D&D 5E Perception and Readiness checks. Please Explain!!

[Baksartha]

Can someone please explain to me when to roll perception or
readiness checks? I realize you roll a Wisdom (Perception) check
to detect a creature that's sneaking. But WHEN do I roll the check?
In the adventure I'm running there's a long tunnel about 1,000' in
in length. When would the PC's roll if a creature is hiding at the end
of the tunnel? What if it's not hiding at all, what if it's just standing in
the dark waiting? Is it still considered hiding? And as far as readiness
checks go, when exactly are they rolled? As soon as both groups
SEE each other? What if one group is just standing in the dark? Does
the other group still roll a readiness check? And am I reading it
right when it says that a readiness check is a Wisdom SAVING
THROW?! Please help.

 

[Li Shenron]

Unfortunately I'm afraid that, as usual, we are on our own...

I think this is the kind of things that you have to make up your own rules of thumbs, after collecting suggestions from other DMs. I am not sure if there were ever comprehensive "rules" for this.

The tricky questions here don't even end at "when do you roll?", but include "who rolls?" and "should they know they are rolling?".

 

[Baksartha]

I agree it's far too vague.

 

[Mistwell]

Well first, it's likely "when the parties can see or hear each other". In the case of your tunnel, darkvision is 60', and most light sources extend around 60', so in all likelihood it's around the 60' mark you can roll to see someone. Hearing them depends on how much noise they are making...someone standing in the dark is more visible than audible, so it's probably again back to that 60' mark for your corridor example for the party. The thing in the dark however might have bee aware of them much earlier, as the party is probably carrying a light source and is visible all the way down the corridor.

 

[Jeff Carlsen]

You roll to detect something when the DM determines that it becomes possible, but not guaranteed, that you'll detect it.

In your example, sight is limited, but sound will probably carry quite far. It's up to the DMs judgement to determine how far sound will carry. So, if a creature is waiting at the end of the tunnel, he might roll a wisdom check to hear the party when they're halfway down the tunnel. But since he isn't making noise, and possibly hiding, the party won't get to roll until the creature is either within the shadows of their light source.

 

[Baksartha]

But if the creature at the end of the tunnel isn't detected, but isn't necessarily hiding, and the creature automatically detects the PC's light source, wouldn't it automatically gain surprise on the PC's?

 

[Baksartha]

The rules are just too vague. The rules also don't take into account distance. A DM could easily adjust the DC of a Perception check to account for distance, but what about a contest/opposed roll when Stealth is involved. It's one thing to say the DC for hearing a conversation at 200 feet is DC 15, and it improves to DC 10 at 50 feet, but what about when detecting a sneaking creature? Should it not also be easier to detect a sneaking creature at 50 feet as opposed to 200 feet?

 

[Mistwell]

But if the creature at the end of the tunnel isn't detected, but isn't necessarily hiding, and the creature automatically detects the PC's light source, wouldn't it automatically gain surprise on the PC's?

It's not automatic, the party failed to detect the creature. Had they detected the creature with their perception check, it wouldn't surprise them. Had they gone down the corridor quietly and without a light source, or with a deceptive light source, the creature would not have spotted them automatically.

The rules are just too vague. The rules also don't take into account distance. A DM could easily adjust the DC of a Perception check to account for distance, but what about a contest/opposed roll when Stealth is involved. It's one thing to say the DC for hearing a conversation at 200 feet is DC 15, and it improves to DC 10 at 50 feet, but what about when detecting a sneaking creature? Should it not also be easier to detect a sneaking creature at 50 feet as opposed to 200 feet?

Sure, so add a modifier. It's not too vague, this is entirely in the realm of normal DM stuff. It's a skill you pick up as you get experience doing it. No rules can cover every situation, you just get some advice on adjudication and work it out as the circumstances dictate.

 

[Baksartha]

I still think they could clarify just a bit. For a new DM this could be (and is) confusing. They've done quite a bit to streamline the rules, for the better I think, but in their effort to smooth things out they've gone a little too far in some areas. But I do appreciate the input.

 

[Mistwell]

I am sure the actual DMG will give lots of advice on this sort of thing. But it's playtest rules, for experienced DMs only.