Determining radius with squares

[Sir Hawkeye]

For fireball, assemble and use the spell area template provided in Dragon magazine #301.

Technically, that template is at least 4 squares too small.

dcollins appears to have better templates.

upon further inspection, any person who uses "simpler rules" and "integral calculus" in the same concept is clearly insane (but probably spot-on in terms of areas).

WOO! Calculus!

 

[Kershek]

dcollins' templates are great, but how come he doesn't list a 15-foot radius centered on a square? I think he needs to add that one.

 

[kreynolds]

dcollins' templates are great, but how come he doesn't list a 15-foot radius centered on a square? I think he needs to add that one.

Eh? It would look just like a 20-foot radius centered on a square, only 5-feet less.

 

[Negative Zero]

Re: Re: Determining radius with squares

dcollins has site with some info on this, and it's really useful. You can check it out here.

awesome resource! very cool. thanks for the heads up, and kudos to dcollins on all the work.

~NegZ

 

[drnuncheon]

Re: Re: Re: Determining radius with squares

Thank you for the mention, KR.

Dave, I've got a question about some of your templates.

The method I have always used is 'counting squares' - basically, I count the distance in squares from the center square to the potential target, using the 5/10 rule, and use that figure to determine whether or not it is affected.

Anyway, for that method, using the 10' radial area centered on a square, I get this result:

. X X X .
X X X X X
X X O X X
X X X X X
. X X X .

...which is significantly larger (8 squares) than yours - but the extra included squares are only 10' away by the 5/10 rule (5' diagonally, 5' either vertically or horizontally). Is this an oversight in your template or am I overlooking something?

This method gives slightly larger spell areas but it is both quick to calculate and consistent with movement and ranges.

J

 

[kreynolds]

Re: Re: Re: Re: Determining radius with squares

Is this an oversight in your template or am I overlooking something?

I don't know about an oversight, but that's a 15-foot sphere you just illustrated, not a 10. Also, you didn't pick an intersecting grid point to start with. You just picked a whole square. That's why your diameter is off.

 

[Negative Zero]

just as a clarification (hopefully) to drnuncheon's comment and kreynolds' response:

it's a 10 foot sphere with a starting point in the center of the square, not a corner, that assumes that if half the square is affected then the entire square is affected. (which is how i've always played it as well.)

~NegZ

 

[kreynolds]

just as a clarification (hopefully) to drnuncheon's comment and kreynolds' response:

it's a 10 foot sphere with a starting point in the center of the square, not a corner,

I know, which is the problem. Even when a spell is centered upon a square or the caster, you still have to choose an intersecting gridline (or corner of the square, if you will) as the originating point of the spell. Otherwise, you're squeezing free extra space out of the spell, and any given radius is actually going to be 5-feet bigger.

EDIT: Also, it's not a 10-foot sphere. It's a 10-foot radius (or radial, as he put it).

 

[drnuncheon]

Re: Re: Re: Re: Re: Determining radius with squares

I don't know about an oversight, but that's a 15-foot sphere you just illustrated, not a 10. Also, you didn't pick an intersecting grid point to start with.

Well, yes, of course I didn't pick a grid intersection, that was the point - I was comparing my 'targeted on a square' to his 'targeted on a square'. I mentioned that.

It's also not a 15' foot radius. If you measure from the midpoint of the target square, it is a 12.5' radius (two and a half squares) - and that extra 2.5' (half square) comes from the fact that you can't only affect half a square. I mentioned that, too.

Basically, I'm trying to understand how he is applying the 5/10 rule, because when I do it, I get different results than he does.

J

 

[dkilgo]

I partially agree with drnuncheon, only on the grounds that it makes no sense to target the area next to a target character, or creature,(ie: the corner, or intersecting grid lines). In my mind it only makes sense to target the person, or creature, inside the square. This only makes sense due to the "no-facing" rule. If a creature of any type has no exact face in combat, then how are you targeting an area next the square that the creature is inhabiting. You need to target the entire creature all together. Hence targeting the center of the square because you know not the creature's exact whereabouts in the square. And, yes I do understand that most area effect spells do not require a creature to target. But, you still have to target something, and not an intersecting grid line between squares.