Perception clarification

[Gruns]

Hey all.
Not a specific rules question here, but more of a general "Am I understanding this right?" sort of thing.

Let's say the highest passive Perception score for anyone in my group is 20.
Now let's say I make a secret door with a Perception DC of exactly 20. This means that it is spotted automatically as soon as they pass by it or get near it? And just how near? Within 10 squares of it and can see it? (The table on PHB 187 says the DC is +2 when more than 10 squares away.)

Does this mean if I put in a secret door that I want to make them actively search for, I simply make the DC 21 (or higher) ? Is this ratbastard DM metagaming, or the way it's supposed to be?

And supposing they do spend the Standard Minor action to actively try to Perceive it, this result could be worse than if they had not tried at all? I guess it doesn't matter too much, since if they could have spotted it passively, they wouldn't have bothered actively searching...

Thanks for the clarifications, smart people.
Gruns

 

[ValhallaGH]

Yeah, you have the jist of it.

If you want to make them actively search for a door then require them to actively search for it. You don't have to set the DC above their passive perception, though if you do then the rules require them to actively search for it.
You are the DM, you can cheat if it makes the game more fun.

 

[Oreot]

Yeah, passive perception is a bit confusing to me too, this came up with some floor tile traps I ran. The best thing I could figure was if he had line of sight (the high percept player) then he might notice something odd about the floor in the spot he could see and on his turn make an active perception roll to check it out. But he didn't instantly know every floor tile in the room or what they did necessarily. As for the hidden door, if his passive perception gets it, ask him to make an active perception roll and see if he hits it. That way its not just insta knowlege from walking past... Dunno, that was just how I planned on handling it.

 

[Kordeth]

Passive Perception is just a constantly-active "take 10 on a Perception check." Any information you'd give out if the PC rolled a 10 (before modifiers) on a Perception check, you should give out with passive Perception. You don't "notice something odd, then roll to figure out what's odd," you notice whatever is there to notice (whether or not you understand its significance is another issue altogether, and probably related to Knowledge skills rather than Perception).

You notice whatever it is as soon as you can see it and as soon as the Perception DC is equal to or less than your passive check result.

Example: A rogue has a passive Perception of 20. There's a secret door in the dungeon whose DC to find is 20. The rogue notices the door as soon as he can see it and comes within 10 squares of it (since when the door is more than 10 squares away the DC is 22).

If you want to force players to roll to find something (and bear in mind that's not always the best idea, especially if the hidden doo-dad is plot-critical), set the DC above the highest passive Perception in the group.

 

[Lauberfen]

Problem with that is, they won't spot it half the time even with active perception.

This is an area where a house rule helps. I generally play that a dice should always get rolled for a check, so if something like a trap has a set DC, I make an active perception check for the party instead of passive. This avoids the all/never problem. I also break down traps etc into several diferent DCs, so that a passive perception might notice a dodgy square, but a higher DC to know what the trap is (much as in DMG).

 

[CovertOps]

Wizard's new concept for passive perception has to do with the idea that you won't be walking down a corridor and run into traps and such with no other threats present. You can see the trap but you can't exactly do something about it since you're being shot at by those evil Kobalds. What they wanted to do in essence is not to have the DM sandbag the players by putting random traps (that you can't see without looking for them) and then just having the party take random damage from said traps. I'm not sure how that translates to random secret doors but perhaps the below suggestion will help.

1. Try putting an encounter in the location of your secret door and set the DC (in your example) to 21. This way they may have a reason to search around after the fight and find the secret door if this is what you want them to do. Perhaps the monsters here have hidden their treasure behind the secret door. You of course will have to provide the reason to get them to search as you did not detail the locale of the door.

2. A second option is to put something else noticable in the location that has a DC 20 perception or lower. This way they find something (a funny looking lever?, strange wall textures?, whatever) and not your door. This MAY lead them to do a more complete search but again it's all about what you want them to do.

3. Perhaps this is a dungeon and somewhere later in the dungeon is a boss that has a map with this room on it and an X. This would cause the party to bypass the door to start and then go back later and search the room.

I would ask a simple question tho. Do you want them to find the door? If the answer is yes then why do you want them to search for it. It adds an unnecessary complication to moving the plot forward and they may never search if you don't tell them to do so. If you don't want them to find the door, then why put it there in the first place?

Otherwise you are exactly correct about the 20 DC/passive perception check and if they don't see the door they won't have any idea to stop and look for it.

 

[ExploderWizard]

Problem with that is, they won't spot it half the time even with active perception.

Someone please correct me if I am mistaken but I think that an active perception check can never be lower than the passive perception score. If a player rolls low on a perception check then the result is treated as if he or she had rolled a 10.

 

[Kordeth]

Someone please correct me if I am mistaken but I think that an active perception check can never be lower than the passive perception score. If a player rolls low on a perception check then the result is treated as if he or she had rolled a 10.

Not exactly, but close. An active Perception check can be lower than passive Perception--but if your passive Perception was high enough to spot whatever the thing is, you would have spotted it before even making the Perception roll. So, unless there's some situation where your passive Perception doesn't work, you've effectively got a minimum Perception check result of 10 + your skill modifier.

That's not quite the same thing as always treating a roll of <10 as 10, which would have weird interactions with powers that key off of success or failure on skill checks.

 

[cmbarona]

One way you may consider this problem is from the player's point of view. Is this perception score particularly high for their level, or compared to the rest of the group? If so, why? Chances are, the player picked the correct stats and skill training to get to that point. It was a sacrifice, however minute it may seem, to get that score so high. Perhaps they put extra points into Wisdom for this purpose, or deliberately chose skill training in Perception rather than any other class skill. And it was certainly a sacrifice if they used a feat to get to this point. Whatever the case, reward that sacrifice. It's worth the blow to your DM ego to have a PC whose Adrian Monk-esque powers of observation pay out for them in exactly these situations.

 

[Kordeth]

Also bear in mind that if you start regularly making traps and secret doors one point higher than the highest passive Perception in the party, you completely obliterate one of the main reasons why there's such a thing as passive Perception in the first place: elimination of the old inchworm dungeoneering style: "I move five feet down the corridor. I roll Perception. I move five feet. I roll Perception. I move five feet...."