Alien mission generation, base generation Qs

[Thornhammer]

Couple of quick questions.

 

Anybody know how an alien mission is generated? How the game determines when a UFO should perform a flyover/landing mission and such?

 

Second, is there a mechanism by which the aliens know when to build a new base? X-Com needs funds, do the aliens need to have obtained a certain number of points, or do they just send out the fleet and do it?

[NKF]

I'm not the best authority on alien mission generation, but I'll give it a shot.

 

It's mostly random, but there seems to be some method to their madness.

 

Generally a normal 'random-encounter' UFO with a crew of a particular type will pop into existence on the Geoscape with a destination and a task in mind. The crew type is generally random at first, but the types seem change as some conditions are met while you play the game. If it's anything like Apocalypse, it's probably score based. The task could be anything, from a scouting mission for infiltration or base construction, harvesting, identifying a terror site, and so on and so forth.

 

Once this happens, the UFOs generally follow the same procedure. The UFO will fly to its target destination at top speed. This speed is well beyond what your Inteceptors can handle - so it's useless to pursue them at this point. The UFO then slows down once it nears its destination, scouts about the area in a random pattern and may occasionally land one or more times. The flyovers raise activity points, however the landing tends to cause the alien activity points for that area to leap up by an amount depending on the mission type. Once done, the UFO heads off at great speeds and pops out of existence, again at a speed that Interceptor's cannot handle.

 

For infiltration, it seems that the withdrawal of a country is determined at the start of the month, and the infiltration attempt is mainly just the aliens going through the pomp and ceremony. We haven't really explored this fully, but it's a theory that explains the inconsistent results lots of players have reported over the years.

 

Depending on the mission type, some UFOs will come in varying amounts. They're usually single UFOs. Sometimes they'll come simultaneously in small numbers (ala a harvesting fleet). In waves or large numbers such as mass infiltration fleet (always 2 battleships and 3 others); a base construction fleet ; or even terror site scouts. Although with terror sites, they don't often have a scouting phase.

 

If there's an alien base on the Geoscape, a supply ship will appear at various intervals throughout the month and head straight for the base. It will land for a few hours and then fly off. Apart from the activity points, it's nothing more than a fat juicy target for you to capture for extreme loot and experience.

 

UFOs on base assaults and terror sites will charge towards their destination at great speeds. For the terror ships, once it arrives, it vanishs and leaves a terror site at the destination city. For a base assault, it initiates the base defence module firing sequence, and if that fails it starts a base battle. Both UFOs will otherwise vanish the moment they reach their destination. For a base assault, if the UFO gets destroyed during the defence module sequence, another UFO will spawn a few days later and repeat the attack. This keeps repeating until it gets through.

 

---

 

There are a few ways a base gets generated.

 

The first method is the most obvious. You let leave a construction fleet alone.

 

The next is through infilration. If you lose a country, there's a high chance that an alien base will get generated in the withdrawing country's land. Not always, but it's worth sending out scouts for any withdrawal.

 

Then there are the bases that your 'agents' locate for you when you're doing poorly. I'm not sure if these bases are created simply for this purpose, or if the base is built by a construction fleet acting beyond your radar range.

 

As I said, I'm not an authority on alien mission generation. These are just some observations I've made over the years. I'll let the experts correct me on any points I've got wrong.

 

- NKF

[Alitorious]

Sounds good. I'll just add a couple of things I've noticed through lots of hyperwave decode watching time. (Normally when you have the entire globe covered by hyperwave decoders - including Hawaii and Antarctica, the game's won. )

 

Missions are planned weeks in advance. Even when you reload from a previous date, you get the same number of ships with the same missions at the same locations. This means that you can reload to try to shoot down that Terror ship, but you can't count on the RNG to not launch the mission unless you go back at least a month.

 

There are often several UFOs working on the same general goal. I'll call these 'campaigns.' All UFOs assigned to the same campaign will always have the same race and the same mission type.

 

Most types of campaign have a scouting phase and an action phase, with the two exceptions being Research and Supply. Research campaigns are only scouting, and Supply are only action.

 

The scouting phase is exactly what it sounds like. One of the three types of scout ships (Very Small or Small on radar) will go to the area and, well, scout.

Alien Retaliation scouts will never land, but zig-zag the area to try to find your base.

Alien Research, Alien Harvest, Alien Abduction, and Alien Base scout missions will fly randomly about a region and land in rural areas. Occasionally the same UFO will land at multiple locations.

Alien Infiltration and Alien Terror missions will fly around populated regions and land in cities. They won't spawn a terror site or cause a country to defect. (I watched a large scout on an alien terror land in a city because I was curious to see how they'd get a full terror load out of an itsy bitsy scout, )

 

The action phase will always occur, whether or not all the scouts report back to base. However, a successful scouting mission will sometimes cause the schedule to move ahead of time and action to be taken immediately - Alien Retaliation comes to mind. Always shoot down those scouts!

 

Alien supply missions are nice and simple - they come in, supply, probably stay for tea, then leave.

 

What happens on Alien Retaliation and Alien Terror missions depends on if the scouts were successful or not. If none of the scouts found your base, the aliens send the Battleship in anyways but it zigzags around and won't find your base. They send a couple battleships before giving up on that campaign.

On Alien Terror I'm a bit more hazy, since I never usually let them leave Earth alive . Sometimes the Terror ship flies around the populated areas, but never actually lands in a city and just leaves. Sometimes the Terror ship flies around the populated areas, then lands and terrorizes a city.

I don't think I've ever seen a Terror ship zoom right in to a city - I've always been able to intercept them with Plasma Beam Interceptors.

 

Alien Harvest and Alien Abduction usually send in two Harvesters/Abductors and land in rural areas. It might just be me, but Harvester missions seem to frequently be floaters (I've had Mutons I'm sure), and Abductors are frequently Sectoids.

 

Alien Infiltration and Alien Base missions are similar, too. The aliens send in a huge flotilla consisting of scouts, supply ships, terror ships, and battleships. In infiltration they all land in cities (even the terror ship, but it doesn't terrorize the city). In Base they all land in rural areas. After some time, a base appears somewhere in the region - not necessarily underneath the Battleship.

 

 

Individual missions themselves consist of three logical phases - reentry, operation, and reorbit. (Or is it just 'entry', because it's for the first time? )

In reentry the ship enters at some location on the globe - sometimes all the way on the other side of the Earth in some cases. It travels to its target location at maximum speed and maximum altitude, slowing down when it nears the region.

Operation is, of course, outlined above.

Reorbit is simple, too. The ship heads off in some random direction, speeding up until it's at maximum speed and maximum altitude. It disappears after some time (again sometimes halfway around the globe.)

 

There are a couple differences in between them. Battleships en route to your base will head at maximum speed until they hit your base. Supply ships head directly to the base, but slow down enough for a Firestorm to catch them, but faster than an Interceptor.

Ships on more exploratory, ziggyzaggy, flight plans (basically all the others, ) do a lot of their slowing down and speeding up during the zigzaggy. I've seen battleships go from 4800 knots to 5200 knots while making a 180-degree turn to reorbit.

 

 

...Oookay, that turned out to be more than a couple cents . Maybe if I get less lazy or if someone has time they can add this to the Wiki.

[Thornhammer]

Fascinating stuff. Thanks, guys!

 

I'm sure I'm not the first person to attempt this, but I've been fiddling with tabletop miniature rules for X-Com. I envision segments that cover most aspects of the game - a world map to function as Geoscape, research and manufacturing, intercept and Battlescape missions.

 

The game rules for Battlescape missions translate surprisingly easily, though I converted to use a d20 instead of percentiles. There are a few things that have to be simplified to make the game quicker to play (for instance, strength is gone - I played with it and it didn't really add more fun to the gameplay than work), but many of the computer game's mechanics can be directly transferred.

 

My sticking point so far has been generating UFO flights and such. I really like the idea that the missions are generated weeks ahead of time, and almost like small alien campaigns. It simplifies things quite a bit - I can have each base launch X number of campaigns per month. Determine target location, campaign type, and fleet composition.

 

Very useful responses, thanks again.

[NKF]

In-game, strength is mainly for controlling your carrying weight capacity, and throwing distance. In fact, it is a much more important stat for grenades than throwing accuracy, although the two do go hand-in-hand (i.e. range and accuracy%). If my memory serves me correctly, melee aliens make use of it for their hand-to-hand attacks.

 

As for your battlescape missions, do you have 10x10 tile cutouts and just piece a 4x4, 5x5 or 6x6 area together with random cutouts for the mission maps? That's basically how the game sets up all the 'random' areas of the map like the farm/urban buildings, fields and wilderness. I seriously don't know if that'd translate well to the d10 system, but it would be semi-faithful to the game.

 

- NKF

[Thornhammer]

In-game, strength is mainly for controlling your carrying weight capacity, and throwing distance. In fact, it is a much more important stat for grenades than throwing accuracy, although the two do go hand-in-hand (i.e. range and accuracy%). If my memory is correct, melee aliens, if I'm not mistaken, make use of it for their hand-to-hand attacks.

 

As for your battlescape missions, do you have 10x10 tile cutouts and just piece a 4x4, 5x5 or 6x6 area together with random cutouts for the mission maps? That's basically how the game sets up all the 'random' areas of the map like the farm/urban buildings, fields and wilderness. I seriously don't know if that'd translate well to the d10 system, but it would be semi-faithful to the game.

 

- NKF

 

I'm just using inches (assigning so many inches to an AP) for movement, so a strict grid system like the game used isn't necessary. It lets us throw together whatever terrain we have available - I set up a very nice attack on a farm, and have a boatload of Plasticville O-Scale buildings for a good old-fashioned Terror Mission.

 

From some of the other threads here, it appears that alien missions aren't tied to a base - I had always assumed that alien craft took off from an alien base and landed there when they finished. If the missions aren't tied to a base, I would guess there are no real limits on the number of alien missions that are generated in a month, so I'll have to come up with something.

 

I have a few more questions, but I'm going to do a little forum research before I post them, in case they've already been answered.

[NKF]

Well, if you've got a lot of free time and want more information about how the game works, we've been collecting our knowledge over on the X-Com wiki at https://www.ufopaedia.org

 

It might be a tad too detailed, but there might be something there that might help.

 

- NKF