Caster Size and Antimagic Field Radius

[Elephant]

By the book, AMF is a 10-ft radius emanation, centered on the caster. I have two questions about this. First, as a Medium caster, am I supposed to pick a corner of my square as the center, giving a radius that extends two corners from it? Or is it truly centered on me, affecting everything within 10 feet of me?

This leads into the second question: What is the result of a Gargantuan creature casting Antimagic Field? Does the spell affect everything within 10 feet of the creature's center (that is, only the internals of the creature itself)? Or does the radius of effect extend from the caster's skin (or, mechanically, the borders of the creature's square)?

 

[dcollins]

You're asking a common question which isn't directly addressed by the 3.5 rules that I can see. Yes, technically on a grid the spell is supposed to be centered on a corner of the caster's choosing (I think a lot of DM's reasonably hand-wave this a bit).

The 3.0 rules had the following note, indicating that very large creatures would in fact not be entirely protected by the field (presumably centered on the corner of any square they touch). The 3.5 SRD is silent on this issue.

Note: Should the character be larger than the area enclosed by the barrier, any part of the character's person that lies outside the barrier is unaffected by the field.

 

[Elephant]

Now that just seems silly. Houserule fodder!

 

[BennyTheBull]

I would houserule that it creates a radius large enough to cover you plus an additional 10' but only if it was centered on you. if you tried to center it on an unwilling creature some for of saving throw or that it just uses the 10' radius and tough luck.

 

[Infiniti2000]

I would houserule that it creates a radius large enough to cover you plus an additional 10' but only if it was centered on you. if you tried to center it on an unwilling creature some for of saving throw or that it just uses the 10' radius and tough luck.

The spell is centered only on you. You cannot cast it on someone else, willing or not.

Since it says centered on you, I think that overrules the general principle that area spells must be on a grid intersection. If you are medium, treat it like you would 10ft reach (anything that you could hit would be affected). If you are large, use the center grid intersection. If you are huge, use a 10ft reach from the center square, etc. Yeah, this makes AMF much less useful for Colossal creatures, but the spell covers a Gargantuan creature. That may be all the gargantuan creatures needs, though, quite honestly.

 

[HellHound]

I rule it the same way Infiniti2000 does, but this is definitely a house rule, in my case.

 

[Infiniti2000]

I rule it the same way Infiniti2000 does, but this is definitely a house rule, in my case.

I don't agree that it's a house rule.

 

[Patryn of Elvenshae]

Since it says centered on you, I think that overrules the general principle that area spells must be on a grid intersection.

...

I don't agree that it's a house rule.

Care to support that with some rules text?

All I can find is:

Area: Some spells affect an area. Sometimes a spell description specifies a specially defined area, but usually an area falls into one of the categories defined below.
Regardless of the shape of the area, you select the point where the spell originates, but otherwise you don’t control which creatures or objects the spell affects. The point of origin of a spell is always a grid intersection.

And ...

Antimagic Field
Abjuration
Level: Clr 8, Magic 6, Protection 6, Sor/Wiz 6
Components: V, S, M/DF
Casting Time: 1 standard action
Range: 10 ft.
Area: 10-ft.-radius emanation, centered on you
Duration: 10 min./level (D)
Saving Throw: None
Spell Resistance: See text

 

[Infiniti2000]

Care to support that with some rules text?

The one you quoted and my previous comment are sufficient. There's nothing else to add.

And, in any case, at worst it would be 2.5ft off and you would have to specify the interesection every round, possibly multiple times per round (is there a limit to rotating the effect in such a case?). What's the rule on changing the interesection point while remaining still? There is none, right?