Where does this "rule of 3" come from in relation to spells with a range of "line" ??


Rules Questions


So, a while ago I was running a game and cast a Lightning Bolt on a line of PCs. 3 of them were in a little L-shaped cluster. I maneuvered my caster and selected the corner of my square to cast from in order to get the line to bisect each of the 3 squares.

One player, who is usually the GM, said no. He said that the PCs needed to be "in a line" for the line effect to "line up" and hit them all. I started to explain that the line effect rules state that you essentially pull a string from one corner of your square to any other corner of a square, and any squares bisected along the way get zapped.

Core rulebook, magic chapter wrote:
It starts from any corner of your square and extends to the limit of its range or until it strikes a barrier that blocks line of effect. A line-shaped spell affects all creatures in squares through which the line passes.

He again said no, and started explaining that there is a set 3-square combination -- you pick the initial 3 squares that it hits, then another 3, and they sorta "Tetris" together. The other players looked at him like he was making stuff up and sorted laughed. At that point he sat down grumpy and let me continue.

I didn't think anything of it until a few days ago. I was in a Pathfinder Society game, and a player was doing another line effect. He was trying hard to figure out which squares were affected, and I finally just said, "Imagine you're pulling a string from a corner of your square, and anything the line cuts over, is hit." The GM immediately told me I was wrong and that the rulebook has specific pictures of how a line works, and it involves three squares at a time.

At that point, I was like whoa, the 3 squares thing again! I pulled up the rules and just showed them the text I quoted above. The GM shook his head and said the rulebook had other rules that superceded that, but he couldn't give me a page number or any citation.

As you might guess, now that I have 2 GMs asserting some weird "3 square rule" about line effects, I'm immensely curious. Where does this come from? What image are they referring to, and why do they imagine that it's a rigid, hard-coded set of squares, instead of straight line, diagonal, etc.?

Does anyone have any insight into where this new "3 squares" rule came from or even what it is?

Silver Crusade

Pathfinder Adventure, Adventure Path, Companion, Lost Omens, Rulebook, Starfinder Adventure Path, Starfinder Roleplaying Game, Starfinder Society Subscriber

I know the Core Rulebook uses 3 figures as an example due to limitations on what all you can fit onto a picture in a page, but for there actually being a "3 square" rule?

I've never heard of it. It might be leaking in from an older edition or from 5th or Starfinder.

The Exchange Owner - D20 Hobbies

Find the magic section with the various templates. On those graphics I believe the line graphics have 3 aquares for each chunk. It’s not a written rule. Call it unwritten. It’s basically an interpretation off the graphic. Why they cling to it so dearly? Because they are human. Humans love patterns. This is a “3” pattern. It’s beautiful.

I kinda do a combination. I like the side of a sheet of paper and I’m happy if 3 in a row are touched.


Here is the image from the rule book:

http://paizo.com/pathfinderRPG/prd/image/SpellAreas.jpg

It doesn't have "3 chunks" or anything for the examples of line effects. Are you referring to another image? Can you give me a page number?

Silver Crusade

Pathfinder Adventure, Adventure Path, Companion, Lost Omens, Rulebook, Starfinder Adventure Path, Starfinder Roleplaying Game, Starfinder Society Subscriber

Ah, sorry, I was misremembering from the combat chapter.


From the sound of it, the people insisting that lines have to go in sets of 3 squares didn't bother to look at the whole image in the rulebook. There are two examples - half of them - in that image where the line isn't done in sets of 3.


Diachronos wrote:
From the sound of it, the people insisting that lines have to go in sets of 3 squares didn't bother to look at the whole image in the rulebook. There are two examples - half of them - in that image where the line isn't done in sets of 3.

All of the templates in the linked image are built of sets of 3. What page are you referencing that has a different layout?


I would assume one linked which has the third use 7 total squares and the third using 4 total.


Pathfinder Companion, Pawns Subscriber; Pathfinder Roleplaying Game Superscriber
Skaldi the Tallest wrote:
Diachronos wrote:
From the sound of it, the people insisting that lines have to go in sets of 3 squares didn't bother to look at the whole image in the rulebook. There are two examples - half of them - in that image where the line isn't done in sets of 3.
All of the templates in the linked image are built of sets of 3. What page are you referencing that has a different layout?

There are 4. One has 6 in a row, one has 3 then 3, one has 2 then 3 then 2, one has 4 in a diagonal. Are you sure you're looking at the same image?

I'd even allow other variations as long as the total number of squares wasn't greater than 7.


taks wrote:
Skaldi the Tallest wrote:
Diachronos wrote:
From the sound of it, the people insisting that lines have to go in sets of 3 squares didn't bother to look at the whole image in the rulebook. There are two examples - half of them - in that image where the line isn't done in sets of 3.
All of the templates in the linked image are built of sets of 3. What page are you referencing that has a different layout?

There are 4. One has 6 in a row, one has 3 then 3, one has 2 then 3 then 2, one has 4 in a diagonal. Are you sure you're looking at the same image?

I'd even allow other variations as long as the total number of squares wasn't greater than 7.

Each of those are repetitions of a pattern of 3 until they reach the actual length of the line.

The first and second can be viewed as repetitions of a line of 3. The third is a repetition of 2 up one over. The fourth is a repetition of a diagonal. All of them, in a logical sense, can be described as repetitions of 3.


The rules state:

"A line-shaped spell shoots away from you in a line in the direction you designate. It starts from any corner of your square and extends to the limit of its range or until it strikes a barrier that blocks line of effect. A line-shaped spell affects all creatures in squares through which the line passes."

(CRB chapter 9, Magic)

The diagrams are simply examples of the squares a 30' line might affect, depending upon which corner you draw the line from and in which direction you extend it.

Use of string and rulers etc. is quite legitimate and is the easiest way to deal with longer lines.


Pathfinder Adventure Path Subscriber
Skaldi the Tallest wrote:
taks wrote:
Skaldi the Tallest wrote:
Diachronos wrote:
From the sound of it, the people insisting that lines have to go in sets of 3 squares didn't bother to look at the whole image in the rulebook. There are two examples - half of them - in that image where the line isn't done in sets of 3.
All of the templates in the linked image are built of sets of 3. What page are you referencing that has a different layout?

There are 4. One has 6 in a row, one has 3 then 3, one has 2 then 3 then 2, one has 4 in a diagonal. Are you sure you're looking at the same image?

I'd even allow other variations as long as the total number of squares wasn't greater than 7.

Each of those are repetitions of a pattern of 3 until they reach the actual length of the line.

The first and second can be viewed as repetitions of a line of 3. The third is a repetition of 2 up one over. The fourth is a repetition of a diagonal. All of them, in a logical sense, can be described as repetitions of 3.

Actually, if you start the "line" from the upper-left corner of the "red-dot" square and end it on the upper-right corner of the end square in each of those pictures, you can see that the shaded squares are the squares that get bisected. Even in the second image (the 3-then-3), the "line" goes strait through the corner in the middle.


Rhyst wrote:
Actually, if you start the "line" from the upper-left corner of the "red-dot" square and end it on the upper-right corner of the end square in each of those pictures, you can see that the shaded squares are the squares that get bisected. Even in the second image (the 3-then-3), the "line" goes strait through the corner in the middle.

I'm not saying that's true. I am saying that the lines in the image are all built one a pattern of 3 blocks.


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Pathfinder Adventure Path Subscriber
Skaldi the Tallest wrote:
Rhyst wrote:
Actually, if you start the "line" from the upper-left corner of the "red-dot" square and end it on the upper-right corner of the end square in each of those pictures, you can see that the shaded squares are the squares that get bisected. Even in the second image (the 3-then-3), the "line" goes strait through the corner in the middle.
I'm not saying that's true. I am saying that the lines in the image are all built one a pattern of 3 blocks.

I believe that "pattern" is just an artifact of "30ft line"


Rhyst wrote:
I believe that "pattern" is just an artifact of "30ft line"

Well put. We don't usually see the word "artifact" used in that sense in this game!


Well, the answer appears to be: no real answer. However, I appreciate that a lot, guys. I seriously expected someone to say, "Oh, the 3 square rule, page 256, totally a real thing." Instead what we appear to have concluded is: the 2 GMs I interacted with probably had a murky reading of the rules. That's actually OK. It will make me more self-assured when I next interact with them. I'll keep a copy of page 215 handy and just constantly refer to it when people insist on turning Lightning Bolts into Tetris.

Thank you everyone!


Rhyst wrote:


Actually, if you start the "line" from the upper-left corner of the "red-dot" square and end it on the upper-right corner of the end square in each of those pictures, you can see that the shaded squares are the squares that get bisected. Even in the second image (the 3-then-3), the "line" goes strait through the corner in the middle.

Right, looks like “3-square rule” and “string from one corner to another” are two metaphors describing the same thing. So, everybody’s right! Hurray!


if the line you drew is one of the ones shown on the page you linked you did it right. and yes all those lines are 3 line chunks out to 30feet, you can keep extending them farther if your line is longer, they call it the 3 square rule because people didn't use to have a computer to look up this stuff but that was just a term we used for it not a real term for it.


Skaldi the Tallest wrote:
The first and second can be viewed as repetitions of a line of 3. The third is a repetition of 2 up one over. The fourth is a repetition of a diagonal. All of them, in a logical sense, can be described as repetitions of 3.

No, not in a logical sense. We mathematicians have formal definitions of repeating patterns. We work with fundamental units, the smallest region that can repeat in the same direction and same distance.

In the first figure, the rectangle one square wide and six squares tall, the fundamental unit is one square (because we would not allow partial squares if the line continued), used 6 times. Its repetions occur one square upward from the previous fundamental unit.

In the second figure, which resembles the first figure but the last three squares are transposed to the right, the fundamental unit is three squares in a vertical 1-by-3 rectangle, used twice. Its repetion is moved three squares upward and one square to the right.

In the third figure, a zigzag of 7 squares, we can view it two ways. The first way is that it is a single piece with no repetitions. The second way is that the fundamental unit is an upsidedown L of three squares, used twice and partially a third time. Its repetition is moved two squares upward and one square to the right. The last rectangle, the 7th one, is a truncated piece of the 3rd upsidedown L.

In the fourth figure, the diagonal line, the fundamental unit is one square. Its repetitions are moved diagonally one square upward and rightward.

Generating a region by selecting the squares that a line segment passes through does not have to create a repeating pattern. Or it can repeat with a fundamental unit of one square, two squares, three squares, four squares, etc.

By the way, "Rule of Three" was originally a mathematical rule taught in schools before algebra became common. It is a system for correct proportions. If I wanted to adjust a recipe that made 20 cookies to make 50 cookies instead, I would multiply the measurement of each ingredient by 50 and divide by 20. Two teaspoons of vanilla in the original recipe would become 5 teaspoons of vanilla in the expanded recipe. 2*50/20 is three numbers, so it was called the Rule of Three. The familiar phrase became popular naming any system of three objects, even after the original mathematical rule was forgotten.


Pathfinder Companion, Pawns Subscriber; Pathfinder Roleplaying Game Superscriber

Indeed.

I hate the diagonal one, btw. It cheats them out of a few critters.


It does cheat them out of a few, but since the caster gets to decide the starting & ending point of the line, he/she can simply declare the line ending point to be such that a bunch of squares are bisected, instead of doing a perfect diagonal. Nobody nowadays would do a perfect diagonal unless that's precisely where the targets were. In D&D 3.5, the rule was different -- you hit everything when your line was on the crosshairs, so perfect diagonals were like "OMG jackpot."

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