Alien psionics - how does the game determine whether or not it can attack me?

[Markus Ramikin]

I know that if aliens spot even one of my soldiers, my whole squad is vulnerable to psi attack.

My question is, is this just for that one round, or does my squad get permanently flagged as "detected and open to psi attack" for that whole battlescape session?

I'm asking because it seems to me that I've been subject to psi attacks when there was no way in hell any alien saw me during their round. But maybe I'm just missing something.

[NoelBuddy]

Once spotted always spotted.  This is why LoS for Psi attacks is among the default mod options. Warning tho, the LoS option will nerf the aliens pretty severely.

[yrizoud]

Sometimes aliens can see your soldiers without you, the player, seeing them.
- First, if there's a blind spot in your defense (aliens approach from a side that none of your soldiers are watching. For example a floater sneaking over a house in your back)
- Second, there seems to be cases where a unit is "visible", but displayed in black over black tiles. I had this situation one time on the "mountain" landscape : Low mountains blocked my sight, but an alien stepped and stayed on a single knee-height rock, so his head could be sighted by my soldiers.
- Third, some maps (especially UFO maps) had "logic holes" in them. Map patches correct most, if not all of them
- Fourth, I think I've found a bug where units at extreme distance can see each other, but are not displayed on the screen. This can explain cases where your units reaction-fire an alien before it even appears on your screen.

[Markus Ramikin]

Once spotted always spotted.

I see, thanks.

I guess as unfair as it seems, it does nicely contribute to an atmosphere of dread, of enemies striking at my team's minds from nowhere.

This is why LoS for Psi attacks is among the default mod options. Warning tho, the LoS option will nerf the aliens pretty severely.

Yeah, the game isn't difficult enough for that. Especially if it involves nerfing Ethereals, which are my favourite alien race ever. (Well, almost.)

[Warboy1982]

I know that if aliens spot even one of my soldiers, my whole squad is vulnerable to psi attack.

false.
no idea where you got this notion.

Once spotted always spotted.

also false.
being spotted sets a counter, specific to that unit, to 0. the alien's intelligence score is compared to this value to determine if the alien "knows" said unit's position.

This is why LoS for Psi attacks is among the default mod options.

also false.
it was included because it was something in ufoextender.

[Falko]

I know that if aliens spot even one of my soldiers, my whole squad is vulnerable to psi attack.

false.
no idea where you got this notion.

really i always thought that was the case
from https://www.ufopaedia.org/index.php?title=Psionics#Psionic_Aliens

If an alien spots any member of your squad, even the tank, during the alien turn, the squad is at risk of attack.

[Hobbes]

false.
no idea where you got this notion.

Does this mean that the whole squad can be attacked regardless of whether the aliens have spotted one of your units?

[Markus Ramikin]

false.
no idea where you got this notion.

Ufopaedia, like Falko said above.

[Warboy1982]

Does this mean that the whole squad can be attacked regardless of whether the aliens have spotted one of your units?

no.

[kikimoristan]

 Aliens also see way farther especially during night time i think 20 for alien vs 9 for human. So once anyone in their team spots you they will psi attack you even if you hide. Correct me if I'm wrong.  If it functions like original Xcom they also remember where you used to be and kinda make up decisions based on where they last saw you.

[7Saturn]

I also wonder, if the AI has any means to determine the likelyhood of a successfull psi-attack. I noticed, that fully psi-trained soldiers, with psi 100 or so, never seemed to be target of an attack. Does the game simply not give any notification (in this case, the shreeking psi-attack-sound), when aliens don't have any success, or don't they even try, when there is no chance of a successfull psi-attack?

[Arthanor]

Aliens will try to psi-attack the weakest soldier to psi that they are aware of, so they have a certain sense of "likelihood of success". It has generated the "bring a psi-rod soldier" strategy (named after lightning rod, a psi-weak soldier that gets hit by all the psi-attacks).

As far as I know, aliens would attack psi-strong soldiers in the absence of weak ones in vanilla, but that might have been fixed in the AI for OpenXCom.

[7Saturn]

It has generated the "bring a psi-rod soldier" strategy (named after lightning rod, a psi-weak soldier that gets hit by all the psi-attacks).

And give him pretty much nothing, so he won't turn on your own soldiers. Yeah, I know that tactic. =) But as your soldiers are getting better and better with psi, there seem to be no attacks at all going on, after a your soldiers have reached a certain minimal level of psi-competence, each one. Looks pretty unfair, if the AI already knows, that psi-attacks are futile, saveing it's TU's and so on for something more useful...

[Dioxine]

Don't forget the fact that if the aliens manage to MC a soldier, everyone *he* sees also becomes spotted by the aliens. Hence a single successful MC often exposes your entire squad. Plus - I don't know if it's true, but I think that every time an alien attempts a psi attack on a soldier, his "spotting clock" seems to be resetted so they can gang up on this soldier pretty indefinitely.

[kikimoristan]

depending on difficulty level aliens will remember units for a certain amount of turns. what that means is if you been spotted and you run away you will still get MCd for a bunch more turns. more fair is line of sight req for PSI makes the game less hard.

this difficulty based memory gets used by aliens for various things like making decisions where to go if to shoot in a certain direction or throw a grenade etc.