Talk:Alien Inventory Use

Aliens must completely ignore the inventory position of all equipment, except those in slot 0 and 1. They simply use slot 2 as the default universal dump where they store stuff whenever they move items out of their hand.

The aliens make no distinction between who owns the weapons (eg human vs alien technology?), so will treat all weapons the same and will fire them based on their available weapon modes. Except aimed. I don't think they know how to use aimed shots - but haven't tested this theory yet.

(By deduction from TUs remaining) they do use Aimed mode but I've only observed it for launchers - all types. This may also explain the unexpected preference for arming unloaded HC-HE over unloaded RL - there were not enough TUs to draw/arm, load and then still get off an Aimed shot with the RL. Spike 04:52, 5 March 2009 (CST)

I don't think the aliens have reason to unload a weapon so they probably won't ever need to do this.

But how do they decide when a weapon takes multiple ammo? I would assume that they just use whatever is loaded. When they do reload the weapon, they might not be terribly fussy with this and go with the one highest up in obdata.dat, basically AP, HE and Incendiary or small rocket, large rocket, incendiary in that order.

With the psi-amp, can the aliens really use this or will the aliens use the MC'd soldier's latent psi abilities just like any other alien? This could be easily tested with one remaining psi alien and a whole army of mediocre psi strength troops - with strong psi skill.

non-standard grenades: Smoke grenade and proximity mine. I have this funny feeling that I have seen them use smoke grenades before, since its mechanics are no different from any other grenade. It just does a different damage type. Proximity mines however are different entirely.

What about blaster launcher dud shells? Do the aliens know how to unload them?

-NKF 00:43, 3 March 2009 (CST)

Concerning Psi: from my tests at the StrategyCore forums years ago, I remember finding that only troopers with a Psi-Amp and under alien control could wage psi-attacks against his ex-buddies. Fairly sure on this. --Zombie 01:14, 3 March 2009 (CST)

Thoughts, and Proposal for AI Unloading/Reloading Test

Given the AI never does anything that could not be immediately lethal to your soldiers, I doubt that the AI has any code in it for using Smoke Grenades, an entirely nonlethal weapon. (This also may be part of why it can't use Stun Rods; they're nonlethal tech the AI normally doesn't even have access to.)

Similarly, since it's pretty well suspected that Prox Grenades were added late in the development, given the shoddy handling of the Prox Grenade matrix, it's unlikely the AI has any code to use them either.

Past that, for loading/unloading, I view it as unlikely...there's only three weapons in the game you'd ever gain a tactical benefit from unloading(unloading an unused clip to store or sell is not a tactical benefit, at least not immediately!), the Rocket Launcher, the Heavy Cannon, and the Auto Cannon. Of course, none of these are normally available to the AI.

Overall, I view it as moderately unlikely that the AI would have unloading/reloading code, due to the fact that the number of times the situation would arise is rather low. However, one possibly effective way to test this would be to give the AI(either through MC or by editing the map) no weapons other than Auto Cannon or Heavy Cannons loaded with Incendiary ammunition and carrying a spare clip or two of AP or HE, faced up against a squad of armored X-COM soldiers. Armored X-COM soldiers are immune to fire, so this would force the issue. (The Rocket Launcher could also be used, but due to the fact that the AI can 'unload' the weapon easily by firing the Incendiary rocket, the test results might be weaker.)

If the AI fires Incendiary shells at the armored X-COM agents, or does not fire at all, then it likely possesses no "unloading" code. (The AI may choose not to fire at all if it cannot damage the units; I'm not sure). If, however, your agents start getting pegged with HE or AP ammo(before the first clip runs out!), then it is clear that it can in fact unload and reload weapons. It may be beneficial to amp up the damage on the HE and AP ammo so it can present a threat to the agents. On a final thought, the Debug Mode hex edit would be useful for this test to monitor alien ammunition as well as if/when they reload. Arrow Quivershaft 00:48, 3 March 2009 (CST)

Again, from my tests at the StrategyCore forums (I believe it's in the "Strange Things In X-COM" thread, aliens are able to reload weapons. I know this for a fact. --Zombie 01:14, 3 March 2009 (CST)

I have no doubt the aliens can reload weapons, given they have both the Small Launcher and Blaster Launcher, each one shot weapons which they use often if given the chance. I was more referring to whether the aliens can unload a clip and then load in a new one. Thus why I suggested giving the aliens a useless weapon, with ammo that could then fix this issue, if the alien would only unload the first clip. Or am I misunderstanding what you wrote entirely? Arrow Quivershaft 01:17, 3 March 2009 (CST)

Um, no. I probably misunderstood you. Anyhow, from what I remember, an alien will always exhaust a clip fully before loading in a new spare. --Zombie 01:22, 3 March 2009 (CST)

That's what I figure too, since the number of times the situation would come up is so small its hard to justify the AI code for it. But I figure it should be tested nonetheless. Arrow Quivershaft 01:25, 3 March 2009 (CST)

Dud clips might be a good test. Just make a battlescape save, then edit the obpos.dat file and set the loaded ammo clips for all alien weapons to 0.

Also just tried the smoke grenades. No, they can't use them. It might be either one of two scenarios. They are only familiar with grenades set to their default HE setting and not smoke or proximity (being later additions - so it's "alien" to them). Or the usage of some obdata slots are hidden to them. Similar how only select special items have their menus available to the player. -NKF 01:27, 3 March 2009 (CST)

Ok in 2 out of 2 tests (!) a Sectoid Navigator armed with an unloaded Auto Cannon and a selection of HE and IN clips, loaded the HE clip both times. Between the 2 tests I reversed the position of the 2 clips ( 1 in backpack, 1 in belt) in case they were just loading the first clip in the slot list. It does look like they favour HE. Alien Intel is better than we thought - they know the strengths and weaknesses of our weapons, and their troops are trained to use them!

Sadly we did not pack any AP rounds in the assault ship - the quartermaster muttered something about them being "obsolete now dat you apes got da Heavy Lasers". (Time to break out BB's editor for some more extensive testing.)

A couple of tentative observations on loading / reloading. The aliens don't reload immediately, they continue on their patrol route (or retreat?) and only reload when they spot a target. This might be a good tactic since if they spot a human, other aliens can attack the target by various means. A hive mentality at work! Spike 11:20, 3 March 2009 (CST)

Spike: Good job! That is helpful, but try to get an AP clip in there. Perhaps the alien loads the highest clip in the order. HE is before IN, and AP is before HE. Alternately, I saw a hack that edited the game to HE was the preeminent clip used by the game over AP(in order that the game would auto-load HE clips into weapons). Another suggestion: Try again by giving the alien the Autocannon with the IN clip already loaded in, along with a spare HE clip, and see what happens. Arrow Quivershaft 11:55, 3 March 2009 (CST)

Alien Encumbrance

My next trials were frustrated. I couldn't find my copy of BB's map editor so instead I tried to rank a Laser Rifle against an unloaded HC-HE. (The alien picked a loaded HC-HE over a Laser Rifle (LR) every time, regardless of what was in which hand and whether or not that weapon was "selected").

But then I was stymied when my test Alien ran out of TUs. The weight of HC, HE clip, an alien clip and the LR was over 2x its strength (32 I think). Which sounds wrong. Even more wrong, its TUs were down to about 20-30% (not the expected 50%), 12-17, and didnt seem to be regenerating at all. So it couldn't load or fire either weapon.

All of which got me wondering if there aren't other factors in TUs, Encumbrance and recovery for aliens: maybe the size factors and unitref(45) factors get used somehow? Otherwise I can't really explain why this unwounded Sectoid was basically paralysed by the weight of human equipment. Anyone got any ideas?

One thing that just occurred to me: maybe there is a bug such that weight does not get subtracted when aliens drop things, but still gets added when they pick things up. An understandable bug since that would hardly ever happen. I will check that too.

Spike 14:33, 3 March 2009 (CST)

Might I suggest using Mutons for further tests? They have a Strength of 70, and are rather easy to Mind Control. Arrow Quivershaft 15:45, 3 March 2009 (CST)

Well I still don't know what exactly was happening. I checked and the weights are the same for Aliens when you add stuff and when you drop it. But for some reason this little Sectoid just ran out of TUs like he had a punctured tire. It did seem to be somehow connected to loading him up with Encumbrance above his Strength. Maybe.

Anyway I used BB's excellent map editor and gave my test subject some steroids (more Strength) and the problem seems to have gone away. I now have a test rig with him sitting on a stack of every weapon and item in the game, ready to try them all out.

Spike 18:47, 3 March 2009 (CST)

AI Weapon Preferences

I'm not sure I want to try every combination of preferences but here are a few AI preferences I've tested so far:

• Loaded AC-I prefered vs reload with AC-HE
• Loaded AC-I prefered vs Laser Rifle (always loaded)
• Loaded HC-HE prefered to RL loaded with Lg Rocket!!! Maybe due to range, or TUs, or ???
• Choice of rocket types:
  • Small then Large then Incendiary (regardless of placement order in inventory)
• Generally seems to prefer a loaded weapon to one that needs loading but...
• Prefers to load and fire a Rocket Launcher vs using an already loaded Pistol!

The testing is pretty sloppy and basic so far. Usually one target but sometimes multiple bunched targets in sight. Usually but not always changing the order of weapons in inventory to see if that makes a difference. I don't think it does. I don't think 'selecting' (as for a Soldier) has any effect. But possibly once an alien gets started with a weapon it might stick with it, so I try to start again from scratch (no weapons) when testing.

Spike 18:47, 3 March 2009 (CST)

Based on your result you got with the Rocket Launcher, I suspect it is simply using available ammunition in the order presented in OBDATA.DAT. This would also imply that it will prefer to load AP clips into the AC and HC over HE clips. This would also imply the computer cannot unload weapons, which isn't surprising. Arrow Quivershaft 20:26, 3 March 2009 (CST)

Yes! Testing your theory's prediction I found agreement:

• Ammo is loaded in this preference order: AC, HE, IN
• HC-AP is preferred to AC-AP

Both results follow OBDATA order.

So far so good. But also some anomies:

• HC-AP is loaded in preference to Rifle. Logical but not OBDATA order.
• Unloaded HC is loaded with AP and fired, in preference to an already-loaded Rifle.
• Heavy Plasma is loaded in preference to Rocket Launcher
• But an already loaded Rocket Launcher (Sm Rocket in the test) is fired (Aimed x 1) in preference to loading and firing a Heavy Plasma (Snap x 2).

So the jury's still out and more data is needed. It could be an OBDATA-like list such as used by the Equip screen defaults / 80 item limit. (I should check that list from Base Defence). It could even be some kind of basic firepower calculation, eg damage per round vs # of rounds that can be fired?

Spike 03:45, 4 March 2009 (CST)

I didn't mean to imply that the AI would always choose weapons based on the order on OBDATA. I meant that when it was presented with multiple ammo forms for the same weapon, it would load based on which came first in OBDATA. I figure the AI has some weapons calculations. I would say that perhaps it draws out of the list that determines the order in which weapons spawn, like in a Base Defense. But it can't be doing that, because then it would choose the Laser Rifle in preference to most other weapons. Though I wonder if the reason it ignores the Laser Rifle has something to do with the fact that the AI might be reading the Laser weapons as having 0 ammunition, and unable to find a clip, discards it as useless in preference to the weapon that is loaded or it can load? (And before you bring up terror units, I'll note that the weapons of the non-melee terror units do indeed have ammunition; they have 254 ammo, if I recall. Far more than they'll ever need in a single mission.) Arrow Quivershaft 19:07, 4 March 2009 (CST)

Aliens Use TUs to Reload

Seen this multiple times now, costing exactly 15 TUs as expected. (Based on known starting TUs, known firing costs, observed shots fired, and remaining TUs.)

This is not to say they never cheat. But at least when they have an unloaded weapon and spare ammo in normal inventory slots, they reload like humans. Not to say they might not cheat when weapons and ammo are in the "magic" slots. And also when the are initially set up, with unloaded weapons - do they load before they first fire?

Spike 03:45, 4 March 2009 (CST)

Cheat Detection Tests

This should be easy. I set the Alien's TUs to just enough to fire the weapon, not enough to load it. If the Alien still fires, looks like a cheat. If not, keep increasing TUs until he fires, to verify the Alien's TU cost of loading the weapon. Similar principle for detecting if they cheat on inventory move TU costs. First though we need to find out in what circumstances (if any) the AI moves items. Spike 18:47, 3 March 2009 (CST)

What about about switching to and from grenades? I know for certain that they'll shift the weapon to their magic slot to arm the grenade. Had this happen with an MC'd unit who ended up throwing a grenade at his allies. Finding the rocket launcher strapped to the solider's leg the turn later when I recovered him was a bit of a shock the first time I saw it!

I recall seeing aliens/MC'd units toss a grenade but end the turn without re-arming the weapon. This suggests that arming and throwing the grenade must've left them without sufficient TUs to put the weapon back. -NKF 05:04, 4 March 2009 (CST)

Interesting. The fact they even bother to move the weapon out of their hand before arming the grenade suggests they would otherwise get a penalty on the (grenade) attack - else why bother? Spike 05:21, 4 March 2009 (CST)

I have NEVER seen an alien holding an item of any type in its Left Hand slot(barring occasions where I placed the item there). Perhaps the AI is not programmed to use the Left Hand slot, so it has to move the weapon into the pocket to use the grenade because it can't use the left hand? Given the aliens never carry more than one firearm, and their only off-hand item is the Alien Grenade, this would be something the programmers might have skipped as not really being needed, especially in context that the AI would probably quickly stuff the grenade into that slot and thus ruin its own accuracy. Arrow Quivershaft 19:07, 4 March 2009 (CST)

Good points. Yes,Lasers are unique in having infinite ammo and the AI may see that as "no ammo", at least when making equip/arm decisions. Aliens will fire a Laser (tried all 3 types) but perhaps only if you put it in their hand. I didn't test it starting out in a backpack etc. Some more testing would be good, eg would the AI prefer a loaded Rifle to a Laser Rifle. Or try it in TFTD, where Gauss Rifles require clips.

Aliens can and will also fire a weapon from their left hand under AI control; and pick their preferred weapon if they have weapons in both hands, but as you say the AI itself never seems to place anything in Left Hand.

On the grenade question, I don't think accuracy of the grenade throw is affected by a weapon in the other hand (right?) but the AI programmers may be trying to avoid something else. Maybe if it has a weapon in its hand and does not complete the draw-prime-throw sequence with the grenade, it goes back to using the primary weapon therafter - at a permanent penalty. Speculation but easily tested. anyway, the current approach by the AI works fine, and actually I've always thought priming a grenade with a rifle in your hand was dubious. Maybe only humans have the ability to pull rings out with our teeth! Spike 15:52, 5 March 2009 (CST)

I've seen the aliens use lasers too, but that was under mind control and that was the only weapon they had available. As for the left hand, perhaps the AI is not programmed to put items there. If it was, perhaps the AI would hold the grenade in its left hand at all times, not even primed to throw or needed, and thusly incur a -20% accuracy to its main plasma weapon(presuming it's not the Plasma Pistol). This would obviously be undesireable! Arrow Quivershaft 16:03, 5 March 2009 (CST)

Honest AI? Major Tactical Implications

From observations (not rigorous tests) I am beginning to think that the AI sticks to the TU rules for inventory, and only 'cheats' in that it stores everything in the same "magic" inventory slot. But it looks like the AI pays 4 TU to pull items out of this slot, 15 TU to reload a weapon, 50% TU (?) to prime grenades, etc. If it does not have sufficient TUs, the AI doesn't perform the action.

It also seems to be the case that although Aliens start the game with all objects (including weapons, grenades and ammo) stored in the "magic" slot, they must move the objects (paying TUs) into the standard slots (hand etc) in order to use, load, fire, reload, prime, throw, etc (again, paying TUs for these actions). This is disputed, see below.

Spike 13:24, 4 March 2009 (CST)

Tactical Implications of Alien AI Inventory Management

IF THIS IS TRUE there are some major tactical implications. If Aliens deploy without weapons loaded and no weapons in their hands they have a serious disadvantage. This is a 19 TU deficit in any 'encounter' situation on the Alien's turn. Even more significant, it suggests a (weapon carrying) Alien will never reaction-fire unless that Alien has previously encountered a human enemy in its own turn phase, and had sufficient TUs left to draw and load its weapon.

This suggests that very aggressive 'lightning raid' tactics are likely to be successful, as Aliens reaction fire will be minimal and counter-attacks will be hampered.

It also suggests another tactic of waiting inside a vehicle until large numbers of unarmed aliens are milling around inside, then bursting out and killing them all with impunity.

Both tactics should work particularly well when the Aliens have no terror units with built-in weapons.

Spike 13:24, 4 March 2009 (CST)

No. Save game at start of turn one before doing anything, then turn-swap. Aliens will have loaded weapons equipped (basically, turn 1 is the only time all of them have three reaction shots).

I sometimes hack Turn 1 so that any alien that could reaction-fire at the exit is facing the exit. This makes the difficulty somewhat more credible. -- Zaimoni 11:42, 5 March 2009 (CST)

HOWEVER, I do not believe this is the case!!!

On EVERY mission I play, the aliens begin the battle with full TUs, and weapons loaded and in their hands. This is evidenced by the ridiculous number of times many commanders have had troops step off the transport and immediately killed by enemy reaction fire.

In fact, it is so bad that I usually only move my troops off the transport on turn 2.

Personally, the only time I have found an empty handed alien is: after he has thrown a grenade.

Jasonred 11:03, 5 March 2009 (CST)

OK this is very interesting as I observe different results. Are either of you using XComUtil? I am using a Win Collectors Edition version, via Seb76's loader, no XComUtil,and I see all the aliens with all their equipment in "magic" slot 2 at the start of the game. Nothing in their hands until they spot a human. Maybe a bug in Seb76's loader? Maybe a difference with DOS versions, or XComUtil? Spike 11:57, 5 March 2009 (CST)

NOTHING in their hands until they spot a human??? ... Spike. Are you playing on Easy? ... Cause in your game, it sounds like the aliens would almost never reaction fire, super sitting ducks... In my games, when I shoot at an alien during turn 1, and they survive, they invariably SHOOT BACK. ... So, what happens when 1 alien spots a human? Do all the other aliens arm themselves, or just that 1 alien? ... Curious... Jasonred 13:12, 5 March 2009 (CST)

Spike my friend, you broke the first cardinal rule of testing: you didn't use an unmodified version of the game. Tsk, tsk, tsk. Who knows what Seb's loader does exactly? Sometimes he's not even sure if his loader is bug-free. LOL. Anyway, my experience is the same as Jasonred's: aliens start with guns in their hands already loaded. The only time when a weapon is placed on the leg is after a grenade has been thrown. --Zombie 15:36, 5 March 2009 (CST)

Yes you're probably right. There's a difficulty here though, it's hard to tell. Seb76's loader is the easiest way to see what the AI is doing, because it shows you their turns. The only other way I know of to see the enemy turns is with XComUtil. I take it as read what Zaimoni is saying, that aliens start out armed in turn 1 of an XComUtil "switch sides" game. But do we know that it's not XComUtil that is 'fixing' the aliens so they have loaded guns in their hands at the start?

But I guess we have all experienced reaction fire when exiting the ramp so that does suggest that aliens start out armed. That has to be the presumption. Up to me to prove the contrary I guess, if I can. I suspect you are right though and it is probably some artefact of Seb76's loader. Spike 15:49, 5 March 2009 (CST)

The aliens start out armed in all matches I've seen; I never deploy on turn one. On a note, Seb's 'view everything on the battlescape' option is in fact an automated version of the Debug Mode I mentioned earlier which can be easily done with a bit of hex-editing skill. I'm not sure of the programmer Debug mode counts as unmodified, but I'm just explaining. Perhaps test with a personal hex edit instead of Seb's loader to find out. Arrow Quivershaft 16:03, 5 March 2009 (CST)

Human Inventory AI

It is not only Alien inventory that is managed by the AI - human inventory is as well. During the Equip phase of each mission, the AI assigns weapons and equipment to Soldiers from the available pool on the transport. It is interesting to compare this with AI management of Alien inventory. Clearly the processes are different, but there may be some common logic. In particular, perhaps the AI uses logic from the Soldier Equip phase, when deciding which weapons to use (on mind-controlled humans or, less commonly, on ex-mind-controlled aliens). Both sets of decisions span nearly the whole range of weapons in the game. Necessarily since late in the game Soldiers will be armed almost entirely with Alien weapons. This is why I suspect there may be some common or re-used logic. I'm going to research what we already know about the human-arming AI.