Another Take on Detection

[Teridax]

To begin: this thread is an offshoot of this homebrew thread from A Butter Idea, whose concept serves as a starting point for this one. I very much recommend reading their post first, as they cover several issues with detection and senses in Pathfinder 2e really well, and that thread gives context to what's being presented here. I initially thought of posting this concept on their thread, but didn't want to crowd out their work with my own divergent homebrew, so I decided to post it here instead. With that established, let's go over a few points of criticism I have for senses and detection in PF2e:

What's Wrong With Detection Rules?:

I think the most obvious way to highlight the problem with detection in Pathfinder is to ask the simple, relatively common question of "How well can I target this creature in the encounter?" and list all the elements that factor into it:

You have different conditions marking states of detection, from observed to unnoticed.

You have different senses, which each have different states from precise to vague (with an implicit fourth state for not having the sense at all).

You have different conditions determining how senses are impaired, i.e. blinded, dazzled, and deafened. There's no conditions for other senses, and more conditions against sight than against hearing.

You have different conditions determining how detectable, rather than detected, something is. This overlaps heavily with detection conditions, and as A Butter Idea points out in their thread, there is a significant bias towards sight over any other senses (both the concealed and invisible conditions affect how others can see you).

You have environmental factors that can provide various conditions, generally localized to the bit of the environment. These can be conditions that impair senses, conditions that affect how detectable someone is, or both (and often it's both). The mist spell, for example, conceals creatures inside from creatures on the outside and vice versa.

You have different player mechanics, such as spells and ancestry abilities, that allow you to counter some of those environmental factors that would hinder your ability to detect others, low-light vision and darkvision being the two most obvious ways of doing so. There is, again, a heavy bias towards sight here.

So from all of this, I think we can draw a few conclusions:

This system is pretty complicated relative to the simple question it is generally meant to answer.

There is a huge bias towards sight: creatures are assumed to rely on sight by default, and the bulk of conditions and mechanics around detection play with sight rather than other senses. A Butter Idea tackles this bias in their homebrew, and correctly points out that this limits the ability to play Daredevil-like characters who rely on senses other than sight, while potentially complicating play in Starfinder 2e when so many creatures across the Universe and beyond have special senses of their own. More specifically, it means having any precise sense other than sight is far more powerful than it needs to be, because that lets a creature bypass the entire current system of counters and counters-to-counters built around sight.

These mechanics and conditions are almost completely dissociated from the game's usual system of bonuses and penalties: the concealed and hidden conditions impose flat checks, for instance, which force rolling twice for the same effect each time instead of leaning into the game's robust system of status and circumstance modifiers.

There's a lot of ambiguity around certain interactions: the Hide action, for instance, again relies heavily on the assumption of trying to escape from sight, so the GM has to start doing a lot of legwork to adjudicate when a creature can Hide when senses other than sight are involved.

In short: detection and senses sit in this little island of highly complex, overlapping, yet also sometimes confusing and ambiguous rules mostly separate from the rest of the game's mechanics. There's a lot to take in, but even then the question of whether or not one can detect a creature or Hide from them isn't super-clear, particularly when senses other than sight get involved. A Butter Idea addresses the bias towards sight in their brew, and I think we can go even further and streamline these rules even further.

Before listing specifics, I think it's worth listing the general roadmap of what I'd like out of an ideal detection subsystem in a game like Pathfinder, which could take on a variety of implementations:

I'd like the process of detecting and targeting creatures to be straightforward, or at least as straightforward as any other general mechanic in Pathfinder.

I'd like modifiers to detection to rely on Pathfinder's overarching system of numeric bonuses and penalties, instead of imposing their own separate checks.

I'd like the subsystem to be open-ended and flexible enough to be able to easily handle a potentially infinite variety of senses.

Here's how I'd go about trying to implement the above:

Binary Sense and Detection States:

The basic rule I'd like to apply here is: either you have a sense or you don't, and either a creature is hidden to you or it's not. What are currently imprecise senses could thus just be senses like your sight, albeit with more limited ranges or other restrictions, and vague senses could either not exist or be even more limited, such as only being able to smell a creature if they're adjacent to you for instance.

As for detection, the principle would be: unless a creature is trying to escape detection or is under some kind of stealth effect, you can just target them normally if they're within range of your senses (which is usually the case if you can see them), and if you can't sense them at all, then they become hidden to you.

What does it mean to be hidden? What about concealment? This is where the next part comes in:

New and Updated Conditions: Disabled & Hidden, Impaired & Occluded:

This is the bit where I'd want to start tying detection states to bonuses and penalties, while opening the system up to work consistently for any sense. Let's start with the hidden condition we mentioned earlier, and its counterpart for turning off senses, the disabled condition:

Hidden: When you're hidden from a creature, that creature doesn't know where you are, or if you're even there at all. A creature you're hidden from is off-guard to you, and you're occluded 4 to it (more on that later); if it tries to target you with an effect, it must select a space it thinks you occupy and the GM makes any rolls for the effect in secret, trying to affect you if you do occupy the space. Because area effects do not target creatures, a creature does not need to select a space when you're in the area of one of its effects, though the GM still rolls in secret to determine how you're affected. You may be hidden to only one or some of a creature's senses and not others, in which case you're not hidden from that creature unless you're hidden from all of its senses. Creatures whose senses you're hidden from are immune to your effects that rely on that sense, such as the visual trait if you're hidden from sight or the auditory trait if you're hidden from hearing.

Disabled: When one of your senses is disabled, it stops working. All creatures and objects are hidden to that sense from you, and you can't use that sense to Seek or Search.

Effectively, the hidden condition would include a bit of the undetected condition, and would be able to cover the invisible condition plus any counterpart for other senses, while the disabled condition would uniformly cover any kind of condition that stops your sense from working, like blinded or deafened. For softer conditions, let's follow up with the occluded condition for being concealed from a sense, and the impaired condition for partially blocking that sense:

Occluded: When you're occluded from a creature, it's harder for that creature to sense you. The occluded condition always includes a value up to 4. You gain a circumstance bonus equal to your occluded value to your defenses against that creature's Seek actions and actions that target you, as well as your Stealth checks against that creature, and a circumstance penalty to your occluded value to the checks and DCs of your actions that require the creature to sense you, such as a visual action if you're occluded from a creature's sight. Because area effects do not target creatures, you do not gain this circumstance bonus against area effects. You may be occluded to only one or some of a creature's senses and not others, in which case your occluded value against that creature is equal to the lowest occluded value you have against any of that creature's senses that can sense you. For instance, if you're occluded 2 to a creature's sight but not occluded to its smell when within range of that sense, you're not occluded to that creature. If you're occluded 4 to a creature, you're hidden from it.

Impaired: When one of your senses is impaired, it's prevented from fully working. The impaired condition always includes a value up to 4. All creatures and objects are occluded to that sense from you, with an occluded value equal to your impaired value.

And with that, that should be a pretty simple, yet flexible way of expressing how well you can detect something with a sense: effects that currently conceal you could instead make you something like occluded 2, and depending on the effect you could choose whether this occludes you to sight, hearing, multiple senses, or just a certain subset. Similarly, the dazzled condition could just make your sight impaired 2, and you'd suddenly have plenty of room to easily apply this to any sense you'd like. While not strictly a part of the above, this kind of framework could also easily lead to other mechanics (and please excuse the weird formatting, it seems lists and spoiler text don't mix well):

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If you wanted to express senses becoming less accurate over a distance, much like range increments on ranged attacks, you could have your impaired conditions for your senses increase with each of their respective increment, with the value capping at 4 and making creatures hidden at that point. This would likely require tweaking senses to have shorter ranges, and giving sight an explicit range increment (which wouldn't be a bad thing, as it'd help adjudicate certain long-distance scenarios a bit better), but could add even more depth to detection using the same rules.

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If you wanted to condense different sense-based traits, you could just have one sense trait that specifies one or more senses each time, and requires creatures to have that sense (or those senses) to be able to be affected, so the visual trait could become "Sense: Sight", the auditory trait could be come "Sense: Hearing", and so on. This could more explicitly tie those effects into specific senses and the conditions that affect them, while making it easy to create new traits for other senses, such as "Sense: Lifesense" for an effect that relies on that specific sense.

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You could easily implement a whole bunch of effects that'd mess with senses. If you have a cold or are in a cold environment, for instance, your smell could be impaired, a short-sighted creature could have their range increment on their sight reduced, or a creature that's hard of hearing or just has a really weak sense of hearing could have the sense permanently impaired. By contrast, creatures that have some kind of natural camouflage or register more dimly to certain senses (for instance, a creature that evolved to muffle its own sound, or an assassin trained to hide their thoughts from thoughtsense) could be occluded to those respective senses. You could potentially even go in the opposite direction and give a negative occluded value to creatures that are particularly detectable through certain senses, like xulgaths with their stench, or create a separate condition just for that.

More Consistent, Flexible, and Streamlined Environmental Effects:

With the above conditions established, let's see how this can be used to simplify how the environment affects senses (and again, apologies for the strange formatting):

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Some environmental features could provide occlusion to certain senses, like dim light or darkness against sight. Occluding terrain renders all creatures and objects inside occluded, with a value determined by the intensity of the occlusion. Standard occlusion, like dim light, could make creatures occluded 2 to the applicable sense, and greater occlusion would make creatures hidden (or occluded 4, as both would be the same).

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Sometimes the occlusion is two-way, as with magical darkness or the area of a silence spell. Just call this kind of terrain two-way occluding terrain, meaning all creatures and objects inside are occluded, but all creatures and objects outside the area are occluded to those creatures too.

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Effects that ignore concealment or let creatures perceive clearly in certain environments could just let you ignore the occlusion of certain terrain: low-light vision could let you ignore the occlusion of dim light, darkvision could let you ignore the occlusion of nonmagical darkness and dim light, and greater darkvision could let you ignore the occlusion of all darkness and dim light, including magical darkness.

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Cover does not automatically provide a bonus to Stealth checks. Instead, opaque objects and surfaces that often provide cover instead often provide occlusion to sight as well, with the objects and surfaces affecting the occlusion: simply having a wall in-between you and a creature may create two-way occlusion, but standing on the transparent side of a one-way mirror would provide one-way occlusion. If a terrain feature that provides two-way occlusion has an opening that takes a bit of positioning to sense through, such as a keyhole in a door, you can Take Cover behind the feature to sense through the feature normally, though the GM might determine that this focus occludes other creatures that you'd normally be able to sense.

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This ought to make adjudicating how terrain affects the senses both fairly flexible but also quite easy: you could have terrain that hinders everyone's senses, like a loud crowd impeding hearing, and certain situations where you're occluding yourself to someone else's senses while keeping your own clear, like concealing yourself behind a bush. Depending on the intensity of the effect, the GM could even scale the occluded value accordingly. For existing effects that create occluding terrain, it'd be easy to describe it as such: a mist spell, for instance, could just provide two-way standard occlusion to sight, and that would be enough to describe the spell's functionality.

Updated, Less Binary Hide and Seek Actions:

Hide is currently an action that's both fairly binary and also quite ambiguous when it comes to hiding from certain specific senses. With the above, this no longer needs to be the case. For instance:

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Hide (One-Action)
Traits: Secret
You attempt to escape a creature's senses, if only momentarily. When you use this action, choose up to two senses you're trying to Hide from. Typically, you'll be trying to Hide from sight and hearing, though you may choose to Hide from other senses instead. You can choose up to three senses if you're an expert in Stealth, four if you're a master, and five if you're legendary. The GM rolls your Stealth check in secret and compares the result to the Perception DC of each creature that can sense you. You automatically critically fail your check if the creature can sense you using a sense you're not trying to Hide from.
Critical Success You become hidden to that creature until immediately after you take an obtrusive action that it can sense. This is typically a hostile action against the creature, but also includes other actions that are highly noticeable, such as Casting a Spell. If you try to perform an otherwise noticeable action in a particularly unobtrusive way, such as trying to quietly trying to Disable a Device, the GM might require you to perform another Stealth check to Hide from detection.
Success As critical success, but you become occluded 2 instead of hidden.
Failure As critical success, but you become occluded 1 instead of hidden.
Critical Failure You fail to escape the creature's senses.

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With this, you'd no longer need to specifically be in cover or specific terrain to successfully Hide, though you'd still benefit from all of that, you'd have a range of effects depending on your degree of success, and you'd be explicitly stating which senses you're trying to Hide from. Seek could be even simpler:

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Seek (One-Action)
Traits: Concentrate, Secret

You scan an area for hidden creatures and objects. The GM attempts a single secret Perception check for you and compares the result to the Stealth DCs of any creatures within range of any of your senses.
Critical Success The creature loses the hidden or occluded condition against you that it gained by Hiding from you. The creature does not lose either of these conditions that are gained from other effects, such as terrain or a spell.
Success As critical success, but the creature remains occluded 2 to you if it was hidden.

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So you'd just extend all your senses and potentially catch creatures trying to Hide from you within their range.

The TL;DR to all this is: rather than have lots of discrete states and conditions for senses, detection states, and levels of impairment or occlusion, use a circumstance bonus instead to determine how much a creature resists targeting and detection, with one single condition for being completely hidden, and have all of those different factors tie into that same bonus in the end, with conditions being able to apply to any sense in particular or in general as needed. Not only could this streamline what already exists and clarify certain specific points, it'd make it much easier to play with detection and stealth via new mechanics, with the GM having many more tools at their disposal for affecting senses and detection situationally. Although the above is quite a significant departure from what we'd got, it'd be a relatively simple process to map this new subsystem onto what already exists, such as by using the occluded condition instead of concealed (and using occluded 2 by default), or impaired instead of dazzled.