Determining line of sight vs cover

deleteme123456 · Oct 16, 2008

In this case you might just need a little DM fiat... it's incredibly hard to shoot back through an arrow slit when you're not adjacent to it. If someone really wanted to, I'd do it at a steep penalty, at least -5 and maybe -10. Or just let the wizard fry them with a scorching burst.

Nikosandros · Oct 16, 2008

infocynic said:
. If someone really wanted to, I'd do it at a steep penalty, at least -5 and maybe -10.

You mean -5 or -10 on top of the penalty for superior cover?

tiornys · Oct 17, 2008

infocynic said:
In this case you might just need a little DM fiat... it's incredibly hard to shoot back through an arrow slit when you're not adjacent to it. If someone really wanted to, I'd do it at a steep penalty, at least -5 and maybe -10. Or just let the wizard fry them with a scorching burst.

I wouldn't penalize like this. An arrow slit is a classic example of superior cover--you have line of effect (which requires that at least one line traced from somewhere within your square to somewhere within the target square be unblocked), and all four lines from one of the attacker's corners to the four defender's corners are blocked. Superior cover, -5 penalty.

Also:

PHB said:
Superior Cover (-5 penalty to Attack Rolls): The target is protected by a significant terrain advantage, such as when fighting from behind a window, a portcullis, a grate, or an arrow slit.

(underlined for emphasis)

t~

Nikosandros · Oct 17, 2008

In principle, I agree with you completely. However the rules state that: if four lines are blocked from every corner, you can’t target the defender. (DMG, p. 43).

Larrin · Oct 17, 2008

Nikosandros said:
In principle, I agree with you completely. However the rules state that: if four lines are blocked from every corner, you can’t target the defender. (DMG, p. 43).

by pretty much this same logic you can't attack from behind an arrow slit, even if you are sitting right behind it.....at the very least they'd have superior cover against you. This would make arrow slits pointless.

The best solution is to simply assume that the arrow slit is located at one corner of the square, thus the attacker inside can use that as his corner for getting a clean shot at the enemy, and the enemy can use that as the one corner he can see (so its still superior cover)

tiornys · Oct 17, 2008

Nikosandros said:
In principle, I agree with you completely. However the rules state that: if four lines are blocked from every corner, you can’t target the defender. (DMG, p. 43).

Interesting, and a clear contradiction of the PHB.

PHB said:
To determine whether you can see a target, pick a corner of your space and trace an imaginary line from that corner to any part of the target's space. You see the target if at least one line doesn't pass through or touch an object or an effect....

Line of Effect: You can target a creature or a square if there's an unblocked path between it and you--that is, if you have line of effect to it. If every imaginary line you trace to a target passes through or touches a solid obstacle, you don't have line of effect to the target.

So, the PHB clearly states that for LoS you can trace to any part of the target's square, not just the corners. It's less explicit for LoE, but it implies at least as liberal an interpretation as for LoS. Arguably, the rules for LoE are even more liberal than for LoS, since LoS explicitly references a path starting at a corner of your space, where as LoE just wants an unblocked line from you to the target.

I'll note that for obstacles that fill squares, the PHB and DMG rules are identical. As Larrin points out, if the arrow slit is at the corner of a square, we have no problems. Discrepancy arises when you have obstacles that fill the corners of a square but leave openings along the border of those squares. According to the DMG, in the following situation, I can't be targeted by anyone:

Code:

         ||         ||         
         ||         ||         
         ||**     **||         
.........||.........||.........
         ||**     **||         
         ||         ||         
         ||    ME   ||         
         ||**     **||         
.........||.........||.........
         ||**     **||         
         ||         ||         
         ||         ||         
         ||         ||         


** = a 6 inch protrusion that blocks the corner of my square

This is clearly absurd. Therefore, I'd rule that the PHB trumps the DMG in cases where partial-square obstacles are concerned.

t~

Ravingdork · Oct 17, 2008

tiornys said:
This is clearly absurd. Therefore, I'd rule that the PHB trumps the DMG in cases where partial-square obstacles are concerned.

t~

And here I thought that everybody knew that the DMG rules for cover were messed up, in need of errata, and shouldn't be used.

Guess that's just true on the WotC forums.

Or perhaps I am just very, very wrong in my blanket statement.

deleteme123456 · Oct 17, 2008

raven_dark64 said:
And here I thought that everybody knew that the DMG rules for cover were messed up, in need of errata, and shouldn't be used.

Guess that's just true on the WotC forums.

Or perhaps I am just very, very wrong in my blanket statement.

I'm curious what in particular is messed up about the DMG rules, except for weird cases with partial-square obstructions (which I think I'll just avoid on principle for now).

Also re: Arrow Slits. The DMG specifically says (p 67)

DMG p. 67 said:
An arrow slit grants a ranged attacker superior cover while granting him or her a clear view of the battlefield. The firer determines the target’s cover from the square just outside the slit.

So yeah, I'd go back to a -5 penalty (and I did say -5 or -10) for superior cover unless you have some special power to bypass that. I don't think there's any problem with this then.

Slightly related: how does a condition like blinded impact area/close burst/blast attacks? My current understanding is that it doesn't, which seems odd, but the PHB says you just need LOE to the origin square and then determine cover from there, and blinded just says your targets have total concealment, and concealment doesn't help against a burst or blast. Would you rule any differently for powers written as area 1 square within 10?

WalterKovacs · Oct 17, 2008

The thing with burst/blast effects is, the attack roll is often not a case of directling multiple single attacks [although some are, especially ones for martial classes]. Still, even in cases of melee weapons used for close burst or a cloud of literal daggers being thrown by the rogue, it is the matter of just attacking an area and seeing what you can hit. So, being unable to see what you are trying to hit in those cases doesn't seem to be a big problem. Although as a blind character they would need to somehow come up with a "guess the square you are targetting" mechanic as if they were attacking a bunch of invisible things.

It makes sense, in a way, that if you can't see, throwing an AoE means you are bound to hit something.

Kordeth · Oct 17, 2008

infocynic said:
Slightly related: how does a condition like blinded impact area/close burst/blast attacks? My current understanding is that it doesn't, which seems odd, but the PHB says you just need LOE to the origin square and then determine cover from there, and blinded just says your targets have total concealment, and concealment doesn't help against a burst or blast. Would you rule any differently for powers written as area 1 square within 10?

No, I wouldn't. The fact that it's an area attack means, by its very nature, means that it hits everything within that square. If the blinded character can guess a square an enemy is in, using the rules on p. 281, and he drops an area 1 square spell on that square, it hits everything in that square without the penalty. If it was meant to take the penalty, it wouldn't be an area attack.