Air Jet damage

[Ghazgkull]

I'm new to GURPS, having just played it a couple times with some friends. One of the spells that has been confusing is Air Jet. I'm wondering if someone here can help us understand how it's supposed to work.

In the 4E Magic book, it says that Air Jet does "2D knockback damage" for every point put into it. Does that mean we roll 2D of damage for every point put into the spell and then calculate knockback? Or does it mean it only does the knockback affect with a strength of 2D?

2D damage per point sounds really powerful, so I wouldn't expect this to be the rule. But the book seems to make a really clear distinction between the "knockback damage" of Air Jet and the simple knockback which doesn't do damage in Shape Air. I don't know why these spell would be explained so differently if they have the same effect.

Thanks for any insights.

[vierasmarius]

First of all, if you're not familiar with the knockback rules I'd suggest you review them (Basic Set pg 378). Basically, crushing attacks, or cutting attacks which fail to penetrate armor, knock a target back based on the total rolled damage (not the injury inflicted). Every full multiple of ST-2 damage (ie, 8 damage against a ST 10 target) knocks them back by 1 yard.

Shape Air and Air Jet both inflict Knockback Only damage. This means that you roll damage for the purpose of determining knockback distance, but it doesn't inflict any injury. Shape Air has a one minute duration - as long as it lasts the wind continues to blow from the starting point. So while it only does 1d knockback per 2 energy spent, that knockback is per second. A strong casting can effectively create a wall of wind for a full minute. Air Jet on the other hand is a more traditional combat spell, dealing 2d knockback per point of energy. If you want to keep it active you have to pay that energy cost every second. Like Shape Air this does not inflict any injury on the target.

[Dinadon]

Originally Posted by vierasmarius

Like Shape Air this does not inflict any injury on the target.

I would reread Air Jet. It can cause injury to things that can be blown apart.

[vierasmarius]

Originally Posted by Dinadon

I would reread Air Jet. It can cause injury to things that can be blown apart.

True, but that's a special case. Likewise, either spell could cause injury if the subject is knocked back into spikes or off a cliff.

[Ghazgkull]

Originally Posted by vierasmarius

Shape Air and Air Jet both inflict Knockback Only damage. This means that you roll damage for the purpose of determining knockback distance, but it doesn't inflict any injury.

This makes sense, but then the book is really confusing. The desription of Shape Air is very clear that the spell only causes knockback and doesn't inflict any direct damage. But then the text for Air Jet says that it causes "knockback damage". If the two spells work the same way, the text should be written the same way for both.

Edit: Actually, I think the problem is just that Air Jet uses the word "damage". If it was written the same way but only said "causes 2D knockback", it would be a lot less confusing.

[Kilmore]

For what it's worth, you can also use it to launch things like, say, a javelin at a person.

[vierasmarius]

Originally Posted by Ghazgkull

This makes sense, but then the book is really confusing. The desription of Shape Air is very clear that the spell only causes knockback and doesn't inflict any direct damage. But then the text for Air Jet says that it causes "knockback damage". If the two spells work the same way, the text should be written the same way for both.

I agree that it's poorly worded. There are several examples throughout Magic of spells with imprecise or contradictory descriptions. Many of these are a result of spells being updated from 3rd edition rules (or earlier) to 4th edition. For example, Sunbolt's describe says that it deals burning damage (like 4e lasers) but the stat block says it deals impaling damage (like 3e lasers). Some of these have been fixed in errata, but others persist, especially if they're not outright wrong, just unclear.

[Nereidalbel]

Originally Posted by Dinadon

I would reread Air Jet. It can cause injury to things that can be blown apart.

Yes, to those beings that have the trait Vulnerability: Air Spells. But, that's a special case of a specific vulnerability, not the spell itself.

[Flyndaran]

Originally Posted by Ghazgkull

...
Edit: Actually, I think the problem is just that Air Jet uses the word "damage". If it was written the same way but only said "causes 2D knockback", it would be a lot less confusing.

That's only confusing if using the common definition of damage rather than the Gurps gaming term. It's a common trap to assume words mean what dictionaries say rather than gaming books specifics.

Damage is not injury.

[Plane]

I'm glad this thread made me take a closer look at Shape Air on M24. It seems a lot better in many situations for keeping enemies back. It gets 5x better range, and actually has a better maximum capacity for knockback since you could spend 10 energy to get 5d compared to 3 energy to get 3d for Air Jet. This could change for Air Magery 6+ of course (Magery and Effect).

One downside is an inability to injure swarm/vapor creatures (only Air Jet can do that) though you might actually desire that in some situations.

The duration is also a huge upside (way more total knockback for small creatures) but of course only helps if damage is high enough to cause knockback in the first place.

Also it says you can Block an Air Jet but it doesn't specify whether or not shields help against Shape Air... actually since SA is "one yard wide" it probably qualifies as an Area Effect attack, meaning it can't be blocked and can't even be dodged normally (you'd need to use a retreat to get into an adjacent hex)

AE would also mean it attacks EVERYONE in the line of fire, probably impeding stuff like Cover or Sacrificial Dodge...

Of course that's a disadvantage in some cases: Air Jet being non-AE (a "thin" jet) has the benefit of being able to ignore allies in the line of fire (-4 to hit per each) to hit an enemy behind them, something you couldn't do with Shape Air.

One proposed house rule I think would make sense for Air Jet: since it sort of works like a shove (except you don't double the damage rolled to determine knockback damage) I'd let them take a penalty to target the leg or head (similar to a Push Kick in Martial Arts) to inflict a penalty on the DX roll to avoid falling. This shouldn't be an option for Shape Air since that's AE and couldn't be that specific. Thoughts?

Of course, being locked-in for 1 minute of knockback could be undesirable, and you'd have to pay 1 energy to terminate Shape Air if it became an inconvenience, unless you knew (M123) Counterspell @ 15 to potentially terminate it for free (if you spent only 1-2 energy that is) in 2-3 seconds (not sure if you round halved casting time up or down)

Originally Posted by Ghazgkull

the book seems to make a really clear distinction between the "knockback damage" of Air Jet and the simple knockback which doesn't do damage in Shape Air. I don't know why these spell would be explained so differently if they have the same effect.

I'm not sure there's that much a distinction on M24, it might be that they just were trying to abbreviate how Shape Air's damage works with a more concise expression in Air Jet.

Originally Posted by Ghazgkull

I think the problem is just that Air Jet uses the word "damage". If it was written the same way but only said "causes 2D knockback", it would be a lot less confusing.

"damage" is also present in Shape Air though:

"Treat this as damage for knockback purposes only".

I think it's meant to be obvious this is how Air Jet normally works, especially since the exception "does injury damage to" at the end. "Vaporous beings or swarms" I figures is a casual way of saying "those with Injury Tolerance: Diffuse".

Originally Posted by Kilmore

For what it's worth, you can also use it to launch things like, say, a javelin at a person.

But does the pointy end hit? I think that's a potential difference between throwing with the Throwing skill or throwing with the Javelin skill.

Of course neither really explain what situation causes a "it twisted midair and just caused a minor crushing wound instead of impaling" outcome. I figure as a house rule maybe you could roll d6 on a MoF 1 : 5/6 chance w/ throwing and 1/6 w/javelin.

The advantage to it happening: it's a hit (normally MoF1 is a miss) because it became a wider attack. The disadvantage: because it's not impaling anymore, if you were aiming at something like an eye, it just morphs into a face attack. Thoughts?

Originally Posted by Nereidalbel

Yes, to those beings that have the trait Vulnerability: Air Spells. But, that's a special case of a specific vulnerability, not the spell itself.

It's not for all diffuse creatures?

Do you figure like the 1st level of Vulnerability (normally x2 damage or +100%) is what changes you from 0% damage to 100% damage (rather than the usual 200% ?) like with spirits taking damage from attacks LACKING affects insubstantial?