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Thread: Improving on the stealth genre

  1. #1
    Member
    Registered: Apr 2011
    Location: Montpellier, France

    Improving on the stealth genre

    Hey taffers. I have a simple question for you that should hopefully produce complex and interesting answers. I'm posting this in ThiefGen but it doesn't necessarily apply to Thief fans only.
    Thief is 22 years old. We've seen many stealth games since then; Metal Gear Solid, Splinter Cell, No One Lives Forever, Mark of the Ninja, Dishonored... the list goes on. Still, it's hard to argue the genre hasn't evolved a whole lot since its inception considering Thief's mechanics are usually said to be the best and most robust of them all, especially when it comes to sound tech.

    So, in your opinion and with hindsight, what aspects of the stealth genre should/could be improved to create better/more fun experiences?

  2. #2
    Member
    Registered: May 2004
    I think you could argue that The Dark Mod has at least some improvements on the original formula and that other games have at least taken it to different directions -- for example Hitman with its social stealth.

    So that's also the answer, I think -- you could improve on the original formula by creating a better AI that's more fun to play with, better physics to aid game design with puzzles and whatnot, better world simulation for more reactivity to make more use of social stealth, and so on.

  3. #3
    Member
    Registered: Oct 2019
    Location: Poland
    The field where most meaningful and crucial improvements could be made is definitely AI, which plays a central role in this type of games. First of all, NPCs should have a much more persistent memory and number of states to accomodate to whatever way the player affected them in. Say, in case you managed to alert the whole mansion, guards should realistically never return to fully relaxed state, or the time needed for this to occur should be very long, provided you'd be able to flee and stay undetected for the cooldown to happen.

    Another kind of thing i pondered about before in Discord server, is the audio propagation and AI's responses to it. Dark Engine doesn't account for the influence of the external noise sources, which could affect the chances of AI hearing you. It's gonna be easier to understand looking at this diagram:

    Assuming the green pentagon is the player and remaining pentagons are enemies, the chances of the AIs getting alerted by the player's actions should be resultant of some kind of equation between the influence of all audio sources in the proximity, with my picture presenting what is probably the most naive method.

    Last thing that comes to my mind at this moment is shadows casted by player which should be visible to the AI, making it possible to alert them that way.

  4. #4
    Member
    Registered: May 2004
    Another thing to keep in mind is how the player is able to take all of this into account and react accordingly. Something like player loudness in contrast with the level of ambient sound at the player's current location might be more immediately understandable and translatable into gameplay actions.

  5. #5
    Member
    Registered: Apr 2011
    Location: Montpellier, France
    Starker: yes of course, my phrasing isn't a jab at TDM or Hitman that are great stealth games too and do things differently. I thought about loud areas impacting AI hearing as well, and have diegetic indications such as signs in the world that say "wear hearing protection beyond this point", or something like that.

    Midori: nice! Your three points are exactly what I think could be improved as well, especially a visible shadow and proper AI behavior on high alert. I would even go so far as to think having the player's silhouette against lit surfaces visible could be interesting, but I don't know exactly how this could be communicated in a simple way. For example when you are in a shadowed doorway but the wall behind you in the next room receives light, you should still be visible.

  6. #6
    Member
    Registered: Mar 2001
    Location: Ireland
    I think a really important thing to bear in mind is that gameplay has to be more important than pure realism.

    Thief generally manages to strike a really good balance in this area.

    Improving the AI to make them smarter and more realistic is only valuable if that increased intelligence makes them more fun to play against.

    For example, if you are ghosting a guard and repeatedly run around behind his back at different times, each enough to illicit a comment but not enough for him to start searching, then that guard would realistically remember that he's heard suspicious sounds 26 times in the last half-hour and decide to go on a higher alert. That would be realistic, but it would make for awful gameplay, as you'd effectively have a limited number of times you could go past the guard before that path becomes permanently locked out to you.

    Good stealth characters need a good balance of both artificial intelligence and artificial stupidity.


    The same should generally apply to other mechanics, too. Does a proposed addition add more interesting gameplay, or just more frustration?



    Another point is that the systems also need to be understandable by the player.

    I was recently playing around with an AI perception system where everything was numeric, with floating point precision. A sound could be 35.53% suspicious, then another sound could be 37.25% suspicious, and combined they could be suspicious enough to make the AI reach high alert, but then there was an environmental background noise that blocked 27.53% of the sound, so it wasn't a high alert any more.
    That whole system was so complicated that it would have been impossible for the player to easily grasp what was going on, especially with how variable it was based on slight changes of distance. (I was even having trouble coding the AI behaviours against it because it was so complicated.)

    The lesson that I learned there was to keep the systems simple. Having a sound be "low alert" suspicious at a given distance is much easier to work with and to understand than having that sound be "12.53% suspicious" at that distance.



    For the actual question, I think one thing that I don't see enough of is AI manipulation.
    Being able to adjust the world so that the AI react in certain ways which will be beneficial to you.
    At its most simple, an example would be turning on a generator so that a guard leaves his post to take a look at it and turn it back off, allowing you to either blackjack that guard while he's alone, or get past his post while he's not there.
    Last edited by Nameless Voice; 17th Apr 2020 at 08:24.

  7. #7
    Member
    Registered: May 2004
    I think I'd like to see some better simulation in general. Proper schedules for NPCs, fire burning things (Underworld Ascendant), ice freezing things (T2X), etc. Thief was already remarkable in that you could trigger/disarm traps with objects and push buttons by shooting arrows at them (compare and contrast with the conteporary Half-Life the rebooted Thief 2014, for example), but I think this could be taken much further.

  8. #8
    Member
    Registered: Apr 2011
    Location: Montpellier, France
    NV: excellent points! Balancing fun vs realistic is definitely the biggest challenge when it comes to AI. You want your AI to be clever but not too clever, otherwise it becomes tedious to play since you have the feeling the computer is cheating. I prefer using the word believable versus realistic, since believable things don't have to be realistic, they just need to make sense in the context of the world the game is showing you and its internal rules.

    Starker: yeah, NPC schedules fall within the believable spectrum to me. It would be interesting for example to have a guard working night shift check out a few rooms every now and then along their patrol route, but not always, and have them be relayed by another guard so they can exchange their shifts after maybe 30 minutes.

  9. #9
    Member
    Registered: Apr 2011
    I have thoughts, but they're all a jumble, so I'm just going to respond to some of the suggestions specifically, and try to put together some more general thoughts later:

    Having loud ambient noise mask player noise is something Thief ought to do already: it's obvious for the player, because their experience of sound in the real world works this way; and the audio implies it already: the player can't hear their own footsteps over all the noise. But the game's audio system doesn't work this way. So this is an area where Thief's sound design is lacking. (Footnote: LGS evidently experimented with this idea for Thief 2: the "Loud Room" property—unused in the shipped game except for one room where it's applied but turned off—dulls sounds that travel into or out of it; but not sounds within the room. It looks like a relatively quick attempt to build a noise-masking feature using the existing sound propagation system without the schedule-wrecking complexity of changing the AI reactions to sound cues.)

    Leaving aside the question of whether being spotted because of your shadow or silhouette is fun or not, making it effective is a problem of player awareness: if the player is not aware that they're visible, they're going to feel like the game is unfair when they get seen. Thief already has an uphill struggle getting players to understand their visibility in light and darkness, even with the light gem communicating this. Most players still operate on the idea that if the ground is dark then they will be hidden there—even if the surrounding light and shadow shows that only their feet and legs would be shadowed. In addition, much of Thief's success in stealth is that its design allows players to observe enemies while remaining themself unobserved; if standing in an open doorway or perched on a high ledge made you more visible (as is likely the real world), this has knock-on consequences for the player's ability to learn about the level and play purposefully instead of merely reactively.

    Thief's AI is much more complicated than most people understand, I think. Take Meowdori's suggestion: an AI that has seen Garrett (reached level 3 alert) will already never go back to their fully relaxed state" (level 0 alert)! They only go back down to level 1. It's true the game doesn't do much with this; the default AI senses and behaviour at level 1 and level 0 are similar enough that only supreme ghosters tend to worry about it; although I think most players have probably had the confusing experience that sometimes in full darkness an AI can walk right into them without seeing them, and sometimes they will discover you when they walk into you; the former happens at level 0, and the latter at level 1. And the only feedback the game gives to communicate this different alertness level is that an AI at level 0 will whistle and hum to themselves; at level 1, they never do, only mutter and grumble. So this is all quite non-obvious to the player already! Which gets right back to that question of feedback and player understanding.

    Similarly the question of numerical vs symbolic levels of 'suspiciousness' and the like that Nameless Voice brings up. Thief's AI awareness, both visual and aural, is a numerical simulation, with stimuli causing changes to awareness based on how intense and how frequent they are. The AI responses to their awareness however (their alertness) happens when their awareness reaches a particular threshold. And this is complicated by an AI's senses (and thus how quickly their awareness changes) also depending on their current alertness level. As NV says, numerical systems like this end up being difficult to design with (as any FM author who's tried to adjust AI parameters could tell you) and even more difficult to communicate back to the player. Thief even does a bad job of communicating AI alertness levels! A guard can be still at high alertness and patrolling seemingly unconcernedly, only to notice you creeping up behind them and swing around, as if they had eyes in the back of their head (again, something most players have probably encountered and been confused by). Thief's AI mostly communicates if they are in combat, or searching for you, or just walking around; these are largely correlated with alertness levels, but not identical to them.

    I really don't think there's much to be gained for the stealth genre by making more complex AI simulations than Thief's already is.

    Edit: a brief comment on burning and freezing mechanics: usually these are just fancy lock-and-key systems or fancy magic-spells-to-kill-opponents. I think the only game that has done fire well is Far Cry 2: and there, fire is a hazard. You can set things on fire intentionally, but it's as likely to get out of hand and hurt you as to help you. And you usually wouldn't try stealthing through an area that's on fire, because it's way too dangerous and unpredictable. (Far Cry 2's stealth system is probably worth another shout out for a detailed system that's badly communicated to the player, and so ineffective and confusing for most players—but highly engaging and effective if you do learn how it works.)
    Last edited by vfig; 17th Apr 2020 at 15:17.

  10. #10
    Member
    Registered: Apr 2011
    Location: Montpellier, France
    I understand the problems that are brought up with shadow and silhouette. Doesn't the AI in TDS notice Garrett's shadow? In any case, I think this could be mitigated somewhat by levels using spotlights effectively thus making the player's shadow quite long and obvious, and have NPCs comment on it if they see it "whose shadow is this?". Of course this is all theory, and maybe it sucks in practice but I'd still like to see this tried to see how well it works.

    You're also correct about the AI not communicating the difference between Alerts 0 and 1 well enough, which is something that should be touched upon in my opinion. I think one thing that can communicate this better is NPC stance, they are relaxed on Alert 0 and look visibly more cautious on Alert 1, and so on, and could also have routines where they stop to check their surroundings while they just go on their merry way on Alert 0.

  11. #11
    Member
    Registered: Mar 2001
    Location: Ireland
    One of the things I was talking about with the levels, which I don't think I was really clear about, is that while obviously AI perceptions are going to be based on numbers and mathematics, those numbers should be turned into discrete states as early as possible, rather than only at the end. That makes everything much easier to deal with, and correspondingly also easier for the player to understand.


    An easy way for AIs to advertise their alertness is for them to ready their weapons. An unaware AI would have their sword or gun sheathed, and would draw it when they are suspicious enough to think that they might need it. That would probably be at Alert 2 in Thief terms, though. Drawing a weapon for Alert 1 seems excessive.

  12. #12
    Member
    Registered: May 2004
    Quote Originally Posted by vfig View Post
    Edit: a brief comment on burning and freezing mechanics: usually these are just fancy lock-and-key systems or fancy magic-spells-to-kill-opponents. I think the only game that has done fire well is Far Cry 2: and there, fire is a hazard. You can set things on fire intentionally, but it's as likely to get out of hand and hurt you as to help you. And you usually wouldn't try stealthing through an area that's on fire, because it's way too dangerous and unpredictable. (Far Cry 2's stealth system is probably worth another shout out for a detailed system that's badly communicated to the player, and so ineffective and confusing for most players—but highly engaging and effective if you do learn how it works.)
    Yes, these very issues came up during the development of UA. Is it worth simulating an entire ecology if it happens off screen for the player and they don't get to see the cause and effect, for example? Not to mention that the player needs to visit the same locations frequently enough to observe the changes in the first place, not something very likely to happen in an action title.

    And of course the simulation can go too far -- it's very easy to end up in UA with the whole level on fire, for example. But I think there's also a lot of fun to have with systems like these and lots of potential for real gameplay applications... freezing a patch of hazardous water to walk over it, breaking otherwise unbreakable lanterns by heating and then freezing them, setting something on fire to get NPCs run over to extinguish it, being able to break a wooden door apart and use a splinter as a makeshift torch, and so on.

  13. #13
    Member
    Registered: Oct 2019
    Location: Poland
    I think Nameless actually has a good point there, it's easy to cross the sweet spot boundary and make it too focused on pure realism at the expense of enjoyable gameplay (though it also depends on what people deem to be enjoyable for them, because this will naturally vary across players).

    I think i might be looking at this from a perspective of someone who's willing to try the hardcore realism (in case i fuck up badly, i can always load a save, which is not a problem for me personally). Can't tell if this would work out for me or not in the long run, but it would still be interesting to see some of these ideas come into life, as Skacky mentioned.

    Also i learned something new today, thanks to vfig. I didn't know about the the subtle difference between the two lowest alertness levels and the fact that once raised it never returns to the 0, that's nice to know.

    Thief already has an uphill struggle getting players to understand their visibility in light and darkness, even with the light gem communicating this. Most players still operate on the idea that if the ground is dark then they will be hidden there—even if the surrounding light and shadow shows that only their feet and legs would be shadowed.
    Honestly that's a foreign perspective to me, i never relied solely on the ligting level of the ground immediately under my feet, but i can see why many people might tend to think of it this way.

    The idea brought up by Skacky, concerning player's visibility, while your silhouette, even while totally hidden in the shadow, should be visible against bright backgrounds also crossed my mind many times, and i'd like to test it in action, personally.

    And yes, i very much agree with the idea of more complex NPC activity schedules, that would make for even more immersive gameplay without making it harder to grasp or feel too hardcore.

    Among other things i pondered about, i'd like to see the AI actually react to any environmental changes caused by the player that look obviously suspiclous (weirdly mislocated objects, rope arrows left stuck in wooden rafters, etc, etc - we already have the mechanic of guard reacting to blood stains implemented, but i'd love to see it being taken to a higher level)

  14. #14
    Member
    Registered: Oct 2004
    Location: Ireland/Poland
    I'd like to give AI stronger navigational abilities like climbing/jumping over small walls or 'cliffs' (let's say around 4 units tall in Dromed) and give them ability to climb ladders. Ladders are sometimes the only way to enter certain area and seeing AI in let's say attic, without stairs access is a bit unbelievable, knowing that they cannot climb. Of course player would still have a lot of advantage, like jumping from a ladder onto another one or onto a ledge or mantling over taller obstacles etc... The levels would have to be designed around these AI skills, of course, to make it balanced, but I think trying to escape from such a chase could be thrilling!

    I also would like to see some "weird behavior" awareness in AIs. Let's say, if a bystander sees you climbing a wall on the street, or jumping over food stalls, throwing boulders and pot plants or just doing anything that is not considered 'normal' in a typical society they would be let's say shouting at you (telling to stop, giving warnings) or/and call for guards and in general bringing attention...

    On the other hand, giving more abilities for the player. I kinda liked the idea of hiding in wardrobes in Thi4f (I only played like 2 levels of that game though), but the execution could be better. This could be potentially expanded on hiding under beds, behind curtains etc... And doing that trick - like assuming an X pose at the ceiling of a narrow corridor, so the guard running after you just runs by, without looking up! A bit cartoonish, I know, but could be interesting (but there would be only so much time you could stay in such a pose, so it couldn't be overused). I also would like to see ability to push things by punching or kicking and to have more than one action per item.

    As for the silhouette detection. This most likely would be impossible to implement in a controllable manner, where too much aesthetic decisions would conflict with gameplay and vice versa (colour of the walls, placement of lights even more restricted etc..). Plus, how would you communicate to a player who of the multiple AIs that have a line of sight with you, can actually see your silhouette? It's an angle dependent thing, unlike the current visibility algorithm. I mean I'd like to see this implemented by somebody somehow somewhere, but just have doubts this could work well, without being frustrating...
    Last edited by PinkDot; 18th Apr 2020 at 11:49.

  15. #15
    Member
    Registered: Oct 2019
    Location: Poland
    Oh gosh, i love every single idea PinkDot just came up with!

  16. #16
    Member
    Registered: Oct 2004
    Location: Ireland/Poland
    One more idea - since stealth games are all about light and shadows - I have not seen a game that allows you to close blinds or curtains on the windows. Again I have not played many stealth games, but due to engine constraints, it was impossible to change the effects of natural (sun/moon) light in original Thief. But with modern engines there should not be a problem.

    As for the tools - kind of a smoke bomb, creating dense localized fog, effectively blocking view (naturally for the player too).

    Also - leaving trails of water, mud or snow, after contact with those. Some kind of wiping or drying ability could be provided. (like stand for 30 seconds beside a fireplace sort of thing... or maybe finding cloths in the environment).

  17. #17
    Member
    Registered: Apr 2011
    Location: Montpellier, France
    Excellent suggestions everyone. Yeah the silhouette idea is just a musing, I realize it may very well be completely impossible to implement and even if it was, may be completely unfun. I agree that the AI needs to be able to vault over obstacles, climb ladders and jump over gaps, I mean a game like Kingpin: Life of Crime had that already twenty years ago so it's definitely possible to do. Alien: Isolation allows you to hide in lockers and in Dishonored you can also hide under tables or props that have enough space to crawl under, so it's not unheard of and is very nice to see.

    Smoke bombs and trails of water etc: yes, I also considered that (especially the smoke bomb). One idea I had a few years back is extremely similar to yours PinkDot and was to have a rainy level where you had to seek warm places (radiators, etc) for your clothes to get dry otherwise you'd leave puddles everywhere. Not sure however if this would be fun.

  18. #18
    One of the things that is great about thief is the attempt to use npc memory/awareness of the environment. "Hey, who left this door open?" or "Who put out this torch?". But it is implemented in a very inconsistent manner. Sometimes something is missing & they come searching the shadows for a minute or two, but often they just ignore it. I mean they have been guarding this same area or traveling the same route for weeks or months. Guards should notice any little thing out of place & react more intelligently than they do. It seems when they do notice things (insignificant or significant), it only bumps the alert up one level. If you are left to guard manor with the most valuable gem in the region, an open window on your route where no one ever goes but you - this should set you on high alert & send you interacting with other guards. For example: I notice the window open, I go high alert & search the room for several minutes all shadows, etc. Then I go to the guard nearest me and ask him if they were smoking by the window again (they have been repremanded previously for doing this by the lord of the manor), if not then I go alert every guard on the floor.

    As someone else mentioned (and builds on my comment above): the guards should notice things turned on / off that are not supposed to be and change them back. These would be items that are not of high alert significance. Imagine if guards would relight the torches on their normal routes? That would require much more planning on the players part. Or closing doors that you opened. If they notice too many torches go out or too many doors are left open, then that should set them to alert the other guards. More realism & challenge.
    Last edited by Estel Randir; 27th Apr 2020 at 10:29.

  19. #19
    Member
    Registered: Apr 2011
    Years ago I had a big discussion with CrashT about Thief and Dishonored and the stealth genre. Some parts of it are relevant here; the biggest point is that stealth is not a genre: it is a game mode.

    One of the key design decisions for a stealth game is What happens when stealth fails? In Thief, you fall back into awkward combat or comedic running away, or (if you're on your toes) flashbangs or invisibility potions to recover stealth mode. In Invisible Inc, failing stealth immediately ratchets up the difficulty for the rest of the level, and also, if your agent was seen by an armed enemy, turns into a one-chance-to-fix-it instadeath puzzle. Many shoehorned-in stealth missions in generally non-stealth games just instafail the mission, which is very unsatisfying. The design of events that trigger failure and of your failure modes will greatly affect how your stealth game feels.

  20. #20
    One detail that could be fun - guards reacting more to increased numbers of small things.

    For example with torches guards could ignore the first one or two (based on difficulty) but at more than that consider it 'odd' and make them a bit more suspicious, a bit more sensitive, at least for a while until they calm down. Another thought is that they could relight them once they've seen a few out. Servants on the other hand might immediately relight torches as that's their job, while guards consider it something distracting them from more important work. That would add more of a danger to the harmless servants, while making it harder for the player to abuse guards' AI by getting them to stop their patrol to relight a torch.

    Loot disappearance, as I mentioned in another thread in Fan Missions, should probably not alert guards, though they could grumble about it. The player can't be punished for such a fundamental part of the gameplay. Although, special loot disappearing causing alert, paired with the ability to buy a replica for it in the shop menu, might add something of value to the game. If you switch the items, guards won't notice it's gone.


    I also agree guard mobility should be increased, at least for some guards. Heavily armed guards could still be rooted to the ground, but lighter guards could give chase at any mantle height. Non-human enemies could be given movement range beyond the player - spiders on walls etc., though in the dark engine this would probably be hard to get working without jank.

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