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I play on Roll20, where it is very easy to automate many parts of game play. As the DM, I frequently need to make hidden perception checks for characters. I currently use Passive Perception, since that is what it is for. However, Roll20 makes it very simple for me to roll perception checks for an entire party. The idea of a randomized outcome has great appeal to me, since it allows the low Wis barbarian to occasionally notice something the others don't, or the high Wis cleric to miss something because he is preoccupied.

An automated group check allows that. Off the bat, I don't see any major game imbalance by actually rolling a secret check rather than using static Passive Perception. Am I missing something, though?

Is there some significant game feature that is changed or lost by rolling secret perception rolls rather than using passive perception?

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Many dungeon features use different DCs for passive v.s. active perception

The secret doors in the Redbrand Hideout, for example, say:

"Secret doors are made of stone and blend in with the surrounding walls. Spotting a secret door from a distance of no more than 10 feet without actively searching for it requires a passive Wisdom (Perception) score of 15 or higher, whereas a character who takes the time to search the wall can find the secret door with a successful DC 10 Wisdom (Perception) check."

Generally, anything that's deliberately hidden but not a creature seems to have a lower notice DC for active perception than passive perception, but not by any fixed amount. To account for this, it would make sense to give players a variable modifier to their perception rolls for actively searching, except that that's against the 5e ethos, so instead it'd probably be more faithful to the system to apply advantage for active searches and just lose the level of detail currently present for secret-stuff detection.

Observant

Also, you'll need to patch or remove the Observant feat if you play with feats; it grants you:

You have a +5 bonus to your passive Wisdom (Perception) and passive Intelligence (Investigation) scores.

which doesn't work with your rule change.

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  • \$\begingroup\$ Like I said in the comment to Miniman, I think I can account for the observer feat with a reminder. Your point about the differing DCs is a something I hadn't considered, but still, I can cover that on the fly. If I roll the secret check, I'm doing it against a DC 15. If they ask for a check, I let them roll for themselves against DC 10. I'd have to make the distinction if I were using the passive rules, so it shouldn't be any different from accounting for it with secret rolls. Unless I'm misunderstanding a distinction? \$\endgroup\$ – keithcurtis Jan 5 '18 at 8:08
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    \$\begingroup\$ @keithcurtis If the sum total of your change is to replace the '10' in Passive Perception with '1d20', you aren't rolling perception rather than using passive perception, you're just using a different method for determining passive perception. \$\endgroup\$ – the dark wanderer Jan 5 '18 at 8:51
  • \$\begingroup\$ That's pretty much what I'm doing, yes. Maybe you can suggest better wording in the question, if this is causing difficulty in answering. Mostly I'm concerned if randomizing that element breaks anything I hadn't considered. Your point about the difference in DCs is important. I don't use a lot of pre-gen material, so I wasn't aware that was a common practice. \$\endgroup\$ – keithcurtis Jan 5 '18 at 14:30
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Ability checks that contest Perception will fail more often: Stealth will be harder

There will be more variance in the PCs' and other creatures' Perception check results. In other words they'll be more swingy. The more PCs or creatures that get to make a Perception check, the more there will be that will occasionally get an extremely good result. So any given Stealth check result is more likely to be exceeded, making the attempt more likely to fail.

Consider a party of five PCs, each of whom has a passive Perception of 15. If you allow each PC to make a Perception check, it's like a single PC making an extra check - which is equivalent to advantage when you make the second player's roll, double advantage when you make the third player's roll, and so on. Overall, the odds of the party as a unit detecting a threat improve markedly.

Finally, when you roll a Perception check, the average result on a d20 is 10.5, rather than the 10 that is assumed for a passive check. Over the course of many checks, that slight difference (2.5%) will also tell.

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  • \$\begingroup\$ Thank you, that is a big difference, considering that a party only really needs one success to ruin someone's stealth. I might reconsider this. \$\endgroup\$ – keithcurtis Jan 6 '18 at 23:02
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Don't let any of your players take the Observant feat. Other than that, you should be all right.

The primary benefit of Observant is:

You have a +5 bonus to your passive Wisdom (Perception) and passive Intelligence (Investigation) scores.

Which becomes rather useless if passive Perception checks are removed. You could consider making it a +5 bonus to all Perception checks, but that's probably too strong. Either way, there's nothing else that specifically affects passive Perception checks.

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  • \$\begingroup\$ It's rare enough that I could remember it or write a reminder into the macro. I would only count it if it were something I would otherwise roll a passive check for. \$\endgroup\$ – keithcurtis Jan 5 '18 at 4:54
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    \$\begingroup\$ @keithcurtis When would you ever roll a passive check? \$\endgroup\$ – Jason_c_o Jan 5 '18 at 7:40
  • \$\begingroup\$ Use a passive check for. Wrote in haste. \$\endgroup\$ – keithcurtis Jan 5 '18 at 8:02

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