Area of Effect Spells, How about something other than a circle? Options

[The Jopp]

This would contradict fundamental laws of SR Magic. With the exception of indirect combat spells, you cannot affect targets you cannot see.

Why? Of course you wont damage anyone you cannot see with a Nexus Stunblast but everyone within your LOS within Magic Meters would feel it. And yes, they would make elemental effect spells a bit more useful.

Which length and height?

That would be deisgnated by the caster and be limited by his/her magic rating in very much the same way as for example a physical barrier.

[Wombat]

It's an interesting concept that hints at a way around the caster being hit with his own AoE spell, but you could just as easily design a spell using the rules in Street Magic. An Area(Standard Sphere with a radius equal to the Force of the spell) +2 DV, and Restricted Target(Enemies) -1 modification to the spell. Which is an awesome way to design a spell, but only affects targets that have hostile intentions towards the caster, not including traps(since they're not alive), nor someone shooting into a crowd at random(the hostility is not directed at the subject[caster] of the spell). It could be used against targets preparing an ambush or other surprise attack. It might even include those that have non-combative hostilities against the caster, such as social rivals or disgruntled teammates.

[Shinobi Killfist]

First of all, there are no exclusive actions in SR4. Complex action =/= exclusive action because the mage can still have multiple IPs an as such can do other things besides moving the AoE. Sustained spells can conciously be moved by the caster with a complex action, but for a mass invisibility/mask spell this is not necessary. The spell stays with its targets. So it is indeed a single -2 for the whole party and all other valid targets in the area of effect.

An actual field of invisibility is achieved more easily with the (trid)phantasm spell. Just create an illusion of the normal scene minus the things you wish to hide.

Exclusive action may have been a poor choice of words, but you have a free action left. And multiple initiative passes wont make it that much easier, you move during every pass unless its one really big area keeping a group of individuals in it at all times will require adjustments probably most if not all of your available passes.

And I would not allow trid phantasm to remove object from the scene. It already does more than it should for its drain level, I wont add invisibility to the mix.

[Shinobi Killfist]

I forgot about the other problem with AoE illusion spells replacing masking or whatever, LOS. Unlike a indirect combat spell you have to see everything you are effecting by the illusion. So if Bob your street Sam buddy turns a corner before you do, ooops it dropped from him. Also you would have to be rear guard to see everyone, and the GM has to rule you can see yourself in the AoE. With a targeted spell sure you can always target yourself, but AoE spells target a point in space and effect everything you can see. Now maybe you can create some special mirror getup that allows you to see yourself while you see others, but I'd make the user make checks of some kind in order to keep it going.(willpower+spell casting probably)

[Dakka Dakka]

This is not a problem. You only have to see all targets for the casting of the spell. To sustain it they don't have to remain in LOS, the caster doesn't even have to be on the same plane.

[Muspellsheimr]

Slight correction: You must be able to see what is affected to cast or move the area spell. Sustaining does not require Line of Sight.

[Dakka Dakka]

AFAIR the BBB does not mention that Area Spells have to target a point in space. The FAQ even suggest otherwise for indirect combat spells. Moving the point in space and thus the area makes sense for certain spells such as clairvoyance but not so much for spells like mass invisibility, levitate or ignite.

The problem is that there are no such spells in the rulebooks and, while street magic does not forbid extending the area of effect for such spells, there are no rules how the addittional targets are affected and if the area has to be moved or if the spell's effect sticks to the targets and the caster only needs to sustain the magic.

Without clarification by the developers this is house rule territory.

[Muspellsheimr]

There is a rule in the BBB - if a subject moves out of the Area of Effect, the spell no longer affects them. If someone moves into the Area of Effect, the spell begins affecting them. There is no clarification needed.

[Wombat]

AFAIR the BBB does not mention that Area Spells have to target a point in space.

I think I addressed this point on the last page.
p.173, SR4
"Some spells target areas or points in space; in this case the caster must be able to see the center of the area affected. All visible targets within the area are affected; area spells can affect more than one target at a time."

p.174, SR4
"If an area-effect spell is sustained, the affected area may be moved with a Complex Action, as long as it remains within line of sight. Characters who 'drop out' of the affected area are no longer affected by the spell; characters who are 'enveloped' by the area must defend against the effects of the spell as appropriate."

[Dakka Dakka]

In the first quote the important word is some. There is no rule against targeting a person with an area effect spell, or to be exact, to make a person the center of the area of effect

The second quote does not forbid moving the target of the center of the affected area. It only talks about how you move the affected area away form the initial target (which IMHO could be a moving object). Also if you actually always applied this rule at least the phantasm spell would not work unless the observers are within Force meters of the targeted point in space. which makes it effectively useless.

[Wombat]

I think we're arguing RAW vs. RAI here. The reason "some" is used is to differentiate from the previous paragraph where they discuss single target spells.

[Dakka Dakka]

Then the question remains how this point in space is defined. Which reference system does the caster use? Is the point of origin a fix point on earth, a fix point in space, in which case the caster would constantly have to expend a complex action as the earth moves through space, or is it the point on a person's nose, in which case he would not have to expend an action even if the person runs around?

[Wombat]

Is the point of origin a fix point on earth, a fix point in space, in which case the caster would constantly have to expend a complex action as the earth moves through space,...

I think that since spells are made of mana, relative location spells (such as AoE spells) would behave in a fashion similar to Wards, in that their position is fixed in relation to the Earth's biosphere(or manasphere)

[Dakka Dakka]

Well actually wards do not have any relation to the Biosphere. There is only the relation between the anchor and the warded space. The Street Magic Errata clarify that. This would translate to the center and the area of effect for spells.

[Shinobi Killfist]

This is not a problem. You only have to see all targets for the casting of the spell. To sustain it they don't have to remain in LOS, the caster doesn't even have to be on the same plane.

Actual for Area spells the rules are different.

"If an area-effect spell is sustained, the affected area may be moved with a complex action, as long as it remains within line of sight." PG 174 SR4 mainbook.

So while moving the area of effect around everything has to stay in LOS, you sam buddy turning the corner, and yourself.

I consider this a good thing, because otherwise they can just reduce the illusion chapter to two spells trid phantasm and cause penalty spell. Without the GM using these rules and rising hard on them the vast majority of spells in the illusion chapter are a waste of space.

I see wombat has the quote above, just pointing out the part not being discussed, that you need los of the area when moving it.