Intro
I couldn't find any info about it on the internet so I did some testing. If this post is a duplicate then please reply with the other post's link! Also note that I don't have any experience with posting on forums so if I make a mistake or neglect some rule then please educate me! Also note that some ideas are under second and third paragraph (including "Intro") but some are only in the last settings' explanations' paragraph (read it all).
I tested the mechanics by being neutral (under disguise) to NPCs. I did the test in Dark Valley Bandit base in the hangar with the disassembled APC (under the medic). When I killed the victim (NPC1, nearest NPC in the image) near the APC then his squadmate (NPC2, not in the image) walked over from the top floor to the body. NPC2 actually registered (noticed) the body (at least in the context of silent kill mechanics) when he was 20 m away. I think this is influenced by other game settings like overall NPC awareness. The test also included NPC3 who was from another squad (furthest NPC in the image). I tried different silent kill settings and scenarions and here are my conclusions.
Silent kill (the act of killing)
- If no-one (including NPC1) sees you and no-one sees NPC1 and squadmates of NPC1 don't "hear" the act then you can kill an NPC without any effects (neither negative nor positive e.g neither reputation drop nor goodwill drop nor rank value increase nor stalkers killed value increase). Otherwise it's a usual agression, usual effects apply and every squadmate will become hostile (NPC1 screams: "Murderer, he is there!").
- Since NPCs have x-ray vision (pun stolen from somewhere) then sometimes killing an NPC behind a bush or in a building with a small crack in the wall isn't enough because others see a few pixels of you. Also note that your character is actually a lot larger than it seems (see 3rd person view) so your knee might be poking out.
- Silent kill results in instadeath for the NPC even if you use the crappiest knife with the slash attack on Nosorog-wearing NPC aiming the NPC's little toe.
- If you one-hit kill NPC1 (axe to the head) but it isn't registered as a silent kill then squadmates will still become hostile (vanilla triology mechanic).
- You don't have to crouch/sneak for the mechanic to work. You can even sprint while hitting NPC1 or stand against (touching) his back. The problem with touching is that if you aren't directly behind the NPC or the NPC reacts to you for touching him then he sees you (not necessarily graphically) and according to the first point silent kill isn't possible.
- Feel_Fried's Quick melee reworked v1.6a | Anomaly 1.5.1 works well with silent kills. I can bash an NPC with my rifle and it still registers as a silent kill.
Getting detected (after silent kill)
- NPC must see both you and the body simultaneously to have any effect.
- Suspicion factors are locked with the death from silent kill. In other words changing the settings after you have silently killed an NPC has no effect for that NPC but has an effect for new silent kills.
- If you are in range of the body (doesn't matter whether you are just standing there or move in range after NPC has seen the body) while suspicion time is still active then NPCs become hostile but he has to see both you and the body simultaneously.
- NPC2 doesn't have memory so if he saw the body but you pull the body behind him then you can walk infront of him inside the detection distance from NPC1 but NPC2 still won't become hostile. However, if he walks so that he can see both you and the corpse again and you are still in the detection distance then he turns hostile.
Silent kills' settings and more in-depth explanations
- Settings are in Main menu => Settings => Gameplay => Stealth kills. I will always reference the mechanic by "silent kills" not "stealth kills".
- Enable silent kills - turns the feature on. If it's off then after killing NPC1, NPC2 will be hostile even if he hasn't seen you nor the body nor "heard" anything (even if you shot NPC1 in the back of the head).
- Allow silent kills with melee weapons - if this is off then silent kills aren't possible with melee weapons (like silent kills aren't enabled)
- All melee weapons are valid for silent kills - if this is on you can use any melee weapon (give him the axe!) but otherwise only weapons with silent kill ability specified in the weapons' files can be used. By default only Spetsnaz switchblade can be used if this option is off.
- Allow silent kills with silenced guns - if this option is off then silent kills can't be made with guns. Also unsilenced guns can't be used for silent kills at all. In case of silent kill it doesn't matter how much damage your shot does just as with melee.
- Headshot necessary for silent kill with guns - when this option is on then you can only shoot NPC1 in the head for silent kill to register. If the option is off then as with melee in case of silent kill it doesn't matter where you shoot the enemy.
- Suspicion time after silent kill - time in seconds after the silent kill during which the body of NPC1 is relevant. After this time has passed it doesn't matter what you do because NPC1 is forgotten by NPC2. In other words teabagging the corpse doesn't bring any hostility from NPC2 after this amount of time has passed as if NPC1's corpse doesn't exist.
- Player distance from corpse for discovery - if you are this far (in meters) from the body during the suspicion time and NPC2 sees you and the body simultaneously then he turns hostile.
- Melee silent kills minimum witness distance - if another squadmate is in range of that distance (in meters) then he will "hear" the act of hitting NPC1 (you know, the gurgling sounds and a quiet thump as you lay the body down) and silent kill fails like you would have hit NPC1 while someone saw the act. NPC3 from another squad doesn't care about sounds, he cares only about visuals.
- Gun silent kills minimum witness distance - same as for melee but now for shooting. NPC2 doesn't "hear" the gun shooting but "hears" instead the bullet hitting (or body dropping). In other words in order for silent kill to register NPC1 and NPC2 have to be that distance apart. You can even stand next to NPC2 if he doesn't see you and he doesn't bat an eye for you shooting someone while standing behind him.
2022.03.26 additional info
Currently you get nothing except for loot when you conduct a silent kill. It's as if you never killed the guy, no goodwill, no rank increase, no money in warfare mode. I made a mod ( Moddb.com ) that increases kill statistics, gives you increase in rank (a.k.a experience) and reputation just like with other kills. Also in warfare mode you get money, goodwill (if Alife Overhaul is installed) and influence.
Edited by: Banjaji
