What's up with the wallhacking AI?

[Lasse76]

So, I have just been on two missions in a row on Normal/Ironman, where the AI is laying waste to my soldiers through blatant wall hacking.

First mission, first incident. I run around a corner with a shield and spot a Harridan. The shape of the walls are so that I can run back and into cover... or so I thought. LOS was lost for the Harridan, yet it lobbed a grenade straight at the wall between us, and even though I was one square away from that wall, it got me.

As the walls formed a H between us, with him at the buttom and me at the top, I felt safe, because the Harridan would have to navigate two corners and turn 90+ degrees from the direction of travel to reacquire LOS, and there was no way it could have seen me choose my position. I had both corners covered by two soldiers, so he would have been spotted and hopefully fired upon had he tried. So... he didn't check my position, go back and lob the grenade as he was not spotted. It was a small enclosure, with hedges and walls all round, and I had all the other approaches locked down. There was no way to get LOS on that soldier, so there was no other spotter. Yet the Harridan just KNEW I was there, even though I could have gone several other places. Since I have never seen the AI throw prediction grenades, the conclusion is obvious.

Next incident involved putting the UFO entry gate under surveillance. An MG was trained on the door from a distance with the MG providing it's own LOS. The AI never opened it, while I scouted out the rest of the map. We are talking perhaps 10 turns. As soon as I placed MGs trained on the doors from a closer distance, a Sibillian guard appeared that opened the gate every turn and patrolled the entrance. It was the exact same turn.

Since I repeatedly failed to catch him on reaction fire, I dispatched him with a bomb, which also blew the gate to pieces. Having no covered approach, I put three soldiers on each side of the gate about 2-3 tiles away from the entrance, flush to the UFO, MGs still trained on the entrace for reaction fire. That gave me 100% block on shots and grenades on the two split squads, unless the AI came out of the UFO, which they had not done previously.

The very next turn a Sibillian runs exactly one tile out from the UFO and grenades three soldiers. His positioning was perfect to avoid reaction fire from anyone but the MGs, and they didn't fire. He knew my entire deployment and exploited it to maximum effect. It was so well timed, that the Sibillian didn't even have TUs to move a single tile after that, so wasn't just lurking at the entrance just out of sight. All 3 soldiers took heavy damage, but survived and I just managed to patch all three up, as they were all bleeding out.

I dispatch the wall hacking grenadier, holding the same positions. One soldier was sent back to the drop ship to pick up additional grenades and ammo, which took some 6-8 turns. No enemies appear. I put the inside of the UFO under observation exactly at the border to the entrance. Fire coverage is provided by the two MGs with a kneeled shield in front of each. Nothing happens. I wait several turns and nothing happens. I move the squads in, in a split, with shields leading and an MG behind each and everyone else spread out in the middle with cover from the teleports. All guns point there. The very next turn a Sibillian uses the left teleporter, moves off it, triggers a series of failed overwatch and one soldier ends up shooting one of my other soldiers with a miss. Like... nothing happened for several turns, but the exact moment I entered the ship, he knew I was inside.

The Sibillian retreats to the teleporter, and I change the setup on the left slightly to maximize reaction fire and avoid friendly fire. Big mistake as two Sibillians enter on the next turn with one of them grenading three soldiers now standing in a small cluster. I end up losing one. The other Sibillian shot the shield and destroyed it. No TUs left for any movement for either Sibillian, which left them ripe for a counter attack. But my gripe is this... No one was on the lower deck, so how did they know I had entered the UFO? And how did they know on the second turn that I was open for that kind of attack? Surely there is no LOS from the upper to the lower deck!

Next mission, I land in a farmland setting. I exit the dropship and set up cover to the left and front, as I am in a corner. Field in front, road top/left. Hedges line the road and the field. On the second turn, I have group of 4 soldiers in breaching formation at the road entrance. The rest is spread out across the field, with one being a few tiles from the hedges. I hit end turn, and "click" a grenade split is pulled and tossed over the hedge. No aliens spotted. But he just knew I was on the other side of the hedge. What's even more disturbing, when I decided to scout for a spotter outside my vision range, I find none with some 70 TUs spent running from the field... There is one outside the field, but he is more than 10 tiles away from a spotting position, and he would have had to turn at least 4 times and jump a low hedge. With 60 being top TUs for a Caesan, this could not be the spotter. Also, he spent his turn killing a farmer - at least he was looking straight at the corpse while standing in the open.

When I turn the corner with my breaching squad, I find two Caesans flush up against a hedge, splitting the back area, right where the grenade was thrown from. And they are both as far away from the breaching squad as they can be, with two rows of 100% blocking cover in between me and them, which they are not using for anything else than line of fire cover. So not only did they know where to throw a grenade over a hedge on an unspotted soldier in cover, they knew that I had a squad ready to storm them from the other side. That squad could never had been spotted by any alien, as I landed in the corner of the map, and everything was walled off by hedges and the map edge, including the road that I was preparing to storm. From the field side, I had vision from at least 10-15 tiles away from that squad, which was the only other approach to achieve LOS. As far as I know, that AI does not get some 15+ tiles of vision to spot.

Needless to say, that's a rage quit. I don't mind that the AI gets extra vision to compensate for the difficulty of programming AI. I also don't mind that they can borg spot, because I can do the same, so we are playing the "same game". But I do mind the AI wall hacking like this. What is the point of a tactical game like this, which has not only a blacked out map that has to be explored and fog of war, if the AI is hindered by neither of these things? I don't see the point of playing the game again under these conditions.

Experimental branch btw. I suspect this could be a "feature" here, as I have noted that the AI is very aggressive from the start and storms the drop position right from the get go... Which I don't recall it doing in the same way in the stable branch.

Edited March 4, 2016 by Lasse76

[Chris]

So there's no changes to the AI in the experimental branch, but I believe there are some changes to the line of sight or at the very least a change to the shooting to stop miss shots going through walls. It might be that they are having unintended consequences with regards to the aliens gaining more vision than they should?

[Lasse76]

Yeah I switch to experimental to get rid of the miss go through walls bug, as I got more than my fair share of team kills because of that. I can say for certain that something is horribly wrong with enemy LOS in the experimental branch, but I can't set up experiments or provide savegames that prove it, due to how long it takes to progress in the campaign to where the AI uses grenades regularly. I would advise you to use whatever dev tools you have to set up a scenario where the Aliens cannot see a soldier, but they are well within grenade range, and then see what happens. I am almost certain you will get a grenaded soldier, thus proving the problem.