Putting a range on vision

[Greywander]

I'm playing with the idea of extending the rules for vision, hearing, and the senses in general. As far as I'm aware, the only reference to the range of vision is the eagle totem barbarian's mile-long sight. I'd like to add rules that give an effective range for vision, the problem is that I'm not sure what to use as a baseline. My initial thought was to base if off how far away you could see a Medium-sized creature, but it seems like the answer to that might be miles away. So maybe use the distance at which you could recognize a creature? Or specifically for noticing hidden creatures? Being above or below a certain range threshold might give you advantage or disadvantage on Perception checks (likely half and double your base range, respectively).

According to a document from the Innocence Project (https://www.innocenceproject.org/can-you-recognize-someone-from-hundreds-of-feet-away/), facial recognition starts dropping at around 25 feet, and is basically zero after 150 feet. Facial recognition might be a bit too specific of a metric, but at least it gives us reasonable numbers.

Pulling some numbers out of my butt, if we assume that a face is roughly a foot in diameter, then we could even multiply all these numbers by 5 to get a rough estimate for how far away you could recognize an entire (Medium-sized) person (e.g. race, build, clothing, equipment, body language and mannerisms, etc.). So that would be something like 125 feet before it starts dropping off, and up to 750 feet away.

Reworking these numbers a bit, you should be able to recognize a creature with no roll up to 120 feet away. After 120 feet, you need a Perception check. The DC could start 5, then increase by 1 every 30 feet, e.g. at 750 feet the DC is 26. We can also notice that 30 is one quarter of 120, so the "step size" can always be one quarter of the base range. For something like an eagle, if we say it has 8x better vision, then its base range (i.e. no roll required) is 960 feet, and the DC increases by 1 every 240 feet beyond that. The DC becomes 26 (equivalent to 750 feet for a human) at 6000 feet. Not sure this is accurate; Wikipedia says eagles have 4x to 8x better vision, and can spot a rabbit (a Tiny creature) up to 3.2 km away, which is roughly 10k feet.

If we start the DC at 10 and use 60 foot intervals (half base range), then at 750 feet (technically, 720 feet) the DC is 20 (the max possible with average WIS and no proficiency). For a DC 26, you'd need to be 1080 feet away. For an eagle, this means they'd have a DC of 26 at 8640 feet, and a DC of 31 (the limit of what's possible with maxed WIS and Perception proficiency) at 11040 feet.

I'm sure this will get more fun once I try putting an effective range on hearing. If you're blinded, how far away does an enemy need to be before you can't reliably locate them via hearing?

[Asisreo1]

I'm playing with the idea of extending the rules for vision, hearing, and the senses in general. As far as I'm aware, the only reference to the range of vision is the eagle totem barbarian's mile-long sight. I'd like to add rules that give an effective range for vision, the problem is that I'm not sure what to use as a baseline. My initial thought was to base if off how far away you could see a Medium-sized creature, but it seems like the answer to that might be miles away. So maybe use the distance at which you could recognize a creature? Or specifically for noticing hidden creatures? Being above or below a certain range threshold might give you advantage or disadvantage on Perception checks (likely half and double your base range, respectively).

According to a document from the Innocence Project (https://www.innocenceproject.org/can-you-recognize-someone-from-hundreds-of-feet-away/), facial recognition starts dropping at around 25 feet, and is basically zero after 150 feet. Facial recognition might be a bit too specific of a metric, but at least it gives us reasonable numbers.

Pulling some numbers out of my butt, if we assume that a face is roughly a foot in diameter, then we could even multiply all these numbers by 5 to get a rough estimate for how far away you could recognize an entire (Medium-sized) person (e.g. race, build, clothing, equipment, body language and mannerisms, etc.). So that would be something like 125 feet before it starts dropping off, and up to 750 feet away.

Reworking these numbers a bit, you should be able to recognize a creature with no roll up to 120 feet away. After 120 feet, you need a Perception check. The DC could start 5, then increase by 1 every 30 feet, e.g. at 750 feet the DC is 26. We can also notice that 30 is one quarter of 120, so the "step size" can always be one quarter of the base range. For something like an eagle, if we say it has 8x better vision, then its base range (i.e. no roll required) is 960 feet, and the DC increases by 1 every 240 feet beyond that. The DC becomes 26 (equivalent to 750 feet for a human) at 6000 feet. Not sure this is accurate; Wikipedia says eagles have 4x to 8x better vision, and can spot a rabbit (a Tiny creature) up to 3.2 km away, which is roughly 10k feet.

If we start the DC at 10 and use 60 foot intervals (half base range), then at 750 feet (technically, 720 feet) the DC is 20 (the max possible with average WIS and no proficiency). For a DC 26, you'd need to be 1080 feet away. For an eagle, this means they'd have a DC of 26 at 8640 feet, and a DC of 31 (the limit of what's possible with maxed WIS and Perception proficiency) at 11040 feet.

I'm sure this will get more fun once I try putting an effective range on hearing. If you're blinded, how far away does an enemy need to be before you can't reliably locate them via hearing?
The DMG lists visibility outdoors on page 243.

For reference, a character can see up to 2 miles on a clear day with no obstructions, 1 mile in rain, 100-300ft in fog, and 40 miles when elevated.

[king_steve]

The DMG lists visibility outdoors on page 243.

For reference, a character can see up to 2 miles on a clear day with no obstructions, 1 mile in rain, 100-300ft in fog, and 40 miles when elevated.

Sure you could see movement from said distances but knowing the difference between a horse and a dog at 1 mile is difficult at best.

Would you say a perception check makes sense at that distance to tell things apart?

[Asisreo1]

Sure you could see movement from said distances but knowing the difference between a horse and a dog at 1 mile is difficult at best.

Would you say a perception check makes sense at that distance to tell things apart?
It depends. Out of something so trivial, I'm hesitant to force the player to roll. If its somehow important, I might, but it also depends on the intent of the players.

I'd probably tell them they see a quadruped in the distance. If they want to see if they can tell what the quadruped is, I'd ask for a perception check (expertise for Rangers with the Grassland terrain since horses are native to grasslands).

[NorthernPhoenix]

I just go with what makes sense in the context of real life. I find no rule-set less than many pages long can adequately cover the vast and varied differences between different species senses. The rules in the book for perception are fine enough for dungeons or equivalent contexts, i.e grid based situations, but in "exploration mode" i play it more loose.

This avoids the problem of eagles being "near-blind by raw" and other such nonsense.

[Greywander]

The DMG lists visibility outdoors on page 243.

For reference, a character can see up to 2 miles on a clear day with no obstructions, 1 mile in rain, 100-300ft in fog, and 40 miles when elevated.
Interesting, I didn't know that. However, given that the range expands while high up, this seems to have more to do with obstruction and the curvature of the planet than it does with visual acuity. Also, you say they can see out to 2 miles, but see what exactly? In a way, visual range is infinite, as we are able to see stars, but that doesn't mean that our perception is the same at a billion miles as it is at 10 feet.


I just go with what makes sense in the context of real life. I find no rule-set less than many pages long can adequately cover the vast and varied differences between different species senses. The rules in the book for perception are fine enough for dungeons or equivalent contexts, i.e grid based situations, but in "exploration mode" i play it more loose.

This avoids the problem of eagles being "near-blind by raw" and other such nonsense.
I think mostly I want a way of grounding visual range and providing a reference point for how good a creature's eyesight is. "You can see [thing]" is pretty vague, and puts a lot of weight on the DM to determine how much detail you can make out. By attaching a number to the distance at which you can see fine details, the DM can figure out how hard of a Perception check might be required based on how far away it is.

Perhaps the simplest thing that would also make the most sense is just to figure out at what distance you would be making a Perception check at disadvantage to see a hidden target. I do like the idea of a scaling DC rather than disadvantage, though, as you can combine it with disadvantage in unfavorable light conditions (e.g. dim light or other light obscurement).

But yeah, I think part of the issue is that many of the things we could choose to use as our baseline are going to be ridiculously long distances (on the order of several miles). Humans have really good eyesight. Like, really good. Sure, eagles have us beat, but we're still one of the best out there.


So after typing all that out, I did some experiments. We measured a hallway in our house to be almost exactly 40 feet, and I could easily see a person at the end of that hallway, and recognize their face (though 40 feet is well within the 150 foot limit, and only slightly beyond the 25 foot optimal range). I also tried putting down an object about a foot long to simulate a Tiny creature or object, and could also see it just fine. So what I'm thinking is that a 30 foot range for faces/Tiny objects and creature works just fine. If the range doubles with each size step up, then that becomes 60 feet for Small objects/creatures, and 120 feet for Medium. So I think these work well as good base ranges.

Then the question is just how they scale. If we start the DC at 5 and add 1 per 60 feet, then at 720 feet the DC for a Medium creature or object is 15. The DC is 30 at 1620 feet. Remember, this is just the range to recognize or notice someone/something. It's not that you can't see them, it's just hard to tell what they are. For the eagle (base range of 960 feet), DC 15 would be at 5760 feet, which is already more than a mile, and DC 30 would be at 12960 feet. But that's for a Medium creature/object. For the eagle to spot a Tiny rabbit, those distances would drop to one fourth their value.

A big part of this is just to give a reference to how good a creature's eyesight is compared to other creatures. The visual range and DCs could and probably will be ignored by many, but even so it should help with roleplaying how far a character can see. There's just not currently a good feel for that when every creature basically has identical visual acuity. Giving, say, an elf double the visual range will help drive home how much better their vision is, moreso than the vagueness that is Perception proficiency.

[SiCK_Boy]

Maybe you could explain, with examples, what kind of issue you ever faced (or expect go face), in a real D&D game, that would require coming up with such rules?

Knowing what the purpose of the rules is should help inform the development of said rules.

Visual acuity is usually covered through the Perception skill (see various keen eyesight creatures having advantage on perception checks relying on vision, or the impact of darkness on said checks), and others have pointed out some existing rules for maximum range of vision.

Why do you deem these rules insufficient? I fail to understand the issue that requires the development of these new rules.

[Greywander]

Hmm. Well, I suppose it started with wanting to put a range on hearing, so that you know how close to an enemy you need to be to locate them by hearing alone (e.g. if blinded, or the enemy is invisible). This is actually a fairly concrete thing that is likely to come up in play, and does come up often in white room analysis.

Then I thought that I might as well give a range to each possible sense. It was when I thought about the sense of smell, a sense that humans are notoriously bad at while many animals are quite good at it, that it occurred to me to give each sense its own use and function, and then give a value to that sense to each creature. Humans have good eyesight, but poor smell, while other animals have poor eyesight, but good smell. It's not a meaningless trade, these actually make them good at different things. I feel like this should matter, even if it's all just ribbon traits.

Maybe simpler is better. Just leave it at "you can recognize a Medium-sized creature/object out to a 120 range without a Perception check", and allow the DM to adjudicate how vision beyond that range is handled. Mostly, I just want you to be able to compare different creatures and understand which ones have better or worse specific senses. If a particularly near-sighted creature only has a visual range out to, say, 30 feet, and they're looking at a Small or Tiny object that is 200 feet away, it should be understood that they're going to have a bit more trouble than human would. Right now, there's no sense of that, and we don't even know how good the eyesight or hearing or sense of smell is for a given creature, only that some have "keen" senses, whatever that means.

Related is that I think this will also matter in terms of stealth. Being, say, lightly obscured and beyond optimal visual range will give you a safer bet. Right now, distance has no impact on perception and stealth unless the DM decides to make it so.

[PhoenixPhyre]

Maybe you could explain, with examples, what kind of issue you ever faced (or expect go face), in a real D&D game, that would require coming up with such rules?

Knowing what the purpose of the rules is should help inform the development of said rules.

Visual acuity is usually covered through the Perception skill (see various keen eyesight creatures having advantage on perception checks relying on vision, or the impact of darkness on said checks), and others have pointed out some existing rules for maximum range of vision.

Why do you deem these rules insufficient? I fail to understand the issue that requires the development of these new rules.

This.

Especially since 5e (in particular) is not a simulation. Rules exist as "tools to help keep the action moving" to quote the DMG (Chapter 8: The Role of Dice). Whenever you're tempted to include a new rule, ask yourself--how does this help me move the action along in a satisfying way? Most mechanically-fiddly, simulationist rule additions fail this test. They exist to impose "realism", something that 5e doesn't attempt to do. And do so in a way that prevents the action from moving along (or at least impedes it). And the net effect is often to damage verisimilitude, not enhance it.

A distance-based rule like this become hellaciously complex very quickly. Just look at 3e's notorious Spot checks, where seeing the moon is basically impossible on a clear night (because the spot check DC scales with distance). So you'd have to balance size, distance, air conditions, etc.

Also to quote from the same chapter of the DMG:


When a player wants to do something, it’s often appropriate to let the attempt succeed without a roll or a reference to the character’s ability scores...Only call for a roll if there is a meaningful consequence for failure.

In this case, the existence (and nature, assuming existence) of the "meaningful consequences for failure" are so situation dependent that a hard and fast rule ends up in a morass of tables or breaks the fiction hard. Much easier, cleaner, and more fiction-friendly to do ad hoc checks (using Wisdom (Perception), that's what it's there for) as needed for the few cases where the exact amount you can see becomes important.

[Asisreo1]

Interesting, I didn't know that. However, given that the range expands while high up, this seems to have more to do with obstruction and the curvature of the planet than it does with visual acuity. Also, you say they can see out to 2 miles, but see what exactly? In a way, visual range is infinite, as we are able to see stars, but that doesn't mean that our perception is the same at a billion miles as it is at 10 feet.

It's exactly enough to consider the distance an "encounter."

When in a very open plain, the time you tell the players that they observe something approaching them is 2 miles. Take note that unless they are moving at a slow pace with stealth, whatever is approaching them has indeed already seen the party as well.

It's basically the maximum distance that two creatures can interact based on sight, even if that sight is very hard to make out. It at least gives the party time to cast buffs, disguise themselves, prepare for a parley, or formulate a strategy before anyone is in effective combat distance.


Also, there's also rules for hearing distance as well. It's in the DM's screen, though. Why they didn't put it in the book with vision? Probably to sell the screen.

Also also, there is vision range when underwater as well.