At the Gates > AtG - General Discussion

Weekly AtG Update #1 The Map


Jon Shafer:
Welcome to the first weekly AtG update in the final countdown to the January 23 release date! Every Sunday afternoon a new article will go up, and each week will have its own theme. This first week our theme has been the map, and you can also follow along with future (or past) daily updates on Twitter.

Map Generation

The map is the most important part of any strategy game, especially a 4X game. I spent 18 months creating the map generation system for AtG, and although in retrospect it was probably a bit much it really is a cool system, and something I'm proud to show off and expect to continue using in future games.

My primary goal with the map generator was to produce realistic-feeling worlds. They aren't perfect, and I've fudged things here and there for the sake of good gameplay, but the goal from day 1 was something that felt right. There should be long mountain chains, vast deserts, lush regions, rivers winding down from high points helping quench the thirst of dense forests.

My primary goal with the maps was to create realistic-feeling worlds.

To accomplish this the map is first constructed by seeding 6-10 "high points" which are randomly grown into mountain ranges, and serve as the "anchor points" for continents and islands. Points which are extensively developed usually turn into large continents, while some might randomly never grow into much. It's not plate tectonics, but it works pretty well. From that point I grow land onto the mountains, first hills and then flat ground. We're then left with the shapes of the land, with nothing on them.

A climate simulation is then run to determine what kind of terrain that land turns into. Maritime currents hit the west edge of continents, resulting in forests and green, fertile areas, but when mountain ranges stop this moisture the result is dry steppe land and even desert. Elevation is also calculated, and this is used to build the paths of rivers down from high points to the sea, and this also helps determine where swamps will end up.

Map generation consists of several simulation layers.


Another element which stands out with AtG's maps are its cyclical transformation. Every 24 turns a full seasonal cycle takes place, chilling and then freezing the landscape and changing its properties in a variety of ways. The climate simulation also has a role to play here though, and some areas are affected more than others - the winter can be much more harsh the further north you get.

Summer is the time of plenty, when it's easy to generate food and conduct military campaigns. But this time only lasts so long, and when the map grows cold food production shuts down and the supply your military units rely on to continue operating diminishes and then usually disappears. Armies can encamp to regain supply for one turn, but this leaves them vulnerable to enemy attack, so doing so when in your opponent's territory is usually ill-advised.

Winter comes with benefits as well though, as rivers freeze over, eliminating them as terrain obstacles. Moving through snow is harder than flat ground, but this will often still be something you can take advantage of. Large rivers are normally completely impassable, and so winter is your only opportunity to cross.

The changing of the seasons gives AtG a distinct gameplay rhythm.


Exploration is usually the most fun of the four Xs the 4X genre has to offer, and this was something I really wanted to emphasize more in AtG.

One way this has been done is by by making the acquisition of resources from the map require an additional stage: not only do you have the find something, like a plant, and then construct a farm on it, but in AtG you must also determine what kind of plant it is. Now, obviously someone would be able to figure out the difference between wheat and grapes pretty quickly, but this is also meant to simulate the time necessary to determine if the source is at all economical for harvesting. If you find a single grape vine it's not going to be enough to fuel your kingdom-wide wine production operation.

This is a mechanic that was inspired somewhat by the old SSI game Imperialism, where a surveyor had to go out and look at individual tiles in order to see if there were any minerals there. That mechanic was a bit tedious and didn't really offer a ton of strategy (just send your surveyor from valid tile to valid tile until they were all checked), but it did feel good in some way. I've aimed to capture that same feeling in AtG, only with some more strategy. After all, if you find a bunch of unidentified minerals near your starting location that's enough information to start moving towards researching and training your clans as miners, but you won't know exactly what you're dealing with until you send someone out to nail down the details.

Most resource deposits must be identified before they can be used.

One other way I've tried to add more strategy and intrigue to the map is through starting location "hints".

Traditionally in 4X strategy games you can see a very small ring around your starting location, and usually also a handful of resource deposits which might help shape your early build and research choices, but often it's just not enough to make these first few choices interesting. In AtG I really wanted to spice things up by giving you more information. Now, I didn't want to just show you half the map to start, so I've instead shown a preview of a half-dozen or so interesting tiles.

These things might be resources, goody huts, or bandit camps, pushing you in not only economic but also military directions. If you see two goody huts nearby then training an explorer probably makes a lot of sense. A couple of bandit camps though and you might want to get some warriors online first. It's a subtle change, but it really adds a lot to the early game.

Starting location "hints" can help inform your strategies in the first few turns.

The theme for next week's updates will one of the game's most important features: the clans. You can follow along throughout the week on Twitter, or simply stay tuned here for the next big update!

- Jon

Thanks for the update; this looks excellent!
The map generation reminds me in the best way of Sid Meier's Alpha Centauri, but applied on more familiar settings. The dry vs wet lands difference is nice and clear.
I'm also impressed by the seasonal changes and the strategical possibilities it opens. Will Major Rivers be possible to bridge with improving technology? Will they be possible to cross by some abstracted form of "boats" (eg. a ferry crossing rather than a bridge)? Will it be dependent on the tiles being within your borders?

Jon Shafer:
Glad you like the system!

Rivers right now are split into two types, small and large. Small rivers normally require an extra turn to cross, whereas large rivers are impassable unless frozen or crossed by a road.

I'd like to do more with them in the future, but they're not traversable by boats or anything like that. Would love to include a feature like that, but getting it to work on the normal 4X map scale would be tough. Seeing a boat sitting in the middle of an otherwise normal tile would feel strange, even if it worked mechanically. On the plus side though all the rivers are inside individual tiles rather than between them, so it's at least possible.

- Jon

Thanks for the quick reply!

Have you considered a two-tiered "road" upgrade for the big rivers?
Tier 1: Make it the same speed to cross as a small river. Could be called "ferry" or something.
Tier 2: The road (bridge?) you mentioned which I assume is as fast to move on as a regular road.

I think it could fit very well with the nomad mentality where the road is a greater investment for when you really want to settle down and need the full benefit of crossing the river quickly. The "ferry crossing" could be cheaper and quicker to build but slower to cross, producing a sweet trade-off.

I believe it could make for some interesting decisions, however, I appreciate that your roadmap is long as it is.

I hope you're having a Merry Christmas Day!

Jon Shafer:
Thank you, and you as well!

The list is indeed long, but I definitely like the gist behind what you suggest. Remind me again in 6 months if I haven't done anything similar by then. ;)

- Jon


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