Homebrew Request: Perception Checks that Make Sense

[Vadskye]

I'm trying to make Spot and Listen checks make sense, and I need some help. There are two main problems with the rules for those checks that I see (though, naturally, there may be more).

First, distance adjustments simply don't work. The classic example of this is that a tree becomes invisible to the average commoner after about 300 feet or so, thanks to the "-1 per 10 feet" rule for Spot checks. This doesn't make sense for obvious reasons. I want a system that allows you to see something far away, even if you can't make out details very well.

Second, seeing and hearing is almost totally binary: either you see/hear something or you don't. I believe that most DMs handwave this aside and give varying descriptions for sounds based on check results. For example: "Dan, you hear the sound of metal coming from somewhere down the hallway. Clara, you hear the sound of about six to eight humanoid creatures in armor from about 120 feet down the hallways. They seem to be moving slowly in your direction". I really like doing this, and I'll keep doing this whether or not I have a perfect system in place. But I want rules to express this concept. As a DM, it helps me know what kind of information to give. As a player, it helps me know what I can reasonably expect.

Those are the things that I see needing to be fixed. It is also vitally important that the resulting system be quick to use, given how often Spot and/or Listen checks can come up in a game. Has anyone come up with a system like this? Are there things I am missing?

[Lord of Shadows]

We are kind of having the same issue here in a Pathfinder game. We are using the "-1/10 ft" rule on Perception checks and we are also requiring a Perception check to determine whether (or how well) a caster can "Target" a distant target. It sort of makes sense for spells that have to hit their mark, like rays, but it kinda breaks down when considering a Fireball or other wide-area artillery.

[Spin]

First, distance adjustments simply don't work. The classic example of this is that a tree becomes invisible to the average commoner after about 300 feet or so, thanks to the "-1 per 10 feet" rule for Spot checks. This doesn't make sense for obvious reasons. I want a system that allows you to see something far away, even if you can't make out details very well.
Don't require rolls for things that everyone should be able to see (obviously the commoner can see the tree), and lower the DC or change the distance penalty to something like -1 per 100 feet for checks to see something far away, without making out the details.



Second, seeing and hearing is almost totally binary: either you see/hear something or you don't. I believe that most DMs handwave this aside and give varying descriptions for sounds based on check results. For example: "Dan, you hear the sound of metal coming from somewhere down the hallway. Clara, you hear the sound of about six to eight humanoid creatures in armor from about 120 feet down the hallways. They seem to be moving slowly in your direction". I really like doing this, and I'll keep doing this whether or not I have a perfect system in place. But I want rules to express this concept. As a DM, it helps me know what kind of information to give. As a player, it helps me know what I can reasonably expect.
Set different DCs for different levels of information: DC 10 to hear the humanoids stomping down the hallway, DC 15 to hear how many they are and how far away, etc.

[Quellian-dyrae]

I had done something like this (http://www.giantitp.com/forums/showthread.php?t=290149) for M&M 3e. A shorter and more D&D-centric one would be something like...

You roll Perception normally at ranges out to 30'. Each doubling of distance is a -4 penalty.

The base DC to detect something is 10. If a character is actively attempting to keep the subject hidden, it may either add its Stealth skill directly to the DC (taking 10 on Stealth), or it may roll a Stealth check to set the DC rather than using the flat DC. Generally speaking, hiding something other than itself or on itself is a standard action, and the benefits end of the hidden subject moves from the spot. Hiding oneself, or hiding an object (or small creature) on your person is a move action and you can retain stealth even while moving. Someone not actively attempting to hide doesn't add Stealth. In the case of a Stealth check, the result generally lasts for the current scene, even if the character reveals itself and attempts to hide again.

This DC is then modified as follows:
Subject is Invisible: DC +20 (reduced from the frankly insane +40).
Subject has Total Concealment or Improved Cover: DC +10.
Subject has Concealment or Cover: DC +0.
Subject is out in the open*: DC -30.

*This only applies for senses as acute as human vision. Less acute senses always use a minimum DC modifier of +0 for concealment.

Further, the "scale" of the subject affects the DC to detect it. A "normal" subject (a Medium-sized creature or object, a human speaking clearly or moving, etc) uses the listed DC. Each halving of scale is +4 to the DC, each doubling is -4. Generally, this means each size category larger or smaller, but there may be other scales (a human speaking softly might be +4, whispering +8, and speaking under one's breath +12, for example). Note that this adjustment already applies to sneaking creatures by means of their size modifier to Stealth.

If you succeed the check, you are aware of the subject, but don't get any detail. If you succeed by 5, you get broad details - not enough to precisely identify the subject, but a general description. This level of detail is not possible if your total check bonus is -20 or less (typically due to extreme distance). If you succeed by 10, you get as full detail as your sense allows. This level of detail is not possible if your total check bonus is -8 or less (typically due to extreme distance).

[Rephath]

As far as perception checks being binary, don't think of it as "noticing everything" vs. "noticing nothing" but "noticing detail x" vs. "missing detail x."

For example, if you fail your perception check you can see the tree but not make out what kind of tree it is, or notice anything unique about it.

If you fail your perception check you hear a metallic noise coming down the hall. If you pass it you can make out what that noise might be. Alternatively, if you fail you hear nothing if you pass you barely make something out.

Whether or not you pass your perception check you will notice the low-hanging bar in front of you in the dark corridor. Passing it means you see it. Failing means you feel it with your forehead. Bonk!

Alternatively, failing means you get information. Passing means that information is correct.

[Debihuman]

I'm trying to make Spot and Listen checks make sense, and I need some help. There are two main problems with the rules for those checks that I see (though, naturally, there may be more).

First, distance adjustments simply don't work. The classic example of this is that a tree becomes invisible to the average commoner after about 300 feet or so, thanks to the "-1 per 10 feet" rule for Spot checks. This doesn't make sense for obvious reasons. I want a system that allows you to see something far away, even if you can't make out details very well.

That's not true. The tree is not invisible at 300 feet unless you are making Spot checks to see the tree at night. Then it might be.

The Spot check isn't used to see the tree at all, it is supposed to be used to see someone HIDING in the tree (which at 300 feet is possible).

Here is how I know you're not using Spot checks correctly This is what the Spot check if for (from the SRD):


The Spot skill is used primarily to detect characters or creatures who are hiding. Typically, your Spot check is opposed by the Hide check of the creature trying not to be seen. Sometimes a creature isn’t intentionally hiding but is still difficult to see, so a successful Spot check is necessary to notice it.

First, you DO NOT make spot checks to see tree at a distance. You use the spot check to see if you notice someone HIDING behind the tree. Now if the tree is hiding, that's another story.

The problem comes in when you read this:

Spot checks may be called for to determine the distance at which an encounter begins. A penalty applies on such checks, depending on the distance between the two individuals or groups, and an additional penalty may apply if the character making the Spot check is distracted (not concentrating on being observant)

Note the word ENCOUNTER. It is not to see things or people and this is entirely discretionary for the DM.

I think you guys have been playing a little too literally.


Second, seeing and hearing is almost totally binary: either you see/hear something or you don't. I believe that most DMs handwave this aside and give varying descriptions for sounds based on check results. For example: "Dan, you hear the sound of metal coming from somewhere down the hallway. Clara, you hear the sound of about six to eight humanoid creatures in armor from about 120 feet down the hallways. They seem to be moving slowly in your direction". I really like doing this, and I'll keep doing this whether or not I have a perfect system in place. But I want rules to express this concept. As a DM, it helps me know what kind of information to give. As a player, it helps me know what I can reasonably expect.

Here's the thing. Most good DMs don't use checks AT ALL for this stuff. The only check is: Is it reasonable. Use the reasonable person standard.

Can the PCs hear something? It's not just binary. They can hear "something" or not but then it's also how clearly can they make out the sound or see the object. You can see a person at 200 feet but can you tell the person's gender from that far or determine whether you know him/her at that distance?

Commoners who can't see trees at 300 feet are severely nearsighted and need glasses. Hell, I am severely nearsighted and can see a tree that far but I surely couldn't tell if someone was HIDING in it and yes, it's the green fuzzy thing over there. Could I tell the difference between a tree and treant at 300 feet? Probably not unless I had on my glasses.

Debby

[Vadskye]

ShadowLord:

We are kind of having the same issue here in a Pathfinder game. We are using the "-1/10 ft" rule on Perception checks and we are also requiring a Perception check to determine whether (or how well) a caster can "Target" a distant target. It sort of makes sense for spells that have to hit their mark, like rays, but it kinda breaks down when considering a Fireball or other wide-area artillery.
Artillery is a great example of how this rule becomes problematic. How does one aim a siege engine, anyway?


Don't require rolls for things that everyone should be able to see (obviously the commoner can see the tree)
While I can always simply ignore the rules (as I have mostly done so far), I would rather have a system that worked.

and lower the DC or change the distance penalty to something like -1 per 100 feet for checks to see something far away, without making out the details.
This idea has promise; perhaps there are different penalty scalings for different levels of detail. Normal detail would have a penalty of -1 per 10 feet, while mere existence or nonexistence might have a penalty of -1 per 100 feet (or more). On the other hand, that doesn't quite express how difficult it is to see a fly 100 feet away. Perhaps the rate at which the DC increases depends on the size of the object being observed?

Set different DCs for different levels of information: DC 10 to hear the humanoids stomping down the hallway, DC 15 to hear how many they are and how far away, etc.
Well, yes, that's what I was suggesting. But that isn't a system yet - just an idea.

Quellian:
You roll Perception normally at ranges out to 30'. Each doubling of distance is a -4 penalty.
Simpler is good, I think. Does this double like 30/60/90/120 or 30/60/120/240?


System system system
I thought this looked weird at first, but after thinking about it some more, I can definitely see the appeal. I'll give this some thought - I particularly like the idea simplicity of assigning "size categories" to sounds. A Medium sound is the sound of a typical Medium creature talking normally. Talking loudly is +1 size category; shouting at the top of your lungs is +2. Speaking quietly is -1; whispering to someone right next to you is -2. I definitely like that, even if it isn't totally fleshed out yet.

Rephath:

As far as perception checks being binary, don't think of it as "noticing everything" vs. "noticing nothing" but "noticing detail x" vs. "missing detail x."

For example, if you fail your perception check you can see the tree but not make out what kind of tree it is, or notice anything unique about it.
I agree in principle, but I want to know the difference is between "noticing the existence of X" and "noticing a detail about X". Maybe size modifiers could come into play here, too - noticing the existence of a human is easy, since it's Medium. Noticing that he has a faint tattoo on his right hand that indicates he belongs to a gang requires a Spot check against a Fine object (the size of the tattoo), giving the tattoo concealment for blending into the skin.


If you fail your perception check you hear a metallic noise coming down the hall. If you pass it you can make out what that noise might be. Alternatively, if you fail you hear nothing if you pass you barely make something out.
Maybe each additional tier of information about a sound is is like 1 lower "size category" of sound.


Alternatively, failing means you get information. Passing means that information is correct.
I like the idea of incorporating incorrect information into these checks. It should probably be a "fail by X or more" mechanic - there should be the potential to correctly recognize that one does not know enough to come to any conclusions.

Debby:
Note the word ENCOUNTER. It is not to see things or people and this is entirely discretionary for the DM.
What is an "encounter" except a noticing a group of things or people that one should react to? Not all encounters are combat-based. It is absolutely possible to "encounter" a strange, bone-white tree with a faint aura of magic in the middle of a long-abandoned field, and I want to know how far away people can see it.


I think you guys have been playing a little too literally.
I've never actually used the Spot and Listen rules as written for stuff like this. But I want to be able to.


Here's the thing. Most good DMs don't use checks AT ALL for this stuff. The only check is: Is it reasonable. Use the reasonable person standard.
Most DMs don't, and shouldn't, roll for things like this. That's different from not using any rules, though. Determining tree-seeing distance isn't something that should take a roll, but your Spot skill should be related to that. The reason I don't like just using a "reasonable person" standard is that D&D characters are only sometimes reasonable people. I have no idea what is reasonable for a elven rogue with a +20 Spot and Listen modifier; that's why I want rules to guide me on what, approximately, "reasonable" is supposed to be.

[Debihuman]

Debby:
What is an "encounter" except a noticing a group of things or people that one should react to? Not all encounters are combat-based. It is absolutely possible to "encounter" a strange, bone-white tree with a faint aura of magic in the middle of a long-abandoned field, and I want to know how far away people can see it.

If it is the only thing in the field and assuming the people are on the ground, they can see it from the horizon -- about 3 miles -- as long as there is light and nothing blocking their view.

You can see the moon in the night sky can you not? Distance from earth: 238,900 miles. Light and line of sight. There is no curvature of the earth blocking your view as there is on the ground.

Obviously, the higher you are, the farther you can see. In a 330-foot tower, you can see about 20 or so miles. There are boring mathematical formulas for this.

Let's say I am 2 miles from the tree. I can see the tree. I may not see the squirrels hiding in the tree. If there is tall grass, I cannot see the base of the tree where a dead body may be. However, I may notice that the grass is bent where the body is and so I make a Spot check to see if I notice that. It is really a visual situational awareness check. That's why it's called Spot and not Seeing.


Most DMs don't, and shouldn't, roll for things like this. That's different from not using any rules, though. Determining tree-seeing distance isn't something that should take a roll, but your Spot skill should be related to that. The reason I don't like just using a "reasonable person" standard is that D&D characters are only sometimes reasonable people. I have no idea what is reasonable for a elven rogue with a +20 Spot and Listen modifier; that's why I want rules to guide me on what, approximately, "reasonable" is supposed to be.

All humanoids see the same way. The Spot check is to notice things that are not obvious and it's primary use is to see things and people who are HIDING. If they're not hiding, you can see them. Now, if you aren't paying attention to your surroundings, it's quite easy to miss obvious things. However, that's called lack of situational awareness, and this is really what the checks are.

Here is what the SRD says:

Spot checks may be called for to determine the distance at which an encounter begins. A penalty applies on such checks, depending on the distance between the two individuals or groups, and an additional penalty may apply if the character making the Spot check is distracted (not concentrating on being observant).

Note the word "may" for this. It's not required. If the party is drinking at a pub they may not notice their nemesis walking in. That's what the Spot check is really for. If the nemesis slams the door on the way in, that's the Listen check. These checks are made for when something significant could happen so that they aren't caught flat-footed. It's the DM's job to determine which events are significant enough to warrant a check.

An elven rogue sees exactly as much as human fighter. However, he may be more situationally aware than fighter thus having a higher Spot check. This is why Spot and Listen checks were combined and changed in Pathfinder to "perception."

Debby

[Rephath]

If you want to add an element of horror to your game, call for a perception check when there is nothing to notice. If the character passes, they notice nothing. If they fail, they pick up on some detail of no consequence. Like the wind is blowing lightly through a nearby bush. Remember to roll these checks secretly for the characters.

[TuggyNE]

I fully support the notion of increasing penalties every doubled distance, although note that, like other real-world quantities in D&D, it's actually doubled, and not fake-doubled.


If it is the only thing in the field and assuming the people are on the ground, they can see it from the horizon -- about 3 miles -- as long as there is light and nothing blocking their view.

You can see the moon in the night sky can you not? Distance from earth: 238,900 miles. Light and line of sight. There is no curvature of the earth blocking your view as there is on the ground.

Obviously, the higher you are, the farther you can see. In a 330-foot tower, you can see about 20 or so miles. There are boring mathematical formulas for this.

Faulty reasoning; despite there being perfectly adequate lighting from stars near them, and despite perfectly good unbroken line of sight, it is entirely impossible for a human to see any of the (hundreds? thousands? how many are we up to, anyway?) of exoplanets. (Elves either, or really anything short of some pretty sophisticated telescopes.) This is, of course, almost entirely because the reflected light from the planet is being spread out way too much to catch more than a few photons. Note that while this doesn't happen much with a tree, it is definitely possible for it to blend together too much for our rods and cones to make it out as distinct from nearby objects: i.e., it's too small to see properly at that distance.


Let's say I am 2 miles from the tree. I can see the tree. I may not see the squirrels hiding in the tree. If there is tall grass, I cannot see the base of the tree where a dead body may be. However, I may notice that the grass is bent where the body is and so I make a Spot check to see if I notice that. It is really a visual situational awareness check. That's why it's called Spot and not Seeing.

Mostly true, although I'm not actually sure at what point the above-mentioned problems kick in to make it more or less physically impossible to discern anything about the tree itself. (Pretty sure, though, that normal eyes simply can't make out squirrels in it at all.)


All humanoids see the same way. The Spot check is to notice things that are not obvious and it's primary use is to see things and people who are HIDING. If they're not hiding, you can see them. Now, if you aren't paying attention to your surroundings, it's quite easy to miss obvious things. However, that's called lack of situational awareness, and this is really what the checks are.

Again, mostly true, although keep in mind that situational awareness is not important merely to spot actively hiding things, but, well, stuff that's just naturally hard to see, whether by its nature close up, or by the nature of optics at long range.

(Also, all humanoids very definitely don't see the same way; some get darkvision, some low-light vision, some nothing special at all.)

[Debihuman]

You're right, I should have qualified my sentence to read that normal seeing (sans darkvision and low-light vision) is the same for all Humanoids. Wasn't thinking about that, but they do not increase how far you can see in broad daylight.

For 1,000 gp you can buy a spyglass. Objects viewed through a spyglass are magnified to twice their size. Every adventurer should have this once the price tag stops being a shock. It's also a lighter way to carry 1,000 gp since it weighs 1 lb.

Debby

[dspeyer]

The classic example of this is that a tree becomes invisible to the average commoner after about 300 feet or so, thanks to the "-1 per 10 feet" rule for Spot checks.

I'm not sure it does. I can't find a general rule for spotting trees, but if we start with the hide rules...
Gargantuan: -12
Immobile: -5
not actually trying to hide: 0 (instead of d20)
300 ft away: +30
----------------------------
Total: 13

So slightly more likely to overlook than notice. Not entirely crazy. And if we set a greater penalty for not actually trying to hide, is becomes more visible.

Still, there are some really crazy scenarios. Like seeing the moon. The problem is that sizes are logarythmic and distances are linear.

Coming up with truly general purpose rules is probably not practical. Getting the spot dc for Barnard's star to be so much higher than Rigel would have to involve counting out their absolute luminosities, probably in units of candles, and having numbers as big as the distances in feet. On the other hand, on a dark night, it is easier to see a candle flame than an elephant, and this might come up in a reasonable campaign.

Maybe something like:

{table=head]condition|dc modifier
{colsp=2}etc.
huge|-8
large|-4
medium|+0
small|+4
tiny|+8
{colsp=2}etc.
|
{colsp=2}etc.
160 ft away|+8
80 ft away|+4
40 ft away|+0
20 ft away|-4
10 ft away|-8
{colsp=2}etc.1
|
hiding|hide check
making no effort to hide|-15
moving2|-20
trying to be seen|-30
|
well-camouflaged (lion in dry grass)3|+12
somewhat similar colors (moose in swamp)|+6
ordinary coloring|0
extremely clashing (blaze vest in forest)|-6
|
glowing like fire indoors|-15
glowing like a firefly in twilight|-15
glowing like fire in twilight|-30
glowing like a firefly on a dark night|-30
glowing like fire on a dark night|-45
{colsp=2}etc.
|
nonglowing in twilight4|+8
nonglowing on moonlit night|+16
nonglowing on dark night|+20
|
against plain background (on piece of paper)|-10
against broken background (signet ring on turkish carpet)|+0
among many items (signet ring on cluttered desk)|+10
among many similar items (signet ring in jewelry box)5|+20
|
partial concealment|+10
[/table]
1: objects over the horizon are always invisible, regardless of dc
2: if a creature is both moving and hiding, use the rules for hiding while moving instead of this modifier. Also, the moving and trying-to-be-seen modifiers go away at sufficient range (exact range at dm's discretion)
3: do not apply camouflage modifiers to spot checks if they were already applied to the hide check (e.g. as a racial bonus)
4: these modifiers change for creatures with darkvision or low-light vision
5: these are for spot checks. A signet ring in a jewelry box is still a dc 0 search check.

[TuggyNE]

I'm not sure it does. I can't find a general rule for spotting trees, but if we start with the hide rules...
Gargantuan: -12
Immobile: -5
not actually trying to hide: 0 (instead of d20)
300 ft away: +30
----------------------------
Total: 13

So slightly more likely to overlook than notice. Not entirely crazy. And if we set a greater penalty for not actually trying to hide, is becomes more visible.

I don't think there should either be a greater penalty for not trying to hide, nor a penalty for being immobile (that's for attacking it, not spotting it); if anything, being immobile makes things harder to spot than if they're moving. So DC 18 with current rules means there's a 15% chance of spotting, which is a little silly.


Coming up with truly general purpose rules is probably not practical. Getting the spot dc for Barnard's star to be so much higher than Rigel would have to involve counting out their absolute luminosities, probably in units of candles, and having numbers as big as the distances in feet. On the other hand, on a dark night, it is easier to see a candle flame than an elephant, and this might come up in a reasonable campaign.

Agreed.

The examples of stars or whatever aren't so much plausible things you'll need to roll for as things that the system should handle automatically as a result of good design, with little or no on-the-fly patching involved; they're a measure of elegance and algorithmic correctness, not practical effectiveness directly, but as such they're quite good at finding fundamental holes in the approach, just like all reductio ad absurdum examples.


{table=head]condition|dc modifier
{colsp=2}[… snip …]
hiding|hide check
making no effort to hide|-15
moving2|-20
trying to be seen|-30[/table]


I think these might be a little excessive; -4, after all, is the difference between knowing how to use a battleaxe and not, and +8 is the difference between a naturally aquatic race and one that needs to learn to swim. -8 or -12 is probably fine for trying to be seen; sometimes even waving and jumping up and down is insufficient to catch someone's attention, after all.


{table]well-camouflaged (lion in dry grass)3|+12
somewhat similar colors (moose in swamp)|+6
ordinary coloring|0
extremely clashing (blaze vest in forest)|-6[/table]

Some of this is already handled by conditional racial Hide modifiers, but you might get rid of those in favor of general rules. Still, I suspect the modifiers should be +8 and +4, not +12 and +6.


glowing like fire indoors|-15
glowing like a firefly in twilight|-15
glowing like fire in twilight|-30
glowing like a firefly on a dark night|-30
glowing like fire on a dark night|-45
{colsp=2}etc.
|
nonglowing in twilight4|+8
nonglowing on moonlit night|+16
nonglowing on dark night|+20
|
against plain background (on piece of paper)|-10
against broken background (signet ring on turkish carpet)|+0
among many items (signet ring on cluttered desk)|+10
among many similar items (signet ring in jewelry box)5|+20
|
partial concealment|+10
[/table]

Now we're getting somewhere. These numbers probably still need some tweaking, especially the backgrounds, but these mostly seem like good categories.

[dspeyer]

I think these might be a little excessive; -4, after all, is the difference between knowing how to use a battleaxe and not, and +8 is the difference between a naturally aquatic race and one that needs to learn to swim. -8 or -12 is probably fine for trying to be seen; sometimes even waving and jumping up and down is insufficient to catch someone's attention, after all.


Except that this isn't the difference between swinging a battleaxe competently and incompetently. It's incompetently vs. not at all.

What does a hide check of zero look like? I'm thinking you duck behind something that isn't actually big enough for you, and knock something over in the process. Still a lot harder to see than just standing there.



Some of this is already handled by conditional racial Hide modifiers, but you might get rid of those in favor of general rules. Still, I suspect the modifiers should be +8 and +4, not +12 and +6.


+12 did seem big, but I copied it from the lion's monster manual entry (polar bears on snow drifts have the same).

[Yakk]

Sun is ~36 doublings of 2 m (5') away.
Sun is ~29 doublings of 2 m (human height) big.

Moon is ~21 doublings of 2 m big
Moon is ~28 doublings of 2 m away

Sun is extremely bright. Moon is less bright, but fully illuminated.

In shadow, you can only see the Moon from what it blocks. In light, the moon can only be hidden by clouds, and only relatively thick clouds.

The moon is roughly as big (linearly) as a person 1/4 km away. The moon is against a dark background that looks nothing like the moon (the sky and stars).