Evocation and the world around you.

[Wraithcannon]

Another GM and I were recently having a discussion about breath weapons and other evocation type effects.

The first point of contention was that RAW, fireball and lightning bolt specifically state that any barriers that interfere with their areas of effect must suffer the damage inflicted by the spell. If they are destroyed, the spell continues to fill the area beyond it up to it's normal size, and if they are not destroyed then the spell stops there.

No other spells say that, not burning hands, not cone of cold, nothing. Also, nowhere in the chapter on magic, or universal monster rules, does it say that any other evocation, conjuration, or other abilities such as breath weapons have this effect.

So, the question is whether or not, RAW, other cones, spheres, or lines that inflict energy damage would share the same characteristics as fireball and lightning bolt and continue past a destroyed barrier.

I know it sounds silly to think you could dive into your camp tent to avoid a red dragon breathing on you for one round, but can you show me where it says you can't?

The second point of contention we had was that of saving throws.

In the case of fireball and lightning bolt (and any other evocation effects that might follow the same rules), we were wondering if you get a bonus to your save for being behind cover, improved cover, or total cover for being behind something like a closed door or other barrier that is destroyed by said effect.

Or would you have no cover bonus because said door or other barrier is now nothing but gently glowing embers/blasted into flinders/dissolved into goo?

[Lifat]

Unless there is a specific rule somewhere that allows spells to generally break barriers, then only spells that specifically say that they do will break barriers.
People behind covers were behind cover when the spell was cast, so even though it goes against the way I would run it, I do believe that they get cover even if the barrier is broken by RAW.

[Jiggy]

So to be clear, question #1 is "When a damaging AoE destroys a constraining barrier, does the AoE extend beyond that point?"

Assuming that's indeed the question, let's do some digging.

Here's one thing I found:

CRB, Magic chapter, Line of Effect wrote:

A burst, cone, cylinder, or emanation spell affects only an area, creature, or object to which it has line of effect from its origin (a spherical burst's center point, a cone-shaped burst's starting point, a cylinder's circle, or an emanation's point of origin).

That seems to leave out "line" areas, but I also found this:

CRB, Magic chapter, Area wrote:

A line-shaped spell shoots away from you in a line in the direction you designate. It starts from any corner of your square and extends to the limit of its range or until it strikes a barrier that blocks line of effect. A line-shaped spell affects all creatures in squares through which the line passes.

The part about lines seems clear that a barrier stops the expanse of the spell, meaning that lightning bolt's ability to keep going is a special exception, at least among line spells.

The first quote, from the definition of line of effect... Well, once you destroy an intervening barrier, do you re-check LoE to determine an adjustment of targets? Seems like maybe it comes down to a question of whether you check LoE once (when the spell goes off) or keep dynamically re-checking every time the scenery changes.

For that, I don't see anything stating one way or the other. However, with lightning bolt apparently being an exception to how line areas work, I'd be inclined to take that as precedent that the default for all types of areas is to determine line of effect (and the resulting area affected) once at the time of casting, and then resolve the effects once.

I'm like, 68% confident on that one.

As for question #2, it sounds like you're basically asking, "What happens when you're hiding behind cover that gets obliterated by the effect?"

Well, let's start with the cover rules:

Cover wrote:

Cover and Reflex Saves: Cover grants you a +2 bonus on Reflex saves against attacks that originate or burst out from a point on the other side of the cover from you. Note that spread effects can extend around corners and thus negate this cover bonus.

...
Improved Cover: In some cases, such as attacking a target hiding behind an arrowslit, cover may provide a greater bonus to AC and Reflex saves. In such situations, the normal cover bonuses to AC and Reflex saves can be doubled (to +8 and +4, respectively). A creature with this improved cover effectively gains improved evasion against any attack to which the Reflex save bonus applies.

And then of course the LoE rules cited above equate total cover with not having LoE, so you wouldn't be affected at all if you have total cover.

So that's our starting point: if you have cover, you get +2 Reflex; improved cover is +4 Reflex and improved evasion; total cover is effectively not being in the AoE.

Now, you're specifically asking about what happens when a spell like lightning bolt blows through your cover, right? Well, let's look:

Lightning Bolt wrote:

If the damage caused to an interposing barrier shatters or breaks through it, the bolt may continue beyond the barrier if the spell's range permits; otherwise, it stops at the barrier just as any other spell effect does.

Side note: Hey, look at that last line! Shoulda looked there earlier and saved myself some trouble for question #1. "Otherwise, it stops at the barrier just as any other spell effect does." So lightning bolt is an exception and it knows it. I guess that settles question #1. But getting back to question #2, let's also check fireball:

Fireball wrote:

If the damage caused to an interposing barrier shatters or breaks through it, the fireball may continue beyond the barrier if the area permits; otherwise it stops at the barrier just as any other spell effect does.

Okay, so basically the same verbiage as bolt.

So, it seems obvious that after breaking a barrier, the spell continues filling its full range. It seems equally obvious that this could change the binary "in area/not in area" issue with total cover.

In the absence of any rules specifically explaining this exact situation, we need to look at what we do know:

FB and LB explicitly recalculate their area after breaking a barrier. That means that you're not done resolving the spell's effects until you're done breaking barriers. Logically, this means that while you're still resolving the destruction of barriers, you haven't finished determining the final effects of the spell.

This in turn implies that the result of the creature's saving throw can't be fully resolved until all barrier-destruction has finished. This further implies that the results of barrier-destruction would have an impact on the resolution of effects on creatures. The third degree of implication is then that since resolving creature damage happens after barrier damage, creature damage would be resolved using the state of the terrain that's left after resolving barrier damage.

So it looks to me like someone whose cover was completely obliterated would gain no benefit (partial obliteration would recalculate the level of available cover).

But that's after several steps of inference, so I'd hardly call it ironclad. :/

[Wraithcannon]

Soooo, what you're saying is.

Right now.

RAW.

A canvas tent completely shields you from an Elder Red Dragon's fire breath.

For the first shot.

Hmmm, how much does a circular shower curtain cost? I think I just found a new Arcane Eye / Unseen servant spell combo.

Bwahahahaha

[Diego Rossi]

Breath weapons aren't spells.
It is a matter of table variation, so ask your GM.

@jiggy: nice work, but I think that the problem is that the general rules for AoE spells reference both damaging and non damaging spells.

My opinion is that all damaging spells will be potentially able to destroy a barrier and still deal damage behind it.
Personally (but it is a home rule) I would reduce the damage dealt by the damage absorbed by the item if it was giving full cover and give the target the benefit of improved cover for the saves.

[Jiggy]

Wraithcannon wrote:

Soooo, what you're saying is.

Right now.

RAW.

A canvas tent completely shields you from an Elder Red Dragon's fire breath.

For the first shot.

Hmmm, how much does a circular shower curtain cost? I think I just found a new Arcane Eye / Unseen servant spell combo.

Bwahahahaha

You appear to be assuming that canvas would count as cover in the first place. Might just be concealment. ;)

[Raven_Black]

I have to agree with Diego. My ruling at my table would be that hiding behind a destructible object would shield you from most of the blast, but once that object is gone the effect would continue through it with a persistent, albeit diminished, force. i.e. whatever damage was 'used up' in destroying your cover would be deducted from the damage that continued onward into your square.
We all know that RAW isn't physics-friendly, but whenever possible I try to either bring the two as close together as possible or provide a plausible reason as to how physics was overcome.

[Devilkiller]

Regarding the tent and shower curtain I guess whether or not they block dragon breath depends on whether or not they'd count as a "solid barrier". I'd say that they probably shouldn't. They block line of sight, but perhaps they're too flimsy to block line of effect. I'm inclined to agree with Jiggy that perhaps they're just concealment. I wonder if the term "solid barrier" is defined anywhere in the rules or if it is just a judgement call for the DM.

As far as spells destroying barriers goes, I think it would be kind of fun if these two classic spells had a unique capability. I personally allow the 10' wide variant of Lighting Bolt and have convinced a few other DMs to do the same. Bouncing it off of things can also create some fun moments though I haven't seen that old rule used in many years.

[Bob Bob Bob]

Hmmm, I swear I had a post but I think it got eaten. Anyway, as they are now, I could totally see a single layer of something reasonably solid protecting from a Great Wyrm dragon's breath weapon. That's because the mechanics are a terrible way of actually representing "breathing fire" (or similar). It's a standard action, so between 3-6 seconds long. Barring specific breath weapons, the effects don't linger. Mechanically it's basically a reusable cone of cold/lightning bolt/other evocation spells. The spell that replicates dragon breath weapons is a burst (so can't even go around corners).

Therefore it makes perfect sense that the super short burst of fire/cold/acid/electricity can only destroy the first barrier it hits and not reach beyond. If breath weapons lasted 1 round instead of a standard action I could see them pushing through barriers, as they are now they have more in common with an incendiary grenade than a flamethrower.

[Wraithcannon]

Funny how people keep focusing on my joke about the shower curtain and seem to miss the main point of barriers vs area effects.

I know the rules are unclear and the mechanics are unwieldy, but I do think that a blast of 3 to 6 seconds in length has the capacity to eat through an intervening barrier and continue on. It would all depend on how solid the barrier is.

If only there were some way to figure out how many hit points said barrier had........or figure out how tough it was, like some sort of degree of hardness...........that way we could figure out if the damage done was enough to penetrate it and continue on (i.e. a burning hands spell against a wooden door vs. a shoji) and how much damage the victim would suffer (did the barrier absorb any of the damage, or does it all go through like a FB/LB).

It seems unclear what happens with these area effects. Common sense says to me that the effect should continue if it penetrates a barrier, the object rules seem to give me a clear indication of how much damage would be required to penetrate said barrier, but the rules don't quite not seem to agree with un-supporting that. Right?

Oh well, I guess I'll just mark Jiggy's post as a FAQ candidate and maybe we'll get a golem to chime in.

[Rynjin]

Your rpost seems to rely on that first assumption, that the blast lasts 3 to 6 seconds, and then extrapolating there based on logic.

However, there is both no indication that the blasts lasts any duration at all (the Standard action could simply be the dragon building up steam and then exhaling it in a burst of short lived flame), nor does logic particularly hold any place in the Pathfinder ruleset. It will do its best to defy your logic at every turn.

[Jiggy]

Wraithcannon wrote:

but I do think that a blast of 3 to 6 seconds in length has the capacity to eat through an intervening barrier and continue on.

Why is the blast itself that long? What if part of the time spent is either the dragon taking a deep breath or the spellcaster doing the requisite finger-wiggling? Maybe the blast itself is gone in an instant.

Oh! That actually reminds me of something:

CRB, Environment chapter, Catching On Fire wrote:

Spells with an instantaneous duration don't normally set a character on fire, since the heat and flame from these come and go in a flash.

That seems relevant.