Hi Saelorn -
I'm down with DM making the call. I just have the preference that passive perception is always on and I think that's the correct interpretation of the rules per everything I've ever read on every thread prior to this one, everywhere I've ever seen one.
Don't get caught up in semantics. I only use "scene" to mean "when a character could reasonably be assumed to be able to sense something. I was initially thinking something basic like "going over the crest of a hill" or "opening the door to a room" but it can mean whatever is appropriate to the game.
So there's a couple of problems with your interpretation of the Rogue ability as it compares to passive perception.
1. The rogue ability only guarantees that your skill roll will never be lower than a 10 and does so across all of your trained skills.
2. Passive perception can be and often is higher than 10. Using your example, if passive is higher than an active roll, with a DC of say 15 and a passive of 15, you should see the object you're looking for when it's in range of your senses before you'd ever have to make an active perception roll. If you roll lower than 15 on the active, you still see the thing you saw before you rolled.
Be well
KB
Yes, that's the previously-stated alternative. Passive Perception is either "always on"; or it's "only on when you're perceiving passively", and turns off when you're perceiving actively. Both methods seem equally supported under the definition of Passive Perception, so it's down to the individual DM for which method works best for them.
I'm down with DM making the call. I just have the preference that passive perception is always on and I think that's the correct interpretation of the rules per everything I've ever read on every thread prior to this one, everywhere I've ever seen one.
That could be where you're losing me, is that I've never been comfortable with thinking in terms of "scenes". Likewise, if something is usable "once per encounter" then that's equally meaningless to me. Surely, what constitutes a "scene" or "encounter" is simply a matter of the observer's perspective. (Fortunately, 4E defined encounters sufficiently through the use of five-minute rests.)
Don't get caught up in semantics. I only use "scene" to mean "when a character could reasonably be assumed to be able to sense something. I was initially thinking something basic like "going over the crest of a hill" or "opening the door to a room" but it can mean whatever is appropriate to the game.
For me, I think in terms of objective metrics, like feet and minutes. If the third pillar on the left has a notable feature that would require a DC 17 Perception check to find, then I wouldn't consult anyone's Passive Perception score until they got close enough to actually see it (probably around ten feet); if they started actively surveying the room before they got over there, then they would only get the result of their active check, which could well be lower than their passive score.
If a high-level rogue is surveying the room, then they're guaranteed a minimum result on their Perception roll (and coincidentally, that minimum result is equal to their Passive Perception score). That's a benefit of being a high-level rogue, under my interpretation of Passive Perception, is that actively looking is never worse than passively looking. Under your interpretation of Passive Perception, everyone gets that benefit.
So there's a couple of problems with your interpretation of the Rogue ability as it compares to passive perception.
1. The rogue ability only guarantees that your skill roll will never be lower than a 10 and does so across all of your trained skills.
2. Passive perception can be and often is higher than 10. Using your example, if passive is higher than an active roll, with a DC of say 15 and a passive of 15, you should see the object you're looking for when it's in range of your senses before you'd ever have to make an active perception roll. If you roll lower than 15 on the active, you still see the thing you saw before you rolled.

Be well
KB