Intrigued by a comment in the Modding devchat by someone (I forget who, apologies
) that they tried to modify the MapSizeDef file to allow for maps larger than Insane (IIRC, they said they modified it by one or two), I decided to take a deeper look at that XML to see if I could suss out a way to make it work. Perhaps the map has to be divisible by a certain number to work.
SPOILER: Nope. At least one value I tried didn't work.
First, an overview. There are presently nine different map sizes in the game. There are various definitions in the MapSizeDef file, but, at least for the purposes of total number of tiles, there is one filed that really stands out:
<HexSectorSize>Foo</HexSectorSize>
Where Foo is the number of tiles on a side of the map.
There is another entry which is slightly interesting called <MapGenSectorSize>Foo</MapGenSectorSize> which presumably slices up the internal map into chunks for the game to do... whatever it does with internal sectors.
For the maps on an unmmodded game we have:
30:8
40:10
60:12
72:14
95:16
180:16
240:16
290:16
380:16
With the first number being the tiles on an edge of a map side and the second number the size of the sectors. There doesn't seem to be a huge correlation between the two at first glance, except the divisibility by 2.
So instead of changing the map width of Insane to 382 or 384, I decided to try out 400. That would be 25 x 16. Theoretically if a 15 x 16 map was good (240), perhaps a 25 x 16 one would be. Well, as I said, no. The game crashed while trying to build the map as mentioned in the chat portion of the devchat.
But I decided to look into the debug.err file to see just when the game actually did crash and compare it to a game whose map did generate. It got as far as actually creating the colonies for each of the starting eight races before crashing:
DebugMessage: *********END dxdiag info.*********
Debug Message: CInitializationListener::OnSetContinentsPerPixelDataTail
Debug Message: CGalCiv3Shell::RequestInitializationState from: LoadingContinentTextures to: CreatingContinentData
Debug Message: Popup Manager Update: Unhiding TitleWnd
Debug Message: CInitializationGfxListener::OnCreatingContinentsTail
Debug Message: CInitializationListener::OnSetContinentsDataTailA
Debug Message: CInitializationListener::OnSetContinentsDataTailB
Debug Message: CGalCiv3Shell::RequestInitializationState from: CreatingContinentData to: DoneCreatingContinentData
Debug Message: Popup Manager Update: Unhiding NewGameWnd
Debug Message: Popup Manager Update: Unhiding LoadingWnd
Debug Message: STARTUP_STATE CreateMap 17.149591
Debug Message: STARTUP_STATE CreateMapBegin 0.002243
Debug Message: STARTUP_STATE SetupPlayers 0.002960
Debug Message: Player 0 CompleteResearch tech Colonization originalResearcher 1
Debug Message: Research Complete [PlayerID 0, Colonization]
Debug Message: Player 0 CompleteResearch tech Engineering originalResearcher 1
Debug Message: Research Complete [PlayerID 0, Engineering]
Debug Message: Player 0 CompleteResearch tech Warfare originalResearcher 1
Debug Message: Research Complete [PlayerID 0, Warfare]
Debug Message: Player 0 CompleteResearch tech Governance originalResearcher 1
Debug Message: Research Complete [PlayerID 0, Governance]
Debug Message: Player 2 CompleteResearch tech Imperialism originalResearcher 1
Debug Message: Research Complete [PlayerID 2, Imperialism]
Debug Message: Player 2 CompleteResearch tech Engineering originalResearcher 1
Debug Message: Research Complete [PlayerID 2, Engineering]
Debug Message: Player 2 CompleteResearch tech Warfare originalResearcher 1
Debug Message: Research Complete [PlayerID 2, Warfare]
Debug Message: Player 2 CompleteResearch tech Intimidation originalResearcher 1
Debug Message: Research Complete [PlayerID 2, Intimidation]
Debug Message: Player 4 CompleteResearch tech Propagation originalResearcher 1
Debug Message: Research Complete [PlayerID 4, Propagation]
Debug Message: Player 4 CompleteResearch tech Engineering originalResearcher 1
Debug Message: Research Complete [PlayerID 4, Engineering]
Debug Message: Player 4 CompleteResearch tech Warfare originalResearcher 1
Debug Message: Research Complete [PlayerID 4, Warfare]
Debug Message: Player 4 CompleteResearch tech Interaction originalResearcher 1
Debug Message: Research Complete [PlayerID 4, Interaction]
Debug Message: Player 6 CompleteResearch tech Colonization originalResearcher 1
Debug Message: Research Complete [PlayerID 6, Colonization]
Debug Message: Player 6 CompleteResearch tech Engineering originalResearcher 1
Debug Message: Research Complete [PlayerID 6, Engineering]
Debug Message: Player 6 CompleteResearch tech Warfare originalResearcher 1
Debug Message: Research Complete [PlayerID 6, Warfare]
Debug Message: Player 6 CompleteResearch tech Influence originalResearcher 1
Debug Message: Research Complete [PlayerID 6, Influence]
Debug Message: Player 8 CompleteResearch tech Expansion originalResearcher 1
Debug Message: Research Complete [PlayerID 8, Expansion]
Debug Message: Player 8 CompleteResearch tech Engineering originalResearcher 1
Debug Message: Research Complete [PlayerID 8, Engineering]
Debug Message: Player 8 CompleteResearch tech Warfare originalResearcher 1
Debug Message: Research Complete [PlayerID 8, Warfare]
Debug Message: Player 8 CompleteResearch tech Economics originalResearcher 1
Debug Message: Research Complete [PlayerID 8, Economics]
Debug Message: Player 8 CompleteResearch tech Trade route optimization originalResearcher 1
Debug Message: Research Complete [PlayerID 8, Trade route optimization]
Debug Message: Player 8 CompleteResearch tech Expanded Trade originalResearcher 1
Debug Message: Research Complete [PlayerID 8, Expanded Trade]
Debug Message: Player 10 CompleteResearch tech Expansion originalResearcher 1
Debug Message: Research Complete [PlayerID 10, Expansion]
Debug Message: Player 10 CompleteResearch tech Engineering originalResearcher 1
Debug Message: Research Complete [PlayerID 10, Engineering]
Debug Message: Player 10 CompleteResearch tech Warfare originalResearcher 1
Debug Message: Research Complete [PlayerID 10, Warfare]
Debug Message: Player 10 CompleteResearch tech Conversion originalResearcher 1
Debug Message: Research Complete [PlayerID 10, Conversion]
Debug Message: Player 12 CompleteResearch tech Colonization originalResearcher 1
Debug Message: Research Complete [PlayerID 12, Colonization]
Debug Message: Player 12 CompleteResearch tech Engineering originalResearcher 1
Debug Message: Research Complete [PlayerID 12, Engineering]
Debug Message: Player 12 CompleteResearch tech Warfare originalResearcher 1
Debug Message: Research Complete [PlayerID 12, Warfare]
Debug Message: Player 12 CompleteResearch tech Communications originalResearcher 1
Debug Message: Research Complete [PlayerID 12, Communications]
Debug Message: Player 14 CompleteResearch tech Adaptation originalResearcher 1
Debug Message: Research Complete [PlayerID 14, Adaptation]
Debug Message: Player 14 CompleteResearch tech Exploration originalResearcher 1
Debug Message: Research Complete [PlayerID 14, Exploration]
Debug Message: Player 14 CompleteResearch tech Warfare originalResearcher 1
Debug Message: Research Complete [PlayerID 14, Warfare]
Debug Message: Player 14 CompleteResearch tech Relations originalResearcher 1
Debug Message: Research Complete [PlayerID 14, Relations]
Debug Message: STARTUP_STATE FixupPlayerSlots 0.117176
Debug Message: STARTUP_STATE SetLocalPlayerID ulPlayerID -1
Debug Message: STARTUP_STATE SetLocalPlayerID ulPlayerID 0
Debug Message: Player 16 CompleteResearch tech PirateBases originalResearcher 1
Debug Message: Research Complete [PlayerID 16, PirateBases]
Debug Message: Player 16 CompleteResearch tech Engineering originalResearcher 1
Debug Message: Research Complete [PlayerID 16, Engineering]
Debug Message: Player 16 CompleteResearch tech Interstellar Travel originalResearcher 1
Debug Message: Research Complete [PlayerID 16, Interstellar Travel]
Debug Message: Player 16 CompleteResearch tech Hyperdrive Specialization originalResearcher 1
Debug Message: Research Complete [PlayerID 16, Hyperdrive Specialization]
Debug Message: Player 16 CompleteResearch tech Warfare originalResearcher 1
Debug Message: Research Complete [PlayerID 16, Warfare]
Debug Message: Player 16 CompleteResearch tech Weapons Systems originalResearcher 1
Debug Message: Research Complete [PlayerID 16, Weapons Systems]
Debug Message: Player 16 CompleteResearch tech Communications originalResearcher 1
Debug Message: Research Complete [PlayerID 16, Communications]
Debug Message: Diplomacy State Changed. [PlayerID 16, PlayerID 0, Foreign -> Enemy]
Debug Message: Diplomacy State Changed. [PlayerID 16, PlayerID 2, Foreign -> Enemy]
Debug Message: Diplomacy State Changed. [PlayerID 16, PlayerID 4, Foreign -> Enemy]
Debug Message: Diplomacy State Changed. [PlayerID 16, PlayerID 6, Foreign -> Enemy]
Debug Message: Diplomacy State Changed. [PlayerID 16, PlayerID 8, Foreign -> Enemy]
Debug Message: Diplomacy State Changed. [PlayerID 16, PlayerID 10, Foreign -> Enemy]
Debug Message: Diplomacy State Changed. [PlayerID 16, PlayerID 12, Foreign -> Enemy]
Debug Message: Diplomacy State Changed. [PlayerID 16, PlayerID 14, Foreign -> Enemy]
Debug Message: StartGame 0.000000
Debug Message: Game Started (New Game).
Debug Message: ShipComponent Created. [AuthorID 0, Name DidThisWork]
Debug Message: Map Generation using seed: 892362229
Debug Message: CreateColony 5027
Debug Message: CreateColony 5037
Debug Message: CreateColony 5049
Debug Message: CreateColony 5063
Debug Message: CreateColony 5077
Debug Message: CreateColony 5092
Debug Message: CreateColony 5107
Debug Message: CreateColony 5117
Debug Message: Dumping Stack Trace: SymInit: Symbol-SearchPath: '.;C:\Program Files (x86)\Steam\steamapps\common\Galactic Civilizations III;C:\Program Files (x86)\Steam\steamapps\common\Galactic Civilizations III;C:\Windows;C:\Windows\system32;SRV*C:\websymbols*http://msdl.microsoft.com/download/symbols;', symOptions: 530,
(Whole bunch of Dump messages snipped)
====
Checking a sucessfully created game, the later portion goes something like this:
Debug Message: Diplomacy State Changed. [PlayerID 16, PlayerID 0, Foreign -> Enemy]
Debug Message: Diplomacy State Changed. [PlayerID 16, PlayerID 2, Foreign -> Enemy]
Debug Message: Diplomacy State Changed. [PlayerID 16, PlayerID 4, Foreign -> Enemy]
Debug Message: Diplomacy State Changed. [PlayerID 16, PlayerID 6, Foreign -> Enemy]
Debug Message: Diplomacy State Changed. [PlayerID 16, PlayerID 8, Foreign -> Enemy]
Debug Message: Diplomacy State Changed. [PlayerID 16, PlayerID 10, Foreign -> Enemy]
Debug Message: Diplomacy State Changed. [PlayerID 16, PlayerID 12, Foreign -> Enemy]
Debug Message: Diplomacy State Changed. [PlayerID 16, PlayerID 14, Foreign -> Enemy]
Debug Message: StartGame 0.000000
Debug Message: Game Started (New Game).
Debug Message: ShipComponent Created. [AuthorID 0, Name DidThisWork]
Debug Message: Map Generation using seed: 738509286
Debug Message: CreateColony 5028
Debug Message: CreateColony 5042
Debug Message: CreateColony 5053
Debug Message: CreateColony 5067
Debug Message: CreateColony 5081
Debug Message: CreateColony 5096
Debug Message: CreateColony 5113
Debug Message: CreateColony 5126
Debug Message: CreateShip
Debug Message: PlaceShipOnMap. tileX 337 tileY 140
Debug Message: Fleet Created. [PlayerID 0] [FleetID 13972]
Debug Message: CreateShip
Debug Message: PlaceShipOnMap. tileX 338 tileY 140
Debug Message: Fleet Created. [PlayerID 0] [FleetID 13974]
Debug Message: CreateShip
Debug Message: PlaceShipOnMap. tileX 338 tileY 141
Debug Message: Fleet Created. [PlayerID 0] [FleetID 13976]
Debug Message: CreateShip
Debug Message: PlaceShipOnMap. tileX 497 tileY 734
Debug Message: Fleet Created. [PlayerID 2] [FleetID 13979]
(and so on and so on and so on for putting ships on the map)
So the game is crashing when it tries to put the actual ships on an actual tile. Which is a little interesting, actually. Out of bounds tiles, maybe? The X/Y value needs to be defined elsewhere in an(other) XML? The fact that it allegedly actually created a map surprised me. As well as creating colonies.
Is this info of any use whatsoever beyond purely academic interest? I have no idea, actually. I just stick my toes into modding and glancing at debug.err files. I leave the heavy lifting to others. 
Still maybe this will inspire someone else to see something that might make this work. Or not. But at least I found out when the game crashes.