-spawning-mechanism that has already been used for sieges, but not to its full potential imho.

Important preconditions

1) I'm using 7 days turns.
2) All artillery units should have an ability that provides them 1 siege-point bonus ONLY when defending against a siege.
3) Artillery power does not matter at all in sieges (parameter set very very high).
4) The influence of luck is reduced a lot (siege res-dice has very few sides).
5) I'm modding the First Silesian War scenario, and, assuming you play Prussia, the AI will not be disadvantaged too much.


The Siege System

Certain units (artillery, siege train) have the ability to initiate a formal siege. When they end in a region with a strucutre that is held by the opponent, they have a 100% chance to spawn exactly one "formal siege" element (I need to add one special artillery element to all artillery units for this).
This "formal siege" element will have a certain chance (still need to find the correct balance) to spawn exactly one "First Parallell"-element. This is ...well....the first parallell, the opening of the ditches!
This "First Parallell" element will have a certain chance to spawn exactly one - you might have guessed it! - "Second Parallell"-element. This will give the besiegers a first siege bonus.
This system goes on and on, with the probabilities to spawn the next "phase of the siege" (Third parallell, capturing of the covered way, etc.) decreasing slightly, while the bonus provided by each phase of the siege is increasing.

Note that only the first spawned element ("formal siege") includes a single element that represents the workforce and consumes supply. The first element should also have a very high patrol value.
If the element that has triggered the formal siege leaves the region (you can't siege without artillery...) or the siege is over, all elements are deleted. Not absolutely perfect (troops could defend the approachment trenches and the parallells, while artillery leaves temporarily) but plausible enough.

While the siege value for the besieger will be slowly increasing by the spawning of the phases, the siege value of the defenders stays the same or varies only slightly (sides of the siege resolution dice). There is also a certain element of luck/randomness involved because of the "spawn" probabilities of the phases. It can happen that the siege does not proceed, or that it proceeds even two phases in a single turn. One can fine-tune the amount of randomness and duration of sieges by simply adding more phases (e.g. approachment trenches in between the parallells).

One could also fine-tune the siege-capacity of different units. E.g. field artillery could have a different "phase-tree" (slower in this case; lower probabilities to spawn next phase) than siege artillery (faster, higher probabilities).

As soon as the besiegers' siege value is so high that is supercedes the defenders' value + the defenders' average troop quality, the defenders surrender. (sooner if breached and out of supply)
Before that, breaches might be made (starting ca. from the second parallell, but depending on the fort level).

Assaulting is still an issue for me. I'd really like to allow assault attempts before a structure is breached. And the assault itself is still not satisfying for me, but I don't want to expand too much on that. Ideally, defenders that "loose" an assault attempt should surrender, while in the game, nothing happens or they simply don't count as loosers. I would like to give forts an extremely small frontage (speaking of ca. 5 elements per side only), the attackers a huge malus for fire combat (so that they only have a chance in assault phase). So either the attackers fail to assault (in which case they suffer from the defenders fire), or they assault successfully, thereby severely reducing the defenders cohesion (I'm still working on assault parameters), so that they should actually "retreat/surrender" - but they just don't do this, they simply die slowly (because of the frontage restrictions) over several turns (as soon as their spirit is broken by an attack, the attacker doesn't suffer a lot of casualties anymore). So actually, setting only a small detachment of elite elements on "assault" should be the way to assault a fort.

To sum it up: I think this system is immersive, transparent (you can always see how the siege is progressing), can be fine-tuned a lot and generates historically plausible results.


PS: I think I've just reached a certain restriction: "TAbiDefs.GetAbility UID 143 too high" ....I guess the slave fighter ability has to go. I'm willing to exchange leader abilities for troop abilities.
PS: Another problem popped up. Just like the spawning of units, the destruction of units also happens turn by turn. So, once the "sappeur/siegetrain"-unit leaves the region, the first parallell (with the irrelevant bonus) is destroyed. In the next turn, the second parallell (also with the irrelevant bonus) is destroyed. In the next turn, two weeks after the siege train has left, the third parallell with the relevant (highest) bonus is destroyed. This is quite a problem. Perhaps I will have to work with only 2 steps instead of 3, so that this problem is less severe. Therefore, I will have to decrease the chances of spawning, which will make the whole process more dependent on luck.
PS: Another small note: obviously elements with a "siege-ability" need to be part of a stack that is actually besieging a structure in order to play their ability. For that purpose, a stack that is made up entirely of leaders and support-units cannot lay siege. So you have to position your artillery in a stack with some battle troops (it is not sufficient to park your artillery in a seperate stack in a region where you're sieging). Pretty nice.
PS: And the stack containing the siege-element must not be passive, otherwise it doesn't count as besieging.


This image should give you an idea of what it looks like in the game (here still triggered by the sappeurs, not artillery or a siege train for testing purposes). I might add nicer graphics

[PhilThib]

Quite nice ideas, I like them and will follow this closely

[JacquesDeLalaing]

Unfortunately I came upon a problem concerning unit-spawning. It's really weird and this time I think it's not my own fault.

It seems as if the chance for an element to spawn units increases with the number of units (or elements?) in the very same stack. I noticed that my siege-spawn-mechanism worked as intended as long as the spawning element was part of a small or mid size stack: The single element spawned a single unit with the chance that was set in the ability. However, when I put an element with the ability to spawn into a larger stack, a single element would often spawn more than one unit, even when the spawn-probability was lowered to e.g. 60!


Just to make sure, here is the ability:

UID = 134
Name = $abi_nam_SiegeWeapons_PRU
Alias = abiSiegeWeapons_PRU
Kind = $abiUnitSpawning
Text = $abi_txt_SiegeWeapons
ImageID = abi_SiegeExpert.png
Color = $colAbi_Green
Appliance = Self
Family = 0
Level = 1
Param0 = 1213
Param1 = 100
Param6 = -100
Param7 = 1
Param8 = 0
Param9 = 0
ListParams0 = $Clear|$Forest|$Wood|$Wilderness|$Mountain|$Hill|$WoodedHills|$Swamp|$Moor

I gave this ability to one single element (artillery) element in a unit of 4 artillery-elements. Based on what's written here, shouldn't this automatically spawn exactly one unit "1213" if besieging? (I've also tried it out with lower values than 100/-100) Does anyone (most likely Pocus...:w00t have any clues? Is this hardcoded? Is it a bug or is it intended?

PS: I've also tried to put but one element (with the spawn-ability) in the unit and get rid of the other elements in the unit (I thought maybe appliance "self" might give the ability to all elements in the unit). But even this single element spawned more than one unit.

EDIT:

After some further investigation, I think it's not related to stack size (tried out the field bakery which works fine in a big stack). Rather I think it becomes an issue if there are two units (or elements?) with the same spawn-ability in one region. Somehow their spawn-probability seems to increase and they can also spawn more units. The problem occurs only when I have two siege units in a region. So perhaps I can circumvent this problem by giving each siege-unit (per faction) its own spawn-ability. Quite a lot of work (and the ability-restriction is bad for this puspose!) but maybe the only way.

[JacquesDeLalaing]

I've set up two seperate spawn-ability-trees for two units of artillery, but still, even though the two units don't have the same spawning-ability, their spawn-probability is increased when they're positioned together in one region.

It's not really a game breaker, but it's not nice and not slender to have 2 units spawn 10+ units (in the second generation...) instead of 2.

On a positive note, I've found awesome new sound-samples for battles and I've managed to create my first event (apart from blocking Saxony)! The Oder-segment at Glogau only gets unblocked once the Prussians take Glogau (then their supply-flotilles can set off*). I've first tried to make the fortguns bombard the bateaux, but for some reason it doesn't work (you always hear the bombardement-sound, but no hits are inflicted). Also implementing a fixed warship ("Oder Blockade") didn't really work. However, for operations in Lower Silesia, the Oder-segment at Breslau is more important because of its length in the game-map - and Breslau itself is hard to model. Basically, the city opened its doors to the Prussians without any resistance.

* Supply by river will be essential due to the "new" supply-system (mixture of local supply/cities everywhere, field-bakery generating some supply wagons, and supply forwarded from depots - supply wagons take by far too long, so river-transport is the way to go!). I've set the loyalty in Lower Silesia to only 50%-50% because most of it was protestant, whereas Upper Silesia was dominated by catholics loyal to Habsburg - so I hope that once in Upper Silesia the Prussians don't get a lot of "local" supply (hoping that loyalty does affect the supply-production of structures?).

[Baris]

Portraits have very much retro feeling. As well as event parchment. Looks cool.

[JacquesDeLalaing]

Retro-look? This is 18th century look. The portraits are all from 1740/41, the Glogau-map in the event picture shows a map or the Prussians' capture of Glogau 1741 (assaults like these are very hard to model in the engine - historically speaking the assaulting Prussians had 51 casualties, the Austrians ca. 60) and the "newspaper" is the official Viennese proto-newspaper from 1741, with a report of Neippergs' actions in Moravia-Silesia.

Anyway, I'm glad you like it so far!

PS the map: http://www.digam.net/image.php?file=dokumente/4252/2.jpg&b=850; Especially nice is the little verdict on the left in rather imperfect French: Si le rat manger le chatte, l'Autriche prendra Gloga(u).

[Baris]

Forgive my English .
Studied journalism and probably missed this paper.
Always joy to read your historical posts ( which I like to see more) and engine analysis. Especially I took note about the low number of casualties in siege if that is special for the specific assault. And thanks for the map.