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D&D 3E
Line of Sight 
28th-Feb-2006 09:14 am
Bitch Please - peanuts
This came up in my last game. What are the actual rules for drawing line of sight? Can I shoot at a bad guy from behind another character? I thought this was represented by the -4 for firing into melee, but the DM said (with some uncertainy, because he wasn't sure) that the character blocked line of sight. I flipped through the PHB and the SRD looking for the exact rules on drawing line of sight, but couldn't find what I was looking for.

28th-Feb-2006 02:18 pm (UTC)
Treat it as cover. LOS is from any part of your control space to any part of thiers. But use a little common sense, think of it like trying to score a goal in hockey. Sure you can see the net, but the goalie gives it cover to reduce your chance 'to hit'

28th-Feb-2006 04:36 pm (UTC)
As an addendum to this post.

Remember that even thou a normal PC occupies a 5' x 5' area they dont actually fill it. The same goes for any and all creatures, they occupy the area but do not fill it. (Except for Gelatinus Cubes of course) Because of that you treat LOS from any point on the occupied square to any point on the targets occupied square. Fairly straight forward for flat battles. Gets a little tricky with elevated battles. An easy way I find is to get a tailors tape measure (the soft flexible tapes they wear around thier necks at fancy clothing stores) and guesstimate the head height of the attacker and again go to any part of the targets square up to a reasonable height for the size of the creature.

Or just remember the answer that is always right, 'Cuz I'm the DM and I said so!'

28th-Feb-2006 03:28 pm (UTC)
Line of sight means you can see the person. Being behind a wall or a hill or whatever blocks line of sight. Being invisible or in darkness would block line of sight. Those are basically the only cases where you don't have a line of sight.

If you're attacking with a ranged weapon, then rules for cover and shooting into melee come into play. But for stuff that only requires a line of sight (like magic missile), then it doesn't matter what kind of cover they have as long as you can actually see them (you can't shoot a magic missile blind).
28th-Feb-2006 05:35 pm (UTC)
yeah, trying to shoot at someone who has somebody in their way has soft cover, or partial cover, and is the -4 to hit. also remember this only applies if the two engaged in melee combat. poster above me has it on line of sight. also, don't forget that if the two are in a grapple, 50% chance to hit either one. ;]
28th-Feb-2006 06:10 pm (UTC)
Cover never applies a penalty to hit; it provides a bonus to Armor Class... And soft cover is not restricted only to when the target is in melee combat; that's the "firing into melee" -4 penalty. Firing into melee past soft cover gives the target a +4 AC bonus and applies a -4 penalty on the attack roll.
28th-Feb-2006 10:35 pm (UTC)
Strictly speaking, a bonus to Armor Class is a penalty to hit. I never understood why they did that, made two different kinds of modifiers. It has the same game effect (a lessened chance to hit). Is there a situation where a character's AC is important that doesn't involve a roll to-hit?
1st-Mar-2006 01:25 am (UTC)
There could be. More importantly, it's a matter of how the situation interacts with the rules. Situations that affect how you can do your task, regardless of target, modify your attack roll. Situations that affect your target's resistance or protection, independent of your attack roll, modify the target's Armor Class.

This is the same reason certain things provide skill penalties or bonuses, and other things provide DC modifiers. Doing all this on only one side leads to inevitable confusion and unnecessary complexity ("so, make sure you write down your attack bonus against targets with cover, and against targets with concealment, and against targets with plate mail, and against...", which is equivalent to going back to 1e days of having to reference an attack matrix).
1st-Mar-2006 01:47 am (UTC)
I guess I can see how that works. Using the original example, if A is shooting at B through a square occupied by C, he will get a penalty to hit, whereas D, who is not shooting through an occupied square, wouldn't get that penalty.
1st-Mar-2006 01:52 am (UTC)
Well, in this case, that affects the protection of the target, so B gets a cover bonus to AC against A, but not against D, or against anyone who ignores cover bonuses to AC (an arcane archer's Phase Arrow ability, for instance).

If, however, A was in the area of a bane spell (and had failed their saving throw), while D was not in the area, or had succeeded at their saving throw, A has a penalty to hit while D does not.

In the first case, the target's position is relevant, which makes it affect the target's AC. In the second, the ability of the attackers is relevant, which makes it affect their attack rolls.
1st-Mar-2006 03:42 am (UTC)
sorry, the post was missing a "there is the -4 to hit". however i thought the soft cover was only +2 AC? i guess i was wrong?
1st-Mar-2006 01:23 pm (UTC)
Soft cover is +4 AC, like any other form of (non-total) cover.

Total cover completely prevents direct attacks, and thus doesn't grant an AC bonus.

There is also a form of "improved cover" (basically equivalent to the 3.0 'nine-tenths cover'), but it's generally up to GM fiat: "In some cases, cover may provide a greater bonus to AC and Reflex saves. In such situations the normal cover bonuses to AC and Reflex saves can be doubled (to +8 and +4, respectively). A creature with this improved cover effectively gains improved evasion against any attack to which the Reflex save bonus applies. Furthermore, improved cover provides a +10 bonus on Hide checks." (SRD)

In any case, cover always grants at least a +4.
28th-Feb-2006 05:45 pm (UTC)
P21 DMG.
P139 PHB.
Not as clear as it could be, but that's where to look.
28th-Feb-2006 06:08 pm (UTC)
Line of sight is an unblocked line between your space and your target's space.

"Two creatures can see each other if they have line of sight to each other. To determine line of sight, draw an imaginary line between your space and the target's space. If any such line is clear (not blocked), then you have line of sight to the creature (and it has line of sight to you). The line is clear if it doesn't intersect or even touch squares that block line of sight. If you can't see the target (for instance, if you're blind or the target is invisible), you can't have line of sight to it even if you could draw an unblocked line between your space and the target's."
D&D Online Glossary, from the PH.

A square only blocks line of sight if it also provides total cover.

"Attacks against a target that has total cover automatically fail. Total cover blocks line of sight and line of effect."
D&D Online Glossary, from the PH.

The only time you cannot attack someone due to line of sight/line of effect is when they have total cover.

"If you don’t have line of effect to your target he is considered to have total cover from you. You can’t make an attack against a target that has total cover."

Creatures do not provide total cover against ranged attacks; they only provide cover.

"Creatures, even your enemies, can provide you with cover against ranged attacks, giving you a +4 bonus to AC. However, such soft cover provides no bonus on Reflex saves, nor does soft cover allow you to make a Hide check."

Firing from behind your ally against someone not directly the other side of your ally will not invoke cover, unless you do not have unbroken line of effect other than through your ally.

"To determine whether your target has cover from your ranged attack, choose a corner of your square. If any line from this corner to any corner of the target’s square passes through a square or border that blocks line of effect or provides cover, or through a square occupied by a creature, the target has cover (+4 to AC)."

In the following diagrams, "Y" is you, "A" are your allies, and "M" is your enemy. A dot (.) is bare floor, no obstacles, and an "X" is a wall.

You cannot draw line of effect from any corner of your square to any corner of your enemy's square without passing through an ally's square's border. Your enemy has cover, giving him a +4 to AC against you (and if you're firing into melee without Precise Shot, you take a -4 penalty to your attack roll).

You can draw a line from a corner of your square to a corner of the enemy's square without going through any ally's square or border. No cover is involved (but you also don't have cover against him, either). You're still firing into melee, so you still take a -4 penalty to your attack roll.

Upshot of this: your DM was wrong according to the rules; creature obstacles do not prevent ranged combat past them, but they do provide cover (but not total cover).

Hope this helps.
28th-Feb-2006 08:07 pm (UTC)
I Vote dacileva as the "DM of the Month". Knowledge of that person is great! =)
28th-Feb-2006 11:22 pm (UTC)
Your last example is wrong, I believe.

As you quoted...if ANY line passes through a square or border that provides cover, there is cover. In your last example, the best possible line to draw from would have been the upper left corner, and drawing from that corner to either of the lower corners of 'M' passes through a border of square 'A(left)'.

Were 'M' five feet further north, you would have been correct.
1st-Mar-2006 01:29 am (UTC)
You're right, I forgot to check every corner of the target, and I always forget about the edges when it's not as clear-cut.

In fact, even were 'M' and 'A(right)' both five feet further north, it would still fail, because the line from upper left of 'Y' to lower-right of 'M' passes through 'A(right)'.

In other words, it's extremely tough to attack an enemy who is in melee with an ally without the enemy gaining cover, unless you are opposite your ally.
1st-Mar-2006 05:47 am (UTC)
Well, to clarify, it's not so much "if any line passes through a square or border that provides cover", but rather:

1. The attacker chooses a corner of their square.
2. The defender chooses a corner of their square.
3. A line is drawn.
4. If the line passes through any other occupied square, there is cover. If not, no cover.

So I think your first example would be correct if you go from the upper left corner of Y to the any corner that is NOT the lower right of M (although again I'd have to have the line). The lower right would clip A (right) as mentioned.

If M was five feet further north and A (right) was not, you'd be fine regardless of corner. If M was five feet further north and A (right) was also five feet further north, the same scenario applies as before.

Hope your DM sucks at picking corners. :)
1st-Mar-2006 11:32 am (UTC)
I've always had the impression that if any line is clear it works.
1st-Mar-2006 01:26 pm (UTC)
Other way around. If any line is blocked, they have cover.

"To determine whether your target has cover from your ranged attack, choose a corner of your square. If any line from this corner to any corner of the target’s square passes through a square or border that blocks line of effect or provides cover, or through a square occupied by a creature, the target has cover (+4 to AC)." (SRD, emphasis mine)

What you might be mixing it up with is the "big creatures" rule, which only applies in melee, and allows the attacker to choose which square of the big creature to attack.

"Any creature with a space larger than 5 feet (1 square) determines cover against melee attacks slightly differently than smaller creatures do. Such a creature can choose any square that it occupies to determine if an opponent has cover against its melee attacks. Similarly, when making a melee attack against such a creature, you can pick any of the squares it occupies to determine if it has cover against you." (SRD)
1st-Mar-2006 05:41 pm (UTC)
It's stuff like this that makes me quite glad we rarely use minis in the games I'm in. Although sometimes they are handy too.
1st-Mar-2006 05:46 pm (UTC)
In most cases, it should be obvious whether something or someone is providing cover to a target or not. These rules should only ever come into play if there's a question, or a marginal situation. If the DM wishes, the DM can ignore these rules, and make an ad hoc decision about it. However, I think it's best if a DM fully understands these rules before making such ad hoc decisions, or their ad hoc decisions are likely to be incorrect when examined, and create unpleasant precedence.
1st-Mar-2006 05:50 pm (UTC)
I'm in 100% in agreement with you, and thanks I think this seems to be something that was confusing a number of us and you've been very helpful in clarifying it.
1st-Mar-2006 01:29 pm (UTC)
Doesn't work that way; see my response to inncubus, below.

This is a good thing, anyway. It's better for the rule to come at least somewhat closer to what would be expected, than for the "corner-picking" to become a game of "Play the DM".

In an ideally-adjudicated game of 3.5, you shouldn't even need a DM's judgment for situations covered by the rules. This is one of the best things about 3.5; as a DM, knowing the rules as well as I do, I can ignore most things like this, and let the rules take care of them, while I do the things that a DM can do that the rules can't, like examining villainous motivations and tactics, and describing the activities of the environment in which the player characters find themselves.
1st-Mar-2006 01:30 pm (UTC)
Er, -below +above.
1st-Mar-2006 06:51 pm (UTC)
Ah, fantastic.

I was pretty sure I'd seen the "both of you pick" syndrome in a Sage Advice column, but either way, the GM would usually pick the square that's going to give cover anyway ;)
1st-Mar-2006 06:52 pm (UTC)
And you're right, I think I may have been mixing it up with the "big creature" rule.

Cover is not normally something that comes up in our games, as we seem to have a predisposition to either ending combats in one round or playing the long range bombardment game.
1st-Mar-2006 07:30 pm (UTC)
I see. At least some of my players have played either Alternity, Star Wars (WEG), Star Wars d20, or d20 Modern, where, in a firefight, "no cover" usually equalled "dead character", with "no chance of resurrection" (those games are in order from hardest to survive a firefight to easiest to survive a firefight; none are as easy as D&D, though).

1st-Mar-2006 07:31 pm (UTC)
Let's have a moment of silence for WEG Star Wars D6...

On another note, I never, ever expected this topic to go on this long :-p
1st-Mar-2006 10:50 pm (UTC)
I've done both Alternity and d20 Modern.

All of the games tended to involve very little gunfighting. When it did break it, it was usually over very quickly, cover or not. ;)
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