Field of Glory: Empires Dev Diary #9 Addendum - Playing Empires Battles in FOG2

[Daniele]

Playing Empires Battles in Fog2
by Richard Bodley Scott

From an early stage in development it was planned that, in addition to the in-game battle resolution system, Empires would also have the option to fight out battles in FOG2 if the player so chooses.
The main objectives were:

1) That Empires battles fought out in FOG2 should be varied and fun. (Number one priority!)
2) That the armies of each nation should be represented by the correct FOG2 units for their nation.
3) That general skill and traits, unit experience, unit effectiveness, hit points etc. from Empires should carry over into the FOG2 battles.
4) That terrain should be representative of the terrain in the region where the battle takes place.
5) That there should be no adjustments to make the battles more “even”, and no adjustments to take into account the FOG2 difficulty setting. The situation should be as per the campaign situation.
6) That the export/import process and switching between the games should be as automated a process as possible.

How does the game decide which FOG2 unit type to convert an Empires unit to?
Empires has a database specifying which FOG2 unit type each Empires unit type maps to, with a quality adjustment for some. The mapping is different depending on the national archetype. This information is passed in the export file, along with various other factors affecting the conversion.
The Empires system potentially gives "Heavy Foot, Warriors, Mercenary Foot, Urban Militia etc." to every nation. The FOG2 conversion system attempts to convert each nation's forces to FOG2 units that are appropriate to their historical prototype. So for example "Warriors" in a Gallic Army will translate to FOG2 Warbands, but those in an Italian army will translate to FOG2 Italian Foot. This means that Empires "Heavy Foot", for example, may translate to FOG2 Medium Foot for some nations, if the nation never actually had any troops that FOG2 would rate as Heavy Foot.
Also some units translate to a mixture of FOG2 units, because this leads to more historically realistic armies. Pre-Marian Roman legionary units translate to a mixture of hastati/principes and triarii units, in approximately a 2:1 ratio. Horse archer units, if present in large numbers, translate to a mixture of Light Horse and Cavalry.

How does the game decide how many FOG2 units each Empires unit maps to?
The Empires : FOG2 unit conversion ratio depends on the unit type, because it is points based. This is because the difference in effectiveness between various Empires units is often significantly greater than the difference between the effectiveness of their FOG2 equivalents. To get the same relative effectiveness as in Empires-resolved battles, the more expensive (and more effective) Empires units translate to more FOG2 units than the cheaper ones. Some of the cheaper Empires units may only map to 1 FOG2 unit, but some of the more expensive ones could potentially map to as many as 4 or 5 (cheap) FOG2 units in armies of nations that historically did not possess powerful units like Pike phalanxes or legions. Most units will have a conversion ratio somewhere between these two extremes.

For example, because Italian Foot in FOG2 are cheaper (and less effective) than Warbands, the unit conversion ratio for Empires Warriors > FOG2 Italian Foot will be higher than the unit conversion rate for Empires Warriors > FOG2 Warbands. Also, where different Empires unit types convert to the same FOG2 unit type, the quality of the FOG2 units may be adjusted depending on which Empires unit type they come from. (Thus, for example, Urban Militia in some national archetypes may be extremely low quality versions of the standard units. They will also have a lower unit conversion ratio as they are much lower rated in Empires points).
Because the points value ratios do not match up to an exact number of FOG2 units, there is a random element. For example, if the points system means that an Empires unit is equivalent to 1.37 FOG2 units, the system will generate at least one FOG2 unit, with a 37% chance of another one. So usually it will generate 1 unit, but 37% of the time it will generate 2.
A damping system on the chances of selecting subsequent "partial" units is used to ensure that the overall strength of the army does not vary excessively (about 3% in tests), and a unique random number generator seed number for each exported battle ensures that if you play the same battle (from the same export file) in FOG2 multiple times, the OOBs (and map) will be the same each time. (Unless you go back to the pre-battle Empires save and re-export it, in which case there will be a different seed number each time).

How does the conversion take into account Empires general skill and traits, unit experience, effectiveness and hit points etc.?
Unit Experience and Effectiveness affect FOG2 unit Experience and Elan respectively. FOG2 unit Quality is the average of those ratings.
Empires Hit Points represent current strength compared with full paper strength, so affects the unit conversion ratio.
Generals use their Empires skill rating for attack or defence depending on which side counts as attacking in Empires. General traits applicable in the regional terrain add their modifiers to those skill ratings. If there is an overall difference between the skill ratings of the opposing generals, then usually an adjustment is made to the quality of the opposing units, representing the effects on morale, physical condition and state of preparedness of the troops resulting from the better general's more skilful pre-battle manoeuvres. Sometimes, instead of a quality adjustment, the lower skilled general will have some of his troops arrive late at the battle.
Unit traits are not explicitly taken into account in the conversion process, because FOG2 already takes into account the different effectiveness of different troop types in different terrain.

Frontage
Empires units convert to an average of 2 to 3 FOG2 units, some more, some less.
We decided not to artificially constrain the frontage in FOG2 battles because it would severely restrict the tactical options – which would rather defeat the point of playing the battle in FOG2. We did not think it would be fun.
Also, as FOG2 battles take some time to play out, we wanted a decisive result, so wanted all of the troops present to be able to take part.

Therefore, the normal FOG2 map generation is used, based on the prevailing terrain in the Empires province. Hence a mountainous, forest or swamp province will result in a mountainous, forested or marshy map, which may result in choke points, but isn’t guaranteed to do so.
This does mean that playing Empires with FOG2 battles will have strategic implications, meaning that the game will play out somewhat differently depending on whether you play all the battles in Empires or not. Personally, I resolve very one-sided battles in Empires and play the rest in FOG2.
Siege assaults are left to the Empires system and cannot be exported to FOG2

[Lysimachos]

Wonderful! It seems really well designed. Cannot wait to play this great game!

[kvnrthr]

Really excited for this! Good to know the Triarii will still be around. If not already planned, a method to preview the unit conversion from Empires to 2 before exporting would be nice. E.g. show the user that warbands-> italian foot, or legionaries->hastati+triarii, etc.

I'm worried about how to sell this to new players though. I already own FOG2 so Empires is a no-brainer, but a new player might be discouraged at having to buy 2 games to access both the strategic layer and the tactical battle system. Especially when the battle export feature is one of the strong distinguishing feature of FoG Empires compared to competitors.

I hope Slitherine will consider a bundle discount or some other price reduction when buying both FOG2 + Empires, so newcomers can access everything at a competitive price.

[SirGarnet]

Sounds good and well conceived. I made a suggestion earlier that may be put best as a question - can an Empires battle be exported such that 2 human players can fight it and import the result (multiplayer opponents in the base case, or trusted stand in players for the AI?

[rbodleyscott]

Cross-posted from STEAM board:

Originally posted by Harry:
Slightly confused by the conversion numbers, I read it as the more expensive units such as heavy infantry will convert to more units in FOG II.

Below seems to contradict my assumption

"Because Italian Foot in FOG2 are cheaper (and less effective) than Warbands, the unit conversion ratio for Empires Warriors > FOG2 Italian Foot will be higher than the unit conversion rate for Empires Warriors > FOG2 Warbands."


Would not a cheaper and less effective unit in FOGE mean a lower conversion rate?

It would.

But the conversion ratio is also affected by what FOG2 unit type the FOGE unit converts to, which will differ from nation to nation, and this is what the quoted paragraph refers to.

Italian Foot are less powerful than warbands in _FOG2_ so a FOGE unit that converts to one of these types (depending on nation) will convert to more FOG2 Italian Foot units than it would FOG2 Warband units.

To put in some specific numbers, if the battle is not so large that it is scaled down, a FOGE Warriors unit converts to 82 FOG2 points, whereas a FOGE unimproved Heavy Infantry unit converts to 159 FOG2 points.

In FOG2, an unadjusted Italian Foot unit costs 36 points, an unadjusted average Warband unit costs 58 points.

Therefore, on average, a unit of FOGE Warriors converts to 2.28 Italian Foot units or 1.41 Warband units. (Other nations' FOGE "Warriors", if they have any, will convert to other FOG2 unit types, depending on the nation).

If Heavy Infantry converted to the same types (they don't, but if they did), a unit of FOGE Heavy Foot would convert to 4.42 Italian Foot units or 2.74 Warband units.

[AinsleeHarriot]

This is a great idea that would greatly improve the game. Thanks for thinking outside the box!