Active Perception and Passive Perception

[Oompa]

Hey all,

This might be a simple problem but i am quite struggling with it..

So we have a active perception ( a player rolling a perception check to notice stuff) and we have passive perception ( a player knows certain things are around him if his passive perception is high enough)

Now lets say we have a hallway (The Gauntlet out the SOW second adventure), the hallway has 4 pressure plates in the beginning of the hallway which the players need to avoid to not activate the turrets..

These plates have a dc of 22 to notice them..

So my highest passive perception check in the party is 18-19, not enough to automaticly see the plates.. but here comes my question..

My party does not use perception, every chamber they enter, every hallway.. they just walk into it.. Now it is clear that the players are going to step on one of the pressure plates, cause they won't notice it..

I told them earlier in the game that should use perception more often so they would notice more stuff around them.. am i going to repeat this everytime a situation like this occurs? Or should i roll a perception check secretly and than tell the players they spot it at the last moment because of a perception check..

Any advices?

 

[UngeheuerLich]

In the development of 4e, the intention of passive check was that you don´t need to roll. But then there were many complaints about this making traps and such redundant.

Then the DCs were lowered so much (by 10 points) that everyone detects those traps when using passive checks.

So make sure your DCs are updated so that they are low enough to be detected by passive perception. And when someone beats them with their passive score, give them an automatic roll or something. (usually a 70% chance to detect the trap)

 

[Oompa]

In the development of 4e, the intention of passive check was that you don´t need to roll. But then there were many complaints about this making traps and such redundant.

Then the DCs were lowered so much (by 10 points) that everyone detects those traps when using passive checks.

So make sure your DCs are updated so that they are low enough to be detected by passive perception. And when someone beats them with their passive score, give them an automatic roll or something. (usually a 70% chance to detect the trap)

So basicly you are saying, make the dc 12 for passive checks, everyone who notices something is wrong gets an chance to make an active perception check at dc 22 to see what is actually wrong?

 

[Benlo]

That works. Also, if you're really worried they'll get themselves hurt doing this, if the trap is weak enough to where they can mostly shrug it off, you might be better off letting them trip it and learn their lesson. If it's more dangerous than that, do what I do: Just point at a player and say "YOU, do (insert check here) check." If they get it, they get it, if not, play accordingly. It can sometimes get them excited that something big is about to happen if I get the checks out of them myself.

 

[Gruns]

My take...

After DMing 4E exclusively since its release, I have found passive Perception to be pretty much useless. I know the Perception skills of my players, and I set the DCs. Soo... Essentially I KNOW if something will be spotted, or if it won't. Therefore, if I put a quote/unquote "secret" door in an area that I expect the players to find, I make the DC within range. If I put a secret door in an area that I don't want them to automatically find, I make it slightly higher than their best Passive check. For example, after the Big Bad Evil Guy fight, the PC's don't find the treasure they were sure was supposed to be here. A little snooping around (Perception roll, perception roll...) a-ha! There's a hidden trapdoor that happens to contain the fat loot.
In the case of traps and whatnot, I almost always make the DC higher than their highest passive. However, I leave a clue or two for them to know that something is amiss, usually in the form of something that their Passive Perception can pick up. "The light reflects oddly off the wall to the left of this room, and you notice a smattering of little dimples and tiny holes throughout." (DC15) This may get them to actively look for, and find the myriad of poison dart traps on the right side of the room (DC18), ready to unleash their payload as soon as the pressure plate in the center of the room (DC20) is tripped.
But all in all, I don't think passive Perception works as the designers intended for someone that writes their own adventures. I do see the benefit in bought adventures though, sort of, as it gives the writers a consitent DC target number. However, I think even then I'd prefer DC's to be "1 less than highest passive Perception in the group" or "2 higher than the highest..." etc... The trick is trusting your DM to know what is imperative to be Perceived automatically (or at all), and what isn't.
Later!
Gruns

 

[Benlo]

That's a good way of doing it, Gruns. Tell them something is amiss, like scorch marks on the floor near a trap, or one area of the tiled floor seems a little discolored.

 

[fba827]

(evil dm mode)

Eh, if their passive perception won't notice it AND they aren't using active perception, then let them step on a few pressure plates. They'll pick up on it and start to use active perception more often, or be dead, eventually. It's "trial by fire," "sink or swim," and whatever other term you want to use...

(/evil dm mode)

But slightly more seriously, perhaps for the first couple rooms, just lower the dc slightly to the point of "you think something is amiss, there are scorch marks" or "you notice scraping against where the floor meets the wall" thus cluing them in to use active perception. But just do this for the first few rooms to get the idea that there are traps, and lots of them. after that, just go with it as written.

(for justification, you can say that the traps near the entrane get trigged much more often by wayward creatures, thus there are more signs and residue around of previously triggered traps - hence making it easier to notice. but traps further in aren't triggered nearly as much since no one ever makes it down that far, thus, less evidence to notice).

 

[Mentat55]

I use Passive Perception as the DC for enemies trying to sneak up on the PCs. I also have given traps and hazards a Stealth modifier, instead of a Perception DC, and I just roll it against the PCs' Passive Perception. If the PCs actually say, "I want to search around, make sure nothing is amiss," then they roll their Perception checks and I use a 10+Stealth modifier DC for traps/hazards/etc.

 

[Starfox]

For traps, there are basically two kinds:

The tactical trap. This is placed as a part of a normal encounter and intended to be spotted. Basically, this kind of trap is terrain: charge and suffer the tripwire.

The hidden trap: This is the static hidden trap trap intended to do damage. It is an encounter in itself or in conjunction with other traps, but rarely with monsters. It lowers the pace of the adventure and is very much discouraged in the 4E DMG. If you use one of these it, foreshadow it so your players have a chance to spot it. Make sure that its lethal enough to be at least a semi-worthy encounter. For this kind of trap, I'd disallow passive checks or have the trap roll Stealth against the players; having an auto-spot rule makes this kind of trap pretty pointless.

 

[Amaroq]

I think the problem here is entirely in a "way that we construct things" manner.

Its perfectly fine for a printed module to use a static check vs Passive Perception, because the writers don't know the Passive Perception numbers of the party that will be going through it.

However, as a DM, with full access to the player's Passive Perceptions, I really shouldn't be picking numbers, because I'm essentially picking the characters that will spot what needs spotting.

To work around that, I use a lot more active-roll-vs-Passive-Perception mechanics, or a bit more "Make the characters roll Active Perception".

In fact, I've even scripted a few things where the script reads "Ask the players for Active Perception checks. Regardless of the results, ..." or .. "The player with the highest roll notices .."

As noted earlier, it keeps the players on their toes, and triggers some anticipation about what's about to come up ..