How do multiple levels affect area of effect spells?

[WarKitty]

How do multi-level terrain surfaces affect spells that have an area of effect? So for example, we had a spell (poison vines) cast on a semi-enclosed platform which is several feet above the ground. Does the spell spill out onto the ground, or do the different levels interfere?

[Necroticplague]

Depends on the type of area. Some can go around corners and 'spill' like that, some can't.

EDIT: just to expand and be more specific:

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, even 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 spreads 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.

[Extra Anchovies]

Poison Vines affects a 10*CL-ft radius spread, and that's the area spread, not the effect spread.


A spread spell spreads 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.

So it's a corner-turning burst.


A burst spell affects whatever it catches in its area, even 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.

Poison Vines (and Vine Mine, from which it inherits its function) contains no mention to how the area is shaped, so it defaults to a sphere. It doesn't even need to be anchored to any surface; you pick a point in space within the spell's range, and a (potentially very large) three-dimensional sphere of vines grows centered on that point. If an object is within the volume of the spell, the spell flows around it.