Sorting out Line of Sight, Cover, etc...

hyphz · Oct 7, 2008

I've been bothered by this for some time, but I wonder if there's any clear plan to sort out the rules on Line of Sight and Effect, and similar.

The rulebook gives an excellent description of the differences between Cover and Concealment, and Line Of Sight and Line Of Effect - and then fails utterly to use it. This leads to ugly situations like Like of Sight being different for different attacks and for actually seeing stuff (whereas Line of Effect would make much more sense to vary in this way - a PC can create lots of different effects, but always has the same eyes), or the hiding rules specifying that "cover or concealment" is required to hide (ie, a Rogue can hide behind a toughened but clear glass wall, because it provides cover - after all, to shoot the Rogue, you'd have to avoid hitting the wall)

A fair bit of this seems to stem from the old 3.5e days in which the distinction between "cover" and "concealment" largely was based on whether a % miss chance or to-hit modifier was to be used to deal with the problem, but now they've been unified, perhaps the rules could be changed something like this:

Line Of Sight. To establish Line of Sight to a target, choose a corner of the square you are in. Trace lines from that corner to all four corners of your target's square (or, if your target is Large, all four corners of any square it occupies). If none of these lines pass through an obstacle that obstructs sight, you have line of sight to the target. (Allies and enemies do not obstruct sight.) If one, two, or three of these lines pass through obstacles that obstruct sight, you have line of sight to the target but the target has partial concealment. If four of these lines pass through obstacles that obstruct sight, the target has total concealment, and you do not have line of sight to it.

Line Of Effect. To establish Line of Effect with a particular attack to a target, first trace a line from the centre of the square you are in to the centre of your target's square (or, if your target is Large, of any square your target occupies). If this line passes through an obstacle that obstructs the attack you are using, you do not have Line Of Effect; stop here.

If this line is unblocked, choose a corner of your square and trace lines to the four corners of your target's square. If none of these lines pass through obstacles that could block your attack, you have line of effect to the target. If one or two lines pass through such obstacles, you have line of effect to the target but the target has cover. If three or four lines pass through such obstacles (but the centre-to-centre line did not), you have line of effect to the target but the target has superior cover.

When calculating the modifier for an attack, check both Line of Sight and Line of Effect. However, if the same obstacle(s) provide both Cover and Concealment to your target, add only the Cover modifier. Calculate the Concealment modifier with reference only to obstacles that block sight but not effect (such as fog).

Hiding requires concealment. It cannot be performed with only cover.

Sorting out Line of Sight, Cover, etc...

hyphz

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