iserith
Magic Wordsmith
If a DM builds a dungeon he has to constantly chose the DC for all of the traps he lays in it, and as most DMs know their players passive perceptions, this means a conscious choice over whether players will detect them or not.
I don't remember the PCs' passive Perception scores so I don't have this problem. I'm also not sure it's a problem, even if the DM does know the passive Perception scores so long as he or she is reasonably consistent as to the DCs (for example, I generally only use DCs from 10 to 20), telegraphs traps and other hidden dangers, and sets things up so the players can make trade-offs to increases their chances of success. So I've never been clear on what issue the random DC method is trying to solve.
While on the other end of the issue DMs could just not use passive perception and therefore have little to no control over traps.
I'm not sure what this means.
I handle it this way (taken from a recent thread on the topic):
First, I describe the environment in general to set up the adventure location. Next, I ask the players what their characters do while exploring, again, in general. This is their exploration task. They know the DCs by pace going in so they can array their party as they see fit. I make a note of this, but I can't narrate a result until it becomes relevant later.
Now I continue to describe the environment as the characters explore. Embedded in that description are clues telegraphing the existence of hidden things - traps, monsters, secret doors, etc. (These are "free" clues that some of you appear to gate behind the passive Perception score.) If someone has chosen to undertake an exploration task that might reveal these hidden things and meets the required passive score, then I tell them they have found something. That might be a pressure plate or tripwire or the outline of a door in the wall, something like that. Bottom line is that it's explicit - I'm no longer beating around the bush with clues at this point since they've found it because that is what the check resolves. If they do not meet the required passive score, then they have only the clues I already provided to go on. They can spend some time poking around more specifically or trying to deduce the relevance of those clues and they might roll or might have automatic success (or failure) depending on what they describe. ("Time" generally means I'm making a wandering monster check.) I narrate the results of the adventurers' actions accordingly. Sometimes failing a check means they find the hidden thing, but I make a wandering monster check because it took a while or made noise, etc.
I set it up this way because the "free" clues in the description provide agency to the players to change the fate of their characters by the decisions they make during play, both when they chose their exploration task and marching order but also in that moment. Telling them they found the trap's trigger or secret door due to their passive check result rewards their choices in play and the ones they may have made when building the character. And, as mentioned, discovering the hidden thing is only the beginning of the challenge. Now comes the investigation, deduction, and efforts to avoid or disarm the trap, open the secret door, or what have you.