D&D 4E Determining cover in 4e: The pingpong dilemma

[Kariotis]

Cover in 4th edition has pretty good, intuitive, usable rules. I've always had one minor issue with them though in terms of clarity, and I've attached the relevant page from the Rules Compendium for reference.

The issue is that, as written, not necessarily as intended, cover is presented as a situation that both combatants find themselves in, not as something that would usually confer an advantage of one combatant over the other. The rules present few clear-cut cases where cover is a one-way street. The clearest one would be the fact that allies grant you cover from enemy attacks, while you are able to shoot through squares occupied by allies. I miss clearer rules for more cases like this, especially when it comes to terrain, as, arguably, terrain advantage used for cover (obstacles, walls, height advantage) is used both in the real world and in fiction and would make intuitive sense, too.

To be more specific, the issue is that the rules are unclear about obstacles conferring one-way bonuses. Two examples:

• The pictured example from the rules compendium, the Zombie right next to the edge of the wall receives the same bonus to cover as the Attacker around the edge even though the attacker is out in the open and NOT next to a wall.
• Even more egregious is RAW for superior cover, where the more "fluffy" and more "crunchy" part of the explanation are in tension with another. Quoted from the Rules Compendium:

More fluffy: "An attacker takes a –5 penalty to attack rolls against a target that has superior cover. 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."

More crunchy: "To determine if a target has cover, choose a corner of a square the attacker occupies, or a corner of the attack’s origin square, and trace imaginary lines from that corner to every corner of any one square that the target occupies. If one or two of those lines are blocked by an obstacle or an enemy, the target has partial cover. (A line isn’t blocked if it runs along the edge of an obstacle’s or an enemy’s square.) If three or four of those lines are blocked yet line of effect remains—such as when a target is behind an arrow slit—the target has superior cover."

The crunch part effectively guarantees that a combatant and their opponent will almost always confer the SAME cover bonus to each other when staying in place, because the imaginary lines drawn from the edges of their squares are necessarily bidirectionally equivalent. If combatant A has partial cover, combatant B has, too. If combatant A has superior cover, combatant B has too. It doesn't matter if one is out in the open and the other can press directly against the corner of the wall. It doesn't matter if one is directly behind the arrow slits and can shoot through them, and one is 10 m away and has to aim through the tiny arrow slit from afar. It doesn't matter if one stands on the ground and the other on a roof, leveraging the edge of the roof for cover. The invisible lines dictate the cover, and as the lines pingpong from A to B and back, their cover is always identical unless the DM takes the more "fluffy" explanation in the rules to heart, uses common sense and says that "of course only the guy directly behind the arrow slits has superior cover, and not the guy 10 squares away out in the open, even though they are both technically behind an arrow slit for each other".

I wanted to ask about your experience with this aspect of cover in 4e. Also, maybe my gaming groups have always missed something in the crunch, in that case please correct me

 

[billd91]

The important factor here that I believe you are missing is that you choose one corner from the attacker’s square and test all of the target’s corners. You don’t have to use all of the attacker’s corners.
For features like arrow slits, I wouldn’t even use the crunch method. Most depictions on map boards aren’t going to be precise enough for it, often being hastily drawn by a DM hopped up on caffeine, lubricated by alcohol, or dusted by Cheetos.

 

[Kariotis]

The important factor here that I believe you are missing is that you choose one corner from the attacker’s square and test all of the target’s corners. You don’t have to use all of the attacker’s corners.

That's factored in. It doesn't matter. If A chooses one corner (the most appropriate one to determine cover), B does the same. It always comes down to the imaginary lines being bidirectional. If there is a connection or connections from a corner of A's square to B's square, there must be the same number of connections from B to A.

Agreed on the second part of your post Which is kind of my issue with the RAW here, they don't really cover the cases where cover is clearly one-sided for an unambiguous ruling.

 

[Mannahnin]

That's factored in. It doesn't matter. If A chooses one corner (the most appropriate one to determine cover), B does the same. It always comes down to the imaginary lines being bidirectional. If there is a connection or connections from a corner of A's square to B's square, there must be the same number of connections from B to A.

You're still misunderstanding.

Look at the example of the Zombie and the "attacker" to its southwest in the diagram. Z and A, for convenience.

While A is attacking, he can and must check LOS from ANY ONE corner of his own square to ALL FOUR corners of Z's square, but no matter which of his four he uses, at least one of Z's four is obscured (the zombie's NW corner is obscured no matter which corner A uses to draw LOS from).

When Z attacks back, it can pick its own southeast corner to draw LOS from and easily draw a clear line to ALL FOUR corners of figure A's square, thus A has no cover from Z.

If A were positioned two squares north he would STILL have no cover, as Z is permitted to draw LOS along the wall from either Z's SW or SE corner. "A line isn’t blocked if it runs along the edge of an obstacle’s or an enemy’s square."

 

[Kariotis]

My bad, you guys are absolutely right, I'm sorry Would you believe nobody in multiple groups ever pointed this out over the years? Some of us can quote 3.5e grappling rules verbatim and never got this one right

 

[billd91]

My bad, you guys are absolutely right, I'm sorry Would you believe nobody in multiple groups ever pointed this out over the years? Some of us can quote 3.5e grappling rules verbatim and never got this one right

Honestly, I have yet to see someone who actually uses it in the wild. I never do, not in my home game, not in the AL games I run at Gamehole Con. We just eyeball it or rely on how someone describes how they're positioning themselves near some bit of cover and we're good to go. The grid we use isn't anything more than an approximation so we allow wiggle room.

 

[Mannahnin]

My bad, you guys are absolutely right, I'm sorry Would you believe nobody in multiple groups ever pointed this out over the years? Some of us can quote 3.5e grappling rules verbatim and never got this one right

Much sympathy! I'm glad to have been able to help break the mental block! If you guys can quote the 3.5 grappling rules you beat me on that one. I tried hard to commit those to memory, and got most of the steps down, but not the whole thing.

Honestly, I have yet to see someone who actually uses it in the wild. I never do, not in my home game, not in the AL games I run at Gamehole Con. We just eyeball it or rely on how someone describes how they're positioning themselves near some bit of cover and we're good to go. The grid we use isn't anything more than an approximation so we allow wiggle room.

My old groups used it all the time. But that may have something to do with several of us having also been miniatures wargamers and having been accustomed to parsing LOS rules closely in particular.

 

[Tigris]

My bad, you guys are absolutely right, I'm sorry Would you believe nobody in multiple groups ever pointed this out over the years? Some of us can quote 3.5e grappling rules verbatim and never got this one right

These things happen its not that unusual. I play in a lot of boardgame groups and in soo many boardgames at some points someone notices that a rule is played wrong. Often someone from another group.


I honestly also think this rule is a bit too complicated. Having from one of your corners a line to the middle of the enemy is more or less enough for cover and would be simpler to understand (corner to middle is also less symetrical than corner to corners)