Burst AoE Targets

[ckdragons]

During my gaming session last night (I was GM), the caster #4 casts the Prayer spell, which is a burst AoE. I was told by my players that everyone except 7 would be affected since the burst effect is touching their squares. I told them no since the spell was being casting in a hallway and the burst wouldn't radiate out. Their argument was that a burst would slightly spread out into the room like a beam of light. We poured over the books and it's doesn't seem to resolve our dispute one way or the other. Does anyone have an "official" ruling (and any FAQ or book references they can point me to)?

This is an example map of the encounter I'm speaking of. The caster #4 is 25 feet from #2, so as a crow flies, everyone but #8 would be in the radius of the prayer's burst effect.

(Ingore the dots; had to use them as space holders to create the example)
_____
|8.....|........|7|
|1.....|_____|6|
|2......__45___|
|3.....|
|____|

P.S. Yes, I know that I'm the GM but our group does prefer to play by the book with only a few house rules to keep our game consistent.

Thank you for your input.

[Ravingdork]

Spreads go around corners and fill up the entire area. Bursts do not. I'll see if I can find or make some diagrams to better explain it.

[RumpinRufus]

Burst, Emanation, or Spread wrote:

Most spells that affect an area function as a burst, an emanation, or a spread. In each case, you select the spell's point of origin and measure its effect from that point.

A burst spell affects whatever it catches in its area, including creatures that you can't see. It can't affect creatures with total cover from its point of origin (in other words, its effects don't extend around corners). The default shape for a burst effect is a sphere, but some burst spells are specifically described as cone-shaped. a burst's area defines how far from the point of origin the spell's effect extends.

An emanation spell functions like a burst spell, except that the effect continues to radiate from the point of origin for the duration of the spell. Most emanations are cones or spheres.

A spread spell extends out like a burst but can turn corners. You select the point of origin, and the spell spreads out a given distance in all directions. Figure the area the spell effect fills by taking into account any turns the spell effect takes.

[ckdragons]

Ravingdork wrote:

Spreads go around corners and fill up the entire area. Bursts do not. I'll see if I can find or make some diagrams to better explain it.

Thank you. I have a picture of the miniature's in combat at the time of the incident. I'll if I can upload it somewhere.

[ckdragons]

Here is a link to the picture:
https://drive.google.com/file/d/0By_lFj-_5eQtZDlmUC1GNlZJY2M/view?usp=shari ng

The caster is the bald guy in the center of the hallway, casting Widened Prayer to maximize number of peeps affected.

I was told it would affect 2 zombies on the left wall (directly in line with hallway + next to), the blob, everyone in the hallway, and red/yellow character. I believe it would only affect everyone in hallway and zombie directly across in line with hallway, regardless of the caster's corner selected as center of spell.

[Jeff Merola]

It would get either the zombies and the guy in red/yellow, or a zombie and a blob, depending on which corner they picked for the spell to burst from, because the caster has both line of sight and line of effect. Total cover blocks bursts, not just regular cover (which just grants +2 to any reflex saves that may result).

[Ravingdork]

Here's a diagram I put together for you, though it looks as though I may have been a little too slow. :P

EDIT: It shows a wall (which grants total cover) being struck by a 20-foot radius spread effect (left) and a similarly sized burst effect (right) and their respective points of origin. The spread wraps around the wall and fills up the entire area, whereas the burst has part of its area blocked by the wall. Therefore, the NPC enemy on the left falls within the spread's area of effect, but the NPC enemy on right dos not fall within the burst's area of effect.

Note that the enemy on the left likely still got cover bonuses to his saves against the spread effect.

[RumpinRufus]

Not sure that diagram is actually correct, RD.

Burst, Emanation, or Spread wrote:

A spread spell extends out like a burst but can turn corners. You select the point of origin, and the spell spreads out a given distance in all directions. Figure the area the spell effect fills by taking into account any turns the spell effect takes.

Updated diagram coming.

[Ravingdork]

Here are the official rules from the Core Rulebook Magic chapter with which I'm familiar with:

Spread: Some effects, notably clouds and fogs, spread out from a point of origin, which must be a grid intersection. The effect can extend around corners and into areas that you can't see. Figure distance by actual distance traveled, taking into account turns the spell effect takes. When determining distance for spread effects, count around walls, not through them. As with movement, do not trace diagonals across corners. You must designate the point of origin for such an effect, but you need not have line of effect (see below) to all portions of the effect.

Burst, Emanation, or Spread: Most spells that affect an area function as a burst, an emanation, or a spread. In each case, you select the spell's point of origin and measure its effect from that point.

A burst spell affects whatever it catches in its area, including creatures that you can't see. It can't affect creatures with total cover from its point of origin (in other words, its effects don't extend around corners). The default shape for a burst effect is a sphere, but some burst spells are specifically described as cone-shaped. A burst's area defines how far from the point of origin the spell's effect extends.

[RumpinRufus]

Spreads as I understand them.

[RumpinRufus]

Actually, I think this might be more accurate: diagram.

This diagram uses the criterion "maximum of 20 foot distance from the point of origin to the furthest corner." Which corresponds to how bursts are drawn, e.g., 10-foot bursts and 20-foot bursts.

The first diagram I made was using something more similar to the movement of a PC, but that kind of breaks down when you are talking about referencing distance from an intersection.

But I would be lying if I said I haven't gotten myself a bit confused.

[ckdragons]

Thank you for the diagrams. I did have one question... why doesn't the burst spell effect in the diagram "wrap" around the wall since the point of origin is centered at the end of it, and technically the intersection of the square behind the wall?

[RumpinRufus]

I was assuming a "thin but not paper-thin" wall, and so it was still blocking line of effect to that one NPC. If the wall ended ~1 foot sooner, it probably wouldn't be blocking LoE and it would hit him as well.