Walls, line of sight, and obscuring terrain

[Al'Kelhar]

Hi guys,

My wizard is about to reach 9th level, and is going to take wall of fire as one of his 9th-level daily attack powers.

The power's description states that a wall of fire "blocks line of sight". It does not state that any of the squares of the wall are obscured in any way. (FWIW the latest version of the wall of fire power, from the Wizard Playtest in Dragon 404, says exactly the same).

Q1. Can a creature see into a square occupied by a wall of fire? Does is make any difference if the creature is itself in a square occupied by the wall?

Q2. Can a creature whose space is wholly within a wall of fire see squares either side of the wall? Does it make any difference if the creature is partly inside and partly outside the wall (e.g. because it is Large or larger)?

On a vaguely related note, my group has always played that an obscured square grants concealment for both creatures inside the square and for targets of that creature. That is, obscuring effects are a two-way street - a creature in a foggy square is harder to hit by a creature outside that square, but equally, the creature in the foggy square has just as much difficulty hitting a creature outside that square. If you can't see into the fog very well, how can a creature in the fog see out of it well?

However, on reading up on lightly and heavily obscured squares and the concealment rules, it would appear that a creature inside an obscured square is concealed as against all others, but does not suffer any penalties attacking creatures outside the obscured square (assuming there are no other obscured squares between them). In which case, it would seem that it's often beneficial for a creature to stay in an obscured square. Particularly a heavily obscured one. And in that case, powers that create zones of obscured squares ostensibly in order to foil attacks by enemies create the perverse incentive to stay inside them.

A case in point - wall of gloom. Whille it expressly states that creatures in the wall (which is heavily obscured) are blinded, it also states that squares adjacent to the wall are lightly obscured. So your enemies simply stay in squares adjacent to the wall, and get a +2 net benefit to defences against melee and ranged attacks, while suffering no penalties. While I can see that placing the wall adjacent to your party's fighter (thereby placing him in a lightly obscured square, ready to smack anything that appears in the heavily obscured squares adjacent to him) might be a feasible use of the wall, that's a fairly specific situation. In most cases, it would be strictly better just to have the wall of gloom create the wall of heavily obscured squares in which creatures are blinded, and do away with the adjacent lightly obscured squares.

Similarly, if I'm a bad guy, it actually benefits me to stick around at the edge of a stinking cloud, if I can stand the (now pathetic) poison damage I'll sustain at the end of my turn. On balance, it's often better for the bad guy to take that damage, be effectively invisible to any PC that's not adjacent to him, and gain a +2 net benefit to defences against adjacent PCs. Particularly if he's a ranged controller or artillery - "thanks for that, I'll just hang around in here blasting you with my ranged powers while you can't see me".

Q3. Is it really the case that if a creature is in an obscured square, it gains concealment, but does not suffer any penalties to its attacks against creatures outside that square?

Cheers, Al'Kelhar

 

[Infiniti2000]

Q1. Yes. No. The wall blocks LOS, but you have to see the wall. There's no rules mechanics that differentiate the interior of a square from the edge (i.e., membrane) of the square. Thus, to even see the wall itself you have to be able to see into the square (and thus out of it).

Q2. Yes. No. There's little reason to make this more complicated than otherwise and there are significant disadvantages to being within the wall that I wouldn't rule you can't see out of a wall.

Q3. Yes. You figure LOS from a corner, not from inside the square or the opposite corner to which you plan to look.

Bonus: However, you can't see "sideways" through a wall. So, two opponents adjacent to each other within squares of the wall can see each other. If they are separated by a section of wall, then they cannot see each other because that would be seeing through the wall (even though they are effectively inside).

 

[DracoSuave]

A creature in the wall can see or be seen by any other creature provided a line between any of the creature's corners can be connected to any of that other creature's corners.

So, if there's no wall between said creatures, visibility is just fine.

HOWEVER

On the question of concealment.

A creature in the wall will have concealment to creatures outside the wall. This is because at least one [back] corner is blocked from the view of an outside creature. With less than four lines of sight, concealment is incurred.

The creature will not have total concealment, however, because the front corners are NOT blocked.

A creature outside the wall will obviously have all four corners accessible to a single [front] corner of the creature in the wall. Thus, a creature outside the wall will not have any concealment vs the creature inside the wall.

PS: Obviously this changes if either creature has to look through other squares of the wall. Adjust lines of sight accordingly.

-----------------------------------

Regarding Obscured terrain:

There's three types of obscured terrain. Lightly, heavily, and totally. Each operates as exceptions to how concealment works, and does not use the standard line of sight rules. There is a difference between 'line of sight is blocked' and 'obscured terrain.' Obscured terrain ignores the corner rules for line of sight completely, and goes ahead and does its own thing.

Lightly Obscured:

Creatures have total concealment if five or more squares are between you and the target, otherwise, normal concealment. However, you can still see through those squares, and have -5 to Perception checks.

Thusly a totally concealed creature will still actually be visible, unless they Stealth.

Heavily Obscured:

Adjacent creatures are concealed. Non-adjacent creatures are totally concealed. You can see one square away, but no further.

Totally Obscured:

You see nothing, not even adjacent creatures.

 

[Infiniti2000]

With less than four lines of sight, concealment is incurred.

Can you point to this rule? I know it's there for cover, but I can't find support for this within the on-line compendium. If it's only within the PHB, I guess I can't find it from here. The "determining cover" stuff is in the on-line compendium.

 

[DracoSuave]

Can you point to this rule? I know it's there for cover, but I can't find support for this within the on-line compendium. If it's only within the PHB, I guess I can't find it from here. The "determining cover" stuff is in the on-line compendium.

Line of Sight, in the PHB.

However, it doesn't include the lines from corners thing.

IF that is the case than this applies:

"You can see
the target if at least one line doesn’t pass through or
touch an object or an effect—such as a wall, a thick
curtain, or a cloud of fog—that blocks your vision."

As every line going to an object inside a wall of fire touches the wall of fire, no line exists that does not, and thus, the object inside cannot be seen, and cannot see out.

 

[Infiniti2000]

That would be irritating if there are extra rules in the PHB that are not in the on-line compendium, but c'est la via. The glossary definition of line of sight is "A clear line from one point to another point in an encounter that doesn’t pass through or touch an object or an effect—such as a stone wall, a thick curtain, or a cloud of fog—that blocks the vision of the viewer." That's very similar to what you quoted, but I dispute your conclusion. There's nothing about number of lines causing concealment. Also, the line that "touches" the wall of fire simultaneously touches the creature. Like I said, there are no rules mechanics on the boundary conditions of the square. The only rules similar to that would, however, support my point. Looking at the cover options (again), it says that "A line that runs parallel right along a wall isn’t blocked."

Anyway, I think we can look at the rules on phasing to help us with this. I think the rules there should be similar. Take a look at what [MENTION=82106]AbdulAlhazred[/MENTION] and [MENTION=2011]KarinsDad[/MENTION] write in these two posts. They seem to concur with you, but I guess I'm the sole dissenter. Actually, I'm more along the lines of "not enough proof" and enough anecdotal evidence to the contrary.

 

[Mr. Teapot]

Line of Sight, in the PHB.

However, it doesn't include the lines from corners thing.

The imaginary lines from the corners in in the DMG, not the PHB. It's also in the compendium, in the glossary entry for "Determining cover for ranged attacks" (there's also a briefer writeup for melee attacks).

 

[DracoSuave]

That would be irritating if there are extra rules in the PHB that are not in the on-line compendium, but c'est la via. The glossary definition of line of sight is "A clear line from one point to another point in an encounter that doesn’t pass through or touch an object or an effect—such as a stone wall, a thick curtain, or a cloud of fog—that blocks the vision of the viewer." That's very similar to what you quoted, but I dispute your conclusion. There's nothing about number of lines causing concealment. Also, the line that "touches" the wall of fire simultaneously touches the creature. Like I said, there are no rules mechanics on the boundary conditions of the square. The only rules similar to that would, however, support my point. Looking at the cover options (again), it says that "A line that runs parallel right along a wall isn’t blocked."

Anyway, I think we can look at the rules on phasing to help us with this. I think the rules there should be similar. Take a look at what [MENTION=82106]AbdulAlhazred[/MENTION] and [MENTION=2011]KarinsDad[/MENTION] write in these two posts. They seem to concur with you, but I guess I'm the sole dissenter. Actually, I'm more along the lines of "not enough proof" and enough anecdotal evidence to the contrary.

The thing is, a wall in that instance refers to a physical wall, not a wall effect. Thus, the rule "You can see the target if at least one line doesn’t pass through or touch an object or an effect—such as a wall, a thick curtain, or a cloud of fog—that blocks your vision." (DMG, btw) kicks in. Are they ANY lines that do not touch the wall of fire? No. Therefire the creature inside cannot be seen at all. The fact the lines also touch the creature is irrelevant, as such lines must do so logically. It's impossible to not touch the creature with a line going to its corner. The only question is, therefore: Does it touch the wall? Yes. Therefore that line is eliminated, and when all lines are eliminated, 'cannot be seen' is the only possible answer.

 

[KarinsDad]

Well, I think that we have to go with the entire writeup of the power:

You conjure a wall that consists of contiguous squares filled with arcane fire. It can be up to 8 squares long and up to 4 squares high. The wall lasts until the end of your next turn. Any creature that starts its turn adjacent to the wall takes 1d6 + Intelligence modifier fire damage. If a creature moves into the wall’s space or starts its turn there, the creature takes 3d6 + Intelligence modifier fire damage. Entering a square occupied by the wall costs 3 extra squares of movement. The wall blocks line of sight.

This tells me that the entire square is filled with the fire and that fire totally blocks LOS.

Q1. No. No.

Q2. No. No.

I would think that there is an argument that a character inside the wall could see out by picking a corner of the square and tracing an imaginary line, but if the creature cannot see to the corner of the square from inside the wall, how can it see beyond? I think that rule is for creatures that can actually see within their own square.

Personally, I think the best interpretation is that the wall totally fills the square (as a totally opaque cube) and creatures cannot see in or out or sideways or any such.

 

[S'mon]

You can't see through the wall, but if a creature's square runs along the edge of the wall, which it normally will do if 'in' the wall, then AFAICS it can see out & be seen ok (as there is no wall there to block line of sight), and there don't appear to be any rules granting it concealment (or granting concealment to those it targetted outside the wall), though that would be a reasonable ad hoc ruling.

The effect would then be that you need at least 1 square of wall to 'block line of sight', which I think fits with RAW & RAI.