D&D 4E How to create a line effect in 4E

(Lots of edits happened.)

The rules for determining cover can be used to create line effects for powers. Important: it's best used sparingly as this takes a lot of time to resolve (you can pick one of four corners and that can result in different stuff between hit). However, if you have a cool effect in mind that would be best described as a line, this is how you can do it.

If you want to do this without creating new terms, have a secondary attack or whatever that targets any creature or object that grants cover to the original target. If you want this to affect allies, it's more difficult . All creatures or objects that would grant cover to the original target if they weren't your ally?

For example:

Magicannon "Final Spark"
Laser... is not difficult.
Daily *** Arcane, Implement, Radiant
Standard Action *** Area 1 square within 10 squares
Target: All creatures in the area
Attack: Int vs. Ref
Hit: 8d8 + Intelligence modifier radiant damage.
Miss: Half damage
Effect: Make a secondary attack against all creatures that provides cover to the square.
Secondary Attack: Int vs. Ref
Hit: 8d8 + Intelligence modifier radiant damage
Miss: Half damage

It's probably better to define a new area instead, since the simple method can't do zones and has trouble with hitting allies. We'll call it a "line" area.

Line X: A line fills X contiguous squares within range, starting from a square adjacent to the origin square (usually the square the user of the power is standing in) and ending in a terminal square within range X. Draw a line from the center of the origin square to the center of the terminal square; all squares in this area must fall on squares passed through by the line. The area cannot include the origin square, nor can any two squares in the area be equally distant from the origin square. You can arrange the area however you like, subject to the above restrictions.


[sblock=Old, doesn't work]To create a line area, pick one square within range (i.e. for an Area line 5 power, pick one square no more than 5 squares away from you), then draw lines from each corner of the origin square to each corner of the chosen square. The line area covers the chosen square and each square one of the lines touches. For example, a Line 5 area covers all squares between the origin square and a chosen square up to 5 squares away, including the chosen square.[/sblock]
For example:

Magicannon "Final Spark"
Laser... is not difficult.
Daily *** Arcane, Implement, Radiant
Standard Action *** Area line 10
Target: All creatures in the area
Attack: Int vs. Ref
Hit: 8d8 + Intelligence modifier radiant damage.
Miss: Half damage

Unroll Red Carpet
The universal symbol of celebrity
Daily *** Martial, Zone
Standard Action *** Area line 5
Effect: You and your allies gain a +5 bonus to Bluff and Diplomacy checks when inside the area. This effect lasts until the end of the encounter or until the red carpet is removed or destroyed (whichever comes first).


[sblock=Old stuff, probably not needed]It's best to define a new "key term" (more like 'cover' than 'necrotic'). Let's use between. The easier to explain but not as flexible definition is: A creature or object is considered between an origin square and a terminal square (or a creature in a terminal square) if it would provide cover to a creature in the terminal square from a ranged attack originating in the origin square. You know the drill: pick a corner from the origin square, draw lines to the four corners of the terminal square, and everyone the line is touching gets a happy face or a frowny face.

The more flexible definition is basically the same as above, except it also "hits" squares (for zones) and allies (for good effects). To determine if a creature or object is between an origin square and a terminal square, pick a corner from the origin square and draw a line from it to every corner on the terminal square. All squares and creatures and objects in those squares are considered between the origin square and the terminal square.

I'd use the more flexible definition. The less flexible definition is useful to explain the general idea (would it provide cover?), but between can also include squares and allies.[/sblock]

This seems like a good idea, what about lines that are more then 1 square wide?

Ick. The easiest way would be to pick multiple adjacent terminal squares, and anything between you and those squares gets hit. That gives you more of a cone shape, but oh well.

EDIT: Alternatively, you could pick two target squares and draw lines from both your square and another square adjacent to you. Not sure how to explain the fluff of this though. Any more than 2 squares each and you can get some weird shapes because you can make L patterns or block patterns with the picked squares.

Zelc said:

It's probably better to define a new area instead. We'll call it a "line" area. To create a line area, pick one square within range (i.e. for an Area line 5 power, pick one square no more than 5 squares away from you), then draw lines from each corner of the origin square to each corner of the chosen square.

Click to expand...

By having the line be checked from each corner of the origin square, you make the line much fatter when used diagonally.

Zelc said:

The line area covers the chosen square and each square one of the lines touches.

Click to expand...

Touches or ENTERS? Big difference there that came up a few times in rules discussions.

The off green show the squares the line enters
The blue show the square the lines touches.
Like a blast, Origin was defaulted to the caster's square.

Shucks, you're right. From looking at the picture, I think the areas would be roughly the same if touching a side of a square makes it hit the square but touching a corner does not. Still, that gets the odd result of the line effect hitting squares right beside the caster when used in a straight line.

Here's something interesting. If you choose the area but no two squares can be equidistant from you, you get the same area for each type of line. But how to word that and implement that without making it a pain?

Edit:
Line X: A line fills X contiguous squares within range, starting from a square adjacent to the origin square (usually the square the user of the power is standing in) and ending in a terminal square within range X. Draw a line from the center of the origin square to the center of the terminal square; all squares in this area must fall on squares passed through by the line. The area cannot include the origin square, nor can any two squares in the area be equally distant from the origin square. You can arrange the area however you like, subject to the above restrictions.

Well, that's no more complicated than the Wall description . Much harder to lay down though. Use sparingly.