With the 3.5 skill set, a player typically needed to make two different skill checks to avoid detection. He would make a Move Silently check opposed by a Listen Check. He would also make a Hide check opposed by a Spot check. The concept of smell based checks wasn't formalized so they typically only happened in the case of the Scent ability.
With PRPG, the Perception skill encompasses hearing, site, smell, and taste (I'll ignore touch for now). We also have Stealth to encompass both moving quietly and staying hidden. So the question is, how many opposed checks does it take to move by someone without being noticed? Do I need to make just one opposed check or do I make three independent checks for sight, sound, and smell?
My initial guess is that you need to make three independent opposed checks because the circumstance modifiers may be very different, depending on which of the senses you're talking about. For example, while the rules don't explicitly say this, I assume that the +20 bonus from Invisibility only applies against sight based perception checks. If there's a silence spell in effect, that shouldn't make it any harder to actually see someone or to smell an Orge in the room.
If this assumption isn't correct, how do you adjudicate the different opposed rolls when all you want to do is just detect someone's presence? The smell DCs make it seem like it's easier to detect an sneaking Ogre than a sneaking elf. An Invisibility spell shouldn't help me to sneak around against a blind opponent. Nor should a Silence spell make any difference against a deaf opponent.
However, if you my assumption of independent checks is correct, there is a potentially unintended side-effect to adding game mechanics for the sense of smell. By mechanizing a third sense, we've now made it harder for someone to remain undetected. Having multiple opposed checks to remain hidden are weighted towards the detector rather than towards the hider. This is because the hider must succeed on all checks and the detector only needs to succeed on one.
Of course, smell is likely to be the least reliable method for detecting someone, but that will be up to DM discretion. Your chances to remain undetected are basically zero when you can be seen (but not heard or smelled), their slightly better when you can only be heard (but not seen or smelled), and I would rule that they are better yet when you can only be smelled (but not seen or heard). All that said, it will definitely be tougher for to remain undetected and the new axis of detection (smell) has no improvement route in the rules as they are today. The Stealth skill doesn't say anything about hiding your smell.
Thoughts? Am I interpreting the rules correctly? Am I overreacting to the new method of detecting someone? Would you include the third opposed roll or just ignore it for simplicity and speed?
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If this assumption isn't correct, how do you adjudicate the different opposed rolls when all you want to do is just detect someone's presence?
My initial reaction is there would be only one opposed roll.
I would first calculate which sense the detector has the best chance of detecting with given the existing environmental conditions, then, calculate which detection method the detection target is most vulnerable to. And roll with those numbers as the opposed check.
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I'd also use only one opposed check - and simply declare it to be the one with the highest total bonus after circumstance bonuses, racial bonuses, etc. Of course, if there's only one sense that could work, then I'd use that one. An example would be listening through a closed door, or sight vs. an incorporeal creature that therefore makes no sound.
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I agree that one "roll" would seem a good choice in the name of keeping the game moving. Then compare to the DC's of each sense and that way you only make one check but can determine in what way the player was detected. Perhaps they were smelt and heard but not seen? Depending on the creature in question I think this allows some interesting DM'ing. I'm picturing a dumb-a**e Ogre thinking of ghosts when he can't see anything - perhaps add a spell and you have his ancestors coming back to give him some "good" advice...
Thanks for bringing up this topic I hadn't thought too much about this before.
Cheers,
S.
First of all, let's talk math.
Keeping it simple, assume that for all three rolls (sight, sound, scent) your rogue has a 50% chance of success (11+ on the d20).
If you only make one roll, the rogue has a 50% chance to sneak by.
If you require all three rolls, then your rogue only has a 12.5% chance to sneak by.
Change that to an alert guard, and you only have a 25% chance with each opposed roll (16+ on the d20).
If you only make one roll, the rogue has a 25% chance to sneak by.
If you require all three rolls, then your rogue only has a 1.5625% chance to sneak by. Yes, that's less than 2%. The odds are 1 success in 64 attempts.
Do you really want to destroy stealth by doing this? Is stealth valuable enough as a fanstay trope, is it important enough to the genre, to expect that sometimes people succeed when they're trying to be sneaky?
Now for the logical gamist application of the mechanic.
As a DM, I would assume that the individual who is sneaking must make an opposed roll against the individual who is trying to be vigilant using whichever of the three rolls is worse.
If the sneaker is invisible, the guard won't likely see him, but might hear him, make one opposed roll as a hearing perception check with the applicable hearing modifiers.
If the sneaker is levitating or using a Silence spell so there is nothing to hear, but relying on hiding (stealth) to remain unseen, then make a sight-based perception check.
If the sneaker is doing nothing but hiding and trying to move silently, and is not particularly stinky, maybe any one of the three opposed rolls would be applicable, so pick the one that favors the observer, not the sneaker. Why?, well, it works as follows:
Assume the rogue needs to roll a 15 to remain hidden, a 13 to remain silent, and a 10 to remain odorless. He rolls a 14. Based on that roll, the guard failed to smell him, failed to hear him, but managed to spot him. If the rogue had rolled a 12, then the guard would have seen and heard him. If he had rolled a 9, the guard would have seen, heard, and smelled him. And if he had rolled a 15+, then the guard would not have seen, heard, or smelled him, and the rogue would have successfully snuck by.
See?
One die roll covers all three senses.
But, chances are you don't have to calculate all the modifiers for all 3 senses. Just decide which one is likely to give the observer the best chance at success.
Is it dark? If the observer can't see well in the dark, then he is much more likely to hear the sneaker than see him.
Is it noisy? The observer will be more likely to hear the sneaker than see him.
Did the sneaker just emerge from the city sewers? Maybe the observer will smell him easier than seeing or hearing him.
And if there is no obvious reason for one to succeed, pick the mode of detection that members of that race would use the most.
Humans rely on sight.
Dogs rely on scent.
Bats rely on sound.
And if you don't know which sense is most useful to the race, then assume it would be whichever one their racial skills give the highest bonus. If all bonuses are equal, or unknown, then assume it is sight, since the vast majority of creatures in the world rely more on sight than any other sense.
That's a long explanation for a simple concept.
Summarized:
Find the sense that the observer will be most likely to succeed in detecting the sneaker and roll vs. that one sense. If that fails, then he had even less chance with the other senses, so the stealth attempt is successful.
In spirit, I agree with the one roll philosophy for game speed reasons, but I still think that the new system adds some complications... regardless of which mechanism you use. DM_Blake hit the nail on the head from my original post that moving from two rolls to three can completely kill off the ability to sneak past a wary opponent. I wanted to pose the question to see which direction most people went in order to give some direction to the thread. Since everyone so far appears more in favor of one roll, let's examine that course.
The first note is the obvious corollary to my prior point. For the same reason that three rolls make it much harder to stay undetected; moving from two rolls to one makes it easier to remain undetected (and harder for the PCs to detect their foes). Since PCs find themselves in both the role of the detector and the sneaker, making sneaking easier changes the game just as much as it did in the three roll case. I'm not necessarily saying that making it easier with one roll (or harder with three rolls) is a bad thing or that it will break the game, but we should be conscious of it's change to the game mechanics.
However, I think the bigger problem is the mechanic around the new axis: scent. In order to maintain any sense of parity, I think that the Stealth ability needs to increase the DC to detection by scent. Without having an equivalent mechanic to increase the scent DC (like you have for sound and sight), that axis will quickly become the Achilles heel of any rogue. It will only take a DC 5 perception check to detect any orc, no matter how good his Stealth check. Even a human rogue will quickly be hampered by the flat DC 15 Perception check. If I'm a character or NPC on guard, I'll quickly start relying on scent more than anything else since it's the hardest of the senses to fool (by skill or spell).
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"Unlike the ability to hear or see an approaching
enemy, smell cannot be used to notice hidden foes unless
the scent is present for more than a 10 minutes."
I guess this sort of covers your concerns? It does how need a little more DM intervention I guess. Is there a wind? Which way is it moving? Etc... That and 10 minutes would equate to 100 rounds of doing something.
2 cents,
S.
Thanks to everyone for the thoughts and suggestions! After playing around a little bit, I've decided to go a slightly different direction, so I thought I would share my findings with you. I decided to incorporate Stefan's suggestion to remove detection via scent from most encounters unless the sneaking person is either in proximity for a long time or if the detector has the Scent ability (like a dog). More controversially, I also decided to go with two rolls (one for sight and one for sound) like in 3.5. Here's a description of the problem we ran into with the one-roll method:
Assume you have a rogue trying to sneak by a guard. Assume that the rogue is moving in an environment where he has cover or concealment (in shadowy torch illumination, in the woods, etc). To make it simple, let's also assume that the rogue's Stealth skill and the guard's Perception skills are equal. So on any given roll, the rogue has a 50% chance of success against the guard.
With the two-roll method, the rogue has a 25% chance of success since he has to win on two separate opposed rolls (0.5 * 0.5). With the one-roll method, we pick either sight or sound since they're equivalent and the rogue has a 50% chance of success. It's a higher value, but that doesn't really matter as long as the rule is always consistent.
But, here's where the problem happens. Let's say that the rogue wants to improve his chances by employing some magic. For example, the rogue could drink a potion of Invisibility to give him +20 to his sight based check. That would make detection by sight impossible (alternatively, he could also have a cleric cast a silence spell on him).
With the two-roll method, this just improved his chances of success a lot (doubled them to be exact). Since one of the two methods is now at 100%, his total chance of success just went up from 25% to 50% (0.5 * 1.0). That's what you would expect to happen since the Stealth skill specifically mentions how Invisibility helps your checks.
However, if you go with the one-roll method, casting the Invisibility or Silence don't change the rogues chances at all. Before the magic, both sight and sound had a 50% chance of detection so it didn't matter which axis we chose to use. After the spell takes affect, one of the axis will have a 50% chance of detection and the other will have a 0% chance of detection. So, we will choose the axis with the 50% chance. In the end, adding magic to the equation had no effect at all on the rogue's chances of success! Definitely not what you would expect and a change that would drastically affect typical gaming situations.
So, do with this info whatever you'd like. While moving to a single roll would certainly speed up game play, I think that the changes to the game with respect to the different circumstances makes it not worth it.