RAW: How to increase height effects of any Area spell?

[hal]

Originally Posted by whswhs

This isn't an answer to your general question, but might address the specific case:

Suppose you yourself are standing on the roof of a tall building, one that puts you, say, twenty feet above the ground. You want to cast an area spell on your foes who are also on that roof. Do you need to cast it twice, once for ground level and once for a layer above that?

To answer the question posed here, the rules on area spells are specific: The spell itself is cast upon a surface. If the surface you cast it upon, is on the roof, then it will affect the occupants of the area of your spell's operation - inclusive of the 4 yards between the surface the spell was cast upon, and above that surface. So no, you don't need to cast it twice, once for ground level, and once to be on the surface that you're on. Just cast it on the surface you're on, and presto - spell goes off as advertised.

Originally Posted by whswhs

I don't think you should. You certainly ought to be able to cast it at the level of your own footing.

(Compare a different case: If I dig a pit sixty feet deep, can I force every hostile wizard to case a spell five times before the sixth casting is based at the level of the boards I've used to cover the pit? Or can they just choose to cast from ground level?)

Now, it might make sense to say that if I'm on the ground, but I can look up and see the enemy standing on the roof of a tower, I can cast the spell on the tower at the level where they're standing. It would be a bit much, perhaps, to level me cast it at an imagined level of the air, but if there's actually footing there, why not allow it to be based specifically at the level of that footing?

This is the relevant quote from GURPS MAGIC page 11 under area spells:

"These spells affect an area instead of an individual. They are cast on a surface
– floor, ground, etc. – and their effects extend four yards (12 feet) up from that surface."

That makes me wonder...

Can one cast a spell of a given "area" or radius, on a surface that does not exist? For instance, suppose I'm on the edge of a cliff, and I'm 9 feet from the edge of the cliff. I cast the spell such that its center of area is on me, and the Radius is 6. Does the rest of the spell continue past the edge of the cliff because it is anchored to the surface of the cliff that I'm on, or does it abruptly end because the cliff ends, and the surface does not extend past the edge of the cliff? If I'm on a slope with a rise over run of 1/2 (ie goes up 1 foot for every 2 feet distant) - does the area spell adhere to the surface of the slope, or does it go parallel with the point it was anchored at?

These are all "niggling details" - probably ones that have to be answered by the GM as part of how he sees it in his world. Largely because there is nothing that is stated in the rules as written either way.

RULES AS WRITTEN is a sort of mantra for those who are rules lawyers right? But it also helps formulate how magic works within a game universe. For one GM, it may work as was suggested (Ie it can be anchored to a single point or surface, and overhang it by as much as the spell energy requires it to overhang - or in other game worlds, it ends when the surface ends.

And to clarify better the original question: The idea was to get EVERYONE in the tower with but a single casting. As written, the spell would have to be cast twice to get everyone in the tower. Not that I was implying that you had to do ground level first, then the next level second per se.