[Magic] Area Spells and Large Subjects

[sir_pudding]

Originally Posted by benz72

Resolution for the large creature-area damage issue should be consistent with the normal damage rules. My instinct is to have the number of occupied hexes apply their attacks separately.

That creates some problems, I think. It certainly makes Create Fire even better than it already is. Since explosions probably shouldn't work like this, I don't have Area spells do it either.

[Anthony]

Originally Posted by benz72

Resolution for the large creature-area damage issue should be consistent with the normal damage rules. My instinct is to have the number of occupied hexes apply their attacks separately.

The way large creature hit points are scaled, damage should only be applied once. If you make damage per-hex, you should also scale HP in a linear manner with mass.

[benz72]

Originally Posted by sir_pudding

That creates some problems, I think. It certainly makes Create Fire even better than it already is. Since explosions probably shouldn't work like this, I don't have Area spells do it either.

Not saying this is wrong, but why SHOULDN'T explosions work like this? If someone is hit with twice as many fragments they might reasonably be expected to take twice as much damage. q.v. shotgun rules.

Making Create Fire better seems like an odd counter-justification to me. It does increase in cost as area increases (admittedly not linearly).

This may be a 'can of worms' that exposes other inconsistencies, but I'm not entirely clear on the rationale. In fragmentation the effect is handled by SM
"Only three
modifiers apply: the range modifier
for the distance from the center of the
blast to the target, the modifier for the
target’s posture (prone, etc.), and the
target’s Size Modifier. It is possible for
several fragments to hit!" B415
so it seems like some effort is made to allow area effects to damage larger targets more heavily.

[benz72]

Originally Posted by Anthony

The way large creature hit points are scaled, damage should only be applied once. If you make damage per-hex, you should also scale HP in a linear manner with mass.

Quite possible, and in doing so some other mechanic may break (ref 'can of worms' above).

[sir_pudding]

I didn't say fragmentation, which does include SM. The crushing or burning damage from explosions isn't increased by size.

[Anthony]

Realistically, the amount of energy absorbed by a creature exposed to an area effect is linear in surface area, but the amount of energy that can be absorbed is linear in mass. The net effect is that a creature that's twice as big (8x as massive) is about twice as tough against area effects (though the effects of overpressure are a complicated special case; realistic ability to survive concussive blast effects has minimal scaling with size).

Currently, the 8x more massive creature has 2x the HP, so it's got the correct level of durability against area effects; the problem is actually that it's too weak vs single target attacks.

[hal]

Originally Posted by Edges

Does a large creature need to be completely within the area of an area spell to be affected? If yes, a long-tailed dragon can escape a Panic spell by managing to sneak the tip of her tail out of the assumed area. If no, a enormous dragon can be affected by Panic by only casting a single hex on the tip of the tail.

Does size modifier influence the spell cost as it would a regular spell? If no, are there instances in which it is cheaper to cast a "mass" version of a spell on a subject than a "non-mass" version?

Regards to the question above...

Pages 11 and 12 in GURPS MAGIC describes the various types of spells: Regular, Area, Melee, missile, and blocking. Each description says what each type does and affects.
So, what precisely does it say about area spells?

• Cast on a surface rather than subject
• effects extend upwards of 4 yards (12 feet) from the surface the spell is cast upon
• Some area spells do not follow standard area effects - see spell description to determine said effects
• Cost of area spell is its base cost (more on this later!)
• Actual cost of a spell is its base cost times radius of spell. Some area spells have a minimum cost and/or radius
• caster controls effects of spell within an area such that it can affect the whole area, or have patches within that are not affects (holes). Base cost for the entire area of effect remains unchanged.
• Skill effects for range are not from caster to center of effect, but to the nearest EDGE of the area affected.

Then there is the FINAL description of area effects on page 11:

"Otherwise, Area spells work like Regular spells."

So, let's take that set of descriptions and see where it takes us.

1) the effects of the spell affect a volume that is equal to its radius on the surface with a height of 12 feet. That means that the volume of effect is equal to the area in square feet times its height in feet for cubic feet in volume (not that this has any real effect in the game!)

2) "otherwise, like a regular spell" (meaning use Regular spell rules) states that the energy cost to affect a creature with a positive size modifier greater than zero, modifies the base energy cost by size modifier + 1.

So, let's take a spell MASS DAZE with the following properties and see how it works...

Mass Daze has the following base cost with a minimum size required. It is 2 to cast, 1 to maintain with a minimum radius of 2 yards.

In order to affect a size +2 creature, its base cost is to be multiplied by Size Modifier +1. +1 and +2 = 3. So base cost for an area spell is 3x normal, or 6 energy to cast. Minimum radius is 2, so minimum cost is a 2 hex radius spell that costs a base 6 energy per hex radius, for 12 energy to cast. Instead of calculating the range penalty as being equal to the actual distance in hexes minus one from the spell caster to the target, the actual range penalty is equal to the distance from the caster in hexes -1 to the EDGE of the area spell.

Note: the dragon's actual description on page 261 of GURPS BASIC SET CHARACTERS says "20 feet long excluding its tail." This is a case where the example given does not match the rules given in GURPS BASIC SET CHARACTERS where it states "If a creature’s longest dimension falls between two entries on the table, base its SM on the higher value." Technically speaking, 20 feet exceeds 15 feet, which means its size modifier SHOULD be +3, not the +2 given as an example (Possible errata?).

None the less, we're talking about an area effect that can affect a dragon size +2 where if any part of the dragon (excluding tail - see description of dragon on page 261) within the area of effect results in the dragon having to resist the spell's effects. Technically? IF you can cast a large enough area of effect, multiple dragons within the area of effect can be affected at the same time - just as multiple size zero humans within an area of effect can be affected at the same time.

So, technically? Discussing whether a Giant falls within a volume/area of effect or not within an AREA type spell is a moot point. A Giant's whose height is less than 4 yards would fall within the effects of a volume for an area spell, but not the limits imposed by size modifier as given as a restriction in normal spells. If your area spell is large enough to handle five giants at the same time, it must also have a corresponding extra energy to handle their size modifier at the same time - or NONE of the giants will be affected by the spell that was cast for size zero targets.

That's based on my strict reading of GURPS MAGIC. I guess that is why I was wondering at the question posed by the original poster of this thread, as this issue has never come up in any of my games since I started using GURPS in 1986. Back then, GURPS even had a BEASTIARY (unlike what GURPS 4e has today alas!) that we could reference our fantastic creatures from. ;)

In any event, hope this helps...

[evileeyore]

Originally Posted by hal

Regards to the question above...

I disagree.

The "base cost" of an Area spell is multiplied by the radius of the area. This determines it's "actual cost" (which is then compared to it's minimum cost, you pay the higher).

The "Otherwise, Area spells work like Regular spells" is meant cover the things that Area spell's description has not covered. It has covered Cost, Area, and a skill penalty based on distance from the subject.

All that is left from Regular spells are "if you cannot see the subject", which is all that Area spells is drawing from Regular spells, as everything else has been covered and works differently.

[sir_pudding]

Again, any interpretation that has you paying more for casting Rain on a mountain or city than on a featureless plain is clearly wrong.

[evileeyore]

Originally Posted by sir_pudding

Again, any interpretation that has you paying more for casting Rain on a mountain or city than on a featureless plain is clearly wrong.

Or try this one:

Cast Mass Daze on a football field. Why is it cheaper to cast on a field filled with hundreds of SM +0 enemies but twice that to cast it on a field containing only a singular SM +1 creature?


The only correct answer: It is not.

There is a bit of breakdown with the rules when using the Area version of a spell to stand in for the non-Area version. But that has always been an artifact of GURPS Magic (in 3e you have the same problem, Daze a horse cost 6 (3 times it's size in hexes, 2, equals 6) or just Mass Daze it's Area which only costs 4 (2 hex radius times base cost 2)).

The real cost comes in as a factor of "opportunity" cost. The Mass versions of spells always require you to have the non-Mass version first, so at the minimum it's a 1 point buy in. In 3e it was a bit more costly as IQ was more expensive to raise and restricting Magery to 3 was the norm (making getting multiple spells to "great" levels a lot harder).